liminix

THOUGHTS.txt (139162B)

---

 Thu Sep 22 00:12:42 BST 2022
 
 Making quite reasonable progress, though only running under emulation.
 Since almost everything so far has been a recap of nixwrt, that's to
 be expected.
 
 The example config starts some services at boot, or at least attempts
 to. Next we shoud
 
  - add some network config to run-qemu
  - implement udhcp and odhcp properly to write outputs
   and create resolv.conf and all that
  - write some kind of test so we can refactor the crap
  - not let the tests write random junk everywhere
 
 Thu Sep 22 12:46:36 BST 2022
 
 We can store outputs in the s6 scan directory, it seems:
 
 > There is, however, a guarantee that s6-supervise will never touch subdirectories named data or env. So if you need to store user information in the service directory with the guarantee that it will never be mistaken for a configuration file, no matter the version of s6, you should store that information in the data or env subdirectories of the service directory.
 
 https://skarnet.org/software/s6/servicedir.html
 
 > process 'store/pj0b27l5728cypa5mmagz0q8ibzpik0h-execline-mips-unknown-linux-musl-2.9.0.1-bin/bin/execlineb' started with executable stack
 
 https://skarnet.org/lists/skaware/1550.html
 
 
 Thu Sep 22 16:14:49 BST 2022
 
 what network peers do we want to model for testing?
 
 - wan: pppoe
 - wan: ip over ethernet, w/ dhcp service provided
 - wan: l2tp over (ip over ethernet, w/ dhcp service provided)
 - lan: something with a dhcp client
 
 https://accel-ppp.readthedocs.io/en/latest/ could use this for testing
 pppoe and l2tp?
 
 
 Thu Sep 22 22:57:47 BST 2022
 
 To build a nixos vm with accel-ppp installed (not yet configured)
 
   nix-build '<nixpkgs/nixos>' -A vm -I nixos-config=./tests/ppp-server-configuration.nix -o ppp-server
   QEMU_OPTS="-display none -serial mon:stdio -nographic" ./ppp-server/bin/run-nixos-vm
 
 To test it's configured I thought I'd run it against an OpenWrt qemu
 install, so, fun with qemu networking ensues. This config in ../openwrt-qemu
 is using two multicast socket networks -
 
 nix-shell -p qemu --run "./run.sh ./openwrt-22.03.0-x86-64-generic-kernel.bin openwrt-22.03.0-x86-64-generic-ext4-rootfs.img "
 
 so hopefully we can spin up other VMs connected either to its lan or
 its wan: *however* we do first need to configure its wan to use pppoe
 
 uci set network.wan=interface
 uci set network.wan.device='eth1'
 uci set network.wan.proto='pppoe'
 uci set network.wan.username='db123@a.1'
 uci set network.wan.password='NotReallyTheSecret'
 
 (it's ext4 so this will probably stick)
 
 
 Fri Sep 23 10:27:22 BST 2022
 
 * mcast=230.0.0.1:1234  : access (interconnect between router and isp)
 * mcast=230.0.0.1:1235  : lan
 * mcast=230.0.0.1:1236  : world (the internet)
 
 
 Sun Sep 25 20:56:28 BST 2022
 
 TODO - bugs, missing bits, other infelicities as they occur to me:
 
 DONE 1) shutdown doesn't work as its using the busybox one not s6.
 
 2) perhaps we shouldn't have process-based services like dhcp, ppp
 implement "address provider interface" - instead have a separate
 service for interface address that depends on the service and uses its
 output
 
 * ppp is not like dhcp because dhcp finds addresses for an existing
   interface but ppp makes a new one
 
 3) when I killed ppp it restarted, but I don't think it reran
 defaultroute which is supposed to depend on it. (Might be important
 e.g. if we'd been assigned a different IP address). Investigate
 semantics of s6-rc service dependencies
 
 DONE 4) make the pppoe test run unattended
 
 5) write a test for udhcp
 
 6) squashfs size is ~ 14MB for a configuration with not much in it,
 look for obvious wastes of space
 
 7) some of the pppoe config should be moved into a ppp service
 
 8) some of configuration.nix (e.g. defining routes) should be moved into
 tools
 
 DONE 9) split tools up instead of having it all one file
 
 10) is it OK to depend on squashfs pseudofiles if we might want to
 switch to ubifs? will there always be a squashfs underneath? might
 we want to change the pseudofiles in an overlay?
 
 11) haven't done (overlayfs) overlays at all
 
 12) overlay.nix needs splitting up
 
 13) upgrade ppp to something with an ipv6-up-script option
 
 14) add ipv6 support generally
 
 15) "ip address add" seems to magically recognise v4 vs v6 but
 is that specified or fluke?
 
 16) tighten up the module specs. (DONE) services.foo should be a s6-rc
 service, (DONE) kernel config should be checked in some way
 
 DONE 17) rename nixwrt references in kernel builder
 
 18) maybe stop suffixing all the service names with .service
 
 19) syslogd - use busybox or s6?
 
 chat -s -S ogin:--ogin: root / "ip address show dev ppp0 | grep ppp0" 192.168.100.1  "/nix/store/*-s6-linux-init-*/bin/s6-linux-init-hpr -p"
 
 
 Working towards a general goal of having a derivation we can
 usefully run `nix path-info` on - or some other tool that will
 tell us what's making the images big. The squashfs doesn't
 have this information.
 
 Towards that end (really? can't remember how ...) what would be a
 way for packages to declare "I want to add files to /etc"? Is that
 even a good idea?
 
 Thinking we should turn s6-init-files back into a real derivation.
 
 Tue Sep 27 00:31:45 BST 2022
 
 > Thinking we should turn s6-init-files back into a real derivation.
 
 This turns out to be Not That Simple, because it contains weird shit
 (sticky bits and fifos).
 
 Tue Sep 27 09:50:44 BST 2022
 
 * allow modules to register activation scripts that are run on the
 root filesystem once all packages are installed
 
   - do they run on build or on host? if we're upgrading in place
   how do we ship filesystem changes to the host?
 
 or:
 
 * allow modules to declare environment.*, use pseudofile on build and
 create real files on host. will need to keep the implementation on
   host faily simple because restricted environment
 
 Tue Sep 27 16:14:18 BST 2022
 
 TODO list is getting both longer and shorter, though longer on
 average.
 
 2) perhaps we shouldn't use process-based services like [ou]dhcp as
 queryable endpoint for interface addresses (e.g. when adding routes).
 Instead have a separate service for interface address that depends on
 the *dhcp and uses its output
 
 3) when I killed ppp it restarted, but I don't think it reran
 defaultroute which is supposed to depend on it. (Might be important
 e.g. if we'd been assigned a different IP address). Investigate
 semantics of s6-rc service dependencies
 
 4) figure out a nice way to fit ppp into this model as it actually
 creates the interface instead of using an existing unconfigured one
 
 5) write a test for udhcp
 
 7) some of the pppoe config should be moved into a ppp service
 
 11) haven't done (overlayfs) overlays at all
 
 13) upgrade ppp to something with an ipv6-up-script option, move ppp and pppoe derivations into their own files
 
 14) add ipv6 support generally
 
 15) "ip address add" seems to magically recognise v4 vs v6 but
 is that specified or fluke?
 
 19) ship logs somehow to log collection system
 
 21) dhcp, dns, hostap service for lan
 
 22) support real hardware
 
 Tue Sep 27 22:00:36 BST 2022
 
 Found the cause of huge image size: rp-pppoe ships with scripts that
 reference build-time packages, so we have x86-64 glibc in there
 
 We don't need syslog just to accommodate ppp, there's an underdocumented
 option for it to log to a file descriptor
 
 Wed Sep 28 16:04:02 BST 2022
 
 Based on https://unix.stackexchange.com/a/431953 if we can forge
 ethernet packets we might be able to write tests for e.g. "is the vm
 running a dhcp server"
 
 Wed Sep 28 21:29:05 BST 2022
 
 We can use Python "scapy" to generate dhcp request packets, and Python
 'socket' model to send them encapsulated in UDP. Win
 
 It's extremely janky python
 
 Thu Sep 29 15:24:37 BST 2022
 
 Two points to ponder
 
 1) where service config depends on outputs of other services, we
 do that rather ugly "$(cat ${output ....})" construct. Can we improve on
 that? Maybe we could have some kind of tooling to read them as environment
 variables ...
 
 2) we have given no consideration yet to secrets. we want the secrets to
 be not in the store; we want some way of refreshing them when they change
 
 Sat Oct  1 14:24:21 BST 2022
 
 The MAC80211_HWSIM kernel config creates virtual wlan[01] devices
 which hostapd will work with, and a hwsim0 which we can use to monitor
 (though not inject) trafic. Could we use this for wifi tests? How do
 we make the guest hwsim0 visible to the host?
 
 
 Sat Oct  1 18:41:31 BST 2022
 
 virtual serial ports: I struggled with qemu for ages to get this to work.
 You also need the unhelpfully named CONFIG_VIRTIO_CONSOLE option in
 kconfig
 
 QEMU_OPTIONS="-nodefaults  -chardev socket,path=/tmp/wlan,server=on,wait=off,id=wlan  -device virtio-serial-pci -device virtserialport,name=wlan,chardev=wlan"
 
 Sun Oct  2 09:34:48 BST 2022
 
 We could implement the secrets store as a service, then the secrets
 are outputs.
 
 Things we can do in qemu
 
 1) make interface address service that depends on dhcp, instead of
   being set by it directly
 2) check out restart behaviour of dependent services when depended-on
   service dies
 3) pppd _creates_ an interface, work out how to fit it into this model
 5) add bridge support for lan
 8) upgrade ppp to something with an ipv6-up-script option, move ppp and pppoe derivations into their own files
 9) get ipv6 address from pppoe
 10) get ipv6 delegation from pppoe and add prefix to lan
 11) support dhcp6 in dnsmasq, and advertise prefix on lan
 12) firewalling and nat
  - default deny or zero trust?
 14) write secrets holder as a service with outputs
 20) should we check that references to outputs actually correspond with
   those provided by a service
 
 Things we probably do on hardware
 
 6) writable filesystem (ubifs?)
 7) overlay with squashfs/ubifs - useful? think about workflows for
 how this thing is installed
 16) gl-ar750
 17) mediatek device - gl-mt300 or whatever I have lying around
 18) some kind of arm (banana pi router?)
 19) should we give routeros a hardware ethernet and maybe an l2tp upstream,
  then we could dogfood the hardware devices.  we could run an l2tp service
  at mythic-beasts, got a /48 there
 
 
 
 https://skarnet.org/software/s6/s6-fghack.html looks like a handy thing
 we hope we'll never have to use
 
 Sun Oct  2 22:22:17 BST 2022
 
 > make interface address service that depends on dhcp, instead of being set by it directly
 
 We can do this for dhcp, but we can't do it for ppp. Running the ppp service
 creates a ppp[012n] interface and assigns it an ipv4 address and there's not
 a whole lot we can easily do to unbundle that.
 
 So
 
 - the ppp service needs to behave as if it were a "link" service
 - either it *also* needs to behave as an address service, or we could
   have an address service that subscribes to it and does nothing other than
   translate output formats
 
 Note regarding that second bullet: at the moment the static address
 service has no outputs anyway!
 
 
 Tue Oct  4 22:43:02 BST 2022
 
 While trying to make the TFTP workflow not awful I seem to have written
 a TFTP server.
 
 
 Thu Oct  6 19:26:40 BST 2022
 
 We have a booting kernel on gl-ar750, but we aren't at a point that it can
 find a root filesystem
 
 I'd *like* to be able to use the same delivery mechanism (kernel uimage
 concatenated monolithic
 
 
 Sat Oct  8 11:12:09 BST 2022
 
 We have it booting on hardware, mounting root fs, running getty :-)
 
 For NixWRT TFTP boots we used a single image with both kernel and squashfs, and
 relied on CONFIG_MTD_SPLIT_FIRMWARE to identify where the boundary was and create
 /dev/mdtn devices at the right offsets so that the kernel could find the
 squashfs
 
 For Liminix we're not going to do that.
 
 * CONFIG_MTD_SPLIT_FIRMWARE is only available in OpenWrt patches
 * it's an uncomfortable level of automagic just to save us doing two TFTPs
   instea of one
 * the generated image is anyway not the one we'd write to flash (has unneeded
    PHRAM support)
 * it means we need to memmap out enough ram for the whole image inc kernel when really
   all we need to reserve is the rootfs bit
 
 
 Sat Oct  8 11:23:08 BST 2022
 
 "halt" and "reboot" don't work on gl-ar750
 
 Sat Oct  8 13:10:00 BST 2022
 
 Where do we go with this ar750?
 
 - wired networking
 - wifi
 
 
 Sun Oct  9 09:57:35 BST 2022
 
 We want to be able to package kernel modules as regular derivations, so that
 they get added to the filesystem
 
 This means they need access to kernel.modulesupport
 
 This means  kernel.modulesupport needs to be in pkgs too?
 
 This is fine, probably, but we'd like to avoid closing over vmlinux because
 there's no need for it to be in the filesystem
 
 Mon Oct 10 22:57:23 BST 2022
 
 The problem is that kernel kconfig options are manipulated in the
 liminix modules, which means that data must be (transitively) available
 to modules, so they can't be regular packages as they're tied so tightly
 to the exact config. Unless we define a second overlay that references
 the configuration object, but my head hurts when I start to think about that
 so maybe not.
 
 Tue Oct 11 00:00:13 BST 2022
 
 Building ag71xx (ethernet driver) as a module doesn't work because
 it references a symbol ath79_pll_base in the kernel that hasn't been
 marked with EXPORT_SYMBOL.
 
 We could forge an object file that "declares" it with a gross and disgusting hack like this
 
 $ echo > empty # not actually "empty", objcopy complains about that
 $ grep ath79_pll_base /nix/store/jcc114cd13xa8aa4mil35rlnmxnlmv09-vmlinux-mips-unknown-linux-musl-modulesupport/System.map
 ffffffff807b2094 B ath79_pll_base
 $ mips-unknown-linux-musl-objcopy   -I binary -O elf32-big --add-section .bss=empty  --add-symbol ath79_pll_base=.bss:0x807b2094  empty f.o
 
 I don't claim this is a good idea, just an idea. Thought was that we would not
 have to declare its type this way. Also it might not work with kaslr
 https://stackoverflow.com/a/68903503
 
 
 Backstory: why are we trying to build this as a module? because the
 openwrt fork of it seems to be a bit more advanced than the mainline,
 and I *suspect* that the mainline version doesn't work with our
 openwrt-based device tree which ahs the mdio as a nested node inside
 the ag71xx node - in mainline the driver seems to have all the mdio
 stuff inline. So, could we build the openwrt driver without patching
 the crap out of our kernel
 
 Sun Oct 16 15:25:33 BST 2022
 
 Executive decision: let's use the openwrt kernel (at least for
 gl-ar750).  Mainline kernel doesn’t have devicetree support for this
 device or the SoC it’s based on, and the OpenWrt dts for it doesn’t
 have the same "compatible"s, which makes me think that an indefinite
 amount of patching will be necessary to make dts/modules for one of
 them work with a kernel for the other
 
 As a result: now we have eth0 appearing, but not eth1?  Guessing we
 need to add some kconfig for the switch
 
 Mon Oct 17 21:23:37 BST 2022
 
 we are spending ridiculous amounts of cpu/io time copying kernel source
 trees from place to place, because we have kernel tree preparation
 and actual building as two separate derivations.
 
 I think the answer is to have a generic kernel build derivation
 in the overlay, and then have the device overlays override it with
 an additional phase to do openwrt patching or whatever else they
 need to do.
 
 Tue Oct 18 23:02:43 BST 2022
 
 * previous TODO list is Aug 02, need to review
 * dts is hardcoded to gl-ar750, that needs cleaning up
 * figure out persistent addresses for ethernet
 * fix halt/reboot
 * "link" services have a "device" attribute, would much rather
   have everything referenced using outputs than having two
   different mechanisms for reading similar things
 * Kconfig.local do we still need it?
 * check all config instead of differentiating config/checkedConfig
 
 Sun Feb  5 18:14:02 GMT 2023
 
 We have resumed.
 commit eb4efab6a215bf03cf5aab10d4ac909e83e9c148
 Author: Daniel Barlow <dan@telent.net>
 Date:   Sat Jan 28 23:18:28 2023 +0000
 
 
 * find out what works
 * add that stuff to hydra
 * fix the rest
 * add that stuff to hydra
 * convert to flake
 * check if routeros can be run interactively
 * some per-device docs in a form that can be transcluded for website
 
 
 ci builds
 
 * each of the tests has hardcoded device/config/etc
 * build an "empty" configuration for each target device
 * build an unstable configuration for qemu
 
 
 Wed Feb  8 16:52:22 GMT 2023
 
 We have hydra builds for all the previously-working devices, though we
 don't yet know if any of those builds actually boots or does anything
 useful.
 
 [DONE] Would be nice to clean up the run-qemu and connect-qemu scripts
 and put them in the buildEnv
 
 Some thought needed about how to hook up the gl-ar750 to the internets,
 ideally in a way that mirrors typical real uses. AAISP have an L2TP
 service, but I would prefer to use pppoe on the device, so how to
 translate one to t'other on an intermediary/gateway machine?
 https://www.rfc-archive.org/getrfc.php?rfc=3817#gsc.tab=0 exists
 as an RFC but I can't find anything that actually implements it
 
 Actual Documentation (e.g.  user and developer manuals) should live in
 the liminix repo so it corresponds with the code, and can be rsynced
 from there to the web site, maybe with a deploy hook or something.
 Haven't decided what a good doc format is yet
 
 If we create a flake for Hydra to run on, that _more or less_ means we
 don't have any manual hydra jobset configuration to document.
 
 There are still some tests that need adding to CI
 
 [DONE] Should the per-device config be a module not an overlay? Given that
 half of what's in it is kernel config (a module could set this)
 and the rest is source tarball download specs (needs nixpkgs,
 a module has this and could set it too) I wonder why it isn't already
 
 [ALREADY DOES] Can we make Hydra report output sizes so we can plot closure size
 trends and see if it all goes awful?
 
 Thu Feb  9 08:14:39 GMT 2023
 
 For better developer experience, I am thinking that either (1)
 swap tasks 2 and 3 (writable filesystem before module system)
 or (2) add NBD support so I can iterate on a real device without
 full rebuilds every time
 
 
 Fri Feb 10 06:18:25 PM GMT 2023
 
 did the overlay->module thing
 
 [DONE] Need to fix all the configuration around PHRAM, I can't see how it
 would ever work
 
 Sat Feb 11 14:37:45 GMT 2023
 
 Consolidated TODO
 
 * figure out persistent addresses for ethernet (?)
 [SEEMS DONE] * fix halt/reboot
 [DONE, NO] * Kconfig.local do we still need it?
 [DONE] * check all config instead of differentiating config/checkedConfig
 
 Things we can do in qemu
 
 * "link" services have a "device" attribute, would much rather
   have everything referenced using outputs than having two
   different mechanisms for reading similar things
 1) make interface address service that depends on dhcp, instead of
   being set by it directly
 2) check out restart behaviour of dependent services when depended-on
   service dies
 3) pppd _creates_ an interface, work out how to fit it into this model
 5) add bridge support for lan
 8) upgrade ppp to something with an ipv6-up-script option, move ppp and pppoe derivations into their own files
 9) get ipv6 address from pppoe
 10) get ipv6 delegation from pppoe and add prefix to lan
 11) support dhcp6 in dnsmasq, and advertise prefix on lan
 12) firewalling and nat
  - default deny or zero trust?
 14) write secrets holder as a service with outputs
 20) should we check that references to outputs actually correspond with
   those provided by a service
 * Actual Documentation (e.g.  user and developer manuals)
 * make a flake
 * There are still some tests that need adding to CI
 
 Things we probably do on hardware
 
 [DONE] * dts is hardcoded to gl-ar750, that needs cleaning up
 6) writable filesystem (ubifs?)
 7) overlay with squashfs/ubifs - useful? think about workflows for
 how this thing is installed
 16) gl-ar750
 [DONE] * decide how to hook up the gl-ar750 to the internets
 17) mediatek device - gl-mt300 or whatever I have lying around
 18) some kind of arm (banana pi router?)
 [DONE DIFERENTLY] 19) should we give routeros a hardware ethernet and maybe an l2tp upstream,
  then we could dogfood the hardware devices.  we could run an l2tp service
  at mythic-beasts, got a /48 there
 
 
 Sat Feb 11 15:57:31 GMT 2023
 
 The reason we would like to run PPPoE instead of L2TP on the "rotuer" device is
 
 - closer to real world scenario
 - means no need to run dhcp client on the wan interface before we
    even get to start the l2tpd
 
 
 Sun Feb 12 14:57:28 GMT 2023
 
 https://github.com/katalix/go-l2tp#kpppoed
 
 
 Mon Feb 13 04:44:09 PM GMT 2023
 
 if the gl-ar750 is connected to an ethernet card that linux is ignoring,
 we're going to have to set up _some_ qemu thing just to run tftp from.
 
 Tue Feb 14 17:59:34 GMT 2023
 
 We should do a derivation that creates an ISO image and a qemu shell
 script based on a configuration.nix, and put it in buildEnv. We'll
 call it "borderNetVm" :
 
 > A broadband remote access server (BRAS, B-RAS or BBRAS) routes
   traffic to and from broadband remote access devices such as digital
   subscriber line access multiplexers (DSLAM) on an Internet service
   provider's (ISP) network.[1][2] BRAS can also be referred to as a
   broadband network gateway or border network gateway (BNG).[3]
 
 (for consistency we should rename the "access" qemu socket network to
 match whatever we call this)
 
  rm border.qcow2 ; nix-shell --argstr liminix `pwd`  --argstr nixpkgs `pwd`/../nixpkgs  --argstr unstable `pwd`/../unstable-nixpkgs/ ci.nix -A buildEnv --run "run-border-vm"
 
 Wed Feb 15 22:56:59 GMT 2023
 
 configuration for border vm needs to come from somewhere so it's good
 for more people than just me
 
 - pci device for setting up the ethernet
 - lns address
 - uid so it can do 9p shares? do we need to map things here?
 
 also need to document the host-side bits so that people can set up
 their spare ethernet as vfio
 
 next step for hacking is to figure out what I was doing with pppoe
 
 Wed Feb 15 22:59:56 GMT 2023
 
 docs ...
 
 * introduction
 
 * user guide
 ** how to build it
 ** how to flash it on your device
 ** what to put in configuration.nix
 ** modules
 
 * developer guide
 ** building/running with qemu
 *** emulated upstream
 ** building/running on hardware
 *** run in place with TFTP
 *** emulated upstream
 ** CI
 ** Roadmap
 ** Contributing
 
 
 
  nix-shell -p sphinx --run "make -C doc html"
 
 https://francis.begyn.be/blog/nixos-home-router contains information about avahi reflector
 
 
 Fri Feb 17 00:09:34 GMT 2023
 
    29 11.282085831 81.187.76.242 → 8.8.8.8      ICMP 106 Echo (ping) request  id=0x0187, seq=2/512, 4
    30 11.286314642 90.155.53.19 → 81.187.76.242 ICMP 78 Destination unreachable (Communication admin)
 
 We're getting packets over the pppoe-l2tp relay thing. Just have to
 work out now why we're not routing
 
 Fri Feb 17 16:54:41 GMT 2023
 
 Haha.  We weren't routing because we'd used the wrong CHAP password
 
 
 
 Fri Feb 17 16:58:27 GMT 2023
 
 This TODO is for nlnet task 1 and for bits of subsequent tasks that
 are annoying enough that I might poke at them anyway:
 
 
 1) gl-ar750, why do we get "ag71xx 19000000.eth: invalid MAC address, using random address"
 2) gl-ar750, wifi
 3) document services so I can remember how they work. Refer back to Oct 18 for notes that no longer make sense
 4) check out restart behaviour of dependent services when depended-on service dies
 5) pppd _creates_ an interface, work out how to fit it into this model
 6) add bridge support for lan
 7) upgrade ppp to something with an ipv6-up-script option, move ppp and pppoe derivations into their own files
 8) get ipv6 address from pppoe
 9) get ipv6 delegation from pppoe and add prefix to lan
 10) support dhcp6 in dnsmasq, and advertise prefix on lan
 11) firewalling and nat - default deny or zero trust?
 13) should we check that references to outputs actually correspond with
 14) make a flake?
 15) see if there are other tests that need adding to CI
 15a) is bordervm derivation tested?
 18) gl-mt300a
 19) gl-mt300n-v2
 20) publish the manual using CI
 
 12) write secrets holder as a service with outputs
 16) writable filesystem (ubifs?)
 17) overlay with squashfs/ubifs - useful? think about workflows for how this thing is installed
 
 
 I could plug tninkpad into the gl-ar750 LAN port to dogfood the wired
 networking
 
 Sat Feb 18 14:26:45 GMT 2023
 
 Apparently we're not currently doing anything special with busybox,
 just using the default nixos build with the default applets.
 
 We'd like to be able to say in modules which applets they need,
 so that we build all necessary applets but don't waste any space.
 But we don't want to build a busybox for each module because that
 would be a big waste of space.
 
 One option:
 - add busybox configuration to `config` so that modules can maul it
 - add a busybox module that builds it with union of all config and
  adds link in /bin
 - make everything else look in /bin instead of referencing pkgs.busybox
 
 It would be good if services could assert somehow that their required
 config is present
 
 Sat Feb 18 23:45:13 GMT 2023
 
 # lsmod
 
 cd /lib/modules/mac80211
 insmod ./compat/compat.ko
 insmod ./net/wireless/cfg80211.ko
 insmod ./net/mac80211/mac80211.ko
 insmod ./drivers/net/wireless/ath/ath.ko
 insmod ./drivers/net/wireless/ath/ath9k/ath9k_hw.ko
 insmod ./drivers/net/wireless/ath/ath9k/ath9k_common.ko
 insmod ./drivers/net/wireless/ath/ath9k/ath9k.ko
 insmod ./drivers/net/wireless/ath/ath10k/ath10k_core.ko
 insmod ./drivers/net/wireless/ath/ath10k/ath10k_pci.ko
 
 [21.344930] ath9k 18100000.wmac: failed to load calibration data from mtd device
 [21.352728] ath: phy0: parsing configuration from OF node
 [21.362576] ath: phy0: serialize_regmode is 0
 [21.367092] ath: phy0: UNDEFINED -> AWAKE
 [21.372051] ath: phy0: Trying EEPROM access at Address 0x03ff
 [21.377999] ath: phy0: Trying EEPROM access at Address 0x0fff
 [21.383940] ath: phy0: Trying EEPROM access at Address 0x01ff
 [21.389879] ath: phy0: Trying OTP access at Address 0x03ff
 [21.400396] Data bus error, epc == 8027964c, ra == 83125880
 [21.406156] Oops[#1]:
 
 
 Sun Feb 19 18:15:27 GMT 2023
 
 We have ath9k listening for packets. To make this ready to use:
 
 - need to load the modules
 - enable bridging lan with wlan
 - packet forwarding
 - firewall
 
 
 Mon Feb 20 20:41:17 GMT 2023
 
 need to fix all the other broken ci jobs :-(
 
 The wlan test is failing because we moved mac80211 to a module and
 there's nothing running to insmod it
 
 Wed Feb 22 18:17:17 GMT 2023
 
 bridge is e2b3738d0f8c3f2fd76ebcef65612de502a7b121 but it's the wrong
 way around: the master interface needs to be up whether or not all
 of its children are, so members depend on master not vice versa
 
 Next steps:
 - re-implement bridge, enable bridging lan with wlan
 - packet forwarding
 - firewall
 - ath10k
 - ipv6
 
 Fri Feb 24 23:37:56 GMT 2023
 
 bridging wlan was made complex because can't add a device to a bridge
 until it's operational, and wlan0 is not operational until hostapd
 has churned awhile. Therefore, "waitup" listens for netlink messages
 and notifies s6 readiness stuff
 
 we have a firewall nft script but we're not running it on boot
 
 we have forwarding but no dns, maybe because we haven't told
 dnsmasq about any upstream servers
 
 Sun Feb 26 21:08:47 GMT 2023
 
 to add firmware we need to put files in /lib/firmware, which means
 a module
 
 i guess we should do that in the device module
 
 we can create the firmware files as packages
 
 
 for the cal data we would like to get it from the device MTD "art"
 partition at
 boot time.
 
 f
 ====from openwrt
 
 
 
 case "$FIRMWARE" in
 "ath10k/cal-pci-0000:00:00.0.bin")
         case $board in
         allnet,all-wap02860ac|\
         araknis,an-500-ap-i-ac|\
         araknis,an-700-ap-i-ac|\
         engenius,eap1200h|\
         engenius,enstationac-v1|\
         glinet,gl-x750|\
         watchguard,ap300)
                 caldata_extract "art" 0x5000 0x844
                 ath10k_patch_mac $(macaddr_add $(mtd_get_mac_binary art 0x0) 2)
 
 
 
 
 caldata_extract part offset count
       caldata_dd $mtd /lib/firmware/$FIRMWARE $count $offset || \
                 caldata_die "failed to extract calibration data from $mtd"
         dd if=$source of=$target iflag=skip_bytes,fullblock bs=$count skip=$offset count=1 2>/dev/null
 
 =======
 
 part=$(basename $(dirname $(grep -l art /sys/class/mtd/*/name)))
 dd if=/dev/$part \
   of=/run/cal-pci-0000:00:00.0.bin iflag=skip_bytes,fullblock \
   bs=0x844 skip=0x5000 count=1
 
 Mon Feb 27 22:46:37 GMT 2023
 
 Found and fixed a bunchg of things that were stopping ath10k from
 working. The remaining problem is (I think) that insmod is not
 synchronous, so "ip link set up dev wlan1" doesn't work immediately
 after the module is inserted. Maybe we need another netlink thing
 to wait until the interface is present.
 
 
 Wed Mar  1 18:26:44 GMT 2023
 
 ath10k works, but the wlan module loading stuff is quite kludgey
 
 I wonder if wlan0, wlan1, eth0, eth1 etc should be defined per-device
 - how does the aplication config know which devices exist? If we
 decide to switch to some form of persistent device naming, the names
 will differ from one device to the next. Perhaps the device should
 also provide standard names where possible?
 
 services.network.links = {
   lan = interface { ... };
   wan = interface { ... };
   wlan_24 = interface { ... };
   wlan_5 = interface { ... };
 }
 
 Thu Mar  2 22:45:11 GMT 2023
 
 We have a flashable image!
 
 Now we can use the gl-ar750 for internet access in the shed, we can
 apppropriate the other device that's in there and try Liminix on it
 
 Fri Mar  3 23:08:58 GMT 2023
 
 If we're going to unplug serial console from the gl-ar750 maybe we
 should install an ssh server first.
 
 0) set a root password
 1) allow setting a root password from configuration.nix
 (means defining config.users properly)
 2) allow authorizedKeys per user
 3) dropbear service
 4) see if the wired lan works! :-)
 
 
 Sat Mar  4 12:31:07 GMT 2023
 
 To improve logging, each service should have its own s6-log service
 which prefixes the service name onto the log line and then sends to
 stdout
 
   https://skarnet.org/software/s6/servicedir.html
   https://skarnet.org/software/s6/s6-log.html
 
 As far as I can tell, the `log` directory inside the service
 directory should itself be a service directory for the s6-log
 process that does this
 
 .... hahaha no that doesn't work
 
 s6-rc, for some reason, ignores the `log` directory and requires
 that loggers be done with consumer-for and producer-for instead
 
 
 Sat Mar  4 23:27:00 GMT 2023
 
 notes for this week's news update
 
 * ath10k kernel support and and firmware
 
 - 5GHz wifi works
 
 - need to retrieve the firmware from a special - partition on the
   device itself, so we do that using a service that - the wlan
   interface depends on
 
 * replace waitup with more generally useful ifwait
 
 to make the ath10k load at boot, we need to insert the module and then
 wait for it to do something or other in the background before we can
 configure the interface. so we need something like waitup but
 for presence not operational state
 
 it turns out that a program that just waits for a particular interface
 state and then exits is quite simple to add into run scripts and
 we don't need all that notification-fd stuff anyway
 
 * move FW_LOADER* config to modules/base
 
 * rejig config a bit.
 - device hardware characteristics are now under
   the `hardware` key and include the available network interfaces.
 - options for users and groups are now defined a bit more
   specifically than "attrset", making it possible to e.g. set a
   root password
 - dts is moved from `boot` to `hardware`
 
 
 * now producing flashable images, so you can generate a liminix config
 and write it to the device instead of having to boot using TFTP and
 a serial console every time
 
 * ssh support
 
 * prefix logs with the service name
 
 Sun Mar  5 22:51:21 GMT 2023
 
 Added swconfig: it was a straight copy from nixwrt and hasn't changed
 upstream since. But don't need it, because the lan port works fine
 without it (I assume both lan ports and the cpu are all connected
 untagged)
 
 Mon Mar  6 09:42:33 GMT 2023
 
 Today I plugged in the mt300a.
 
 echo 17 >/sys/class/gpio/export
 echo out >/sys/class/gpio/gpio17/direction
 
 
 why are our images getting big
 
 - lua links ncurses
 - hostapd links openssl and sqlite
 - nftables needs
   - iptables?
   - jansson? what is that?
   - libedit/readline
 - ifwait needs bash
 
 
   File: result/squashfs
   Size: 10371072        Blocks: 20256      IO Block: 4096   regular file
 
 with smaller nftables:    9617408        Blocks: 18784
 
 hostapd wqithout sqlite   9003008        Blocks: 17584
 
 without bash:             8622080         Blocks: 16840      IO Block: 4096   regular file
 
 without lua readline: bigger?!  8769536         Blocks: 17128      IO Block: 4096   regular file
 
 
 Mon Mar  6 20:57:49 GMT 2023
 
 [    0.539992] mtk_soc_eth 10100000.ethernet: mdio-bus disabled
 [   10.493918] platform regulatory.0: Direct firmware load for regulatory.db fail
 ed with error -2
 [   10.502828] cfg80211: failed to load regulatory.db
 
 Check in morning, but whichever port the ethernet cable is plugged into,
 is considered by the kernel as port 0 - which I think we should treat as
 WAN
 
 VLAN 1:
         vid: 1
         ports: 1 2 3 4 5 6t
 VLAN 2:
         vid: 2
         ports: 0 6t
 
 ip link add link eth0 name lan type vlan id 1
 ip link add link eth0 name wan type vlan id 2
 
 figure out how to add these to gl-mt300a device config
 then extedner.nix can add a bridge
 
 Tue Mar  7 20:13:15 GMT 2023
 
 We need NTP or some other way to get accurate time
 
 [done] Need to add regulatory.db somewhere standard, maybe modules/wlan?
 
 Tue Mar  7 21:43:56 GMT 2023
 
 When we get to phase 2, need to review how network interfaces and
 their addresses interplay. It should be possible to have a network
 interface and interrogate the addresses associated with it - esp
 with ipv6 where there are multiple addresses for the device
 
 This thought prompted by looking at the loopback interface, which is
 a bundle of addresses and therefore we can't see what any of them are
 
 
 Tue Mar  7 22:05:44 GMT 2023
 
 [phase 1]
 20) publish the manual using CI
 30) document flashing process
 31) go through all the unexpected dmesg and triage it
 25) ntp or some other accurate time source
 
 [phase 1.5]
 26) ssh keys
 8) get ipv6 address from pppoe
 9) get ipv6 delegation from pppoe and add prefix to lan
 10) support dhcp6 in dnsmasq, and advertise prefix on lan
 11) firewalling and nat - default deny or zero trust?
 7) upgrade ppp to something with an ipv6-up-script option, move ppp and pppoe derivations into their own files
 32) set up iperf and do some performance measurement
 35) also we need to check our wireless country code
 
 
 [phase 2]
 3) document services so I can remember how they work. Refer back to Oct 18 for notes that no longer make sense
 4) check out restart behaviour of dependent services when depended-on service dies
 13) check that references to outputs correspond with declared outputs
 33) network interfaces vs the services that manage their addresses
 34) write a short guide explaining how to use s6-svc
 
 [phase n]
 12) write secrets holder as a service with outputs
 16) writable filesystem (ubifs?)
 17) overlay with squashfs/ubifs - useful? think about workflows for how this thing is installed
 
 
 dmesg lines to investigate for gl-mt300a:
 [    0.467314] OF: Bad cell count for /palmbus@10000000/spi@b00/flash@0/partition
 [    0.539709] mtk_soc_eth 10100000.ethernet: mdio-bus disabled  ?
 [    8.778513] compat: loading out-of-tree module taints kernel.
 [   17.686561] ieee80211 phy0: rt2800_wait_bbp_rf_ready: Error - BBP/RF register access failed, aborting
 [   17.696025] ieee80211 phy0: rt2800_loft_iq_calibration: Warning - RF RX busy in LOFT IQ calibration
 [   17.875147] ieee80211 phy0: rt2800_rxiq_calibration: Warning - Timeout waiting for MAC status in RXIQ calibration
 
 for gl-ar750:
 [    0.000000] Unknown kernel command line parameters "earlyprintk=serial,ttyS0", will be passed to user space.
 [    0.416679] OF: Bad cell count for /ahb/spi@1f000000/flash@0/partitions
 [    0.825495] ag71xx 19000000.eth: Could not connect to PHY device. Deferring probe.
 [    1.632700] pci_bus 0000:00: root bus resource [mem 0x10000000-0x13ffffff]
 [    1.639824] pci_bus 0000:00: root bus resource [io  0x0000]
 [    1.645601] pci_bus 0000:00: No busn resource found for root bus, will use [bus 00-ff]
 [   32.032326] ath10k_pci 0000:00:00.0: pdev param 0 not supported by firmware
 [   36.627844] ath10k_pci 0000:00:00.0: failed to receive initialized event from target: 00000000
 
 
 Fri Mar 10 13:17:56 GMT 2023
 
 Lunchtime notes on images for real devices, vs ci.nix
 
 * successfully building an image doesn't mean that the image boots
 or does anything useful
 
 * don't want to faff with serial wires on every device every time
 to test it. so
 
 * ideally, build ram-based images of rotuer, extneder, arhcive in CI
 with a watchdog timer that will reboot if it can't see the network
 
 * figure out how to boot into the new image from an ssh connection.  I
 assume the challenging bit here is grabbing x MB of contiguous phys
 mem after boot: I think we'd have to reserve it at _first_ boot and
 then somehow copy into it before rebooting
 
 An easier first goal might be a tool to flash from the shell command line,
 but that runs a greater risk of bricking
 
 
 Fri Mar 10 14:35:40 GMT 2023
 
 programs.busybox = {
   enable = true;
   applets = [... ];
   config = {
   };
 }
 
 Fri Mar 10 23:49:04 GMT 2023
 
 Well, we have the backup host config up and running - though haven't
 plugged it back into its disk yet.
 
 For task 1 what remains is
 
 1) ntp sync
 2) write up the flashing procedure
 3) a video?
 
 
 Sat Mar 11 13:58:20 GMT 2023
 
 ================== for video
 
 what is liminix
 - nix-based system for creating OS images for routers
 - not "nixos on your router"
   - nixos-like module system,
   - musl for libc
   - s6/s6-rc for services
   - entirely cross-compiled
 
 why am i making a video?
 - unless you have a suitable spare device to install on,
   and you want to take it apart, it's currently hard to
   take liminix for a spin
 - I have these things, so I can give you a tour
 
 let's have a look at how the hardware's hooked up
 
 web site & manual
 
 a config file:
 - observe the comments:
   - not going to spend ages on this because it's not in its final form.
   - as we get more configs for more use cases, we will
     get a better feel for what can be abstracted
   - that will come later: work so far has been on the
     hardware support side
 
 to show that it builds, we're going to add a package. otherwise,
 everything from this build is probably already cached
 
 build the config
 
 tftpboot on hardware
 
 flash on hardware
 
 show ci
 
 show a qemu target
 
 Mon Mar 13 22:46:46 GMT 2023
 
 1) rsync on arhcive is failing because no nogroup group
 
   "/nix/store/gfzzl157r8xyp38lpcfxydkiiy6zrs3c-rsync-3.2.6/bin/rsync" "--verbose" "--stats" "--password-file" "/etc/nixos/secrets/arhcive-rsync" "-rltgoDz" "/var/spool/backup" "backup@arhcive.lan::srv/"
 @ERROR: invalid gid nogroup
 rsync error: error starting client-server protocol (code 5) at main.c(1837) [sender=3.2.6]
 
 2) we can run findfs in a loop until the disk appears
 
 3) still haven't decided how to do ntp but maybe we should just use
 the busybox one
 
 4) some way to do upgrades over the wire
 
 - boot with reserved mem and a phram device at 110-128MB even in the
   flashable version
 
 - watchdog timer in kernel
 
 - kexec in kernel
 
 - userland service to feed the dog as long as local network is up
  (may need to start it a couple of minutes after boot, how do we
   do that?)
 
 - can we use flashcp on a phram mtd?
 
 5) maybe setup a vhost for hydra or something
 
 [nix-shell:~/t]$ wget --reject-regex '\?' -D localhost -N -r --exclude-directories=/api --level=2 --convert-links -e robots=off http://localhost:3003/jobset/liminix/build/
 
 is almost a mirror
 
 Tue Mar 14 20:17:35 GMT 2023
 
 - do we have a phram mtd? need config for size and location
 
 - how do we set the boot device
  - for first boot need to boot real flash, use  dtb, ignore bootloader args
  - for kexec, boot phram, specify args somehow (could rewrite dtb)
 
  => can use same kernel for both if we can give kexec a dtb with
     different params, which seems to be possible
 
 so we need a module for the initial kernel to say
 - create phram mtd
 - boot from real mtd (will be index + 1)
 - enable KEXEC in kernel
 - add kexec-tools
 
 and for the kernel we boot into
 - most of the above
 - except for the boot device
 - create an output with objects that kexec(8) can parse
 
 Could be same module for both with different outputs
 
 what do we call this thing? "revertable"
 
 Wed Mar 15 19:11:09 GMT 2023
 
 "revertable" implies mtd support for the rootfs and a ramdisk at
 defined location
 
 "tftpboot" implies "revertable", because it will use the same ramdisk
 
 
 Fri Mar 17 11:44:40 GMT 2023
 
 - patch the kernel kexec code to pass DTB to new kernel unconditionally
 - unpatch pernel to pass command line to kexec (breaks DTB passing)
 - decide how we specify rootfs. doing it by number is awkward
   - may be phram
   - may be real mtd root
   - may be real mtd root but renumbered becuase phram exists
 
 Wild idea: we could probably get rid of the need for declaring a phram
 device in the first kernel, if we can use kexec to copy the squashfs into
 physical ram. As far as I can see this is a simple(sic) matter of
 specifying it as a segment, but we would have to extend kexec-tools
 to do this and it's quite a niche option if we make it do all the
 mtd setup.
 
 kexec --dtb=foo.dtb --map-file=squashfs@0x120000
 
 
 Sat Mar 18 18:02:26 GMT 2023
 What if: we added derivations for "apply openwrt changes" as packages,
 which could then be called from the kernel derivation's extraPatchPhase?
 There could be one for generic and one for each openwrt targetop
 
 Mon Mar 20 18:40:53 GMT 2023
 
 - kexec patch is sent to mailing list, keep an eye for replies
 - watchdog
 - ntp
 - rebuild images for live devices
 - can we build a static busybox with flashcp applet and scp it
  to arhcive etc?
 - [DONE] install mailman and hyperkitty on myhtic, create mailing list
 
 Tue Mar 21 22:59:54 GMT 2023
 
 I haven't found a way to arm the watchdog before userland runs, which
 would be really nice: although there's WATCHDOG_HANDLE_BOOT_ENABLED
 and WATCHDOG_OPEN_TIMEOUT it doesn't seem to be sufficient, Maybe
 those options work only when the hardware watchdog is already
 armed. It might not be completely awful insofar as any failure to
 mount root usually results in panic anyway, so provided we start
 watching early in boot then there's not a big window for anything
 to go wrong
 
 What should the watchdog service do?  Ideally we want something that
 "ratchets" : can be started in early boot and signals health as long
 as the system is starting up, then once the system is in "steady
 state" it stops pinging as soon as any part of that steady state
 becomes unhealthy. This feels like a refinement for a much later
 phase though.
 
 Maybe the health criteria might be
 (sshd and lan services are running) or (time since boot < 120s)
 
 Thu Mar 23 00:11:23 GMT 2023
 
 tftpboot and (kexecboot || flashable) have incompatible DTB-finding
 strategies which is painful if you add both modules and then
 expect tftp booting to still work
 
 Maybe we could patch the kernel to use some better strategy for when
 to use/ignore the bootloader command line: e.g "only if it
 contains the string 'liminix'". Could do this by patching
 arch/mips/kernel/setup.c bootcmdline_init to
 
 if(strstr(arcs_cmdline, "liminix") == NULL) arcs_cmdline[0] = '\0'
 and then defining CONFIG_MIPS_CMDLINE_DTB_EXTEND. The
 bootloader command line then needs to specify only the
 _additional_ parameters that weren't in the DTB
 
 (later: that turned out to be quite straighforward)
 
 Fri Mar 24 23:45:12 GMT 2023
 
 - add ntp support
 - [DONE] expose hydra to internet
 - check MAC address weirdness?
 - call Task 1 "done"
 
 Sun Mar 26 00:19:15 GMT 2023
 
 Would be nice to have a flash.sh built in outputs.flashable
 
 Sun Mar 26 15:27:14 BST 2023
 
 Let's think about services and modules.
 
 Module
 + can change global config
   * add users, groups etc
   * change kernel config
   * change busybox config
 + well-typed parameters
 - is a "singleton": can't have the same module included twice
   with different config. e.g. can't have two hostap modules running on
   different wlan radios.
 - can't express dependencies: a depends on b
 
 suppose:
 
 * modules add service functions to the config? then there's no
 way to define a service while forgetting to import the module
 
 * we use the lib.types stuff for service function arguments
 
 * maybe we stop naming services.foo for every damn thing
 
 * but remember, s6 services do need unique names
 
 
 imports = [ ../modules/dhcp4 ];
 
 services.dhcp4 = config.services.udhcp {
   interface = lan.device;
   options = {
     foo = true;
     bar = 42;
   };
   depends = [ services.some_other_thing ];
 }
 
 modules/dhcp4 udhcp fn needs to define a type for its argument, then
 use something like
 
   if arg_type.check def.value then res
             else throw "The option value `${showOption loc}' in `${def.file}' is not a ${arg_type.name}.")
 
 (where def comes from I don't know yet)
 
 Tue Mar 28 10:44:40 BST 2023
 
 we should reserve the name "service" for actual instantiated
 services. This means we need a name for the functions that
 make services. "class", "template", "fn", "maker", "factory"?
 And a namespace name so they're not interleaved with real
 services, which sort of suggests they are packages
 
 if we want to do services = {
  foo = longrun { ... };
  bar = longrun { ... };
 }
 
 without repeating the `name` as an attribute of the longrun,
 then longrun can't return a derivation: it has to return some
 function that accepts `name` as a parameter.
 
 where services.a depends on services.b, at the time its builder is run
 it needs to know what name s6-rc will use for service b
 
 maybe an s6 service definition should be an attrset not a derivation.
 
 maybe this is outside scope for phase 2
 
 Tue Mar 28 13:22:06 BST 2023
 
 Reading nixos/doc/manual/development/building-parts.chapter.md it
 suggests to me that we should rename config.outputs to
 config.system.outputs. The more general question here is whether it's
 good to be augmenting a variable called "config" with all this
 generated stuff that is patently not configuration - perhaps putting
 it under a "system" key will keep it all in one place
 
 Tue Mar 28 13:32:30 BST 2023
 
 how should we handle filesystem state? e.g. resolvconf service
 
 if a service provides a file at a known global pathname, it can't be
 parametrised - it must be a singleton.
 
 Tue Mar 28 20:25:20 BST 2023
 
 wondering if we should swap phases 2 and 3. We can't really address
 modules without addressing services, which is phase +n, whereas we
 can tackle overlay/ubi whenever
 
 nand flash may have bad blocks
 nor flash (supposedly) doesn't
 
 ubi provides erase counts and bad block remapping on top of the mtd
 interface. this means we should avoid flashcp of a ubi image straight
 onto (nand) mtd as we will lose the erase counts and bad block information
 that UBI tracks.
 
 overlayfs works on a filename basis, so might not be very effective :
 any change that results in a new store path will mean the entire package
 appears in two places. I think it's reasonable to offer squashfs or
 ubifs without overlay.
 
 open questions:
 
 1) if uboot doesn't support UBI, we can't boot a kernel on a ubifs
 so we need reserved space for the kernel.
 
 - unless we add some padding after the kernel, every new kernel
 that's bigger than its predecessor will trash the start of the
 ubi space (and wipe out its erase count)
 - This suggests we should build more stuff as modules and less as
 compiled-in
 
 2) once a device has had a ubi volume created on it, probably we want
 to use ubi-aware tools to update that volume in future instead of a
 whole new flash, because we wish to preserve erase counts. This means
 running ubiformat --image-file=foo.ubi on the device instead of flashcp
 
 we can add a "ubi-flashable" output that creates a .ubi image and
 a flashcp image that wraps it, with instructions on which to use.
 
 Fri Mar 31 22:13:54 BST 2023
 
 Error: too small LEB size 3968, minimum is 15360
 
 > This error means that you are trying to mount too small UBI
 volume. Probably because your flash is too small? Try to use JFFS2,
 then, because it suits small flashes better since it has much lower
 space overhead. Indeed, UBIFS stores much more indexing information on
 the flash media than JFFS2, so it has much higher overhead. Also, UBI
 has some overhead (see here). Thus, if you have a small flash device
 (e.g., about 64MiB), it makes sense to consider using JFFS2.
 
 
 Argh. Oh well,
 
 Sat Apr  1 15:27:39 BST 2023
 
 There's limited value in recreating pseudofiles for jffs2 because
 the system is writable - changes made to /bin, /dev etc in config.filesystem
 should take effect on a running system.
 
 Can we take inspiration from https://grahamc.com/blog/erase-your-darlings/ ?
 
 in early boot:
  mount ramfs on /
  mount the writeable filesystem on /persist/
  bind mount /persist/nix on /nix
  run script to populate rootfs from pseudofiles
 
 on a router, do we need _anything_ persistent that's outside the store?
 
  - state for dhcp leases and stuff
  - secrets
  - maybe, files that the user has downloaded
 
 this will probably require initramfs. if just use jffs2 as the rootfs and
 don't worry about /persist, we can skip that step.
 
 
 
 
 [ aside: I think we may be putting two busyboxes in the image:
 see modules/s6/default.nix s6-init-scripts has buildInputs = [busybox];  ]
 
 Mon Apr  3 18:34:26 BST 2023
 
 suppose
 - we boot the system with systemConfig=/nix/store/eeeeee-system
 - the early-init script runs /target/$systemConfig/create-root /target
   after mounting /target
 - then it runs chroot /target $systemConfig/bin/init "$@"
 
 or maybe we could combine those steps?
 or maybe it doesn't matter too much ...
 
 Thu Apr  6 21:25:41 BST 2023
 
 what now?
 
 - put a jffs2 onto some hardware device
   - what do we do with uboot?
   - should we pad the kernel?
   - maybe kernel module support would be good if we're making it
     hard to do kernel updates
 - try the nix-copy-closure thing and work out what else we don't know
 - [done] detect endian correctly
 
 
 to ask a different question, what else do we need to dogfood a router?
 
 Sun Apr  9 10:06:08 BST 2023
 
 - rename outputs.flashable to outputs.flashimage
 - rename modules/flashable to modules/flashable_ro
 - create outputs.flashable in modules/jffs2
 - rename modules/jffs2 to modules/flashable_rw
 - add enable config to both?
 - enable kernel module compilation
 
 
 Mon Apr 10 23:50:41 BST 2023
 
 - initramfs parses /proc/cmdline to find root fs, might not play
 nice with defaulting
 
 - how to build kernel modules
 
 - look at closure size, is it this big because we've broken it
 or is jffs2 usually this much bigger than squashfs
 
 - maybe squashfs with overlay might be better if we could
 ensure hardlinks?
 
 - maybe there's something like overlayfs but content-addressable?
 
 Sat Apr 15 18:57:46 BST 2023
 
 for the same configuration:
 
 -r--r--r-- 1 root root 6066176 Jan  1  1970 /nix/store/0x271rg45mcjjgbma9wi31h1yd109fpy-frob-squashfs
 -r--r--r-- 1 root root 12255232 Jan  1  1970 /nix/store/zx11adagcbzqsnqkyz5kgvr392vhlrpr-make-jffs2
 
 may want to reconsider not using squashfs with overlay
 
 Wed Apr 19 22:22:48 BST 2023
 
 Where next?
 
 Sun Apr 23 18:24:34 BST 2023
 
 - we are down to ~ 11MB image for a barely functional (IPV4) router
   this is by avoiding all dependencies on openssl or gnutls
 - rotuer is not recognising when  I set the hostname
 - I may have forgotten the root password :-(
 - why is hello world 70K unless hardeningDisable?
 
 Fri Apr 28 20:51:52 BST 2023
 
 To do nix-copy-closure we need nix-store, which is a symlink to nix,
 which is
 
 -rwxr-xr-x 1 dan users 2.3M Apr 28 21:08 nix
 
 (stripped). This is a lot bigger than, say, a simple script to
 loop through the closure of a derivation and copy only the store
 folders that don't exist already.
 
 * we'd like to only transmit the packages that aren't already present
 
 * we'd like to use a single ssh connection
 
 
 S: here is a list of package names
 C: these are the names of the packages I want
 S: here are the packages
 
 while read $f ; do
   test -d $f || echo $f
 end
 
 Tue May  2 21:53:08 BST 2023
 
 1) we have a script that runs on the receiver, which
 
  - accepts a list of store paths
  - prints the missing store paths
  - runs cpio -i < stdio
 
 2) we need a script for the sender that
 
  - refs=$(nix-store -q --references $1 && echo end)
  - opens ssh connection
  - print ssh $refs
  - needed= capture result until "end" received
  - find needed | cpio -o  > ssh-connection
  - close connection
 
 3) to have a reasonable hope of testing this we should do it with qemu. It would be nice
 if we could connect without faff to the qemu lan interface : either we do this by bringing up
 another qemu vm (preferably with the host store shared, otherwise it has to build a mips cross
 compiler/libc) or maybe we could do something unholy with ssh ProxyCommand
 
 ssh -o ProxyCommand "socat - UDP4-DATAGRAM:230.0.0.1:1234,sourceport=1234,reuseaddr,ip-add-membership=230.0.0.1:127.0.0.1"
 
 
 
 4) we haven't solved garbage collection, though I think "remove everything not in
 nix-path-registration" might be what's needed there
 
 Wed May  3 22:01:19 BST 2023
 
 Something weird is going on with qemu net device enumeration: when I
 run it interactively I'm getting the access network (mac ending :02)
 on eth0 and the lan (mac ending :01) on eth1, and if it's behaving the
 same in CI then how come any of the tests work? vanilla-confinguration.nix
 definitely assumes lan=eth0
 
 By switching from  -device virtio-net-pci to     -device virtio-net then
 I get the desired behaviour back
 
 Sat May  6 18:42:28 BST 2023
 
 Next:
 
 - package min-copy-closure
 - see if we can use it on some output to copy the whole system closure
 - post-copying symlink munging
 - try it on a real device, see if it works for config file updates
 - collect-garbage/delete-old-generation
 
 
 Sun May  7 23:03:03 BST 2023
 
 Shortly after all the work to reduce system closure size last time, I
 tried adding the necessary packages to support nix-copy-closure and
 saw it start building a complete C++ system with Boost. My fears that
 this would lead to quite a large increase in the system size were, it
 turned out, entirely founded.
 
 So I wrote my own - or at least, a quite minimal substitute. The core
 logic is simple - on the sender, we get the list of required packages,
 then we check for the existence of `/nix/store/eeeeeee-foo` for
 each of them on the target, and whatever's missing we send across the
 link using cpio.
 
 It sounds simple, and it should be simple, and in retrospect it _was_
 simple. Along the way I went on a bit of a Qemu networking tangent and
 learned quite a lot about the bash `coproc` command
 
 Tue May  9 21:06:53 BST 2023
 
 General direction of my thoughts:
 
 - get a baseline working rotuer system
 - prove that min-copy-closure works with it
 - refactor the crap out of it
 - configurablise the bordervm usb ethernet setup
 - when we have a good idea of how/whether min-copy-closure *actually*
  works, declare "writeable filesystem" to be done
 - start to get more of a feel for how the services/config hang together
 
 ? why does rotuer not have a hostname?
 
 ? how can we get a device hooked up to rotuer's lan port that we can
 control remotely
 
 Sun May 14 23:25:46 BST 2023
 
 the outputs.systemConfiguration attribute builds a derivation
 containing a single file bin/activate
 
 _Presumably_, copying its closure will copy all the things, as
 we already use it as the roots for jffs2 creation. However, there
 is also a symlink created from /init at jffs2 creation
 
 Mon May 15 21:32:38 BST 2023
 
 Had a neat idea about uing an overlayfs combining jffs2 and ramfs
 to do upgrades that would otherwise be larger than the flash.
 Could use "overlay merge" from https://github.com/kmxz/overlayfs-tools
 
 Wed May 17 15:18:55 BST 2023
 
 liminix-rebuild doesn't collect garbage (this is a mising feature, not
 a bug). We think we can fix this using nix-path-registration: specifically,
 by deleting anything not in it.
 
 What we're going to do: build a fresh system image for rotuer, then
 dogfood liminix-rebuild until we've succeeded in getting it to
 change its hostname
 
 Also wondering if we should drop outputs.default, but maybe not
 
 * systemConfiguration: used for updates
 * vmroot: used for qemu
 * flashimage: used for flashing
 * tftproot: used for dev/test
 
 As long as we're consistently setting the default output to whichever
 is the appropriate "full production image" I think we're good.
 
 Wed May 17 22:45:40 BST 2023
 
 Random thought: when we bind mount /target/persist/nix to /target/nix
 we could make it read-only. worth doing?
 
 Thu May 18 10:59:39 BST 2023
 
 - liminix-rebuild can't find reboot: probably the PATH is just
   generally wrong for ssh sessions (maybe all non-login sessions?)
 
 - need to copy path registration file somewhere useful and
   delete stuff not in it at the appropriate time. Would be safest
   to do that either late in the shutdown process before rebooting,
   or during boot.
 
 Fri May 19 15:18:13 BST 2023
 
 If we make min-collect-garbage - just a command you can run whenever -
 that will be fine for current capabilities.  It won't work with the
 theoretical overlayfs system, though: we need to copy-down from the
 ramfs to real flash before rebooting, and that can't happen until
 there's disk space to do it
 
 Sat May 20 22:35:25 BST 2023
 
 We have a working min-collect-garbage (seems to, anyway ...)
 
 - having ssh host key wiped on reboot is sucky. maybe we can have
 /persist/secrets and a service that looks there?
 
 - find out what files ash sources on non-login shell startup
   [ set ENV=/etc/ashrc in parent process env ]
 
 - services.default is suboptimal as there is no way to add to it
 without wiping it
 
 - decide whether to use liminix- or min- as our prefix for nixy
   commands
 
 - should we move config.outputs  -> config.system.outputs ? see Mar 28
 
 - less crap firewall
 
 - add ipv6 support to rotuer
 
 - create an l2tp configuration
 
 - iperf and tuning
 
 - wlan country code
 
 
 dropbear weak hashes? https://github.com/mkj/dropbear/issues/138
 
 Sun May 21 11:48:07 BST 2023
 
 dropbear will generate host keys on first connection. It's (probably) good that the
 key is generated on-device and also that we wait until there's some randomness.
 It's not so good that it will only write the key to DSS_PRIV_FILENAME which is
 hardcoded to /run
 
 Sun May 21 17:27:31 BST 2023
 
 What do we need for ipv6?
 
 -  upgrade ppp to something with an ipv6-up-script option, move ppp and pppoe derivations into their own files
 -  get ipv6 address from pppoe
 -  get ipv6 delegation from DHCPv6
 -  support dhcp6 in dnsmasq, and advertise prefix on lan
 -  firewall settings
 
 Sun May 21 21:30:17 BST 2023
 
 Making hydra build the docs is straightforward, but making it
 _publish_ the docs is outside scope, really. It can serve the files
 but they're all text/plain
 
 Should hydra push the docs to www.liminix.org or should www.liminix.org
 pull?
 
 TODO-at-some-point: assign uids and gids dynamically, somehow
 
 Tue May 23 22:56:33 BST 2023
 
 following the guidance at https://support.aa.net.uk/IPv6:
 
 we run odhcp6c to do router solicitation/advertisement dance
 
 
 odhcp6c environment variables:
 
 RA_ADDRESSES=
 RA_REACHABLE=0
 CER=
 PASSTHRU=00170020200108b0000000000000000000002020200108b0000000000000000000002021
 SERVER=fe80::203:97ff:fed6:0
 RA_MTU=0
 RA_ROUTES=::/0,fe80::203:97ff:fed6:0,65535,512
 OPTION_1=00030001e4956e4ef2fa
 NTP_FQDN=
 OPTION_2=00030001000397d60000
 RA_DOMAINS=
 DOMAINS=
 AFTR=
 SIP_IP=
 NTP_IP=
 PREFIXES=2001:8b0:de3a:40dc::/64,7198,7198
 RA_HOPLIMIT=64
 RA_DNS=
 RDNSS=2001:8b0::2020 2001:8b0::2021
 SNTP_IP=
 RA_RETRANSMIT=0
 SIP_DOMAIN=
 ADDRESSES=2001:8b0:1111:1111:0:ffff:51bb:4cf2/128,3598,7198
 
 # ip -6 route |grep default
 default via fe80::203:97ff:fed6:0 dev ppp0  metric 1024  expires 65211sec
 
 presumably from RA_ROUTES but why is the metric appaently doubled?
 
 Tue May 30 21:25:37 BST 2023
 
 We have an odhcpc script that preserves the prefix delegation from the
 ISP.  We need a service that notices whenever the state is
 available/has changed, and updates the LAN IPv6 address.
 
 The service can depend on odhcp
 
 add inotify to packages
 use writeFennelScript with that dep
 see if it works
 
 Wed May 31 23:33:00 BST 2023
 
 We have a thing that sets ipv6 address on lan interface, yay us
 
 A firewall would be a very good idea
 
 Thu Jun  1 18:46:59 BST 2023
 
 TODO for now:
 
 - services.default is suboptimal as there is no way to add to it
 without wiping it
 
 - decide whether to use liminix- or min- as our prefix for nixy
   commands
 
 - should we move config.outputs  -> config.system.outputs ? see Mar 28
 
 - less crap firewall
 
 - create an l2tp configuration
 
 - iperf and tuning
 
 - wlan country code
 
 Thu Jun  1 21:26:37 BST 2023
 
 how can a client machine "opt out" of using the firewall, to allow
 incoming connections?  Most convenient would be to have a separate SSID
 for grownups. Assuming it shows up as a separate wlan device, we can
 write firewall rules to allow incoming connections on that interface
 (can we? only if the packet is identifiable as destined for that interface)
 
 https://www.rfc-editor.org/rfc/rfc6092.html
 https://emailstuff.org/rfc/rfc7084
 
 We could block incoming for slaac and dhcp addresses and permit it for
 stable private addresses. If we were fairly sure that devices won't
 ask for stable private addresses just for funsies.
 
 https://wiki.archlinux.org/title/IPv6_#Stable_private_addresses
 
 
 
 Fri Jun  2 14:42:43 BST 2023
 
 I found a handy guide to nftables at https://ww.telent.net/2023/6/2/turning_the_nftables
 
 Mon Jun  5 16:56:44 BST 2023
 
 
 How are we going to do this firewall thing then?
 I can see no reason to have more than one table per family, so lets
 just name the tables after families
 
 There is nothing in nftables for functionally grouping rules by
 requirement that may touch multiple hooks/chains, so we need our own
 abstraction - and we can't call it any name that nftables uses already
 (so, not "ruleset"). rulegroup?
 
 "policy" would be a good name except that it's already taken
 
 "concern"? "requirement"? "feature"?
 
 Mon Jun 19 20:45:48 BST 2023
 
 why is chrony using libedit?
 
 Thu Jun 22 09:52:57 BST 2023
 
 - There is a lot more lua being installed (luac, docs, static
   libraries etc) than we really need.
 
 - update User docs to include a list of supported  targets
 
 Thu Jun 22 23:43:06 BST 2023
 
 - is there a sysfs to enable ipv6 forwarding?
 - we haven't an ipv4 firewall yet
 
 
 PATH=`echo /nix/store/*nftables*/bin`:$PATH
 nft list ruleset
 
 Thu Jun 22 23:58:58 BST 2023
 
 Looks like we're missing at least one kernel config setting for
 nftables. Would this be a good time to do a derivation for building
 kernel modules?
 
 
 Sun Jul  9 21:21:17 BST 2023
 
 
 Tue Jul 11 22:10:17 BST 2023
 
 - s6 cheatsheet, find or write
 - could we have > 1 module add to services.default?
 - odhcp should parse values from environ and write more files, to save readers
  from parsing it
 - pkgs.liminix, who knows what thats for any more?
 - interface.device, as a  general rule, doesn't work because the
   device name may be known only at runtime (e.g. for ppp)
 - iperf
 - figure out wifi regdomain
 
 Tue Jul 11 23:01:59 BST 2023
 
 We can make services depend on kernel modules, however not on bakedin
 kernel config
 
 [from March: "Let's think about services and modules."]
 
 Module
 + can change global config
   * add users, groups etc
   * change kernel config
   * change busybox config
 + well-typed parameters
 - is a "singleton": can't have the same module included twice
   with different config. e.g. can't have two hostap modules running on
   different wlan radios.
 - can't express dependencies: a depends on b
 
 thought I had then was: modules provide services. requiring the
 ppp module causes config.services.ppp to exist, so you can
 
 services.default = [
   (config.services.ppp {
     tty = "17";
     baud = "57600";
     secrets = blah;
     })
   ...
 ]
 
 this might work. also though we should find out how to do type checking on
 service params
 
 Wed Jul 12 23:23:02 BST 2023
 
 https://github.com/NixOS/mobile-nixos/pull/406 // why mobile nixos uses
 mobile.outputs instead of system.build
 
   suggests that system.build may not be a thing to blindly emulate
 
 if a service is a derivation should we expect to want to be able to call
 it with .override? maybe we want to override the package containing the
 daemon it runs. How do we best pass service config as well?
 
 Maybe a service template is a function that returns a derivation
 
 
 imports = [ ./modules/pqmud.nix ];
 services.mud = system.services.pqmud {
   realm = "A deep cavern";
   port = 4067;
   users = import ./allowed-users.nix;
   # etc etc
 };
 services.mudBeta = let mud =
   system.services.pqmud {
     realm = "A very deep cavern";
     port = 4068;
     users = import ./allowed-users.nix;
   };
   in mud.overrideAttrs { pqmud = pkgs.pkmudLatest; };
 
 so we have
 
 config.system.services # services provided by modules
 config.system.outputs  # build artefacts of various types
 
 the services provided by a module must be introspectable in some way
 so that we can compile a list of service options per module
 
 service parameters are defined using the module type system.
 Something like this?
 
 # mud.nix
 
 system.services.pqmud = args :
   let t = {
     name = mkOption { type = types.str; };
     realm = mkOption { type = types.str; };
     port = mkOption { type = types.port; default = 12345; };
     users = mkOption { type = types.any; };
   };
   in assert isType (submodule { options = t; }) args; longrun {
      inherit (args) name;
      run = "${pkgs.pqmud}/bin/pqmud --port ${port} ....."
   };
 
 Fri Jul 14 19:07:59 BST 2023
 
 It works for pppoe, though typechecking error messages could be
 better.
 
 - We need to find a good place to keep the typeCheck function so that
 everyone can use it.
 
 - also the type_service type defn exists only locally in modules.nix,
 and we would like to refer to it elsewhere
 
 Thu Aug 10 21:46:36 BST 2023
 
 to finish service/modules milestone
 
 [done] there are some modules not using serviceDefn
 - modules included by standard.nix should have all their options
   grouped together in docs
   how can we determine which they are? or maybe "modules that
    don't contain services" is an acceptable criterion
   maybe this is not actually an issue, if the modules are
    reasonably coherent. It looks odd now because base.nix is a mess
 [done] print the module pathname so people know what to import
 [done] docs don't print the examples
 [check?] and seem to be getting the default wrong too
 - decide what we deem to be "internal" (if anything)
    is `filesystem` internal, for example? or `busybox`? they're
    both mostly _used_ internally but may still be valuable to expose
 [done] maybe document outputs separately or not at all?
 [done] bridge to be one service instead of two?
 [done] get rid of services/
 - anything else in rotuer.nix that we should servicify
 - services for liminix.networking
 - a nice way to specify service dependencies
 [done] - do another video
 
 Mon Aug 21 20:02:55 BST 2023
 
 a nice way to do dependencies would be somethng like
 
 services.thething =
   let s = svc.thing { .... };
   in addDependencies s (with config.services; [otherthing yetanother]);
 
 except that addDependencies is a really klunky name. dependsOn is very
 slightly better? or maybe it could be a function of the derivation?
 
 services.thething =
   svc.thing { .... }.depends (with config.services; [otherthing yetanother]);
 
 ---
 
 what does it mean to be dependent on an interface? that's it up? running?
 has an address? has a collection of addresses?
 
 
   services.defaultroute4 = route {
     name = "defaultroute4";
     via = "$(output ${services.wan} address)";
     target = "default";
     dependencies = [ services.wan ];
   };
 
 - this route requires the interface to have an address (if wan is an
   interface, anyway ...)
 
 - but otoh a dhcp client doesn't want to wait for an address, because
    it is assigning the address.
 
 should an address provider have "interface name" as an output?
 is there a set of outputs that every address provider should have -
 whether static, dhcp, pppoe?
 
 maybe we're in decision paralysis and should just move forward with
 what we know
 
 Wed Aug 23 18:56:08 BST 2023
 
 We may want to change the hardware device files to specify network
 interface names not services. Otherwise hardware devices (boards)
 depend on module-based-services, which is a bit weird.
 
 Thu Aug 24 18:54:03 BST 2023
 
 - we want network and bridge to be separate modules, because bridge
 introduces extra kernel config
 
 - bridge/service wants to create a network device ("ip link"),
 using quite similar code as network/link.nix
 
 - but bridge/service is a derivation: it has sight of pkgs but not
 config
 
 offtopic: useful s6-rc commands at https://www.skarnet.org/software/s6-rc/faq.html
 
 Fri Aug 25 23:37:57 BST 2023
 
 where we left off: bridge is a bundle, and bundles can't have outputs,
 so how do we set the ifname of the bridge?
 
 - ifname of the primary is set
 - actually, most things that depend on the bridge really just depend
   on the primary anyway (it's OK if 1 <= n < #members are down)
 - but *something* should depeond on all the members
 
 turns out maybe we needed two services after all?
 
 Sun Aug 27 23:50:18 BST 2023
 
 I've done enough to make rotuer build, but in the process
 trashed vanilla-configuration as I entirely forgot we don't have
 a dhcpv4 client service. Need to fix that ...
 
 - anything else in rotuer.nix that we should servicify
 - anything in vanilla-configuration ditto
 - and arhcive (rsync, watchdog)
 - services for liminix.networking
 - tidy up the dependency handling in serviceDefn build
    (interface is fine, implementation is a bit brutal)
 - write a blog entry
 
 Mon Aug 28 16:58:49 BST 2023
 
 - [done] ntp is not setting the time
 - nftables syntax error
 
 Thu Aug 31 23:53:54 BST 2023
 
 - anything else in rotuer.nix that we should servicify
  [done] - packet forwarding
   - dhcp6 client
   - what to do with acquire-{wan,lan} scripts?
   - resolvconf
 - [done] anything in vanilla-configuration ditto
   - packet forwarding
 - and arhcive
   - [not doing] rsync
   - [done] watchdog
   - [done] mount
 - nftables syntax error
 - tidy up the dependency handling in serviceDefn build
    (interface is fine, implementation is a bit brutal)
 - [done] services for liminix.networking
 - [done] write a blog entry
 - [done] ntp is not setting the time
 - [done] static dhcp(6) lease support reqd for dogfooding
 
 Sat Sep  2 21:35:41 BST 2023
 
 Considerations for "mount" service: each filesystem needs to depend on
 any mount points for its parent directories, and maybe also on other
 services (e.g. filesystem modules, network devices, routes)
 
 mountpoints = {
  mnt = {
    media = svc.mountpoint.build {
      fstype = "msdos";
      device = "/dev/sda1";
      options = [ ...];
    };
    archive = svc.mountpoint.build {
      fstype = "ext4";
      device = "/dev/sda2";
      options = [ ...];
      mountpoints = {
        remote = svc.mountpoint.build {
          fstype = "nfs";
 	 device = "doc.ic.ac.uk:/public";
        };
      };
    };
   };
 }
 
 services.somethingelse = svc.ftpd.build {
   # ...
   dependencies = [ mountpoints.mnt.archive ];
 }
 
 what don't we like about this? we have to walk the nested attrset in a
 weird way, because the services may contain other mountpoints. Maybe
 just keep it simple and do
 
 
 services.mountpoints = bundle {
  name = "mountpoints";
  contents = [
    svc.mountpoint.build {
      device = "/dev/sda2"; fstype = "ext4"; directory = "/mnt/isos";
    };
    svc.mountpoint.build {
      device = "/dev/sdb1"; fstype = "msdos"; directory = "/mnt/backup";
      dependencies = [ load-vfat-module ];
    };
  ];
 }
 
 Sun Sep  3 17:34:36 BST 2023
 
 how to dogfood
 
 DHCP6 server: static lease support
 DHCP client and acquire-{lan-prefix,wan-address}
 
 The emergency boot thingy in glinet u-boot won't help because it
 expects to flash from its tftp request instead of booting it. So we
 could use kexec instead except that the openwrt install doesn't have
 it.  So we could swap the hardware devices, the only downside of that
 being that then I don't have a test system any more. Or we could YOLO it.
 
 Sun Sep  3 22:11:02 BST 2023
 
 I think we should rejigger the documentation ...
 
 - "getting started": worked example, building and installing Liminix
 with a very simple config (wifi AP with ssh daemon)
 
 - using modules
   - link to module reference
 
 - creating custom services
   - longrun or oneshot
   - dependencies
   - outputs
 
 - creating your own modules
 
 - hacking on Liminix itself
 
 - contributing
 
 - external links and resources
 
 - module reference
 
 - hardware device reference
 
 ---
 
 I think we might rename wlan_24 to wlan and wlan_5 to wlan1.
 This is on the assumption that almost no device is 5GHz only, so
 would make it easier to write a basic wlan example that works
 both on 2.4GHz boards and dual radio boards
 
 Mon Sep  4 23:15:26 BST 2023
 
 If dhcpcd parsed the update-script output into separate files, half
 the complexity of acquire-lan-prefix would go away. The other half is
 because it subscribes to changes in the outputs instead of just
 running once. Perhaps there's a better way to do that?
 
 Could separate prefixes and addresses something like this...
 
 outputs/prefix/2001\:8b0\:de3a\:40dc\:\:/prefix
 outputs/prefix/2001\:8b0\:de3a\:40dc\:\:/length
 outputs/prefix/2001\:8b0\:de3a\:40dc\:\:/preferred
 outputs/prefix/2001\:8b0\:de3a\:40dc\:\:/valid
 outputs/prefix/2001\:8b0\:de3a\:80\:\:/prefix
 outputs/prefix/2001\:8b0\:de3a\:80\:\:/length
 outputs/prefix/2001\:8b0\:de3a\:80\:\:/preferred
 outputs/prefix/2001\:8b0\:de3a\:80\:\:/valid
 
 the directory name is arbitrary as long as it's unique. Might even be better to
 remove the colons
 
 outputs/prefix/200108b0de3a40dc/valid
 
 or we could adopt the MS convention and replace with hyphens
 
 outputs/prefix/2001-8b0-de3a-40dc--/prefix
 
 Also: we should write some kind of test for this...
 
 
 Tue Sep  5 21:36:39 BST 2023
 
 How do we set the cpu governor?
 
 
 Fri Sep  8 21:26:36 BST 2023
 
 We want a fennel thing that reads a filesystem tree into a nested
 table. And a thing to diff two tables
 
 Sat Sep  9 22:40:50 BST 2023
 
 Subscribers to odhcp6c outputs need to be able to tell which addresses
 are new and which have been removed since the last run, which now we
 have ohdcp-script  producing parsed data means they need to compare
 tables by value. Which is a faff.
 
 What if the directory name were a hash of all the relevant fields
 such that clients could just say "new directory, must be new address"
 
 We can have literal prefix, then need to encode
 length,preferred,valid,extra space-efficiently. I cannot currently see
 any way to use whatever hashing Lua uses for its table lookups,
 which is a bit disapppointing, so we might have to make our own
 
 
 https://gist.github.com/scheler/26a942d34fb5576a68c111b05ac3fabe
 this is DJBHash, though doesn't appear to deal with integer overflow
 
 
 function hash(str)
     h = 5381;
 
     for c in str:gmatch"." do
         h = ((h << 5) + h) + string.byte(c)
     end
     return h
 end
 
 
 Mon Sep 11 20:31:25 BST 2023
 
 acquire-lan/wan-foo have no tests, and the test setup is a bit of a
 faff as they are both waiting on the filesystem
 
 also, testing lua scripts is a faff without splitting them into
 script/module
 
 am wondering if we could do some kind of convention that we only write
 modules not scripts but something in the fennel->lua can call the
 module's `run` method.
 
 Tuesday
 
 Here is a working shebang for write-fennel:
 
 #!/nix/store/5iwv3h2jjbk2vib2bpwx3g9knpb02x3y-lua-5.3.6/bin/lua -e dofile(arg[0]).run()
 
 Tue Sep 12 20:47:52 BST 2023
 
 We don't handle unbound or stopped states in odhcp consumers. I think
 probably we should do this in odhcp-script by deleting the outputs,
 rather than making each consumer do it.
 
 ... turns out that odhcp6c itself unsets ADDRESSES and PREFIXES before
 calling the script with "unbound", so maybe we don't need to do
 anything special.
 
 Wed Sep 13 17:55:33 BST 2023
 
 
 
 @400000000000001f2723b3cb eth1.link.pppoe Script /nix/store/nyks8zl86dcp44k5sjcc76digrnfgm17-ip-up finished (pid 403), status = 0x0
 @400000000000001f27b2db3b eth1.link.pppoe Script /nix/store/ds0lc4qd1zfiyxsva87rpplyr21awjh1-ip6-up finished (pid 404), status = 0x1
 
 @400000000000001f30a7c5c5 /nix/store/v9ijgyywizqbbd9y73r2wifkxc0d1jjm-route-default-1a22c69d0e1f-up: line 4: input: not found
 @400000000000001f31abf9b5 ip: command line is not complete, try "help"
 @400000000000001f31ca1395 s6-rc: warning: unable to start service route-default-1a22c69d0e1f: command exited 1
 @400000000000001f31f236b4 s6-rc: info: service route-default-d2586cf00da0 successfully started
 @
 
 
 Wed Sep 13 18:05:38 BST 2023
 
 TODO
 
 - service for dhcp6 client
 - move acquire-{wan,lan} scripts out of examples/
 - service for resolvconf
 - nftables syntax error
 - tidy up the dependency handling in serviceDefn build
    (interface is fine, implementation is a bit brutal)
 - docs
 
 considerations:
 
 1) in some ways, we should be able to specify acquire-{wan,lan} as if
 they were just additional addresses on the respective
 interfaces. However, they're longruns so the implementation of
 "address" doesn't really fit.
 
 2) should they be bundled into a dhcp client service? I think the
 answer is "no" because which of the dhcp config we want to
 honour locally (and how) is policy not mechainmsm
 
 svc.dhcp6c.client.build { interface = wan; };
 svc.dhcp6c.address.build {
   inherit client;
   interface = lan;
 };
 svc.dhcp6c.address.build {
   inherit client;
   interface = wan;
 };
 svc.dhcp6c.prefix.build {
   inherit client;
   interface = lan;
   index = 1;			# default to first interface
 };
 svc.dhcp6c.prefix.build {
   inherit client;
   interface = vpn;
   index = 2;
 };
 
 
 
 Fri Sep 15 12:04:25 BST 2023
 
 Qemu worked example provides dhcp and ssh service
 
 Hardware worked example needs to be plugged into same lan as build
 machine if we are going to tftp the image onto it - so it might be
 awkward if we run dhcp on it
 
 The device I have lying around is the A
 
 How do we do the actual flash step? Assuming the device is running
 stock firmware, from a laptop we can wifi to it and use the web ui to
 upgrade
 
 we can't build the hellonet config because it requires tftp
 
 plug in mt300a
 put stock firmware on it
 
 Sun Sep 17 00:08:03 BST 2023
 
 I don't think the user manual needs a full justification of why we
 have the module/service split. Maybe we should have "decision records"
 in the git tree instead
 
 Sun Sep 17 16:44:31 BST 2023
 
 Can we figure out which bits of the old doc are missing from the new
 one and just transplant those? Then we can merge it sooner
 instead of blocking on writig all the new stuff
 
 Mon Sep 25 16:58:51 BST 2023
 
 jffs2 on mt300a isn't finding root partition in initramfs, and it
 seems to be because MTD_SPLIT_UIMAGE_FW isn't working
 
 [    0.426792] spi spi0.0: force spi mode3
 [    0.431305] spi-nor spi0.0: w25q128 (16384 Kbytes)
 [    0.436322] 5 fixed-partitions partitions found on MTD device spi0.0
 [    0.442875] OF: Bad cell count for /palmbus@10000000/spi@b00/flash@0/partitions
 [    0.450400] OF: Bad cell count for /palmbus@10000000/spi@b00/flash@0/partitions
 [    0.458208] OF: Bad cell count for /palmbus@10000000/spi@b00/flash@0/partitions
 [    0.465751] OF: Bad cell count for /palmbus@10000000/spi@b00/flash@0/partitions
 [    0.473522] Creating 5 MTD partitions on "spi0.0":
 [    0.478466] 0x000000000000-0x000000030000 : "u-boot"
 [    0.484447] 0x000000030000-0x000000040000 : "u-boot-env"
 [    0.490888] 0x000000040000-0x000000050000 : "factory"
 [    0.497110] 0x000000050000-0x000000fd0000 : "firmware"
 [    0.596423] 0x000000ff0000-0x000001000000 : "art"
 [    0.611508] gsw: setting port4 to ephy mode
 
 with squashfs root it's the same but for the extra split partitions:
 
 [    0.468715] Creating 5 MTD partitions on "spi0.0":
 [    0.473653] 0x000000000000-0x000000030000 : "u-boot"
 [    0.479652] 0x000000030000-0x000000040000 : "u-boot-env"
 [    0.486085] 0x000000040000-0x000000050000 : "factory"
 [    0.492318] 0x000000050000-0x000000fd0000 : "firmware"
 [    0.499304] 2 uimage-fw partitions found on MTD device firmware
 [    0.505457] Creating 2 MTD partitions on "firmware":
 [    0.510543] 0x000000000000-0x000000260000 : "kernel"
 [    0.516616] 0x000000260000-0x000000f80000 : "rootfs"
 [    0.522570] mtd: device 5 (rootfs) set to be root filesystem
 [    0.528565] 0x000000ff0000-0x000001000000 : "art"
 
 turns out this is because the device thinks it has 4k erase block size
 because MTD_SPI_NOR_USE_4K_SECTORS was set, and that was causing
 mtdsplit to look in the wrong place for a root filesystem
 
 Mon Sep 25 18:50:05 BST 2023
 
 No, that wasn't it. Turned out to be an endianness-dependent check for
 JFFS2 magic in mtdsplit.
 
 setenv serverip 10.0.0.1
 setenv ipaddr 10.0.0.8
 tftp 0xa00000 result/uimage
 bootm 0xa00000
 
 Fri Sep 29 20:50:39 BST 2023
 
 setenv bootargs 'liminix mtdparts=phram0:M(rootfs) phram.phram=phram0,0x40411f28,4194304,65536 memmap=4194304$0x40411f28 root=/dev/mtdblock0 console=ttyAMA0,115200 earlycon'
 
 setenv serverip 10.0.0.1
 setenv ipaddr 10.0.0.5
 setenv bootargs 'liminix console=ttyS0,115200  panic=10 oops=panic earlycon=uart8250,mmio32,0x11002000 root=/dev/mtdblock0'
 tftp 0x4007ff28 result/uimage ;  tftp 0x40432f28 result/rootfs
 bootm 0x4007ff28
 
 setenv bootargs 'liminix console=ttyS0,115200  panic=1 oops=panic earlycon  root=/dev/mtdblock0'
 
 md 0x42ff0000
 
 Cannot find regmap for /infracfg@10000000: -524.
 
 # "console=ttyAMA0,38400 panic=10 oops=panic init=/bin/init loglevel=8 root=/dev/mtdblock0 rootfstype=squashfs fw_devlink=off"
 
 
 40812468: 69726553 203a6c61 41424d41 304c5020    Serial: AMBA PL0
 40812478: 55203131 20545241 76697264 3c0a7265    11 UART driver.<
 40812488: 61723e33 706f6f6d 61203a73 6165726c    3>ramoops: alrea
 40812498: 69207964 6974696e 7a696c61 3c0a6465    dy initialized.<
 408124a8: 61723e34 706f6f6d 70203a73 65626f72    4>ramoops: probe
 408124b8: 20666f20 66663234 30303030 6d61722e     of 42ff0000.ram
 408124c8: 73706f6f 69616620 2064656c 68746977    oops failed with
 408124d8: 72726520 2d20726f 3c0a3232 61433e33     error -22.<3>Ca
 408124e8: 746f6e6e 6e696620 65722064 70616d67    nnot find regmap
 408124f8: 726f6620 6e692f20 63617266 31406766     for /infracfg@1
 40812508: 30303030 3a303030 32352d20 333c0a34    0000000: -524.<3
 40812518: 6e61433e 20746f6e 646e6966 67657220    >Cannot find reg
 MT7622>
 40812528: 2070616d 20726f66 666e692f 66636172    map for /infracf
 40812538: 30314067 30303030 203a3030 3432352d    g@10000000: -524
 40812548: 3e333c0a 6e6e6143 6620746f 20646e69    .<3>Cannot find
 40812558: 6d676572 66207061 2f20726f 72666e69    regmap for /infr
 40812568: 67666361 30303140 30303030 2d203a30    acfg@10000000: -
 40812578: 0a343235 433e333c 6f6e6e61 69662074    524.<3>Cannot fi
 40812588: 7220646e 616d6765 6f662070 702f2072    nd regmap for /p
 40812598: 63697265 31406766 32303030 3a303030    ericfg@10002000:
 408125a8: 32352d20 313c0a34 616e553e 20656c62     -524.<1>Unable
 408125b8: 68206f74 6c646e61 656b2065 6c656e72    to handle kernel
 408125c8: 67617020 20676e69 75716572 20747365     paging request
 408125d8: 76207461 75747269 61206c61 65726464    at virtual addre
 408125e8: 66207373 66666666 66666666 66666666    ss fffffffffffff
 408125f8: 0a656666 4d3e313c 61206d65 74726f62    ffe.<1>Mem abort
 
 
 CONFIG_SERIAL_8250_FSL=y
 CONFIG_SERIAL_8250_MT6577=y
 CONFIG_SERIAL_8250_NR_UARTS=3
 CONFIG_SERIAL_8250_RUNTIME_UARTS=3
 CONFIG_SERIAL_DEV_BUS=y
 CONFIG_SERIAL_DEV_CTRL_TTYPORT=y
 CONFIG_SERIAL_MCTRL_GPIO=y
 CONFIG_SERIAL_OF_PLATFORM=y
 
 Mon Oct  2 10:17:04 BST 2023
 
 We have a bootable aarch64 kernel for the Belkin, but it does not
 understand the memmap= parameter we're using to protect the
 phram image from being used as general memory.
 
 One option is to add a reserved-memory stanza in the device tree,
 using u-boot "fdt" command, but we don't know the fdt address in u-boot
 because it doesn't have any commands to parse the image and set
 variables pointing at the sub-components. (There's iminfo, but it's
 onyl human-readable)
 
 Second option is to amend the dtb in the tftpboot module: this
 would mean regenerating the uimage
 
 Third option: for tftpboot do we _have_ to use FIT? maybe we could
 grab the fdt as a separate tftp transaction
 
 we need to apply kernel patch 9401911f2d9f89035f7acebab16e72d43d1282fb
 to avoid using ioremap on sysem ram which is not allowed on arm
 
 
 Tue Oct  3 14:15:38 BST 2023
 
 Progress on Liminix ARM support. The device I'm starting with is
 the Belkin RT3200 (also known as [Linksys E8450](https://openwrt.org/toh/linksys/e8450)) which seems to be a featureful piece of kit, and whioch I snagged for a
 very good price on the Bay of E
 
 # Where are we right now?
 
 * we can TFTP boot it to userland
 * ethernet works
 
 ## What else needs doing?
 
 * it has dual band wifi with many interesting features. I've built the
 
 * we're only running in RAM, probably need to add some kernel config
   to support the flash
 * initramfs support is not yet implemented
 * the flash is NAND flash and it's quite large compared with the
   existing Liminix devices, so we're going to add UBIFS which will
   use it better than  JFFS2 does
 * all this work is on a branch and needs to be cleaned up a lot before
    I'm letting it into main
 
 ## What have we found?
 
 There are some significant differences between this and the MIPS
 devices (yes, other than an entirely different architecture), mostly
 to do with "legacy boot" support or the lack thereof. For example:
 
 * there aren't any options like `MIPS_RAW_APPENDED_DTB` to glom
   together a kernel and device tree (FDT), because the bootloader is
   expected to be able to provide a FDT following "standards".
   U-Boot will do this, provided that we use the newer "FIT" Uimage
   format which allows a kernel and DTB and initrd to be combined in
   the same container.  (Sadly we can't use FIT everywhere because a
   lot of MIPS devices use really old forks of U-Boot that don't
   understand it)
 
 * for tftpboot, on MIPS we use the `memmap` kernel command line option
   to reserve some RAM for the root filesystem. On Arm there's no such
   option, so we have to add a
   [reserved-memory](https://github.com/torvalds/linux/blob/master/Documentation/devicetree/bindings/reserved-memory/reserved-memory.yaml)
   node in the device tree instead. Which means, given that we _only_
   want to do this when tftp booting (the memory is wasted
   otherwise), we have to rewrite the device tree in that
   scenario.
 
 * then it turns out that phram doesn't (didn't) work anyway, because
   it calls ioremap() and [you can't use ioremap on system memory on ARM](https://lwn.net/Articles/409689/). In newer kernels this is
   fixed: there is a [conditional](https://github.com/torvalds/linux/blob/master/drivers/mtd/devices/phram.c#L127) here to use whichever of ioremap or
   memremap is appropriate for the memory passed to phram, but it looks
   non-trivial to backport so I've gone for a [much less sophisticated approach](https://gti.telent.net/dan/liminix/commit/f7cd9c2b6e6c99a228e066b09e3febcf71c63fa1#diff-d8e355f1b2dcde7378ebb40c92cdd2ce3125753c)
 
 * we're using [DSA](https://www.kernel.org/doc/Documentation/networking/dsa/dsa.txt) instead of the OpenWrt [swconfig](https://openwrt.org/docs/techref/swconfig) program. There was actually surprisingly little work needed to adjust to this.
 
 
 Other than that, it was mostly the usual process of "did the kernel
 crash silently, or has it just been unable to open a console device?".
 In this regard, *one neat trick*: even though U-Boot on this device
 doesn't support pstore, we can use it anyway if we don't do compression.
 Enable
 
 ```
         PSTORE = "y";
         PSTORE_RAM = "y";
         PSTORE_CONSOLE = "y";
         PSTORE_DEFLATE_COMPRESS = "n";
 ```
 
 then boot with `panic=3 oops=panic`, then when it resets use the
 U_Boot `md` command to see what happened:
 
 ```
 MT7622> md 0x42ff0000
 42ff0000: 43474244 00000000 00000ff4 3d3d3d3d    DBGC........====
 42ff0010: 39342e31 36373031 500a442d 63696e61    1.491076-D.Panic
 42ff0020: 50203123 31747261 3e363c0a 20505050    #1 Part1.<6>PPP
 42ff0030: 20445342 706d6f43 73736572 206e6f69    BSD Compression
 [....]
 42ff0ca0: 20676e69 73756e75 6b206465 656e7265    ing unused kerne
 42ff0cb0: 656d206c 79726f6d 3731203a 0a4b3832    l memory: 1728K.
 42ff0cc0: 523e363c 2f206e75 74696e69 20736120    <6>Run /init as
 42ff0cd0: 74696e69 6f727020 73736563 3e373c0a    init process.<7>
 ```
 
 Wed Oct  4 21:08:44 BST 2023
 
 By randomly including chinks of the openwrt config we have made it
 find the mt7915e on the pcie bus. I just don't yet know which bit of
 the openwrt config it was.
 
 It doesn't actually work yet though. 5GHz wifi gets calibration data
 from the flash, so it is not going to work unless (1) we reflash the
 firmware partition, or (2) we find another way to provide it
 calibration data.
 
 https://forum.openwrt.org/t/belkin-rt3200-linksys-e8450-wifi-ax-discussion/94302/401
 
 Sat Oct  7 22:56:40 BST 2023
 
 We're almost ready to merge the rt3200 support (it's not finished
 but it mostly won't break mips) except for the uimage module
 which needs all that FIT stuff, and the tftpboot contortions
 to amend the dtb for memmap
 
 For legacy uimage
 
 1) add commandline params to dtb
 2) objcopy fdt into vmlinux.elf
 3) strip to raw image and compress
 4) mkimage
 
 
 For FIT uimage
 
 1) add commandline params to dtb
 2) strip to raw image and compress
 3) create its file
 4) mkimage
 
 Do we still want to handle the no-dtb case? what about
 standards-compliant boot, where u-boot is providing the dtb? No option
 to provide a commandline in that case, but maybe also no need to.
 
 For tftpboot, am undecided. We could use the dtb rewriting thing
 everywhere, in the interest of consistency.
 
 Mon Oct  9 20:45:54 BST 2023
 
 we bumped the kernel entry point to the 32MB mark, as
 
 (1) when using jffs2 (big rootfs image) it was clobbering the dtb at
 the end of the filesystem
 
 (2) it should be 2MB aligned anyway and wasn't
 
 However, this has given us the next problem:
 
 OF: fdt: Reserved memory: failed to reserve memory for node 'secmon@43000000': base 0x00000000430B
 OF: reserved mem: OVERLAP DETECTED!
 phram-rootfs (0x0000000040400000--0x0000000053a31488) overlaps with ramoops@42ff0000 (0x000000004)
 Zone ranges:
   DMA      [mem 0x0000000040000000-0x000000005fffffff]
   DMA32    empty
   Normal   empty
 Movable zone start for each node
 
 the end of that phram-rootfs region looks well sus.
 
 [ turns out that decimal is not hex ]
 
 Tue Oct 10 21:37:31 BST 2023
 
 UBI bleurgh ...
 
 The DTB for this device, and/or the OpenWrt installer,  seems to
 expect already that mtd4 is a UBI thing
 
 mtdinfo -a says:
 mtd4
 Name:                           ubi
 Type:                           nand
 Eraseblock size:                131072 bytes, 128.0 KiB
 Amount of eraseblocks:          1000 (131072000 bytes, 125.0 MiB)
 Minimum input/output unit size: 2048 bytes
 Sub-page size:                  2048 bytes
 OOB size:                       64 bytes
 Character device major/minor:   90:8
 Bad blocks are allowed:         true
 Device is writable:             true
 
 <5>UBI: auto-attach mtd4
 <5>ubi0: attaching mtd4
 <5>ubi0: scanning is finished
 <5>ubi0: attached mtd4 (name "ubi", size 125 MiB)
 <5>ubi0: PEB size: 131072 bytes (128 KiB), LEB size: 126976 bytes
 <5>ubi0: min./max. I/O unit sizes: 2048/2048, sub-page size 2048
 
 we made a volume using "ubimkvol /dev/ubi0 -N liminix -S 825"
 
 and from ubinfo -a we can see
 
 0 ubootenv
 1 ubootenv2
 2 recovery
 3 boot_backup
 4 liminix
 
 Now we could use "ubiupdatevol /dev/ubi0_4 /path/to/ubifs.img"
 to put a ubifs on that volume, but obviously we'd have to boot the
 device into Liminix somehow first.
 
 Alternatively in the build environment we could use ubinize to
 create the entire image that can be flashed to MTD, but
 
 - this will overwrite erase counters.
 - we have to give it a config file that describes all the volumes,
  and I'm guessing they need to match up with the existing ones
  otherwise we trash the uboot env
 
 
 Wed Oct 11 17:37:09 BST 2023
 
 We can write ubi volumes from u-boot.  Let's for the moment use
 mkfs.ubifs and tftp those files to u-boot - we can figure out the
 ubinize dance later
 
 We need either
 
 (a) to write an analogue of our jffs2 graft option for mkfs.ubifs, or
 (b) to have a "cpio-like" mkfs.ubifs variant that reads filenames on stdin
   and writes only those, or
 (c) to create a "staging" directory during build with all the store folders that need to go into the filesystem
 
 although the least elegant, option (c) is the simplest and probably
 not even slow, at least by comparison with unpacking the kernel source
 tarball
 
 we used
 uboot> tftpboot 0x40400000 result/rootfs
 uboot> ubi write 40400000 liminix $filesize
 
 then can use ubifsmount ubi0:liminix ; ubifsls / to check that it wrote
 something valid. To boot this:
 
 setenv serverip 10.0.0.1
 setenv ipaddr 10.0.0.8
 setenv bootargs 'liminix console=ttyS0,115200 panic=10 oops=panic init=/bin/init loglevel=8 root=ubi0:liminix  rootfstype=ubifs fw_devlink=off'
 tftpboot 0x4007ff28 result/uimage
 bootm 0x4007ff28
 
 The other thing we had to fix here is that activate wasn't being built
 statically. Have to add -Xlinker -static to CFLAGS - I don't know if
 this is a no-op on MIPS
 
 Mon Oct 16 20:51:08 BST 2023
 
 Here's a thing: the u-boot installed by openwrt on this device has a
 ubifsload command, and it has a writable ubootenv. So instead of
 having a separate partition for the kernel we could put the kernel in
 the actual filesystem
 
 I think we should do this by excluding flashimage and including some
 other module (to be written) instead. ubimage or somesuch, perhaps.
 
 So the image we wish to create is a ubifs with a kernel inside it in
 /boot and we also need to change the u-boot env value of
 
 boot_production=led $bootled_pwr on ; run ubi_read_production && bootm $loadaddr#$bootconf ; led $bootled_pwr off
 
 so that it mounts the rootfs and finds /boot/uimage inside it
 
 From uboot this is setenv and saveenv; from a running linux this is fw_setenv
 
 Thu Oct 19 09:34:15 BST 2023
 
 setenv bootargs 'liminix console=ttyS0,115200 panic=10 oops=panic init=/bin/init loglevel=8 root=ubi0:liminix  rootfstype=ubifs fw_devlink=off'
 
 
 ubifsmount ubi0:liminix
 ubifsload 4007ff28 boot/uimage
 bootm 0x4007ff28
 
 
 Thu Oct 19 23:11:17 BST 2023
 
 Assuming you've done the openwrt installer to repartion the device,
 what are the steps to install Liminix?
 
 1) build rootfs, which incorporates kernel
 
 2) from u-boot:
 
 uboot> ubimkvol /dev/ubi0 -N liminix -S 825
 uboot> tftpboot 0x40400000 result/rootfs
 uboot> ubi write 40400000 liminix $filesize
 uboot> setenv boot_production 'led $bootled_pwr on ; ubifsmount ubi0:liminix; ubifsload 4007ff28 boot/uimage; bootm 4007ff28'
 
 What if we don't have a serial console? can we do all this from openwrt?
 
 Fri Oct 27 23:21:08 BST 2023
 
 setenv serverip 10.0.0.1
 setenv ipaddr 10.0.0.8
 setenv bootargs 'liminix earlyprintk earlycon=uart8250,mmio32,0xf1012000 ramoops.mem_address=0x8000000 ramoops.mem_size=0x40000 ramoops=max_reason=2 mem=128M earlycon=ttyS0 console=ttyS0,115200 panic=10 oops=panic init=/bin/init loglevel=8 root=ubi0:liminix  rootfstype=ubifs fw_devlink=off'
 setenv bootargs 'liminix  ramoops.mem_address=0x8000000 ramoops.mem_size=0x40000 ramoops=max_reason=2 mem=128M console=ttyS0,115200 panic=10 oops=panic init=/bin/init loglevel=8 root=ubi0:liminix  rootfstype=ubifs fw_devlink=off'
 tftpboot ${kernel_addr_r} result
 bootm ${kernel_addr_r}
 
 
 ---
 this is potentially worth checkng out because we do have very slow
 decompress speed
 
 https://scm.linefinity.com/common/u-boot/commit/5818198e6a184963c6afc82178b23a64435ace6a
 
 Commit 5bb2c550b1 ("arm: mvebu: Move internal registers in
 arch_very_early_init() function") implemented code movement according to
 (now incomplete) comments which resulted in semi-broken code.
 
 The result is that I-cache is currently disabled for all Armada 38x boards
 and maybe there are some other (unreported / undetected) issues.
 
 [...] After this change lzmadec command with lzma image of 0x7000000 bytes is
 doing decompression just 5 seconds. Before this change it was 30 seconds.
 
 
 Mon Oct 30 21:03:55 GMT 2023
 
 We have a kernel that boots on the Omnia, now we need to build a
 rootfs. Given this device uses mmc for its primary storage, we should
 use a block filesystem not a flash filesystem.
 
 
 setenv serverip 10.0.0.1
 setenv ipaddr 10.0.0.8
 setenv bootargs 'liminix console=ttyS0,115200 panic=10 oops=panic init=/bin/init loglevel=8 root=/dev/mtdblock0 rootfstype=ext4fs fw_devlink=off mtdparts=phram0:22M(rootfs) phram.phram=phram0,0x1300000,23068672,65536 root=/dev/mtdblock0'
 tftpboot 0x1000000 tftpboot/uimage ; tftpboot 0x1300000 tftpboot/dtb ; tftpboot 0x29b0000 tftpboot/dtb; tftpboot 0x29c0000 initrd.img
 
 
 Sat Nov  4 12:22:37 GMT 2023
 
 setenv serverip 10.0.0.1
 setenv ipaddr 10.0.0.8
 setenv bootargs 'liminix console=ttyS0,115200 panic=10 oops=panic init=/bin/init loglevel=8 root=/dev/mtdblock0 rootfstype=ext4 fw_devlink=off mtdparts=phram0:22M(rootfs) phram.phram=phram0,0x40300000,23068672,65536 root=/dev/mtdblock0'
 tftpboot 0x40000800 tftpboot/uimage ; tftpboot 0x419b0800 tftpboot/dtb ; tftpboot 0x41a00000 initrd.img  ; tftpboot 0x40300000 tftpboot/rootfs
 bootm 0x40000800  0x41a00000 0x419b0800
 
 kernel  0x40000800 + 2af400 = "402afc00"
 rootfs  0x40300000 + 15f9400 = "418f9400"
 dtb     0x419b0800 + 4e00 = "419b5600"
 
 Sun Nov  5 00:01:56 GMT 2023
 
 Open questions
 
 1) using -device loader for qemu phram, how do we choose appropriate
 start address for all architectures? we could try to unify this
 with the tftpboot approach, but that would mean providing the dtb
 ourselves somehow which seems silly when qemu already does it
 
 2) flash erase block size for tftpboot phram, it need to match the hardware
  - we don't use it at all for squashfs
  - for jffs2 it needs to match if tftpboot is to use same rootfs image
    as flash
  - we don't have any way to do a tftpboot ubifs
  - ext4 doesn't care
 
 3) the rootfstype needs thought.
 
 - for all but squashfs it implies an initramfs
 - jffs2 can be flashed naively
 - ubifs needs an installer to not clobber erase counts
 - ext4 (for omnia) needs a block device and can't be flashed along
   with the kernel/initramfs because it's a separate disk. or maybe
   the omnia can load kernel from mmc?
 
 phram plus mtd_block is ok for ext4 for qemu, so that's one thing
 fewer to deal with
 
 4) for tftpboot with a separate initramfs, is there any way to
 make address selection easier?
 
 5) ubifs needs a different set of flash parameters (PEB, LEB etc)
 
 Tue Nov  7 23:19:10 GMT 2023
 
 We can flash the turris omnia from a USB stick
 https://docs.turris.cz/hw/omnia/rescue-modes/
 
 it looks for omnia-medkit-latest.tar.gz and (I'm guessing) just
 unpacks it onto the emmc.
 
 Perhaps we need per-device installation instructions in the docs.
 
 * rename defaultOutput to installerOutput
 * attach some docs to the various options for installerOutput
 * add a link from the device's rendered manual section to the
  relevant installer output doc
 
 do we expect that outputs will build on each other? e.g.
 turris omnia output is basically a tarball (other devices
 might want this too) but with docs describing how to reset the
 device and hold the button down until the led flashes four times
 (other devices probably won't want this). maybe the model here
 is that the turris output is a directory with a symlink to the
 tarball and an informative README containing the instructions.
 Although we also want the instructions in the manual where people
 can read them before building anything.
 
 Fri Nov 10 21:27:50 GMT 2023
 
 Realising now that outputs and installers aren't the same thing.
 
 e.g. flashimage can be installed from u-boot or from kexecboot
 
 perhaps we distinguish between the
 
 "installation image":
 - firmware.bin
 - tarball
 - ubifs image
 - kernel + rootfs
 
 and "installer"
 - kexecboot script
 - u-boot script to flash squashfs image
 
 Sun Nov 12 17:17:30 GMT 2023
 
 What TODO?
 
 - "does the kernel live on the filesystem" depends on the bootloader
   not the filesystem
    - could we implement this with a module that adds to config.filesystem ?
      it would depend on whether the bootloader can follow symlinks to
      files not in /boot (probably fine unless crossing filesystems)
    - the other question is how much futzing around in u-boot can/do we do
      to tell u-boot how to boot? for grown-up u-boot it's not a
      problem as we can saveenv but are there broken u-boots that would
      prevent this?
 
 - kexecboot is unloved and documented in the wrong place. do we have a
   test for it even?
    - it won't work on aarch64 because it needs memmap=
    - hardcodes memory size, which we should probably work out dynamically
 
 - how to put device name into the device docs
   maybe devices
 
 - make config.boot.commandLine a single string
 - finish omnia
 - for installation on turris omnia we need tarball not ext4 image
   (but keep the ext4 image anyway for tftpboot and possibly kexecboot)
 [done] - now we have lim.parseInt should we use it consistently?
 - usefulness tiers for devices ("stable", "experimental", "wip")
 - params for ubi(fs) are a mess
 - create an l2tp configuration
 - iperf and tuning
 - wlan country code
 
 
 Fri Nov 17 17:30:39 GMT 2023
 
 kexec is fraught. I spent some time trying (unsuccesfully) to get a
 kexecboot test running, but it doesn't work in qemu for the reason
 that the kernel I built for qemu has SMP support but does not have
 kexec_nonboot_cpu_func() - which is the needed function to stop
 non-boot CPUs before jumping into the new kernel.  That this code is
 all MIPS-specific (I have to assume that other architectures have
 entirely different ways to stop non-boot CPUs?) is a bit worrisome: how
 many other ways is kexec hardware-dependent?
 
 We have two scenarios where we may want to use it:
 
 1) the "installer": e.g. for UBI platforms, we want to plonk
 a new ubifs on the device without clobbering the erase counters, which
 means either doing it from U-Boot - needs serial connection -
 or doing it from a Linux of some kind that is not running on the
 filesystem we're toasting.
 
 2) reinstalling after the initial install - this is a big deal for
 squashfs where there is no other way to change data, and an only slightly
 smaller deal for jffs2, where there isn't much room to change much
 data.
 
 Maybe instead of kexec we could do this by stopping services and then
 pivot_root into a ramfs. We would, I assume, need to stop any processes
 that have open files on the root fs, but we would need to have network
 interfaces running. So we need a subset of services that run in recovery:
 can make this a bundle
 
 * mount a ramfs
 * copy the closure of the bundle into the ramfs
 * stop all processes (including init?)
 
 sending pid 1 a signal FOO will cause it to run .s6-svscan/SIGFOO
 
 Fri Nov 17 23:53:43 GMT 2023
 
 So we need to extend .s6-svscan/finish to
 
 if test -e /maintenance/bin/init
   cd /maintenance
   mount --bind /maintenance/ /
   chroot .
   exec /bin/init -D maintenance
 fi
 
 
 foreground {
   if { test -e /maintenance/bin/init }
     cd /maintenance
     foreground { mount --move /maintenance/ / }
     foreground { chroot . }
     redirfd -r 0 /dev/console
     redirfd -w 1 /dev/console
     fdmove -c 2 1
     emptyenv /bin/init -D maintenance
 }
 ${s6-linux-init}/bin/s6-linux-init-hpr -fr
 
 
 https://openwrt.org/docs/techref/sysupgrade
 
 s6-svscanctl -t /run/service
 
 Sun Nov 19 10:23:17 GMT 2023
 
 # cat `type -p reboot`
 #!/nix/store/0v3q2lnh7bwg0ldk24lzmsdnmidmdvm6-execline-mips-unknown-linux-musl-2.9.3.0-bin/bin/execlineb -S0
 /nix/store/j41b85ccx0rmf7lm5g13zqb7fs68l8y2-s6-linux-init-mips-unknown-linux-musl-1.1.1.0-bin/bin/s6-linux-init-hpr -r \$@
 
 
 s6-linux-init-hpr calls hpr_send("", 0)
 then
 hpr_shutdown(what, &tain_zero, 0))
 which sends "Shpr"[what] to  SCANDIRFULL "/" SHUTDOWND_SERVICEDIR "/" SHUTDOWND_FIFO
 
 which I assume is s6-linux-init-shutdownd.c
 
 it calls prepare_shutdown on socket read, which sets deadline, grace_time.
 later (when?) it calls
 
   run_stage3(basedir) ; # we can see this by adding a message to rc.shutdown
                         # this causes s6-rc services to be downed gently
   s6-rc -v2 -bDa change
 
   prepare_stage4(basedir, what)
 
     creates a file STAGE4_FILE  with the contents:
      s6-linux-init-umountall
      scripts/rc.shutdown.final
      s6-linux-init-hpr -f -r
 
   unsupervise_tree() ;
 
      goes through /run/service/*/supervise/control fifos
      except shutdownd and logger, sending
      "d" to each
 
      then does
      s6_svc_write(SCANDIRFULL "/" S6_SVSCAN_CTLDIR "/control", "an", 2)
      (this is a rescan not a terminate)
 
 #define SCANDIRFULL S6_LINUX_INIT_TMPFS "/" S6_LINUX_INIT_SCANDIR
       (works out to be /run/service "/" ".s6-svscan")
 
 ls
   kill(-1, SIGTERM) ;
 
 s6-rc -v2 -bDa change
 cd /run/service
 for i in s6-linux-init-runleveld s6rc-oneshot-runner s6rc-fdholder eth* getty ; do  s6-svc -d /run/service/$i; done
 
 
 s6-rc -v2 -bDa change
 cd /run/service
 for i in  s6-linux-init-runleveld s6rc-oneshot-runner s6rc-fdholder eth*  ; do  s6-svc -d /run/service/$i; done
 s6-svscanctl -an /run/service
 
 Wed Nov 22 22:01:02 GMT 2023
 
 - define a subset of services that run in maintenance mode.
 - write a command that copies the closure of this bundle into
   /run/maintenance
 - create enough non-store filesystem (proc dev etc) to make it run
 
 Thu Nov 23 00:09:44 GMT 2023
 
 I was as surprised as anybody that this seems to work, at least
 insofar as it has started a busybox sh process. there is a serious
 deficit of symlinks to busybox, so almost no shell scripts work. and I
 think we need an rc.init
 
 It would be worth tidying up the main s6 run-image quite a lot before
 we go further with this
 
 We'd like to be able to reuse the s6 pseudofile structure (/etc/s6-rc
 and /etc/s6-linux-init) but we can't make it a derivation because it's
 pseudofiles (with funny permissions) not real files. Maybe we can
 invoke the module as a function?
 
 Fri Nov 24 23:29:48 GMT 2023
 
 Turris TODO
 
 - see if network works (eth[012], which is which?)
 - wireless drivers
   [DONE] ath9k and ath10k, it's like old times
   https://docs.turris.cz/hw/omnia/omnia/#turris-omnia-wi-fi-6
   (note: other variant of the device has a MT7915AN, should we add
    support for that as well?)
 
 - [DONE] feed the watchdog
    it looks like compiling watchdog support is sufficient to stop the
    thing from rebooting after three minutes, there is no need to actually
    feed it from userspace.
 
 - "does the kernel live on the filesystem" depends on the bootloader
   not the filesystem
    - could we implement this with a module that adds to config.filesystem ?
      it would depend on whether the bootloader can follow symlinks to
      files not in /boot (probably fine unless crossing filesystems)
    - the other question is how much futzing around in u-boot can/do we do
      to tell u-boot how to boot? for grown-up u-boot it's not a
      problem as we can saveenv but are there broken u-boots that would
      prevent this?
    - perhaps we need different boot "recipes" - e.g. some device
      might want boot.scr and another something different
 
 - create installable tarball and test
 - gpio thingy for SFP switching
 - iperf
 
 - document the watchdog
 - remove kexecboot? it's unloved and documented in the wrong place. do we have a
   test for it even?
    - it won't work on aarch64 because it needs memmap=
    - hardcodes memory size, which we should probably work out dynamically
 
 - how to put device name into the device docs
 
 - [WONT] make config.boot.commandLine a single string
   this sounds sensible but it just makes it harder to put useful comments
   against command line fragments so that we know why they're there
 
 - usefulness tiers for devices ("stable", "experimental", "wip")
 - params for ubi(fs) are a mess
 - iperf and tuning
 - wlan country code
 - create an l2tp configuration
 
 Sun Nov 26 15:37:07 GMT 2023
 
 hatching a plan ... we could do "predictable" network interfaces like this:
 
  . add a devpath attr to network/link.nix
  . get the kernel-issued name from "/sys${devpath}/net"
  . use ip link set ${oldname} name ${newname}
 
 if we had the full iproute2 thng we could keep the old name as well:
 # ip link property add dev wan altname eth1
 
 maybe we could do this with lua/netlink? no support in there currently
 for RTM_NEWLINKPROP though
 
 Maybe we'll skip doing the altname. The attraction of it is that it
 means the existing name isn't removed, so there's no possibility of a
 race.
 
 The kernel will allocate eth0 when asked for eth%d and there is no
 eth0. This might be the case where eth0 previously existed but it
 just got renamed to lan
 
 Sun Nov 26 21:20:23 GMT 2023
 
 The wrinkle here is ifwait: using netlink we can't wait for an
 interface by devpath but have to do it by name - which is a problem if
 the interface is not yet present, because there won't be a devpath
 in which to look up the name until it is.
 
 So we need a new flow
 
  - wait for devpath to exist
  - get the ifindex (which shouldn't change, even if the name does)
  - churn rtnetlink messages for that index
 
 We don't want to poll the sysfs file, but we can check it whenever
 we get a netlink message
 
 Sun Nov 26 22:33:16 GMT 2023
 
 There is no way to refer to the hardware device for a bridge interface
 by sysfs path because it has none. This is probably true of other
 virtual devices as well.
 
 ls: cannot access '/sys/class/net/vbridge0/device': No such file or directory
 
 Also, there is no way to refer to the _netdevice_ of a hardware
 interface without also knowing its default name, which doesn't help us
 if enumeration changes
 
 ls /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/net/
 enp1s0
 
 So we should only be specifying devices by devpath if they're
 hardware devices discovered by the kernel, not synthetic devices (that
 we pick the name of anyway).
 
 So maybe we don't need to rewrite ifwait, we just do it after renaming
 the device
 
 Wed Nov 29 21:28:37 GMT 2023
 
 How do we name outputs?
 
 fileystem image
 with-boot filesystem image (e.g. ubifs for belkin)
 tarball
 with-boot tarball (e.g. omnia)
 flashable combined image of kernel + filesystem (e.g. gl-mt*)
 kernel + filesystem image + dtb + tftpboot glue
 kernel + filesystem image + qemu script
 
 we could add initramfs as a separate thing for tftpboot and qemu
 (and FIT images) but it would mean not sharing a kernel with
 the outputs that require embedded initramfs
 
 we can enable with-boot variants of outputs by adding a
 boot.loader config option. if we go that route, can we
 use config options to drive the whole output thingy?
 We could have a config option that just changes "defaultOutput"
 but is that useful?
 
 Maybe the question is: we can choose a different output at build time
 rather than editing configuration - how often is this useful? I think
 tftpboot vs installable is about the only case.
 
 adding a /boot to a filesystem differs from making a combined
 flashable image because it is a config change and not a composition
 of two other already-built outputs.
 
 we could have done tftpboot that way as well, but we chose to unpack
 and repack the fdt so we don't have to build two kernels - and also so
 that we can have both outputs from the same configuration without
 editing any files.
 
 for tftpboot we don't want to make the filesystem embed the kernel
 if we need a separate kernel for booting (guessing we can't usually make
 u-boot loopback mount a downloaded filesystem image). so that points to
 not making it a config option,  _or_ to making the inclusion logic
 (hardware wants a kernel in filesystem) && !(output == tftpboot)
 which itself means the output somehow needs to be injected into the
 config
 
 nix-build  -I liminix-config=./examples/hello-from-mt300.nix  --arg device "import ./devices/my-device" --arg output=tftpboot
 
 let's see if we can not do that?
 
 repacking a ubifs to add /boot is awkward and unpleasant
 
 Thu Nov 30 14:33:08 GMT 2023
 
 ~~We need a new boot-in-rootfs output which calls rootfs with
 (config.filesystem  // { /boot ... }) when the device
 boot type is extlinux~~
 
 ~~Do we need to put it in systemConfiguration as well? Yes,
 otherwise liminix-rebuild won't install it~~
 
 We may have a problem here actually: if /boot is only set up after
 reboot, by adding a link while running the initramfs, how did the
 bootloader  find the kernel to boot in the first place? So
 we need /boot to exist and to point to the new kernel before rebooting
 into it, so we need to create it as a real directory along with /nix/store
 when making the filesystem,
 instead of relying on activate which will be too late.
 
 maybe we could extract the root directory structure creation
 as a separate output from rootfs, then there is a single place
 to put "and also add /boot"
 
 we will need to update pkgs/min-copy-closure/liminix-rebuild.sh
 to add /boot
 
 we could make the contents of /boot a derivation and then
 /boot itself is just a symlink to it. we would need to ensure that
 the derivation is part of the system closure, though
 
 Sat Dec  2 15:33:07 GMT 2023
 
 - make rootfs the directory structure
 
 Sun Dec  3 23:31:35 GMT 2023
 
 Spent too much of the weekend first fighting run-liminix-vm.sh and
 then rewriting it in Fennel, but we are now at the point that we can
 boot u-boot in qemu. However, it maps the rootfs into high memory
 where phram can find it, instead of putting it into a flash that
 _qemu_ can see as flash, so u-boot is not able to boot the kernel or
 at least not in a similar-to-hardware fashion. Once we've added that,
 we need to write a test for boots-a-kernel-in-the-filesystem
 
 Mon Dec  4 19:46:58 GMT 2023
 
 We wanted a test that we are creating an image that u-boot can boot
 using extlinux. Turns out that u-boot only has scripts to do this in
 the case that the storage device has a partition table. Which is
 representative of the Omnia mmc, but maybe not going to work for
 jffs2/ubifs
 
 (For ubifs it might be OK, there's some concept of partitions
 
 ubifs_boot=if ubi part ${bootubipart} ${bootubioff} && ubifsmount ubi0:${bootubivol}; then devtype=ubi; devnum=ubi0; bootfstype=ubifs; distro_bootpart=${bootubivol}; run scan_dev_for_boot; ubifsumount; fi
 
 )
 
 So what do we need? a disk image with a partition table and an ext4fs
 image in the only partition, and that partition to be bootable. Then
 run-liminix-vm gets a --disk-image option which causes it to use
 U-Boot instead of direct load (can we wrap it with something that sets
 up the paths so it can find u-boot and qemu?)
 
 ok, we're going to define outputs.diskimage which is like
 outputs.flashimage but it has a partition table. Then we can make a
 qemu configuration with an ext4 filesystem and defaultOutput="diskimage"
 and config.boot.loader.extlinux.enable = true
 
 sfdisk default behaviour for GPT partitioned disk is to start at sector 2048
 (sectors are 512 bytes)
 
 Device     Start   End Sectors Size Type
 disk.bin1   2048 14335   12288   6M Linux filesystem
 
 Tue Dec  5 23:54:22 GMT 2023
 
 Need mbr not gpt. At least, it takes up less space and it doesn't
 inveigle us into EFI boot.
 
 This is close to working except that it doesn't want to boot a uimage
 
 Enter choice: 1
 1:      Liminix
 Retrieving file: /boot/initramfs
 Retrieving file: /boot/kernel.gz
 append: console=ttyAMA0 panic=10 oops=panic init=/bin/init loglevel=8 root=/dev/mtdblock0 rootfstype=ext4 fw_devlink=off
 zimage: Bad magic!
 
 Thu Dec  7 19:33:02 GMT 2023
 
 virtio devices don't have standard major/minor so we can't create
 device nodes for them at build time. Either we mount devtmpfs in the
 initramfs (do we then have to move it to /target?) or we parse the
 /sys/block/vda/vda1/dev node to get 253:1 or whatever
 
 Fri Dec  8 16:36:07 GMT 2023
 
 We'd like to remove the ugly special handling of qemu dtb. Here are
 some thoughts
 
 1) qemu provides its guest the correct DTB for the configured hardware.
 This is a desirable thing and we wish more platforms did it, so would
 like not to replace it with a static dtb if we can avoid that
 
 2) so we need some kind of config option that says "platform provides the
 device tree" (or alternatively, "we need a static dtb, platform doesn't
 provide it").
 
 config.boot.platformProvidesDeviceTree
 
 
 
 Monday
 
 so where are we? we've removed the need for every hardware device to
 be able to build flashimage, because not every hw device (looking at you,
 bellkin/turris) works like that.
 
 for the belkin we can have imports = [ modules/outputs/ubimage ]
 and extlinux enabled
 
 for the nwa from Raito we'd like to have imports = [ modules/outputs/ubimage ]
 but the bootloader is mtd partition-based (or ubi volume? check?) -
 so ubimage needs to know how to do that
 
 perhaps we need an output for "smash together a kernel and a
 filesystem image that does not also contain a kernel, and don't
 put a partition table on the front"
 
 diskimage {
   partitionType = "mtd" ;  # or "mbr" or maybe "gpt"
   partitions = [ o.uimage o.rootfs ];
 }
 
 
 
 
 for the turris we need to check but proceeding on the assumption
 it wants a tarball with extlinux enabled
 
 https://docs.turris.cz/geek/schnapps/schnapps/#export-and-import
 https://wiki.turris.cz/en/howto/omnia_booting_from_external_storage
 
 if we adopt this as our installation format then we are not
 reformatting the flash and will keep the btrfs that the device
 was shipped with.
 
 https://forum.turris.cz/t/update-to-5-1-x-by-medkit/13986/12
 suggests that we could install a custom medkit from the
 vendor OS
 
 => btrsubvol mmc 0:1
 ID 257 parent 5 name /@
 ID 259 parent 5 name /@factory
 
 there don't seem to be any other btr commands in u-boot
 
 Tue Dec 12 14:38:53 GMT 2023
 
 from the source code, to get to the various omnia revovery modes
 
 uboot> setenv omnia_reset 3 # or 1..n
 uboot> setenv boot_targets rescue
 uboot> boot
 
 // reset boot_targets to default value.
 
 Tue Dec 12 22:44:34 GMT 2023
 
 The hold-down-reset-until-n-leds-flash support depends quite heavily
 on the post-boot Linux environment, in that it appears to be passing
 omniarescue=3 rescue_mode=3 to the kernel command line -> pid 1
 cmdline
 
 On the other hand, it is described as being able to boot from usb
 stick if there's a boot.scr on the usb stick, so maybe we just do
 that. The installation process could then be "boot usb, dd the
 disk image to mmc, reboot, remove usb, realise we got the wrong root=".
 Hmm.
 
 * Could we edit extlinux.conf for first boot? But bear in mind it's a
 link to a store file.
 
 * Could we have extlinux.conf point at mmc0 and somehow override it for the
 usb stick boot?
 
 * Could preinit try multiple root mounts until it gets one that works?
 
 * maybe we could detect omniarescue on kernel command line and switch to
 usb root?
 
 * maybe outputs.usbstick could generate a customised rootfs image?
 it might be unworkable to
 
 (narrator: it boots from mmc0 first and usb stick second, so that's not
 particularly useful)
 
 
 
 
 Device 0: Vendor: SanDisk Rev: 1.00 Prod: Cruzer Blade
             Type: Removable Hard Disk
             Capacity: 7632.0 MB = 7.4 GB (15630336 x 512)
 ... is now current device
 Scanning usb 0:1...
 No EFI system partition
 fdt_find_or_add_subnode: chosen: FDT_ERR_BADSTRUCTURE
 ERROR: /chosen node create failed
  - must RESET the board to recover.
 
 Thu Dec 14 15:32:39 GMT 2023
 
 from the omnia rescue image, we have
 
 ## Loading kernel from FIT Image at 01700000 ...
 
      Load Address: 0x00800000
      Entry Point:  0x00800000
 
 
 int lzmaBuffToBuffDecompress(unsigned char *outStream, SizeT *uncompressedSize,
                              const unsigned char *inStream, SizeT length)
 
     err = image_decomp(os.comp, load, os.image_start, os.type,
                            load_buf, image_buf, image_len,
                            CONFIG_SYS_BOOTM_LEN, &load_end);
 
 configs/mvebu_db_armada8k_defconfig:CONFIG_SYS_BOOTM_LEN=0x800000
    default 0x4000000 if PPC || ARM64
    default 0x1000000 if X86 || ARCH_MX6 || ARCH_MX7
    default 0x800000
 
 Fri Dec 15 19:21:53 GMT 2023
 
 Let's put some English words on the page to explain the above
 gibberish. Since I upgraded the U-Boot on my Turris Omnia, it has
 stopped being able to tftpboot.
 
 Uncompressing Kernel Image
 lzma compressed: uncompress error 7
 Must RESET board to recover
 
 "uncompress error 7" means there is not enough space in the output
 buffer, and the output buffer is set by CONFIG_SYS_BOOTM_LEN which is
 8192k, smaller than the uncompressed 12104200 of our kernel.
 
 So how can we fix?
 
 * one possibility is to do what the turris rescue mode does: build an
 uncompressed uimage and then lzma the result.  u-boot can uncompress
 the received file using lzmadec command. we'd want to do this without
 breaking tftpboot on every other device that might not have an lzmadec
 command
 
 * is there bloat in the kernel we could trim? probably not 4MB of it
 
 * we could build a custom u-boot with a bigger buffer. this _might_
 not be a completely stupid idea as it's only the people prepared to
 open the box that would be doing tftp workflows anyway, so provided
 it's possible to replace u-boot without bricking it
 
 * we could try building zimage instead of uimage and use bootz to
 start it
 
 Sat Dec 16 11:15:56 GMT 2023
 
 there is another use case for weird tftpboot derivation, which is the
 device Raito has ported to where you need to wave a magic chicken at
 u-boot on each command line
 
 Sat Dec 16 23:32:11 GMT 2023
 
 Turns out that even when using an uncompressed uimage, u-boot runs the
 code to check the decompressed size, so that doesn't help at all.  But
 booting a zImage works fine. I am committing a first pass of
 modules/outputs/tftpbootlz.nix which does this using a lot of
 copy-paste and (ironically) no lzma stuff at all.
 
 Sun Dec 17 16:25:30 GMT 2023
 
 it's started failing to mount root on arm32 because it's not recognising
 the reserved-memory and something is trashing the phram filesystem
 
         reserved-memory {
 
                 phram-rootfs {
                         reg = <0x1400000 0x1900000>;
                         compatible = "phram";
                 };
         };
 
 Sun Dec 17 17:13:54 GMT 2023
 
 * We need to write the fdt phram differently on 64 bit vs 32 bit
   (address-cells and size-cells should be 2 or 1)
 
 * this might be why it wasn't working on mips (can we test this
 somehow in qemu or do we need to plug a device in?)
 
 qemu user-mode networking has a builtin tftp server.
 
 so we need a test that builds the tftpboot target for each qemu arch,
 and then does run-liminix-vm with the --lan and --u-boot options, then
 drives it with expect
 
 
 * maybe tftpboot[lz] could be reintegrated with the regular one somehow
 
 Fri Dec 22 15:11:35 GMT 2023
 
 We have a working test for tftpboot, on all platforms, which took a
 while.
 
 * tftpbootlz needs to be updated with what we learned, or merged
 back into it
 
 * omnia install
 
 - build a stripped-down installer image which can be put on a
  usb stick
 - from openwrt on the device, use fw_setenv to set boot order
 - boot into the installer image-
  reformat the emmc as per requirements
 - PREFIX=/mnt  liminix-rebuild
 - profit
 
 Could we liminix-rebuild into /some/prefix/nix/store this would
 actually be useful both for this boot-from-usb scenario and for
 levitate. Looks like min-copy-closure doesn't need anything much on
 the destination system except a working sshd and maybe an empty
 /nix/store and /persist. Potentially we could even do it without
 chroot (which would save running a second sshd), just add a prefix on
 the paths
 
 what's the fallback? we're not touching the turris rescue
 system (which is in nor flash) so we can expect all the
 knightrider modes to continue to workto be able to
 boot back into that and restore the vendor os? I think so
 
 Fri Dec 22 16:56:40 GMT 2023
 
 If we're going to use fw_setenv to change boot order,
 we could equally well boot from tftp and not need the
 usb stick
 
 fw_setenv boot_targets "tftp mmc0 nvme0 scsi0 usb0 pxe dhcp"
 setenv bootcmd_tftp "echo TFTP BOOT"
 
 how can we get a tftp boot into few enough characters to reasonably
 put it in an environment variable?
 - use dhcp?
 - embed bootargs into the fdt
 
 Fri Dec 22 21:10:53 GMT 2023
 
 * dtb needs size and offset of uncompressed root filesystem to add
 reserved-memory and cmdline params
 
 * setting these in the dtb will change the size of the dtb
 
 * am assuming that we don't want the kernel to relocate into
  ram that clashes with the root fs
 
 * should we care about phys mem fragmentation?
 
 conclusion:
 
 hardware.loadAddress
 		  <uncompressed/relocated kernel>
 tftp.loadAddress
 		  <space for uncompressed root>
 		  uimage or zimage
 		  dtb
 		  compressed root
 
 
 [ should we rename hardware.loadAddress to something that expresses
 more clearly it's the _kernel_ load address? ]
 
 [ another thing we need to do is stop building two kernels
  because the uimage and zimage derivations are different ]
 
 Sat Dec 23 18:07:43 GMT 2023
 
 Addendum: for a zimage we need the compressed kernel to be at the
 highest address, otherwise it prints "Starting" and then hangs
 indefinitely.
 
 I believe this to be because the kernel decompressor sets up a stack
 directly after the compressed payload, so will trash the fdt if it was
 also there. The bug didn't exhibit on Turris Omnia with the same
 layout, but maybe that was just luck.
 
 Sat Dec 23 18:11:04 GMT 2023
 
 Here is scope of work for Turris:
 
 (I) we need to build a suitable tftpboot image for
 recovery/install.
 
 - disk partitioning tools and mkfs stuff
 - kernel with all the filesystems
 - dhcp client for connecting to wired network
 
 (II) we need instructions for building the real system
 and using min-copy-closure to copy and install the system
 configuration of the real one into /mnt
 
 (III) probably try the same recovery image as a USB stick
 
 (IV) I've lost track of what we're doing with /boot, does that work?
 
 (V) gpio thingy for SFP switching
 
 (VI) iperf, performance testing
 
 (VII) put device name and usefulness tiers ("stable", "experimental", "wip") in the docs
 
 (VIII) params for ubi(fs) are a mess
 
 (IX) wlan country code
 
 Tue Dec 26 16:23:37 GMT 2023
 
 I seem to have lost a chunk of notes here. Have added
 systemConfiguration/bin/install which does the stuff to copy the right
 files into /bin and wherever. There is currently no test for it though
 
 We could further simplify liminix-rebuild by adding --reboot as a flag
 to install
 
 Tue Dec 26 21:38:43 GMT 2023
 
 To be any use, the test needs to be end-to-end - as in, rather than
 just checking some files are copied, test that the machine rebooted
 successfully
 
 Fri Dec 29 18:36:16 GMT 2023
 
 Our test for liminix-rebuild uses qemu block device and ext4 instead
 of phram because -device loader doesn't seem to survive a reboot.
 And it needs some free space in the ext4 partition inside the
 mbr image so that it can install new stuff. However, the
 filesystem is sized to be near-full.
 
 If the mbrimage output is to be much use, probably there should be
 some way of telling it how big the disk is. Maybe it should use
 hardware.flash.size?
 
 UBI also does a bad job of integrating into the hardware.flash hierarchy
 (but ubi is also more complicated as the ubi volumes are "nested" inside
 an MTD partition)
 
 To move forwards with this test I think I will make it not depend on
 mbrimage for now, but we have to come back to this. Maybe importing
 the mbrimage module provides new hardware.disk = { partitions, size etc}
 config options.
 
 Sun Dec 31 23:52:04 GMT 2023
 
 https://developer.ridgerun.com/wiki/index.php/Setting_up_fw_printenv_to_modify_u-boot_environment_variables#Preparing_the_fw_env.config_file
 
 can we extract the fw_env config data somehow to produce an appropriate
 file for the device?
 
 the device config needs to specify partition name and offset at minimum,
 possibly also size.
 
 we can create a service that writes the config based on those values. but
 if we are to be using fw_setenv from the shell, there is no service
 which depends on that service. whatever defines the service also needs
 to add it to system.services so that the recovery system can specify it
 
 Sat Jan  6 12:30:27 GMT 2024
 
 How do we min-copy-closure to the device when we don't have anything
 hooked to the LAN port? It's rather easy to break the WAN  connection
 when it involves going out to the internet and back
 
 * Don't want to plug it into the actual lan because it's doing dhcp service
  and that is going to confuse
 
 * the machine we're copying from is loaclhost
 
 * we could do some kind of port forwarding thing? maybe a port forward on
   run-border-vm qemu user networking ...
 
 * static route on loaclhost?
 
   512  sudo ip netns add test-lan
   514  sudo ip link set dev enp1s0 netns test-lan
 
   525  sudo ip link add veth-test-lan type veth peer veth1 netns test-lan
   533  sudo  ip netns exec test-lan ip link add name br0 type bridge
   536  sudo  ip netns exec test-lan ip link set veth1 master br0
   537  sudo  ip netns exec test-lan ip link set enp1s0 master br0
        sudo  ip netns exec test-lan /nix/store/dh66q9k402pwpmmgc983xwmwb3vvvjbr-busybox-1.36.1/bin/busybox udhcpc -i br0
 
 then we could add a route to 10.8.0.1/32 with dev veth-test-lan ?
 
 Sat Jan  6 20:52:45 GMT 2024
 
 This is all beside the point right now because the _recovery_ system
 does not run all this stuff - it just has a dhcp client on the lan
 interface. We could plug it straight into the switch.
 
 
 As we already just plugged it into enp1s0 on loaclhost, could we
 do somethin to put it on the lan from there? add it to vbridge0?
 
 Sun Jan  7 15:30:57 GMT 2024
 
 Turns out we should have used a working ethernet cable.
 
 Sun Jan  7 15:31:14 GMT 2024
 
 OK, so
 
 # on device
 mount /dev/mmcblk0p1 /mnt
  [ take a snapshot if needed ]
  [ clear out the turrisos files ]
 ls /mnt/@
 
 # on build
 
 $ nix-build -I liminix-config=./examples/rotuer.nix --arg device "import ./devices/turris-omnia" -A outputs.systemConfiguration
 $ nix-shell --run "min-copy-closure -r /mnt/@  root@recovery.lan   result "
 
 # on device
 
 $ mkdir /mnt/@/persist
 $ /mnt/@/nix/store/swf3vn9bzx198c0cwp6naq0glqa9192n-make-stuff-armv7l-unknown-linux-musleabihf/bin/install /mnt/@/
 
 this fails because it tries to copy from the unprefixed nix
 store. Also probably it should mkdir $prefix/persist. Also it needs to
 create $prefix/boot: it's too late to do that with `activate`
 because u-boot will need it to exist in order to load the initramfs
 that runs activate
 
 Thu Jan 11 23:36:47 GMT 2024
 
 squashfs rootfsType doesn't rebuild when the kernel config is changed
 
 Mon Jan 22 19:04:45 GMT 2024
 
 setenv serverip 10.0.0.1
 setenv ipaddr 10.0.0.8
 compraddr=0x01000000
 tftpboot ${compraddr} recovery.img.lzma
 setexpr writeaddr ${filesize} + $compraddr
 lzmadec ${compraddr} $writeaddr
 usb start
 usb dev 0
 wdt dev watchdog@20300
 wdt stop
 usb write ${writeaddr} 0 ${filesize}
 
 
 Thu Jan 25 11:55:36 GMT 2024
 
 openwrt:
 CONFIG_BROADCOM_PHY=m
 CONFIG_FIXED_PHY=y
 CONFIG_GENERIC_PHY=y
 CONFIG_IP17XX_PHY=m    ?
 CONFIG_MARVELL_PHY=y
 CONFIG_MVSW61XX_PHY=y  ?
 CONFIG_RTL8366RB_PHY=m ?
 CONFIG_RTL8366S_PHY=m ?
 CONFIG_RTL8367B_PHY=m ?
 CONFIG_SWPHY=y
 CONFIG_USB_PHY=y
 
 CONFIG_FIXED_PHY=y
 CONFIG_GENERIC_PHY=y
 CONFIG_MARVELL_PHY=y
 CONFIG_PHY_MVEBU_A3700_COMPHY=y
 CONFIG_PHY_MVEBU_A38X_COMPHY=y
 CONFIG_SWPHY=y
 #
 
 Sat Jan 27 18:14:13 GMT 2024
 
 To make the recovery system (and tftpboot generally) more useful, it
 would be good to resize the root fs on boot. Need to do this before
 anything that writes to it
 
 Mon Jan 29 21:50:59 GMT 2024
 
 something is corrupted in the uncompressed rootfs
 
 
 $ head -c $(printf "%d" 0x2be0000) rootfs | sha1sum
 142571fe0436c18191727d1d4c2fd32163c1f2e1  -
 => sha1sum 0x1000000 2be0000
 sha1 for 01000000 ... 03bdffff ==> 142571fe0436c18191727d1d4c2fd32163c1f2e1
 
 but!
 
 $  head -c $(printf "%d" 0x2bf0000) rootfs | sha1sum
 7aa004ba87c6772bade491fbade164e2dfe100f9  -
 => sha1sum 0x1000000 2bf0000
 sha1 for 01000000 ... 03beffff ==> 1a0923a94784d0c0b86006c5e6fff1649770dad3
 
 something is trashing something in the range 03be0000 - 03beffff
 or else it's not being decompressed properly
 
 pxefile_addr_r=0x1900000
 ramdisk_addr_r=0x2200000
     scriptaddr=0x1800000
 fdt_addr_r=0x2000000
 fdtcontroladdr=7fb19b30
 fdtfile=armada-385-turris-omnia.dtb
      fdt_high=0x10000000
   initrd_high=0x10000000
 kernel_addr_r=0x1000000
               0x1700000;
               0x10000000
 
 Sun Feb  4 11:55:00 GMT 2024
 
 restructuredtext headings:
 
 https://devguide.python.org/documentation/markup/#sections
 
 
 ####### chapter (one per filename)
 *******
 =======
 -------
 
 Mon Feb  5 09:57:52 GMT 2024
 
 Before calling the Omnia "done" I'd like to get it to the point that
 I can actually use it as a CPE. This means
 
 - writing something down about how we handle static addresses
   - hosts that need static ipv6 can configure it themselves as ::n
     where n is a small number. this won't clash with slaac
   - the `hosts` param to dnsmasq can specify static ipv4
 
 - dealing with port forwards and allowed incoming in the firewall
 
 - would be quite cool to run sniproxy instead of forwarding to
   loaclhost (extra credit)
 
 Sat Feb 10 18:23:54 GMT 2024
 
 ARGH KERNEL
 
 You can't define CONFIG_NETFILTER=y in a monolithic kernel and expect
 later to separately build some modules that use it, because there are
 a bunch of symbols that only get defined if certain other CONFIG
 options are set at the time that the monolithic kernel is built.
 
 https://github.com/torvalds/linux/blob/master/net/netfilter/core.c#L689
 
 Another example is
 https://github.com/torvalds/linux/blob/master/include/linux/netdevice.h#L160
 - if you decide after building the kernel that you're going to build
 some wireless modules, you can't do that without rebuilding the kernel
 so that it knows to expect them
 
 The moral of the story seems to be: if you have a compiled Linux kernel source tree and you change some symbol from "is not set" to m and then run  make modules, you cannot in general expect that newly compiled  module to work.
 
 AP advertised VHT without HT, disabling HT/VHT/HE
 
 TODO
 
 - [done] support kernel version as parameter to builder pkgs/kernel/default.nix
 - [done] extract the change in how module loading works from omnia device config,
   and fix the other thing that uses it
 - [axed] wlan module to take 'backported' as a parameter
   half of the omnia conditionalConfig can go into the module
 - [done] upgrade omnia to kernel v6
 - figure out what mdns we need for local hostname resolution
   (maybe bridging lan/wlan)?
 - [DONE] slow wifi because "AP advertised VHT without HT, disabling HT/VHT/HE"
 - [DONE] add local domain to secrets
 - run sniproxy instead of forwarding
 - [test] forward some port to loaclhost 22 for inbound ipv4 ssh
 
 
 Mon Feb 12 21:50:35 GMT 2024
 
 # find  /run/service-state/dhcp6c.wan.link.pppoe/address/
 /run/service-state/dhcp6c.wan.link.pppoe/address/
 /run/service-state/dhcp6c.wan.link.pppoe/address/2001-8b0-1111-1111-0-ffff-51bb-4cf2_LFoo015bSsM
 /run/service-state/dhcp6c.wan.link.pppoe/address/2001-8b0-1111-1111-0-ffff-51bb-4cf2_LFoo015bSsM/valid
 /run/service-state/dhcp6c.wan.link.pppoe/address/2001-8b0-1111-1111-0-ffff-51bb-4cf2_LFoo015bSsM/preferred
 /run/service-state/dhcp6c.wan.link.pppoe/address/2001-8b0-1111-1111-0-ffff-51bb-4cf2_LFoo015bSsM/len
 /run/service-state/dhcp6c.wan.link.pppoe/address/2001-8b0-1111-1111-0-ffff-51bb-4cf2_LFoo015bSsM/address
 #
 
 valid 7199 preferred 3599
 
 Tue Feb 13 19:44:57 GMT 2024
 
 Before we put this back live, would be good to
 
 [done] 1) move the leases file into /persist
 
 I think we'll do /persist/service/<name>/ and change ssh to use the same
 scheme.
 
 we could put mkpersist() in serviceFns which would check for /persist
 and return a directory in /persist/service/ or /run/service-state
 
 (will something bad happen if we use /run/service-state? it will also
 expose the thingy as an output, but whether it's accessible that way
 will depend on whether there's a writable fs or not, which is unexpected)
 
 : rename service-state to  /run/services/outputs
 : on boot
 :  if /persist
 :    create /persist/services/state and symlink /run/services/state to it
 :  else create /run/services/state
 
 
 [done] 2) maybe change the local domain back to .lan?  setting up
   systemd-networkd with search domains is an awful faff
 
 [done] 3) work out what to do with incoming ssh from wan
 
 - For noetbook and thinkpad we have a vpn anyway so can expect to
   reach loaclhost directly using ipv6
 
 - stop ssh from ever trying to get to our ipv4 address.
   - we could get rid of A record for loaclhost.telent.net but
     there are a bunch of CNAMES pointing at it for web servers.
   - we could reject incoming connections to tcp4 port 22 in firewall
     and then there is a clear signal to Dont Do That Then
 
 - for emergency use, dnat ipv4 2200 and 2201 to rotuer and loaclhost
 
 Tue Feb 13 22:31:03 GMT 2024
 
 * the reason we can't reboot is that there is a service to add each
 lan device to the bridge which does ifwait $dev running, which doesn't
 return until there's something plugged in. So s6-rc hangs indefinitely
 until the lan switch is fully populated. This is definitely a "next
 milestone" thing.
 
 * another example of "thing that depends on other thing but which it
   is actually OK if neither of them happen" might be "mount a
   filesystem if there is a usb mass storage device attached"
 
 * I don't know if failover also fits into the model we don't quite
   have. LTE route depends on pppoe not being healthy
 
 we can have services (or bundles) that aren't part of the default target,
 and plumb them into events of some kind (netlink?) to bring them up/down?
 
 we can use s6-rc instanced services:
 https://skarnet.org/software/s6/instances.html
 
 "s6-instance-create and s6-instance-delete are relatively expensive operations, because they have to recursively copy or delete directories and use the synchronization mechanism with the instance supervisor, compared to s6-instance-control which only has to send commands to already existing supervisors. If you are going to turn instances on and off on a regular basis, it is more efficient to keep the instance existing and control it with s6-instance-control than it is to repeatedly create and delete it. "
 
 Probably we need something that reads netlink messages and converts
 them to a format that we can use to control services. Is there a
 benefit to using services here and not just running commands? it means
 the system state change we desire will stay changed.
 
 TODO items not to lose track of
 
 - speed testing (iperf)
 - make gl-ar750 tftpboot build again
 - finish belkin
 - install sniproxy
 - is there something simple we can do to make it reboot again?
 - turn rotuer,extneder examples into "profiles" that don't embed
   hardware specifics
 
 Thu Feb 15 11:50:56 GMT 2024
 
 1) to make tftpboot work with old bootm implementations we need
 
 - compressed root
 - uncompressed root
 - kernel with dtb
  dtb needs to know where uncompressed rootfs is and how big
 
 2) if the image is a zImage (arm32) or an Image (arm64) we have to stick
 with the three-arg bootz, and the dtb has to be lower in ram than the kernel
 
 Fri Feb 16 15:43:32 GMT 2024
 
 DHCP6c refresh is still wrong. We get updates for an address that
 hasn't changed prefix or length, when the expiry times have changed,
 and we can't action that by remove;add because remove will wipe out
 any routes through the interface but add won't put them back
 
 We can use "change" for both adds and changes, but we need to know that
 a change is not a delete
 
 The "identity" of an address is the address itself: kernel won't
 let you add the same address with two different prefixes.
 
 Keeping it simple, we could call "change" on every address in the
 new-addresses list and "del" on every address in old-addresses
 that is no longer in new-addresses
 
 If the upstream has changed length, "ip addr change" is ignored,
 so it needs to be in deleted as well as added/changed