add netlink socket

it's not hooked up to anything yet, but it proves we can
do this with lualinux

THOUGHTS.txt

@@ -4676,3 +4676,57 @@ needs to filter, but the client will anyway have to do some message
 parsing so they can distinguish add from remove
 
 * where do we start?
+
+Sun Apr 21 13:31:48 BST 2024
+
+We have the mechanics of it working (albeit implemented in the
+simplest possible terms), we need to glue it to some I/O
+
+1) open a netlink socket and read the events from it
+
+2) "create a PF_UNIX socket of type SOCK_STREAM, and accept connections on it, then each time you accept a connection, you get a new fd"
+
+- accept connection
+- read terms from it
+- register callback that writes event to connected socket
+
+minisock has no support for "test if fd is ready" or "wait for [fds]
+to become ready", either we need poll() or we could add a call for "is
+this fd ready to read" and use coroutines. Fork minisock or add as
+another library?
+
+[ if we fork minisock we could expose the protocol param to Lua
+so we could use it for netlink ]
+
+Tue Apr 23 19:13:45 BST 2024
+
+we could convert from minisock to lualinux. if we can also use that to
+get rid of nellie and/or lfs, the size tradeoff is minimal
+
+---
+
+Is there some way we could test the devout event loop?
+
+I can register a fd with a callback
+when the fd is ready, my callback is called
+when the callback return true it remains registered
+when the callback return true it is unregistered and the fd is closed
+
+loop.register
+loop.registered?
+loop.feed
+
+Tue Apr 23 20:34:03 BST 2024
+
+I think we could make the event loop abstraction leak less?
+It's not actually a _loop_, all the actual GOTO 10 happens
+outside of it
+
+1) see if we can do netlink in lualinux
+2) if so, convert it to lualinux
+3) add netlink socket to event loop
+4) make it send messages to subscribers
+5) package it
+6) make inout test use it instead of uevent-watcher
+7) write an inout test variant that has the stick inserted
+  at boot time already

pkgs/default.nix

@@ -71,6 +71,7 @@ in {
   levitate = callPackage ./levitate {};
   libubootenv = callPackage ./libubootenv {};
   linotify = callPackage ./linotify {};
+  lualinux = callPackage ./lualinux {};
 
   # we need to build real lzma instead of using xz, because the lzma
   # decoder in u-boot doesn't understand streaming lzma archives

pkgs/devout/default.nix

@@ -6,7 +6,7 @@
 , fennel
 , stdenv
 , fennelrepl
-, minisock
+, lualinux
 }:
 stdenv.mkDerivation {
   name = "devout";
@@ -15,12 +15,12 @@ stdenv.mkDerivation {
   installPhase = ''
     mkdir -p $out/bin
     cp -p ${writeFennel "devout" {
-      packages = [fennel anoia nellie lua.pkgs.luafilesystem minisock];
+      packages = [fennel anoia nellie lua.pkgs.luafilesystem lualinux];
       mainFunction = "run";
     } ./devout.fnl} $out/bin/devout
   '';
   checkPhase = ''
-    LUA_CPATH=${minisock}/lib/lua/5.3/?.so\;$LUA_CPATH \
+    LUA_CPATH=${lualinux}/lib/lua/5.3/?.so\;$LUA_CPATH \
     fennelrepl ./test.fnl
   '';
   doCheck = true;

pkgs/devout/devout.fnl

@@ -1,8 +1,8 @@
-(local sock (require :minisock))
+(local ll (require :lualinux))
 (local { : view } (require :fennel))
 
 (fn trace [expr]
-  (doto expr (print :TRACE (view expr))))
+  (do (print :TRACE (view expr)) expr))
 
 (fn parse-uevent [s]
   (let [at (string.find s "@" 1 true)
@@ -50,29 +50,39 @@
      :unsubscribe (fn [_ id] (tset subscribers id nil))
      }))
 
-;; #define POLLIN          0x0001
-;; #define POLLPRI         0x0002
-;; #define POLLOUT         0x0004
-;; #define POLLERR         0x0008
-;; #define POLLHUP         0x0010
-;; #define POLLNVAL        0x0020
+;; grepped from kernel headers
+
+(local POLLIN          0x0001)
+(local POLLPRI         0x0002)
+(local POLLOUT         0x0004)
+(local POLLERR         0x0008)
+(local POLLHUP         0x0010)
+(local POLLNVAL        0x0020)
+
+(local AF_LOCAL 1)
+(local AF_NETLINK 16)
+(local SOCK_STREAM 1)
+(local SOCK_DGRAM 2)
+(local SOCK_RAW 3)
+(local NETLINK_KOBJECT_UEVENT 15)
 
 (fn unix-socket [name]
-  (let [addr (.. "\1\0"  name  "\0\0\0\0\0")
-        (sock err) (sock.bind addr)]
-    (assert sock err)))
+  (let [addr (.. "\1\0"  name  "\0\0\0\0\0")]
+    (match (ll.socket AF_LOCAL SOCK_STREAM 0)
+      fd (match (ll.bind fd addr)
+           0 (doto fd (ll.listen  32))
+           (nil err) (values nil err))
+      (nil err) (values nil err))))
 
 (fn pollfds-for [fds]
-  (table.concat (icollect [_ v (ipairs fds)] (string.pack "iHH" v 1 0))))
+  (icollect [_ v (ipairs fds)]
+    (bor (lshift v 32) (lshift 1 16))))
 
 (fn unpack-pollfds [pollfds]
-  (var i 1)
-  (let [fds {}]
-    (while (< i (# pollfds))
-      (let [(fd _ revents i_) (string.unpack "iHH" pollfds i)]
-        (if (> revents 0) (tset fds fd revents))
-        (set i i_)))
-    fds))
+  (collect [_ v (ipairs pollfds)]
+    (let [fd (band (rshift v 32) 0xffffffff)
+          revent (band v 0xffff)]
+      (values fd revent))))
 
 (fn parse-terms [str]
   (print :terms str)
@@ -80,7 +90,7 @@
     (string.match n "(.-)=(.+)")))
 
 (fn handle-client [db client]
-  (match (trace (sock.read client))
+  (match (ll.read client)
     "" (do
          (db:unsubscribe client)
          false)
@@ -88,11 +98,18 @@
         (db:subscribe
          client
          (fn [e]
-           (sock.write client (view e)))
+           (ll.write client (view e)))
          (parse-terms s))
         true)
     (nil err) (do (print err) false)))
 
+(fn open-netlink [groups]
+  (match (ll.socket AF_NETLINK SOCK_RAW NETLINK_KOBJECT_UEVENT)
+    fd (doto fd (ll.bind (string.pack "I2I2I4I4" ; family pad pid groups
+                                      AF_NETLINK 0 0 groups)))
+    (nil errno) (values nil errno)))
+
+
 (fn event-loop []
   (let [fds {}]
     {
@@ -101,27 +118,30 @@
              (each [fd revent (pairs revents)]
                (when (not ((. fds fd) fd))
                  (tset fds fd nil)
-                 (sock.close fd))))
+                 (ll.close fd))))
      :fds #(icollect [fd _ (pairs fds)] fd)
     :_tbl #(do fds)                    ;exposed for tests
      }))
 
 (fn run []
-  (let [[sockname] arg
+  (let [[sockname nl-groups] arg
         s (unix-socket sockname)
         db (database)
+        nl (open-netlink nl-groups)
         loop (event-loop)]
     (loop:register
      s
-     #(match (sock.accept s)
+     #(match (ll.accept s)
         (client addr)
         (do
           (loop:register client (partial handle-client db))
           true)))
+    (loop:register
+     nl
+     #(do (print :netlink (ll.read nl)) true))
     (while true
-      (let [pollfds (pollfds-for (loop:fds))
-            (rpollfds numfds) (sock.poll pollfds 1000)]
-        (when (> numfds 0)
-          (loop:feed (unpack-pollfds rpollfds)))))))
+      (let [pollfds (pollfds-for (loop:fds))]
+        (ll.poll pollfds 5000)
+        (loop:feed (unpack-pollfds pollfds))))))
 
 { : database : run : event-loop  }

pkgs/lualinux/default.nix

@@ -0,0 +1,22 @@
+{ lua, lib, fetchFromGitHub }:
+let
+  pname = "lualinux";
+  src = fetchFromGitHub {
+    repo = "lualinux";
+    owner = "philanc";
+    rev = "1d4c962aad9cbe01c05df741b91e8b39c356362c";
+    hash = "sha256-+Ys4sERG+TI8nRzG38UP+KqbH0efspaX0j4IHCt56RI=";
+  };
+in lua.pkgs.buildLuaPackage {
+  inherit pname;
+  version = "0.1";              # :shrug:
+
+  inherit src;
+  makeFlags = [ "LUADIR=."  "lualinux.so" ];
+
+  installPhase = ''
+    mkdir -p "$out/lib/lua/${lua.luaversion}"
+    cp ${pname}.so "$out/lib/lua/${lua.luaversion}/"
+  '';
+
+}