From 210b41efc0b0d3c27297fa4b1da36937d03ab5dd Mon Sep 17 00:00:00 2001
From: Daniel Barlow <dan@telent.net>
Date: Mon, 31 Mar 2025 23:17:50 +0100
Subject: [PATCH] improve robustness of ppp readiness notification

there was a race where ip-up could write ifname and then
ip6-up could write its outputs and then test ifname and
signal ready before ip-up had written the rest of its outputs
---
 modules/ppp/common.nix | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/modules/ppp/common.nix b/modules/ppp/common.nix
index 352add5..cb48eb5 100644
--- a/modules/ppp/common.nix
+++ b/modules/ppp/common.nix
@@ -40,15 +40,17 @@ let
     set +o nounset
     if test -n "''${DNS1}" ;then echo ''${DNS1} > ns1 ; fi
     if test -n "''${DNS2}" ;then echo ''${DNS2} > ns2 ; fi
-    test -e ipv6-address && echo >/proc/self/fd/10
+    touch ip-up
+    test -e ipv6-up && echo >/proc/self/fd/10
   '';
   ip6-up = writeAshScript "ip6-up" { } ''
     exec >&5 2>&5
     . ${serviceFns} 
     in_outputs ${name}
-    echo $4 > ipv6-address
     echo $5 > ipv6-peer-address
-    test -e ifname && echo >/proc/self/fd/10
+    echo $4 > ipv6-address
+    touch ipv6-up
+    test -e ip-up && echo >/proc/self/fd/10
   '';
   literal_or_output =
     let