From 1ff4b838758f36dc8c54995e104dd17ba08a65a4 Mon Sep 17 00:00:00 2001
From: "William A. Kennington III" <william@wkennington.com>
Date: Sun, 13 Jul 2014 10:39:59 -0500
Subject: [PATCH] nixos/network-interfaces: Add flush upon interface going down

---
 nixos/modules/tasks/network-interfaces.nix | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/nixos/modules/tasks/network-interfaces.nix b/nixos/modules/tasks/network-interfaces.nix
index 30e2a143419..e8c770d077c 100644
--- a/nixos/modules/tasks/network-interfaces.nix
+++ b/nixos/modules/tasks/network-interfaces.nix
@@ -639,6 +639,19 @@ in
                 ''
                   echo 1 > /proc/sys/net/ipv6/conf/${i.name}/proxy_ndp
                 '';
+            preStop =
+              ''
+                echo "releasing configured ip's..."
+              ''
+              + flip concatMapStrings (i.ip4 ++ optionals cfg.enableIPv6 i.ip6) (ip:
+                let
+                  address = "${ip.address}/${toString ip.prefixLength}";
+                in
+                ''
+                  echo -n "Deleting ${address}..."
+                  ip addr del "${address}" dev "${i.name}" >/dev/null 2>&1 || echo -n " Failed"
+                  echo ""
+                '');
           };
 
         createTunDevice = i: nameValuePair "${i.name}"