From 35be9c66bfa6dd03437f919ec610aed0e9b20b58 Mon Sep 17 00:00:00 2001
From: tv <tv@krebsco.de>
Date: Wed, 12 Dec 2018 00:34:32 +0100
Subject: [PATCH] lib.normalize-ip6-addr: no :: for single section

---
 lib/default.nix | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/lib/default.nix b/lib/default.nix
index 64b2d48ab..347830e8c 100644
--- a/lib/default.nix
+++ b/lib/default.nix
@@ -93,7 +93,13 @@ let
           in
             if max.pos == 0
               then a
-              else "${concatStringsSep ":" lhs}::${concatStringsSep ":" rhs}";
+              else let
+                sep =
+                  if 8 - (length lhs + length rhs) == 1
+                    then ":0:"
+                    else "::";
+              in
+                "${concatStringsSep ":" lhs}${sep}${concatStringsSep ":" rhs}";
 
         drop-leading-zeros =
           let