From ea56d2e85e1cae7a7998ccce879d50f574e86e0f Mon Sep 17 00:00:00 2001
From: tim <tim@treehouse.org.za>
Date: Fri, 17 Sep 2021 09:58:18 +0200
Subject: [PATCH] Only send an ipv6 address when one exists.

---
 update_ip.sh | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/update_ip.sh b/update_ip.sh
index 70c25f4..11befec 100755
--- a/update_ip.sh
+++ b/update_ip.sh
@@ -5,9 +5,10 @@ server=ns1.example.com
 zone=dyn.example.com
 host=desktop
 secret=""
+iface=eth0
 
 new_ip4=$( wget -4 -q -O - https://treehouse.org.za/ip )
-new_ip6=$( ip -6 addr show eth0 | grep global | grep -oP '(?<=inet6\s)[\da-f:]+' )
+new_ip6=$( ip -6 addr show ${iface} | grep global | grep -oP '(?<=inet6\s)[\da-f:]+' )
 
 cur_ip4=$( nslookup -type=a ${host}.${zone} | grep -oP '(?<=^Address:\ )\d+(\.\d+){3}$' )
 cur_ip6=$( nslookup -type=aaaa ${host}.${zone} | grep -oP '(?<=^Address:\ )[\da-f:]+$' )
@@ -44,13 +45,18 @@ else
         rm -f "${HOME}/${cache}"
 fi
 
+ipv6_line=""
+if [ -n "${new_ip6}" ]; then
+    ipv6_line="update add ${host}.${zone}. 60 AAAA ${new_ip6}"
+fi
+
 update=$( cat <<-EOF
         server ${server}
         zone ${zone}.
         key ${host}.${zone} ${secret}
         update delete ${host}.${zone}.
         update add ${host}.${zone}. 60 A ${new_ip4}
-        update add ${host}.${zone}. 60 AAAA ${new_ip6}
+        ${ipv6_line}
         update add ${host}.${zone}. 60 TXT "Updated on $( date )"
         send
 EOF