fix: always use ipv6 to connect to nameserver

docker's internal resolver may return ipv4 addresses

opendkimd.sh

@@ -50,9 +50,14 @@ case $1 in
 
     txt="`cat $tkey | tr -d "\n" | cut -d '"' -f 2,4 | tr -d '"' | tr -d " "`"
 
+    # Register the TXT record on every nameserver. Log failures but
+    # continue anyway.
+    ok "Registering public key records"
+    for node in `drill -Q ns $SUTTY`; do
+
       # Craft record
       cat >/tmp/dns <<DNS
-server knot.$node
+server `drill -Q aaaa knot.$node`
 zone _domainkey.${SUTTY}.
 origin _domainkey.${SUTTY}.
 ttl 60
@@ -61,11 +66,6 @@ add ${dkey}. TXT "${txt}"
 send
 quit
 DNS
-
-    # Register the TXT record on every nameserver. Log failures but
-    # continue anyway.
-    ok "Registering public key records"
-    for node in `drill -Q ns $SUTTY`; do
       if knsupdate /tmp/dns; then
         ok "Registered public key record at ${node}"
       else