Better job with domain for DHCPv6 information-request.

src/domain.c

@@ -224,7 +224,7 @@ char *get_domain6(struct in6_addr *addr)
 {
   struct cond_domain *c;
 
-  if ((c = search_domain6(addr, daemon->cond_domain)))
+  if (addr && (c = search_domain6(addr, daemon->cond_domain)))
     return c->domain;
 
   return daemon->domain_suffix;

src/rfc3315.c

@@ -1015,6 +1015,15 @@ static int dhcp6_no_relay(int msg_type, struct in6_addr *link_address, struct dh
 	    context->netid.next = NULL;
 	    state.context_tags =  &context->netid;
 	  }
+
+	/* Similarly, we can't determine domain from address, but if the FQDN is
+	   given in --dhcp-host, we can use that, and failing that we can use the 
+	   unqualified configured domain, if any. */
+	if (state.hostname_auth)
+	  state.send_domain = state.domain;
+	else
+	  state.send_domain = get_domain6(NULL);
+
 	log6_packet(&state, "DHCPINFORMATION-REQUEST", NULL, ignore ? _("ignored") : state.hostname);
 	if (ignore)
 	  return 0;