From b5214f65e7828960259766670326c1f50126a15c Mon Sep 17 00:00:00 2001
From: Bryan Boreham <bjboreham@gmail.com>
Date: Fri, 10 Oct 2014 15:41:09 +0100
Subject: [PATCH] Forward DNS requests that aren't for our 'weave' domain

---
 server/mdns_server.go |  1 +
 server/server.go      | 23 +++++++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/server/mdns_server.go b/server/mdns_server.go
index ac605a66..b9ccd6ba 100644
--- a/server/mdns_server.go
+++ b/server/mdns_server.go
@@ -27,6 +27,7 @@ func NewMDNSServer(zone *ZoneDb) (*MDNSServer, error) {
 func makeDNSReply(r *dns.Msg, name string, addr net.IP) *dns.Msg {
 	m := new(dns.Msg)
 	m.SetReply(r)
+	m.RecursionAvailable = true
 	hdr := dns.RR_Header{Name: name, Rrtype: dns.TypeA,
 		Class: dns.ClassINET, Ttl: 3600}
 	a := &dns.A{hdr, addr}
diff --git a/server/server.go b/server/server.go
index e90cd99e..36adf65c 100644
--- a/server/server.go
+++ b/server/server.go
@@ -39,6 +39,14 @@ func findInterface(ifaceName string) (iface *net.Interface, err error) {
 	return
 }
 
+func makeDNSFailResponse(r *dns.Msg) *dns.Msg {
+	m := new(dns.Msg)
+	m.SetReply(r)
+	m.RecursionAvailable = true
+	m.Rcode = dns.RcodeNameError
+	return m
+}
+
 func queryHandler(zone Zone, mdnsClient *MDNSClient) dns.HandlerFunc {
 	return func(w dns.ResponseWriter, r *dns.Msg) {
 		q := r.Question[0]
@@ -64,6 +72,20 @@ func queryHandler(zone Zone, mdnsClient *MDNSClient) dns.HandlerFunc {
 	}
 }
 
+func notUsHandler() dns.HandlerFunc {
+	return func(w dns.ResponseWriter, r *dns.Msg) {
+		q := r.Question[0]
+		addrs, err := net.LookupIP(q.Name)
+		if err == nil {
+			m := makeDNSReply(r, q.Name, addrs[0])
+			w.WriteMsg(m)
+		} else {
+			m := makeDNSFailResponse(r)
+			w.WriteMsg(m)
+		}
+	}
+}
+
 func StartServer(ifaceName string, dnsPort int, httpPort int, wait int) error {
 
 	var zone = new(ZoneDb)
@@ -91,6 +113,7 @@ func StartServer(ifaceName string, dnsPort int, httpPort int, wait int) error {
 
 	LocalServeMux := dns.NewServeMux()
 	LocalServeMux.HandleFunc(LOCAL_DOMAIN, queryHandler(zone, mdnsClient))
+	LocalServeMux.HandleFunc(".", notUsHandler())
 
 	mdnsServer, err := NewMDNSServer(zone)
 	if err != nil {