From 8ebc06315c4609a4c3e9264c8dda4dd45676ede9 Mon Sep 17 00:00:00 2001
From: Bryan Boreham <bjboreham@gmail.com>
Date: Tue, 14 Oct 2014 16:06:08 +0100
Subject: [PATCH] Detect duplicate add

---
 server/zone.go | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/server/zone.go b/server/zone.go
index d80fcfbd..6957b040 100644
--- a/server/zone.go
+++ b/server/zone.go
@@ -31,6 +31,15 @@ func (ops LookupError) Error() string {
 	return "Unable to find " + string(ops)
 }
 
+type DuplicateError struct {
+	Name    string
+	WeaveIp net.IP
+}
+
+func (err DuplicateError) Error() string {
+	return "Duplicate " + err.Name + "," + err.WeaveIp.String()
+}
+
 // Stop gap.
 func (zone *ZoneDb) match(name string) (net.IP, error) {
 	for _, r := range zone.recs {
@@ -42,6 +51,15 @@ func (zone *ZoneDb) match(name string) (net.IP, error) {
 	return nil, LookupError(name)
 }
 
+func (zone *ZoneDb) indexOfNameAddr(name string, addr net.IP) int {
+	for i, r := range zone.recs {
+		if r.Name == name && r.WeaveIp.Equal(addr) {
+			return i
+		}
+	}
+	return -1
+}
+
 func (zone *ZoneDb) MatchLocal(name string) (net.IP, error) {
 	zone.mx.Lock()
 	defer zone.mx.Unlock()
@@ -51,6 +69,10 @@ func (zone *ZoneDb) MatchLocal(name string) (net.IP, error) {
 func (zone *ZoneDb) AddRecord(identifier string, name string, ip net.IP, weave_ip net.IP, weave_subnet *net.IPNet) error {
 	zone.mx.Lock()
 	defer zone.mx.Unlock()
-	zone.recs = append(zone.recs, Record{identifier, dns.Fqdn(name), ip, weave_ip, weave_subnet})
+	fqdn := dns.Fqdn(name)
+	if zone.indexOfNameAddr(fqdn, weave_ip) != -1 {
+		return DuplicateError{fqdn, weave_ip}
+	}
+	zone.recs = append(zone.recs, Record{identifier, fqdn, ip, weave_ip, weave_subnet})
 	return nil
 }