From 94220f22b2b04a87f4404b8fe6549402027c33ad Mon Sep 17 00:00:00 2001
From: Matthias Radestock <matthias.radestock@gmail.com>
Date: Sun, 14 Jun 2015 08:47:51 +0100
Subject: [PATCH] allow dynamic addition of gossip channels

---
 router/gossip.go | 31 ++++++++++++++++++++++++++-----
 router/router.go |  6 ++++--
 2 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/router/gossip.go b/router/gossip.go
index f8d026ae..eba13174 100644
--- a/router/gossip.go
+++ b/router/gossip.go
@@ -1,5 +1,9 @@
 package router
 
+import (
+	"fmt"
+)
+
 type GossipData interface {
 	Encode() []byte
 	Merge(GossipData)
@@ -88,17 +92,34 @@ type GossipChannels map[string]*GossipChannel
 
 func (router *Router) NewGossip(channelName string, g Gossiper) Gossip {
 	channel := NewGossipChannel(channelName, router.Ourself, router.Routes, g)
-	router.GossipChannels[channelName] = channel
+	router.gossipLock.Lock()
+	defer router.gossipLock.Unlock()
+	if _, found := router.gossipChannels[channelName]; found {
+		checkFatal(fmt.Errorf("[gossip] duplicate channel %s", channelName))
+	}
+	router.gossipChannels[channelName] = channel
 	return channel
 }
 
 func (router *Router) gossipChannel(channelName string) (*GossipChannel, bool) {
-	channel, found := router.GossipChannels[channelName]
+	router.gossipLock.RLock()
+	defer router.gossipLock.RUnlock()
+	channel, found := router.gossipChannels[channelName]
 	return channel, found
 }
 
+func (router *Router) gossipChannelSet() map[*GossipChannel]struct{} {
+	channels := make(map[*GossipChannel]struct{})
+	router.gossipLock.RLock()
+	defer router.gossipLock.RUnlock()
+	for _, channel := range router.gossipChannels {
+		channels[channel] = void
+	}
+	return channels
+}
+
 func (router *Router) SendAllGossip() {
-	for _, channel := range router.GossipChannels {
+	for channel := range router.gossipChannelSet() {
 		if gossip := channel.gossiper.Gossip(); gossip != nil {
 			channel.Send(router.Ourself.Name, gossip)
 		}
@@ -106,7 +127,7 @@ func (router *Router) SendAllGossip() {
 }
 
 func (router *Router) SendAllGossipDown(conn Connection) {
-	for _, channel := range router.GossipChannels {
+	for channel := range router.gossipChannelSet() {
 		if gossip := channel.gossiper.Gossip(); gossip != nil {
 			channel.SendDown(conn, channel.gossiper.Gossip())
 		}
@@ -117,7 +138,7 @@ func (router *Router) SendAllGossipDown(conn Connection) {
 
 func (router *Router) sendPendingGossip() bool {
 	sentSomething := false
-	for _, channel := range router.GossipChannels {
+	for channel := range router.gossipChannelSet() {
 		channel.Lock()
 		for _, sender := range channel.senders {
 			sentSomething = sender.flush() || sentSomething
diff --git a/router/router.go b/router/router.go
index c0805d14..3473b05d 100644
--- a/router/router.go
+++ b/router/router.go
@@ -7,6 +7,7 @@ import (
 	"io"
 	"log"
 	"net"
+	"sync"
 	"syscall"
 	"time"
 
@@ -45,7 +46,8 @@ type Router struct {
 	Peers           *Peers
 	Routes          *Routes
 	ConnectionMaker *ConnectionMaker
-	GossipChannels  GossipChannels
+	gossipLock      sync.RWMutex
+	gossipChannels  GossipChannels
 	TopologyGossip  Gossip
 	UDPListener     *net.UDPConn
 }
@@ -64,7 +66,7 @@ type PacketSourceSink interface {
 }
 
 func NewRouter(config Config, name PeerName, nickName string) *Router {
-	router := &Router{Config: config, GossipChannels: make(GossipChannels)}
+	router := &Router{Config: config, gossipChannels: make(GossipChannels)}
 	onMacExpiry := func(mac net.HardwareAddr, peer *Peer) {
 		log.Println("Expired MAC", mac, "at", peer)
 	}