Choose a random subset from given STUN servers

Only chooses a subset as long as we have over 2 STUN servers to choose
from.

client/client_test.go

@@ -49,8 +49,8 @@ func TestICEServerParser(t *testing.T) {
 
 			So(len(servers), ShouldEqual, test.length)
 
-			for i, server := range servers {
+			for _, server := range servers {
-				So(server.URLs, ShouldResemble, test.urls[i])
+				So(test.urls, ShouldContain, server.URLs)
 			}
 
 		}

client/snowflake.go

@@ -6,6 +6,7 @@ import (
 	"io"
 	"io/ioutil"
 	"log"
+	"math/rand"
 	"net"
 	"os"
 	"os/signal"
@@ -77,6 +78,7 @@ func socksAcceptLoop(ln *pt.SocksListener, snowflakes sf.SnowflakeCollector) {
 }
 
 // s is a comma-separated list of ICE server URLs.
+// chooses a random subset of servers from inputs
 func parseIceServers(s string) []webrtc.ICEServer {
 	var servers []webrtc.ICEServer
 	s = strings.TrimSpace(s)
@@ -90,6 +92,13 @@ func parseIceServers(s string) []webrtc.ICEServer {
 			URLs: []string{url},
 		})
 	}
+	rand.Seed(time.Now().Unix())
+	rand.Shuffle(len(servers), func(i, j int) {
+		servers[i], servers[j] = servers[j], servers[i]
+	})
+	if len(servers) > 2 {
+		servers = servers[:len(servers)/2]
+	}
 	return servers
 }
 

client/torrc

@@ -4,7 +4,7 @@ DataDirectory datadir
 ClientTransportPlugin snowflake exec ./client \
 -url https://snowflake-broker.azureedge.net/ \
 -front ajax.aspnetcdn.com \
--ice stun:stun.l.google.com:19302 \
+-ice stun:stun.voip.blackberry.com:3478,stun:stun.altar.com.pl:3478,stun:stun.antisip.com:3478,stun:stun.bluesip.net:3478,stun:stun.dus.net:3478,stun:stun.epygi.com:3478,stun:stun.sonetel.com:3478,stun:stun.sonetel.net:3478,stun:stun.stunprotocol.org:3478,stun:stun.uls.co.za:3478,stun:stun.voipgate.com:3478,stun:stun.voys.nl:3478 \
 -max 3
 
 Bridge snowflake 192.0.2.3:1