From d4f0a67323dec12e5b84ba4907970267a2e27601 Mon Sep 17 00:00:00 2001
From: Felix Lange <fjl@twurst.com>
Date: Fri, 8 May 2015 16:09:38 +0200
Subject: p2p: drop connections with no matching protocols

---
 p2p/peer.go   | 12 ++++++++++++
 p2p/server.go | 13 +++++++++----
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/p2p/peer.go b/p2p/peer.go
index cdf9ba965..ac691f2ce 100644
--- a/p2p/peer.go
+++ b/p2p/peer.go
@@ -211,6 +211,18 @@ func (p *Peer) handle(msg Msg) error {
 	return nil
 }
 
+func countMatchingProtocols(protocols []Protocol, caps []Cap) int {
+	n := 0
+	for _, cap := range caps {
+		for _, proto := range protocols {
+			if proto.Name == cap.Name && proto.Version == cap.Version {
+				n++
+			}
+		}
+	}
+	return n
+}
+
 // matchProtocols creates structures for matching named subprotocols.
 func matchProtocols(protocols []Protocol, caps []Cap, rw MsgReadWriter) map[string]*protoRW {
 	sort.Sort(capsByName(caps))
diff --git a/p2p/server.go b/p2p/server.go
index 171798a1d..3c6fb5893 100644
--- a/p2p/server.go
+++ b/p2p/server.go
@@ -518,7 +518,7 @@ func (srv *Server) startPeer(fd net.Conn, dest *discover.Node) {
 		conn:    fd, rtimeout: frameReadTimeout, wtimeout: frameWriteTimeout,
 	}
 	p := newPeer(fd, conn, srv.Protocols)
-	if ok, reason := srv.addPeer(conn.ID, p); !ok {
+	if ok, reason := srv.addPeer(conn, p); !ok {
 		glog.V(logger.Detail).Infof("Not adding %v (%v)\n", p, reason)
 		p.politeDisconnect(reason)
 		srv.peerWG.Done()
@@ -564,13 +564,18 @@ func (srv *Server) runPeer(p *Peer) {
 	})
 }
 
-func (srv *Server) addPeer(id discover.NodeID, p *Peer) (bool, DiscReason) {
+func (srv *Server) addPeer(conn *conn, p *Peer) (bool, DiscReason) {
+	// drop connections with no matching protocols.
+	if len(srv.Protocols) > 0 && countMatchingProtocols(srv.Protocols, conn.protoHandshake.Caps) == 0 {
+		return false, DiscUselessPeer
+	}
+	// add the peer if it passes the other checks.
 	srv.lock.Lock()
 	defer srv.lock.Unlock()
-	if ok, reason := srv.checkPeer(id); !ok {
+	if ok, reason := srv.checkPeer(conn.ID); !ok {
 		return false, reason
 	}
-	srv.peers[id] = p
+	srv.peers[conn.ID] = p
 	return true, 0
 }
 
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