[FAB-2710] Gossip: Log WARN upon bad network config

This commit adds a log warning in case a peer detects peers
with the same PKI-ID as itself but with different endpoints.
The only reason that this can happen is that someone configured different
peers with the same identity.

Change-Id: Ie29d871627b521cb586a50bb447e1615710b366c
Signed-off-by: Yacov Manevich <yacovm@il.ibm.com>
Signed-off-by: Artem Barger <bartem@il.ibm.com>

gossip/discovery/discovery_impl.go

@@ -436,6 +436,16 @@ func (d *gossipDiscoveryImpl) handleAliveMessage(m *proto.SignedGossipMessage) {
 	pkiID := m.GetAliveMsg().Membership.PkiId
 	if equalPKIid(pkiID, d.self.PKIid) {
 		d.logger.Debug("Got alive message about ourselves,", m)
+		diffExternalEndpoint := d.self.Endpoint != m.GetAliveMsg().Membership.Endpoint
+		var diffInternalEndpoint bool
+		secretEnvelope := m.GetSecretEnvelope()
+		if secretEnvelope != nil && secretEnvelope.InternalEndpoint() != "" {
+			diffInternalEndpoint = secretEnvelope.InternalEndpoint() != d.self.InternalEndpoint
+		}
+		if diffInternalEndpoint || diffExternalEndpoint {
+			d.logger.Error("Bad configuration detected: Received AliveMessage from a peer with the same PKI-ID as myself:", m.GossipMessage)
+		}
+
 		return
 	}