diff --git a/contrib/ansible/genkeys.go b/contrib/ansible/genkeys.go
index 81397386..5213e8b8 100644
--- a/contrib/ansible/genkeys.go
+++ b/contrib/ansible/genkeys.go
@@ -117,6 +117,8 @@ func bubbleUpTo(sets []keySet, num int) []keySet {
 			var tmp = sets[i]
 			sets[i] = sets[i+1]
 			sets[i+1] = tmp
+		} else {
+			break
 		}
 	}
 	return sets
diff --git a/src/yggdrasil/session.go b/src/yggdrasil/session.go
index 4f632fad..cdabaf2b 100644
--- a/src/yggdrasil/session.go
+++ b/src/yggdrasil/session.go
@@ -554,17 +554,30 @@ func (sinfo *sessionInfo) doSend(bs []byte) {
 	}
 	// code isn't multithreaded so appending to this is safe
 	coords := sinfo.coords
-	// Read IPv6 flowlabel field (20 bits).
-	// Assumes packet at least contains IPv6 header.
-	flowkey := uint64(bs[1]&0x0f)<<16 | uint64(bs[2])<<8 | uint64(bs[3])
-	// Check if the flowlabel was specified
-	if flowkey == 0 {
-		// Does the packet meet the minimum UDP packet size? (others are bigger)
-		if len(bs) >= 48 {
-			// Is the protocol TCP, UDP, SCTP?
+	// Work out the flowkey - this is used to determine which switch queue
+	// traffic will be pushed to in the event of congestion
+	var flowkey uint64
+	// Get the IP protocol version from the packet
+	switch bs[0] & 0xf0 {
+	case 0x40: // IPv4 packet
+		// Check the packet meets minimum UDP packet length
+		if len(bs) >= 24 {
+			// Is the protocol TCP, UDP or SCTP?
+			if bs[9] == 0x06 || bs[9] == 0x11 || bs[9] == 0x84 {
+				ihl := bs[0] & 0x0f * 4 // Header length
+				flowkey = uint64(bs[9])<<32 /* proto */ |
+					uint64(bs[ihl+0])<<24 | uint64(bs[ihl+1])<<16 /* sport */ |
+					uint64(bs[ihl+2])<<8 | uint64(bs[ihl+3]) /* dport */
+			}
+		}
+	case 0x60: // IPv6 packet
+		// Check if the flowlabel was specified in the packet header
+		flowkey = uint64(bs[1]&0x0f)<<16 | uint64(bs[2])<<8 | uint64(bs[3])
+		// If the flowlabel isn't present, make protokey from proto | sport | dport
+		// if the packet meets minimum UDP packet length
+		if flowkey == 0 && len(bs) >= 48 {
+			// Is the protocol TCP, UDP or SCTP?
 			if bs[6] == 0x06 || bs[6] == 0x11 || bs[6] == 0x84 {
-				// if flowlabel was unspecified (0), try to use known protocols' ports
-				// protokey: proto | sport | dport
 				flowkey = uint64(bs[6])<<32 /* proto */ |
 					uint64(bs[40])<<24 | uint64(bs[41])<<16 /* sport */ |
 					uint64(bs[42])<<8 | uint64(bs[43]) /* dport */
@@ -612,5 +625,8 @@ func (sinfo *sessionInfo) doRecv(p *wire_trafficPacket) {
 	sinfo.updateNonce(&p.Nonce)
 	sinfo.time = time.Now()
 	sinfo.bytesRecvd += uint64(len(bs))
-	sinfo.core.router.toRecv <- router_recvPacket{bs, sinfo}
+	select {
+	case sinfo.core.router.toRecv <- router_recvPacket{bs, sinfo}:
+	default: // avoid deadlocks, maybe do this somewhere else?...
+	}
 }