From d3f67ad0170cba1e8f4c9d0e668875864fdcb3a5 Mon Sep 17 00:00:00 2001
From: Neil Alexander <neilalexander@users.noreply.github.com>
Date: Mon, 21 Jan 2019 16:22:49 +0000
Subject: [PATCH] Improve command flow

---
 src/yggdrasil/session.go | 48 +++++++++++++++++++---------------------
 1 file changed, 23 insertions(+), 25 deletions(-)

diff --git a/src/yggdrasil/session.go b/src/yggdrasil/session.go
index b756ec99..23b27a3e 100644
--- a/src/yggdrasil/session.go
+++ b/src/yggdrasil/session.go
@@ -554,33 +554,31 @@ func (sinfo *sessionInfo) doSend(bs []byte) {
 	}
 	// code isn't multithreaded so appending to this is safe
 	coords := sinfo.coords
+	// 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
-	// Try to read IPv6 flowlabel field (20 bits)
-	if bs[0]&0xf0 == 0x60 {
-		flowkey = uint64(bs[1]&0x0f)<<16 | uint64(bs[2])<<8 | uint64(bs[3])
-	}
-	// Check if the flowlabel was specified. If not then try to use known
-	// protocols' ports: protokey: proto | sport | dport
-	if flowkey == 0 {
-		// Is the protocol TCP, UDP, SCTP?
-		switch bs[0] & 0xf0 {
-		case 0x40: // IPv4 packet
-			if len(bs) >= 24 {
-				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 */
-				}
+	switch bs[0] & 0xf0 {
+	case 0x40: // IPv4 packet
+		// Check the packet meets minimum UDP packet length
+		if len(bs) >= 24 {
+			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
-			// Does the packet meet the minimum UDP packet size? (others are bigger)
-			if len(bs) >= 48 {
-				if bs[6] == 0x06 || bs[6] == 0x11 || bs[6] == 0x84 {
-					flowkey = uint64(bs[6])<<32 /* proto */ |
-						uint64(bs[40])<<24 | uint64(bs[41])<<16 /* sport */ |
-						uint64(bs[42])<<8 | uint64(bs[43]) /* 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 {
+				flowkey = uint64(bs[6])<<32 /* proto */ |
+					uint64(bs[40])<<24 | uint64(bs[41])<<16 /* sport */ |
+					uint64(bs[42])<<8 | uint64(bs[43]) /* dport */
 			}
 		}
 	}