From fb7b1f2c20a7c2a77d9a1755a522d6dc27b0a3ed Mon Sep 17 00:00:00 2001
From: vadym <vadym.vikulin@gmail.com>
Date: Sun, 11 Jul 2021 12:40:00 +0300
Subject: [PATCH] 1. added FlowKeyMessage type

---
 src/util/util.go | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/src/util/util.go b/src/util/util.go
index 507426d0..f4331e4d 100644
--- a/src/util/util.go
+++ b/src/util/util.go
@@ -8,6 +8,11 @@ import (
 	"time"
 )
 
+type FlowKeyMessage struct {
+	FlowKey uint64
+	Message []byte
+}
+
 // TimerStop stops a timer and makes sure the channel is drained, returns true if the timer was stopped before firing.
 func TimerStop(t *time.Timer) bool {
 	stopped := t.Stop()
@@ -35,3 +40,41 @@ func FuncTimeout(timeout time.Duration, f func()) bool {
 		return false
 	}
 }
+
+// GetFlowKey takes an IP packet as an argument and returns some information about the traffic flow.
+// For IPv4 packets, this is derived from the source and destination protocol and port numbers.
+// For IPv6 packets, this is derived from the FlowLabel field of the packet if this was set, otherwise it's handled like IPv4.
+// The FlowKey is then used internally by Yggdrasil for congestion control.
+func GetFlowKey(bs []byte) uint64 {
+	// 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
+		ihl := (bs[0] & 0x0f) * 4 // whole IPv4 header length (min 20)
+		// 8 is minimum UDP packet length
+		if ihl >= 20 && len(bs)-int(ihl) >= 8 {
+			switch bs[9] /* protocol */ {
+			case 0x06 /* TCP */, 0x11 /* UDP */, 0x84 /* SCTP */ :
+				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 {
+			switch bs[9] /* protocol */ {
+			case 0x06 /* TCP */, 0x11 /* UDP */, 0x84 /* SCTP */ :
+				flowkey = uint64(bs[6])<<32 /* proto */ |
+					uint64(bs[40])<<24 | uint64(bs[41])<<16 /* sport */ |
+					uint64(bs[42])<<8 | uint64(bs[43]) /* dport */
+			}
+		}
+	}
+	return flowkey
+}