From 99a18ec8b4cc98694b8bc61a35b360d5fca1a075 Mon Sep 17 00:00:00 2001
From: Zeling Feng <zeling@google.com>
Date: Mon, 18 May 2020 11:30:04 -0700
Subject: Support TCP options for packetimpact

PiperOrigin-RevId: 312119730
---
 test/packetimpact/testbench/layers.go | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

(limited to 'test/packetimpact/testbench/layers.go')

diff --git a/test/packetimpact/testbench/layers.go b/test/packetimpact/testbench/layers.go
index 49370377d..1b0e5b8fc 100644
--- a/test/packetimpact/testbench/layers.go
+++ b/test/packetimpact/testbench/layers.go
@@ -689,6 +689,7 @@ type TCP struct {
 	WindowSize    *uint16
 	Checksum      *uint16
 	UrgentPointer *uint16
+	Options       []byte
 }
 
 func (l *TCP) String() string {
@@ -697,7 +698,7 @@ func (l *TCP) String() string {
 
 // ToBytes implements Layer.ToBytes.
 func (l *TCP) ToBytes() ([]byte, error) {
-	b := make([]byte, header.TCPMinimumSize)
+	b := make([]byte, l.length())
 	h := header.TCP(b)
 	if l.SrcPort != nil {
 		h.SetSourcePort(*l.SrcPort)
@@ -727,6 +728,8 @@ func (l *TCP) ToBytes() ([]byte, error) {
 	if l.UrgentPointer != nil {
 		h.SetUrgentPoiner(*l.UrgentPointer)
 	}
+	copy(b[header.TCPMinimumSize:], l.Options)
+	header.AddTCPOptionPadding(b[header.TCPMinimumSize:], len(l.Options))
 	if l.Checksum != nil {
 		h.SetChecksum(*l.Checksum)
 		return h, nil
@@ -811,6 +814,7 @@ func parseTCP(b []byte) (Layer, layerParser) {
 		WindowSize:    Uint16(h.WindowSize()),
 		Checksum:      Uint16(h.Checksum()),
 		UrgentPointer: Uint16(h.UrgentPointer()),
+		Options:       b[header.TCPMinimumSize:h.DataOffset()],
 	}
 	return &tcp, parsePayload
 }
@@ -821,7 +825,12 @@ func (l *TCP) match(other Layer) bool {
 
 func (l *TCP) length() int {
 	if l.DataOffset == nil {
-		return header.TCPMinimumSize
+		// TCP header including the options must end on a 32-bit
+		// boundary; the user could potentially give us a slice
+		// whose length is not a multiple of 4 bytes, so we have
+		// to do the alignment here.
+		optlen := (len(l.Options) + 3) & ^3
+		return header.TCPMinimumSize + optlen
 	}
 	return int(*l.DataOffset)
 }
-- 
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