From fd28ccfaa48a6b4c15aedb2bdd490211589c42d7 Mon Sep 17 00:00:00 2001
From: Bruno Dal Bo <brunodalbo@google.com>
Date: Fri, 4 Dec 2020 10:08:50 -0800
Subject: Introduce IPv4 options serializer and add RouterAlert to IGMP

PiperOrigin-RevId: 345701623
---
 test/packetimpact/testbench/layers.go | 39 +++++++++++++++++++++--------------
 1 file changed, 23 insertions(+), 16 deletions(-)

(limited to 'test/packetimpact')

diff --git a/test/packetimpact/testbench/layers.go b/test/packetimpact/testbench/layers.go
index 9df072cfd..dcff4ab36 100644
--- a/test/packetimpact/testbench/layers.go
+++ b/test/packetimpact/testbench/layers.go
@@ -298,14 +298,12 @@ func (l *IPv4) ToBytes() ([]byte, error) {
 	// An IPv4 header is variable length depending on the size of the Options.
 	hdrLen := header.IPv4MinimumSize
 	if l.Options != nil {
-		hdrLen += l.Options.SizeWithPadding()
+		if len(*l.Options)%4 != 0 {
+			return nil, fmt.Errorf("invalid header options '%x (len=%d)'; must be 32 bit aligned", *l.Options, len(*l.Options))
+		}
+		hdrLen += len(*l.Options)
 		if hdrLen > header.IPv4MaximumHeaderSize {
-			// While ToBytes can be called on packets that were received as well
-			// as packets locally generated, it is physically impossible for a
-			// received packet to overflow this value so any such failure must
-			// be the result of a local programming error and not remotely
-			// triggered. A panic is therefore appropriate.
-			panic(fmt.Sprintf("IPv4 Options %d bytes, Max %d", len(*l.Options), header.IPv4MaximumOptionsSize))
+			return nil, fmt.Errorf("IPv4 Options %d bytes, Max %d", len(*l.Options), header.IPv4MaximumOptionsSize)
 		}
 	}
 	b := make([]byte, hdrLen)
@@ -323,10 +321,6 @@ func (l *IPv4) ToBytes() ([]byte, error) {
 		DstAddr:        tcpip.Address(""),
 		Options:        nil,
 	}
-	// Leave an empty options slice as nil.
-	if hdrLen > header.IPv4MinimumSize {
-		fields.Options = *l.Options
-	}
 	if l.TOS != nil {
 		fields.TOS = *l.TOS
 	}
@@ -373,18 +367,31 @@ func (l *IPv4) ToBytes() ([]byte, error) {
 	if l.DstAddr != nil {
 		fields.DstAddr = *l.DstAddr
 	}
-	if l.Checksum != nil {
-		fields.Checksum = *l.Checksum
-	}
+
 	h.Encode(fields)
-	if l.Checksum == nil {
-		h.SetChecksum(^h.CalculateChecksum())
+
+	// Put raw option bytes from test definition in header. Options as raw bytes
+	// allows us to serialize malformed options, which is not possible with
+	// the provided serialization functions.
+	if l.Options != nil {
+		h.SetHeaderLength(h.HeaderLength() + uint8(len(*l.Options)))
+		if got, want := copy(h.Options(), *l.Options), len(*l.Options); got != want {
+			return nil, fmt.Errorf("failed to copy option bytes into header, got %d want %d", got, want)
+		}
 	}
+
 	// Encode cannot set this incorrectly so we need to overwrite what it wrote
 	// in order to test handling of a bad IHL value.
 	if l.IHL != nil {
 		h.SetHeaderLength(*l.IHL)
 	}
+
+	if l.Checksum == nil {
+		h.SetChecksum(^h.CalculateChecksum())
+	} else {
+		h.SetChecksum(*l.Checksum)
+	}
+
 	return h, nil
 }
 
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