From 1cd76d958a9b3eb29f6b55a8bea71fbe464e67d3 Mon Sep 17 00:00:00 2001
From: Ting-Yu Wang <anivia@google.com>
Date: Wed, 3 Mar 2021 16:03:04 -0800
Subject: Make dedicated methods for data operations in PacketBuffer

One of the preparation to decouple underlying buffer implementation.
There are still some methods that tie to VectorisedView, and they will be
changed gradually in later CLs.

This CL also introduce a new ICMPv6ChecksumParams to replace long list of
parameters when calling ICMPv6Checksum, aiming to be more descriptive.

PiperOrigin-RevId: 360778149
---
 pkg/tcpip/header/parse/parse.go | 30 ++++++++++++++++--------------
 1 file changed, 16 insertions(+), 14 deletions(-)

(limited to 'pkg/tcpip/header/parse/parse.go')

diff --git a/pkg/tcpip/header/parse/parse.go b/pkg/tcpip/header/parse/parse.go
index 2042f214a..ebb4b2c1d 100644
--- a/pkg/tcpip/header/parse/parse.go
+++ b/pkg/tcpip/header/parse/parse.go
@@ -41,7 +41,7 @@ func ARP(pkt *stack.PacketBuffer) bool {
 //
 // Returns true if the header was successfully parsed.
 func IPv4(pkt *stack.PacketBuffer) bool {
-	hdr, ok := pkt.Data.PullUp(header.IPv4MinimumSize)
+	hdr, ok := pkt.Data().PullUp(header.IPv4MinimumSize)
 	if !ok {
 		return false
 	}
@@ -62,27 +62,29 @@ func IPv4(pkt *stack.PacketBuffer) bool {
 	ipHdr = header.IPv4(hdr)
 
 	pkt.NetworkProtocolNumber = header.IPv4ProtocolNumber
-	pkt.Data.CapLength(int(ipHdr.TotalLength()) - len(hdr))
+	pkt.Data().CapLength(int(ipHdr.TotalLength()) - len(hdr))
 	return true
 }
 
 // IPv6 parses an IPv6 packet found in pkt.Data and populates pkt's network
 // header with the IPv6 header.
 func IPv6(pkt *stack.PacketBuffer) (proto tcpip.TransportProtocolNumber, fragID uint32, fragOffset uint16, fragMore bool, ok bool) {
-	hdr, ok := pkt.Data.PullUp(header.IPv6MinimumSize)
+	hdr, ok := pkt.Data().PullUp(header.IPv6MinimumSize)
 	if !ok {
 		return 0, 0, 0, false, false
 	}
 	ipHdr := header.IPv6(hdr)
 
-	// dataClone consists of:
+	// Create a VV to parse the packet. We don't plan to modify anything here.
+	// dataVV consists of:
 	// - Any IPv6 header bytes after the first 40 (i.e. extensions).
 	// - The transport header, if present.
 	// - Any other payload data.
 	views := [8]buffer.View{}
-	dataClone := pkt.Data.Clone(views[:])
-	dataClone.TrimFront(header.IPv6MinimumSize)
-	it := header.MakeIPv6PayloadIterator(header.IPv6ExtensionHeaderIdentifier(ipHdr.NextHeader()), dataClone)
+	dataVV := buffer.NewVectorisedView(0, views[:0])
+	dataVV.AppendViews(pkt.Data().Views())
+	dataVV.TrimFront(header.IPv6MinimumSize)
+	it := header.MakeIPv6PayloadIterator(header.IPv6ExtensionHeaderIdentifier(ipHdr.NextHeader()), dataVV)
 
 	// Iterate over the IPv6 extensions to find their length.
 	var nextHdr tcpip.TransportProtocolNumber
@@ -98,7 +100,7 @@ traverseExtensions:
 		// If we exhaust the extension list, the entire packet is the IPv6 header
 		// and (possibly) extensions.
 		if done {
-			extensionsSize = dataClone.Size()
+			extensionsSize = dataVV.Size()
 			break
 		}
 
@@ -110,12 +112,12 @@ traverseExtensions:
 				fragMore = extHdr.More()
 			}
 			rawPayload := it.AsRawHeader(true /* consume */)
-			extensionsSize = dataClone.Size() - rawPayload.Buf.Size()
+			extensionsSize = dataVV.Size() - rawPayload.Buf.Size()
 			break traverseExtensions
 
 		case header.IPv6RawPayloadHeader:
 			// We've found the payload after any extensions.
-			extensionsSize = dataClone.Size() - extHdr.Buf.Size()
+			extensionsSize = dataVV.Size() - extHdr.Buf.Size()
 			nextHdr = tcpip.TransportProtocolNumber(extHdr.Identifier)
 			break traverseExtensions
 
@@ -127,10 +129,10 @@ traverseExtensions:
 	// Put the IPv6 header with extensions in pkt.NetworkHeader().
 	hdr, ok = pkt.NetworkHeader().Consume(header.IPv6MinimumSize + extensionsSize)
 	if !ok {
-		panic(fmt.Sprintf("pkt.Data should have at least %d bytes, but only has %d.", header.IPv6MinimumSize+extensionsSize, pkt.Data.Size()))
+		panic(fmt.Sprintf("pkt.Data should have at least %d bytes, but only has %d.", header.IPv6MinimumSize+extensionsSize, pkt.Data().Size()))
 	}
 	ipHdr = header.IPv6(hdr)
-	pkt.Data.CapLength(int(ipHdr.PayloadLength()))
+	pkt.Data().CapLength(int(ipHdr.PayloadLength()))
 	pkt.NetworkProtocolNumber = header.IPv6ProtocolNumber
 
 	return nextHdr, fragID, fragOffset, fragMore, true
@@ -153,13 +155,13 @@ func UDP(pkt *stack.PacketBuffer) bool {
 func TCP(pkt *stack.PacketBuffer) bool {
 	// TCP header is variable length, peek at it first.
 	hdrLen := header.TCPMinimumSize
-	hdr, ok := pkt.Data.PullUp(hdrLen)
+	hdr, ok := pkt.Data().PullUp(hdrLen)
 	if !ok {
 		return false
 	}
 
 	// If the header has options, pull those up as well.
-	if offset := int(header.TCP(hdr).DataOffset()); offset > header.TCPMinimumSize && offset <= pkt.Data.Size() {
+	if offset := int(header.TCP(hdr).DataOffset()); offset > header.TCPMinimumSize && offset <= pkt.Data().Size() {
 		// TODO(gvisor.dev/issue/2404): Figure out whether to reject this kind of
 		// packets.
 		hdrLen = offset
-- 
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