Update {LinkEndpoint,NetworkEndpoint}#WritePacket to take a VectorisedView

Makes it possible to avoid copying or allocating in cases where DeliverNetworkPacket (rx)
needs to turn around and call WritePacket (tx) with its VectorisedView.

Also removes the restriction on having VectorisedViews with multiple views in the write path.

PiperOrigin-RevId: 211728717
Change-Id: Ie03a65ecb4e28bd15ebdb9c69f05eced18fdfcff

1 files changed, 18 insertions, 12 deletions

diff --git a/pkg/tcpip/link/sniffer/sniffer.go b/pkg/tcpip/link/sniffer/sniffer.go
index 1e302f557..3bdc85210 100644
--- a/pkg/tcpip/link/sniffer/sniffer.go
+++ b/pkg/tcpip/link/sniffer/sniffer.go
@@ -118,7 +118,7 @@ func NewWithFile(lower tcpip.LinkEndpointID, file *os.File, snapLen uint32) (tcp
 // logs the packet before forwarding to the actual dispatcher.
 func (e *endpoint) DeliverNetworkPacket(linkEP stack.LinkEndpoint, remoteLinkAddr tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, vv *buffer.VectorisedView) {
 	if atomic.LoadUint32(&LogPackets) == 1 && e.file == nil {
-		logPacket("recv", protocol, vv.First(), nil)
+		logPacket("recv", protocol, vv.First())
 	}
 	if e.file != nil && atomic.LoadUint32(&LogPacketsToFile) == 1 {
 		vs := vv.Views()
@@ -188,19 +188,19 @@ func (e *endpoint) LinkAddress() tcpip.LinkAddress {
 // WritePacket implements the stack.LinkEndpoint interface. It is called by
 // higher-level protocols to write packets; it just logs the packet and forwards
 // the request to the lower endpoint.
-func (e *endpoint) WritePacket(r *stack.Route, hdr *buffer.Prependable, payload buffer.View, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
+func (e *endpoint) WritePacket(r *stack.Route, hdr *buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
 	if atomic.LoadUint32(&LogPackets) == 1 && e.file == nil {
-		logPacket("send", protocol, hdr.UsedBytes(), payload)
+		logPacket("send", protocol, hdr.UsedBytes())
 	}
 	if e.file != nil && atomic.LoadUint32(&LogPacketsToFile) == 1 {
 		hdrBuf := hdr.UsedBytes()
-		length := len(hdrBuf) + len(payload)
+		length := len(hdrBuf) + payload.Size()
 		if length > int(e.maxPCAPLen) {
 			length = int(e.maxPCAPLen)
 		}
 
 		buf := bytes.NewBuffer(make([]byte, 0, pcapPacketHeaderLen+length))
-		if err := binary.Write(buf, binary.BigEndian, newPCAPPacketHeader(uint32(length), uint32(hdr.UsedLength()+len(payload)))); err != nil {
+		if err := binary.Write(buf, binary.BigEndian, newPCAPPacketHeader(uint32(length), uint32(len(hdrBuf)+payload.Size()))); err != nil {
 			panic(err)
 		}
 		if len(hdrBuf) > length {
@@ -211,12 +211,18 @@ func (e *endpoint) WritePacket(r *stack.Route, hdr *buffer.Prependable, payload
 		}
 		length -= len(hdrBuf)
 		if length > 0 {
-			p := payload
-			if len(p) > length {
-				p = p[:length]
-			}
-			if _, err := buf.Write(p); err != nil {
-				panic(err)
+			for _, v := range payload.Views() {
+				if len(v) > length {
+					v = v[:length]
+				}
+				n, err := buf.Write(v)
+				if err != nil {
+					panic(err)
+				}
+				length -= n
+				if length == 0 {
+					break
+				}
 			}
 		}
 		if _, err := e.file.Write(buf.Bytes()); err != nil {
@@ -226,7 +232,7 @@ func (e *endpoint) WritePacket(r *stack.Route, hdr *buffer.Prependable, payload
 	return e.lower.WritePacket(r, hdr, payload, protocol)
 }
 
-func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, b, plb []byte) {
+func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, b buffer.View) {
 	// Figure out the network layer info.
 	var transProto uint8
 	src := tcpip.Address("unknown")