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

2 files changed, 11 insertions, 8 deletions

diff --git a/pkg/tcpip/link/fdbased/endpoint.go b/pkg/tcpip/link/fdbased/endpoint.go
index 449acdfdd..12c249c0d 100644
--- a/pkg/tcpip/link/fdbased/endpoint.go
+++ b/pkg/tcpip/link/fdbased/endpoint.go
@@ -161,10 +161,12 @@ func (e *endpoint) LinkAddress() tcpip.LinkAddress {
 
 // WritePacket writes outbound packets to the file descriptor. If it is not
 // currently writable, the packet is dropped.
-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 e.handleLocal && r.LocalAddress != "" && r.LocalAddress == r.RemoteAddress {
-		hdrView := hdr.View()
-		vv := buffer.NewVectorisedView(len(hdrView)+len(payload), []buffer.View{hdrView, payload})
+		views := make([]buffer.View, 1, 1+len(payload.Views()))
+		views[0] = hdr.View()
+		views = append(views, payload.Views()...)
+		vv := buffer.NewVectorisedView(len(views[0])+payload.Size(), views)
 		e.dispatcher.DeliverNetworkPacket(e, r.RemoteLinkAddress, protocol, &vv)
 		return nil
 	}
@@ -178,11 +180,11 @@ func (e *endpoint) WritePacket(r *stack.Route, hdr *buffer.Prependable, payload
 		})
 	}
 
-	if len(payload) == 0 {
+	if payload.Size() == 0 {
 		return rawfile.NonBlockingWrite(e.fd, hdr.UsedBytes())
 	}
 
-	return rawfile.NonBlockingWrite2(e.fd, hdr.UsedBytes(), payload)
+	return rawfile.NonBlockingWrite2(e.fd, hdr.UsedBytes(), payload.ToView())
 }
 
 func (e *endpoint) capViews(n int, buffers []int) int {
diff --git a/pkg/tcpip/link/fdbased/endpoint_test.go b/pkg/tcpip/link/fdbased/endpoint_test.go
index 89e791543..408169bbe 100644
--- a/pkg/tcpip/link/fdbased/endpoint_test.go
+++ b/pkg/tcpip/link/fdbased/endpoint_test.go
@@ -152,13 +152,14 @@ func TestWritePacket(t *testing.T) {
 					b[i] = uint8(rand.Intn(256))
 				}
 
-				// Buiild payload and write.
-				payload := make([]byte, plen)
+				// Build payload and write.
+				payload := make(buffer.View, plen)
 				for i := range payload {
 					payload[i] = uint8(rand.Intn(256))
 				}
 				want := append(hdr.UsedBytes(), payload...)
-				if err := c.ep.WritePacket(r, &hdr, payload, proto); err != nil {
+				vv := buffer.NewVectorisedView(len(payload), []buffer.View{payload})
+				if err := c.ep.WritePacket(r, &hdr, vv, proto); err != nil {
 					t.Fatalf("WritePacket failed: %v", err)
 				}