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, 6 insertions, 12 deletions

diff --git a/pkg/tcpip/link/loopback/loopback.go b/pkg/tcpip/link/loopback/loopback.go
index 015275721..4a750fa12 100644
--- a/pkg/tcpip/link/loopback/loopback.go
+++ b/pkg/tcpip/link/loopback/loopback.go
@@ -72,18 +72,12 @@ func (*endpoint) LinkAddress() tcpip.LinkAddress {
 
 // WritePacket implements stack.LinkEndpoint.WritePacket. It delivers outbound
 // packets to the network-layer dispatcher.
-func (e *endpoint) WritePacket(_ *stack.Route, hdr *buffer.Prependable, payload buffer.View, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
-	if len(payload) == 0 {
-		// We don't have a payload, so just use the buffer from the
-		// header as the full packet.
-		v := hdr.View()
-		vv := v.ToVectorisedView([1]buffer.View{})
-		e.dispatcher.DeliverNetworkPacket(e, "", protocol, &vv)
-	} else {
-		views := []buffer.View{hdr.View(), payload}
-		vv := buffer.NewVectorisedView(len(views[0])+len(views[1]), views)
-		e.dispatcher.DeliverNetworkPacket(e, "", protocol, &vv)
-	}
+func (e *endpoint) WritePacket(_ *stack.Route, hdr *buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
+	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, "", protocol, &vv)
 
 	return nil
 }