Update WritePacket* API to take ownership of packets to be written.

Updates #2404.

PiperOrigin-RevId: 313834784

pkg/tcpip/stack/nic.go

@@ -1304,13 +1304,16 @@ func (n *NIC) forwardPacket(r *Route, protocol tcpip.NetworkProtocolNumber, pkt
 		pkt.Header = buffer.NewPrependable(linkHeaderLen)
 	}
 
+	// WritePacket takes ownership of pkt, calculate numBytes first.
+	numBytes := pkt.Header.UsedLength() + pkt.Data.Size()
+
 	if err := n.linkEP.WritePacket(r, nil /* gso */, protocol, pkt); err != nil {
 		r.Stats().IP.OutgoingPacketErrors.Increment()
 		return
 	}
 
 	n.stats.Tx.Packets.Increment()
-	n.stats.Tx.Bytes.IncrementBy(uint64(pkt.Header.UsedLength() + pkt.Data.Size()))
+	n.stats.Tx.Bytes.IncrementBy(uint64(numBytes))
 }
 
 // DeliverTransportPacket delivers the packets to the appropriate transport

pkg/tcpip/stack/registration.go

@@ -240,16 +240,17 @@ type NetworkEndpoint interface {
 	MaxHeaderLength() uint16
 
 	// WritePacket writes a packet to the given destination address and
-	// protocol. It sets pkt.NetworkHeader. pkt.TransportHeader must have
-	// already been set.
+	// protocol. It takes ownership of pkt. pkt.TransportHeader must have already
+	// been set.
 	WritePacket(r *Route, gso *GSO, params NetworkHeaderParams, pkt PacketBuffer) *tcpip.Error
 
 	// WritePackets writes packets to the given destination address and
-	// protocol. pkts must not be zero length.
+	// protocol. pkts must not be zero length. It takes ownership of pkts and
+	// underlying packets.
 	WritePackets(r *Route, gso *GSO, pkts PacketBufferList, params NetworkHeaderParams) (int, *tcpip.Error)
 
 	// WriteHeaderIncludedPacket writes a packet that includes a network
-	// header to the given destination address.
+	// header to the given destination address. It takes ownership of pkt.
 	WriteHeaderIncludedPacket(r *Route, pkt PacketBuffer) *tcpip.Error
 
 	// ID returns the network protocol endpoint ID.
@@ -382,9 +383,8 @@ type LinkEndpoint interface {
 	LinkAddress() tcpip.LinkAddress
 
 	// WritePacket writes a packet with the given protocol through the
-	// given route. It sets pkt.LinkHeader if a link layer header exists.
-	// pkt.NetworkHeader and pkt.TransportHeader must have already been
-	// set.
+	// given route. It takes ownership of pkt. pkt.NetworkHeader and
+	// pkt.TransportHeader must have already been set.
 	//
 	// To participate in transparent bridging, a LinkEndpoint implementation
 	// should call eth.Encode with header.EthernetFields.SrcAddr set to
@@ -392,7 +392,8 @@ type LinkEndpoint interface {
 	WritePacket(r *Route, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt PacketBuffer) *tcpip.Error
 
 	// WritePackets writes packets with the given protocol through the
-	// given route. pkts must not be zero length.
+	// given route. pkts must not be zero length. It takes ownership of pkts and
+	// underlying packets.
 	//
 	// Right now, WritePackets is used only when the software segmentation
 	// offload is enabled. If it will be used for something else, it may
@@ -400,7 +401,7 @@ type LinkEndpoint interface {
 	WritePackets(r *Route, gso *GSO, pkts PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, *tcpip.Error)
 
 	// WriteRawPacket writes a packet directly to the link. The packet
-	// should already have an ethernet header.
+	// should already have an ethernet header. It takes ownership of vv.
 	WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error
 
 	// Attach attaches the data link layer endpoint to the network-layer

pkg/tcpip/stack/route.go

@@ -158,12 +158,15 @@ func (r *Route) WritePacket(gso *GSO, params NetworkHeaderParams, pkt PacketBuff
 		return tcpip.ErrInvalidEndpointState
 	}
 
+	// WritePacket takes ownership of pkt, calculate numBytes first.
+	numBytes := pkt.Header.UsedLength() + pkt.Data.Size()
+
 	err := r.ref.ep.WritePacket(r, gso, params, pkt)
 	if err != nil {
 		r.Stats().IP.OutgoingPacketErrors.Increment()
 	} else {
 		r.ref.nic.stats.Tx.Packets.Increment()
-		r.ref.nic.stats.Tx.Bytes.IncrementBy(uint64(pkt.Header.UsedLength() + pkt.Data.Size()))
+		r.ref.nic.stats.Tx.Bytes.IncrementBy(uint64(numBytes))
 	}
 	return err
 }
@@ -175,9 +178,12 @@ func (r *Route) WritePackets(gso *GSO, pkts PacketBufferList, params NetworkHead
 		return 0, tcpip.ErrInvalidEndpointState
 	}
 
+	// WritePackets takes ownership of pkt, calculate length first.
+	numPkts := pkts.Len()
+
 	n, err := r.ref.ep.WritePackets(r, gso, pkts, params)
 	if err != nil {
-		r.Stats().IP.OutgoingPacketErrors.IncrementBy(uint64(pkts.Len() - n))
+		r.Stats().IP.OutgoingPacketErrors.IncrementBy(uint64(numPkts - n))
 	}
 	r.ref.nic.stats.Tx.Packets.IncrementBy(uint64(n))
 
@@ -198,12 +204,15 @@ func (r *Route) WriteHeaderIncludedPacket(pkt PacketBuffer) *tcpip.Error {
 		return tcpip.ErrInvalidEndpointState
 	}
 
+	// WriteHeaderIncludedPacket takes ownership of pkt, calculate numBytes first.
+	numBytes := pkt.Data.Size()
+
 	if err := r.ref.ep.WriteHeaderIncludedPacket(r, pkt); err != nil {
 		r.Stats().IP.OutgoingPacketErrors.Increment()
 		return err
 	}
 	r.ref.nic.stats.Tx.Packets.Increment()
-	r.ref.nic.stats.Tx.Bytes.IncrementBy(uint64(pkt.Data.Size()))
+	r.ref.nic.stats.Tx.Bytes.IncrementBy(uint64(numBytes))
 	return nil
 }