6 files changed, 52 insertions, 14 deletions
diff --git a/pkg/tcpip/transport/icmp/endpoint.go b/pkg/tcpip/transport/icmp/endpoint.go
index f9a15efb2..00497bf07 100644
--- a/pkg/tcpip/transport/icmp/endpoint.go
+++ b/pkg/tcpip/transport/icmp/endpoint.go
@@ -329,6 +329,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcp
 		route = r
 	}
 
+	// TODO(https://gvisor.dev/issue/6538): Avoid this allocation.
 	v := make([]byte, p.Len())
 	if _, err := io.ReadFull(p, v); err != nil {
 		return 0, &tcpip.ErrBadBuffer{}
diff --git a/pkg/tcpip/transport/packet/endpoint.go b/pkg/tcpip/transport/packet/endpoint.go
index 8e7bb6c6e..89b4720aa 100644
--- a/pkg/tcpip/transport/packet/endpoint.go
+++ b/pkg/tcpip/transport/packet/endpoint.go
@@ -207,8 +207,52 @@ func (ep *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResul
 	return res, nil
 }
 
-func (*endpoint) Write(tcpip.Payloader, tcpip.WriteOptions) (int64, tcpip.Error) {
-	return 0, &tcpip.ErrInvalidOptionValue{}
+func (ep *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcpip.Error) {
+	if !ep.stack.PacketEndpointWriteSupported() {
+		return 0, &tcpip.ErrNotSupported{}
+	}
+
+	ep.mu.Lock()
+	closed := ep.closed
+	nicID := ep.boundNIC
+	ep.mu.Unlock()
+	if closed {
+		return 0, &tcpip.ErrClosedForSend{}
+	}
+
+	var remote tcpip.LinkAddress
+	proto := ep.netProto
+	if to := opts.To; to != nil {
+		remote = tcpip.LinkAddress(to.Addr)
+
+		if n := to.NIC; n != 0 {
+			nicID = n
+		}
+
+		if p := to.Port; p != 0 {
+			proto = tcpip.NetworkProtocolNumber(p)
+		}
+	}
+
+	if nicID == 0 {
+		return 0, &tcpip.ErrInvalidOptionValue{}
+	}
+
+	// TODO(https://gvisor.dev/issue/6538): Avoid this allocation.
+	payloadBytes := make(buffer.View, p.Len())
+	if _, err := io.ReadFull(p, payloadBytes); err != nil {
+		return 0, &tcpip.ErrBadBuffer{}
+	}
+
+	if err := func() tcpip.Error {
+		if ep.cooked {
+			return ep.stack.WritePacketToRemote(nicID, remote, proto, payloadBytes.ToVectorisedView())
+		}
+		return ep.stack.WriteRawPacket(nicID, proto, payloadBytes.ToVectorisedView())
+	}(); err != nil {
+		return 0, err
+	}
+	return int64(len(payloadBytes)), nil
 }
 
 // Disconnect implements tcpip.Endpoint.Disconnect. Packet sockets cannot be
diff --git a/pkg/tcpip/transport/packet/endpoint_state.go b/pkg/tcpip/transport/packet/endpoint_state.go
index e729921db..5c688d286 100644
--- a/pkg/tcpip/transport/packet/endpoint_state.go
+++ b/pkg/tcpip/transport/packet/endpoint_state.go
@@ -34,17 +34,11 @@ func (p *packet) loadReceivedAt(nsec int64) {
 
 // saveData saves packet.data field.
 func (p *packet) saveData() buffer.VectorisedView {
-	// We cannot save p.data directly as p.data.views may alias to p.views,
-	// which is not allowed by state framework (in-struct pointer).
 	return p.data.Clone(nil)
 }
 
 // loadData loads packet.data field.
 func (p *packet) loadData(data buffer.VectorisedView) {
-	// NOTE: We cannot do the p.data = data.Clone(p.views[:]) optimization
-	// here because data.views is not guaranteed to be loaded by now. Plus,
-	// data.views will be allocated anyway so there really is little point
-	// of utilizing p.views for data.views.
 	p.data = data
 }
 
diff --git a/pkg/tcpip/transport/raw/endpoint.go b/pkg/tcpip/transport/raw/endpoint.go
index 55854ba59..3bf6c0a8f 100644
--- a/pkg/tcpip/transport/raw/endpoint.go
+++ b/pkg/tcpip/transport/raw/endpoint.go
@@ -281,6 +281,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcp
 			return nil, nil, nil, &tcpip.ErrInvalidEndpointState{}
 		}
 
+		// TODO(https://gvisor.dev/issue/6538): Avoid this allocation.
 		payloadBytes := make([]byte, p.Len())
 		if _, err := io.ReadFull(p, payloadBytes); err != nil {
 			return nil, nil, nil, &tcpip.ErrBadBuffer{}
@@ -600,6 +601,9 @@ func (e *endpoint) HandlePacket(pkt *stack.PacketBuffer) {
 	// We copy headers' underlying bytes because pkt.*Header may point to
 	// the middle of a slice, and another struct may point to the "outer"
 	// slice. Save/restore doesn't support overlapping slices and will fail.
+	//
+	// TODO(https://gvisor.dev/issue/6517): Avoid the copy once S/R supports
+	// overlapping slices.
 	var combinedVV buffer.VectorisedView
 	if e.TransportEndpointInfo.NetProto == header.IPv4ProtocolNumber {
 		network, transport := pkt.NetworkHeader().View(), pkt.TransportHeader().View()
diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index ac7ecb5f8..4b6bdc3be 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -366,6 +366,7 @@ func (e *endpoint) prepareForWrite(p tcpip.Payloader, opts tcpip.WriteOptions) (
 		return udpPacketInfo{}, err
 	}
 
+	// TODO(https://gvisor.dev/issue/6538): Avoid this allocation.
 	v := make([]byte, p.Len())
 	if _, err := io.ReadFull(p, v); err != nil {
 		ctx.Release()
diff --git a/pkg/tcpip/transport/udp/endpoint_state.go b/pkg/tcpip/transport/udp/endpoint_state.go
index 20c45ab87..2ff8b0482 100644
--- a/pkg/tcpip/transport/udp/endpoint_state.go
+++ b/pkg/tcpip/transport/udp/endpoint_state.go
@@ -36,17 +36,11 @@ func (p *udpPacket) loadReceivedAt(nsec int64) {
 
 // saveData saves udpPacket.data field.
 func (p *udpPacket) saveData() buffer.VectorisedView {
-	// We cannot save p.data directly as p.data.views may alias to p.views,
-	// which is not allowed by state framework (in-struct pointer).
 	return p.data.Clone(nil)
 }
 
 // loadData loads udpPacket.data field.
 func (p *udpPacket) loadData(data buffer.VectorisedView) {
-	// NOTE: We cannot do the p.data = data.Clone(p.views[:]) optimization
-	// here because data.views is not guaranteed to be loaded by now. Plus,
-	// data.views will be allocated anyway so there really is little point
-	// of utilizing p.views for data.views.
 	p.data = data
 }