Set the NetworkProtocolNumber of all PacketBuffers.

NetworkEndpoints set the number on outgoing packets in Write() and
NetworkProtocols set them on incoming packets in Parse().

Needed for #3549.

PiperOrigin-RevId: 325938745

2 files changed, 21 insertions, 11 deletions

diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index 6c4f0ae3e..9ff27a363 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -173,9 +173,10 @@ func (e *endpoint) writePacketFragments(r *stack.Route, gso *stack.GSO, mtu int,
 			newPayload := pkt.Data.Clone(nil)
 			newPayload.CapLength(innerMTU)
 			if err := e.linkEP.WritePacket(r, gso, ProtocolNumber, &stack.PacketBuffer{
-				Header:        pkt.Header,
-				Data:          newPayload,
-				NetworkHeader: buffer.View(h),
+				Header:                pkt.Header,
+				Data:                  newPayload,
+				NetworkHeader:         buffer.View(h),
+				NetworkProtocolNumber: header.IPv4ProtocolNumber,
 			}); err != nil {
 				return err
 			}
@@ -192,9 +193,10 @@ func (e *endpoint) writePacketFragments(r *stack.Route, gso *stack.GSO, mtu int,
 			newPayloadLength := outerMTU - pkt.Header.UsedLength()
 			newPayload.CapLength(newPayloadLength)
 			if err := e.linkEP.WritePacket(r, gso, ProtocolNumber, &stack.PacketBuffer{
-				Header:        pkt.Header,
-				Data:          newPayload,
-				NetworkHeader: buffer.View(h),
+				Header:                pkt.Header,
+				Data:                  newPayload,
+				NetworkHeader:         buffer.View(h),
+				NetworkProtocolNumber: header.IPv4ProtocolNumber,
 			}); err != nil {
 				return err
 			}
@@ -206,9 +208,10 @@ func (e *endpoint) writePacketFragments(r *stack.Route, gso *stack.GSO, mtu int,
 			startOfHdr.TrimBack(pkt.Header.UsedLength() - outerMTU)
 			emptyVV := buffer.NewVectorisedView(0, []buffer.View{})
 			if err := e.linkEP.WritePacket(r, gso, ProtocolNumber, &stack.PacketBuffer{
-				Header:        startOfHdr,
-				Data:          emptyVV,
-				NetworkHeader: buffer.View(h),
+				Header:                startOfHdr,
+				Data:                  emptyVV,
+				NetworkHeader:         buffer.View(h),
+				NetworkProtocolNumber: header.IPv4ProtocolNumber,
 			}); err != nil {
 				return err
 			}
@@ -249,10 +252,11 @@ func (e *endpoint) addIPHeader(r *stack.Route, hdr *buffer.Prependable, payloadS
 func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.NetworkHeaderParams, pkt *stack.PacketBuffer) *tcpip.Error {
 	ip := e.addIPHeader(r, &pkt.Header, pkt.Data.Size(), params)
 	pkt.NetworkHeader = buffer.View(ip)
+	pkt.NetworkProtocolNumber = header.IPv4ProtocolNumber
 
-	nicName := e.stack.FindNICNameFromID(e.NICID())
 	// iptables filtering. All packets that reach here are locally
 	// generated.
+	nicName := e.stack.FindNICNameFromID(e.NICID())
 	ipt := e.stack.IPTables()
 	if ok := ipt.Check(stack.Output, pkt, gso, r, "", nicName); !ok {
 		// iptables is telling us to drop the packet.
@@ -304,6 +308,7 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 	for pkt := pkts.Front(); pkt != nil; {
 		ip := e.addIPHeader(r, &pkt.Header, pkt.Data.Size(), params)
 		pkt.NetworkHeader = buffer.View(ip)
+		pkt.NetworkProtocolNumber = header.IPv4ProtocolNumber
 		pkt = pkt.Next()
 	}
 
@@ -570,6 +575,7 @@ func (*protocol) Parse(pkt *stack.PacketBuffer) (proto tcpip.TransportProtocolNu
 		parseTransportHeader = false
 	}
 
+	pkt.NetworkProtocolNumber = header.IPv4ProtocolNumber
 	pkt.NetworkHeader = hdr
 	pkt.Data.TrimFront(len(hdr))
 	pkt.Data.CapLength(int(ipHdr.TotalLength()) - len(hdr))
diff --git a/pkg/tcpip/network/ipv4/ipv4_test.go b/pkg/tcpip/network/ipv4/ipv4_test.go
index ded97ac64..63e2c36c2 100644
--- a/pkg/tcpip/network/ipv4/ipv4_test.go
+++ b/pkg/tcpip/network/ipv4/ipv4_test.go
@@ -150,6 +150,9 @@ func compareFragments(t *testing.T, packets []*stack.PacketBuffer, sourcePacketI
 		if got, want := packet.Header.AvailableLength(), sourcePacketInfo.Header.AvailableLength()-header.IPv4MinimumSize; got != want {
 			t.Errorf("fragment #%d should have the same available space for prepending as source: got %d, want %d", i, got, want)
 		}
+		if got, want := packet.NetworkProtocolNumber, sourcePacketInfo.NetworkProtocolNumber; got != want {
+			t.Errorf("fragment #%d has wrong network protocol number: got %d, want %d", i, got, want)
+		}
 		if i < len(packets)-1 {
 			sourceCopy.SetFlagsFragmentOffset(sourceCopy.Flags()|header.IPv4FlagMoreFragments, offset)
 		} else {
@@ -285,7 +288,8 @@ func TestFragmentation(t *testing.T) {
 			source := &stack.PacketBuffer{
 				Header: hdr,
 				// Save the source payload because WritePacket will modify it.
-				Data: payload.Clone(nil),
+				Data:                  payload.Clone(nil),
+				NetworkProtocolNumber: header.IPv4ProtocolNumber,
 			}
 			c := buildContext(t, nil, ft.mtu)
 			err := c.Route.WritePacket(ft.gso, stack.NetworkHeaderParams{