Count IP OutgoingPacketErrors in the NetworkEndpoint methods

Before this change, OutgoingPacketErrors was incremented in the
stack.Route methods. This was going to be a problem once
IPv4/IPv6 WritePackets support fragmentation because Route.WritePackets
might now know how many packets are left after an error occurs.

Test:
  - pkg/tcpip/network/ipv4:ipv4_test
  - pkg/tcpip/network/ipv6:ipv6_test
PiperOrigin-RevId: 334687983

3 files changed, 59 insertions, 6 deletions

diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index 34d3f8474..1f6e14c3f 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -278,6 +278,7 @@ func (e *endpoint) writePacketFragments(r *stack.Route, gso *stack.GSO, mtu int,
 
 		// Send out the fragment.
 		if err := e.linkEP.WritePacket(r, gso, ProtocolNumber, fragPkt); err != nil {
+			r.Stats().IP.OutgoingPacketErrors.IncrementBy(uint64(n - i))
 			return err
 		}
 		r.Stats().IP.PacketsSent.Increment()
@@ -349,6 +350,7 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.Netw
 		return e.writePacketFragments(r, gso, int(e.linkEP.MTU()), pkt)
 	}
 	if err := e.linkEP.WritePacket(r, gso, ProtocolNumber, pkt); err != nil {
+		r.Stats().IP.OutgoingPacketErrors.Increment()
 		return err
 	}
 	r.Stats().IP.PacketsSent.Increment()
@@ -379,6 +381,9 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 		// faster WritePackets API directly.
 		n, err := e.linkEP.WritePackets(r, gso, pkts, ProtocolNumber)
 		r.Stats().IP.PacketsSent.IncrementBy(uint64(n))
+		if err != nil {
+			r.Stats().IP.OutgoingPacketErrors.IncrementBy(uint64(pkts.Len() - n))
+		}
 		return n, err
 	}
 	r.Stats().IP.IPTablesOutputDropped.IncrementBy(uint64(len(dropped)))
@@ -403,6 +408,7 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 		}
 		if err := e.linkEP.WritePacket(r, gso, ProtocolNumber, pkt); err != nil {
 			r.Stats().IP.PacketsSent.IncrementBy(uint64(n))
+			r.Stats().IP.OutgoingPacketErrors.IncrementBy(uint64(pkts.Len() - n - len(dropped)))
 			// Dropped packets aren't errors, so include them in
 			// the return value.
 			return n + len(dropped), err
@@ -461,9 +467,12 @@ func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBu
 		return nil
 	}
 
+	if err := e.linkEP.WritePacket(r, nil /* gso */, ProtocolNumber, pkt); err != nil {
+		r.Stats().IP.OutgoingPacketErrors.Increment()
+		return err
+	}
 	r.Stats().IP.PacketsSent.Increment()
-
-	return e.linkEP.WritePacket(r, nil /* gso */, ProtocolNumber, pkt)
+	return nil
 }
 
 // HandlePacket is called by the link layer when new ipv4 packets arrive for
diff --git a/pkg/tcpip/network/ipv4/ipv4_test.go b/pkg/tcpip/network/ipv4/ipv4_test.go
index ad3bc53ae..33cd5a3eb 100644
--- a/pkg/tcpip/network/ipv4/ipv4_test.go
+++ b/pkg/tcpip/network/ipv4/ipv4_test.go
@@ -450,6 +450,9 @@ func TestFragmentation(t *testing.T) {
 			if got, want := len(ep.WrittenPackets), int(r.Stats().IP.PacketsSent.Value()); got != want {
 				t.Errorf("no errors yet got len(ep.WrittenPackets) = %d, want = %d", got, want)
 			}
+			if got := r.Stats().IP.OutgoingPacketErrors.Value(); got != 0 {
+				t.Errorf("got r.Stats().IP.OutgoingPacketErrors.Value() = %d, want = 0", got)
+			}
 			compareFragments(t, ep.WrittenPackets, source, ft.mtu)
 		})
 	}
@@ -465,11 +468,44 @@ func TestFragmentationErrors(t *testing.T) {
 		payloadViewsSizes     []int
 		err                   *tcpip.Error
 		allowPackets          int
+		fragmentCount         int
 	}{
-		{"NoFrag", 2000, 0, []int{1000}, tcpip.ErrAborted, 0},
-		{"ErrorOnFirstFrag", 500, 0, []int{1000}, tcpip.ErrAborted, 0},
-		{"ErrorOnSecondFrag", 500, 0, []int{1000}, tcpip.ErrAborted, 1},
-		{"ErrorOnFirstFragMTUSmallerThanHeader", 500, 1000, []int{500}, tcpip.ErrAborted, 0},
+		{
+			description:           "NoFrag",
+			mtu:                   2000,
+			transportHeaderLength: 0,
+			payloadViewsSizes:     []int{1000},
+			err:                   tcpip.ErrAborted,
+			allowPackets:          0,
+			fragmentCount:         1,
+		},
+		{
+			description:           "ErrorOnFirstFrag",
+			mtu:                   500,
+			transportHeaderLength: 0,
+			payloadViewsSizes:     []int{1000},
+			err:                   tcpip.ErrAborted,
+			allowPackets:          0,
+			fragmentCount:         3,
+		},
+		{
+			description:           "ErrorOnSecondFrag",
+			mtu:                   500,
+			transportHeaderLength: 0,
+			payloadViewsSizes:     []int{1000},
+			err:                   tcpip.ErrAborted,
+			allowPackets:          1,
+			fragmentCount:         3,
+		},
+		{
+			description:           "ErrorOnFirstFragMTUSmallerThanHeader",
+			mtu:                   500,
+			transportHeaderLength: 1000,
+			payloadViewsSizes:     []int{500},
+			err:                   tcpip.ErrAborted,
+			allowPackets:          0,
+			fragmentCount:         4,
+		},
 	}
 
 	for _, ft := range fragTests {
@@ -488,6 +524,9 @@ func TestFragmentationErrors(t *testing.T) {
 			if got, want := len(ep.WrittenPackets), int(r.Stats().IP.PacketsSent.Value()); err != nil && got != want {
 				t.Errorf("got len(ep.WrittenPackets) = %d, want = %d", got, want)
 			}
+			if got, want := int(r.Stats().IP.OutgoingPacketErrors.Value()), ft.fragmentCount-ft.allowPackets; got != want {
+				t.Errorf("got r.Stats().IP.OutgoingPacketErrors.Value() = %d, want = %d", got, want)
+			}
 		})
 	}
 }
diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go
index 7458c3795..c8a3e0b34 100644
--- a/pkg/tcpip/network/ipv6/ipv6.go
+++ b/pkg/tcpip/network/ipv6/ipv6.go
@@ -424,6 +424,7 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.Netw
 	}
 
 	if err := e.linkEP.WritePacket(r, gso, ProtocolNumber, pkt); err != nil {
+		r.Stats().IP.OutgoingPacketErrors.Increment()
 		return err
 	}
 	r.Stats().IP.PacketsSent.Increment()
@@ -453,6 +454,9 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 		// faster WritePackets API directly.
 		n, err := e.linkEP.WritePackets(r, gso, pkts, ProtocolNumber)
 		r.Stats().IP.PacketsSent.IncrementBy(uint64(n))
+		if err != nil {
+			r.Stats().IP.OutgoingPacketErrors.IncrementBy(uint64(pkts.Len() - n))
+		}
 		return n, err
 	}
 	r.Stats().IP.IPTablesOutputDropped.IncrementBy(uint64(len(dropped)))
@@ -477,6 +481,7 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 		}
 		if err := e.linkEP.WritePacket(r, gso, ProtocolNumber, pkt); err != nil {
 			r.Stats().IP.PacketsSent.IncrementBy(uint64(n))
+			r.Stats().IP.OutgoingPacketErrors.IncrementBy(uint64(pkts.Len() - n + len(dropped)))
 			// Dropped packets aren't errors, so include them in
 			// the return value.
 			return n + len(dropped), err