TUN-6856: Refactor to lay foundation for tracing ICMP

Remove send and return methods from Funnel interface. Users of Funnel can provide their own send and return methods without wrapper to comply with the interface.
Move packet router to ingress package to avoid circular dependency

ingress/icmp_posix.go

@@ -43,24 +43,54 @@ type flow3Tuple struct {
 
 // icmpEchoFlow implements the packet.Funnel interface.
 type icmpEchoFlow struct {
-	*packet.RawPacketFunnel
+	*packet.ActivityTracker
+	closeCallback  func() error
+	src            netip.Addr
+	originConn     *icmp.PacketConn
+	responder      *packetResponder
 	assignedEchoID int
 	originalEchoID int
 	// it's up to the user to ensure respEncoder is not used concurrently
 	respEncoder *packet.Encoder
 }
 
-func newICMPEchoFlow(src netip.Addr, sendPipe, returnPipe packet.FunnelUniPipe, assignedEchoID, originalEchoID int, respEncoder *packet.Encoder) *icmpEchoFlow {
+func newICMPEchoFlow(src netip.Addr, closeCallback func() error, originConn *icmp.PacketConn, responder *packetResponder, assignedEchoID, originalEchoID int, respEncoder *packet.Encoder) *icmpEchoFlow {
 	return &icmpEchoFlow{
-		RawPacketFunnel: packet.NewRawPacketFunnel(src, sendPipe, returnPipe),
+		ActivityTracker: packet.NewActivityTracker(),
+		closeCallback:   closeCallback,
+		src:             src,
+		originConn:      originConn,
+		responder:       responder,
 		assignedEchoID:  assignedEchoID,
 		originalEchoID:  originalEchoID,
 		respEncoder:     respEncoder,
 	}
 }
 
+func (ief *icmpEchoFlow) Equal(other packet.Funnel) bool {
+	otherICMPFlow, ok := other.(*icmpEchoFlow)
+	if !ok {
+		return false
+	}
+	if otherICMPFlow.src != ief.src {
+		return false
+	}
+	if otherICMPFlow.originalEchoID != ief.originalEchoID {
+		return false
+	}
+	if otherICMPFlow.assignedEchoID != ief.assignedEchoID {
+		return false
+	}
+	return true
+}
+
+func (ief *icmpEchoFlow) Close() error {
+	return ief.closeCallback()
+}
+
 // sendToDst rewrites the echo ID to the one assigned to this flow
 func (ief *icmpEchoFlow) sendToDst(dst netip.Addr, msg *icmp.Message) error {
+	ief.UpdateLastActive()
 	originalEcho, err := getICMPEcho(msg)
 	if err != nil {
 		return err
@@ -80,17 +110,21 @@ func (ief *icmpEchoFlow) sendToDst(dst netip.Addr, msg *icmp.Message) error {
 	if err != nil {
 		return err
 	}
-	return ief.SendToDst(dst, packet.RawPacket{Data: serializedPacket})
+	_, err = ief.originConn.WriteTo(serializedPacket, &net.UDPAddr{
+		IP: dst.AsSlice(),
+	})
+	return err
 }
 
 // returnToSrc rewrites the echo ID to the original echo ID from the eyeball
 func (ief *icmpEchoFlow) returnToSrc(reply *echoReply) error {
+	ief.UpdateLastActive()
 	reply.echo.ID = ief.originalEchoID
 	reply.msg.Body = reply.echo
 	pk := packet.ICMP{
 		IP: &packet.IP{
 			Src:      reply.from,
-			Dst:      ief.Src,
+			Dst:      ief.src,
 			Protocol: layers.IPProtocol(reply.msg.Type.Protocol()),
 			TTL:      packet.DefaultTTL,
 		},
@@ -100,7 +134,7 @@ func (ief *icmpEchoFlow) returnToSrc(reply *echoReply) error {
 	if err != nil {
 		return err
 	}
-	return ief.ReturnToSrc(serializedPacket)
+	return ief.responder.returnPacket(serializedPacket)
 }
 
 type echoReply struct {