TUN-8640: Add ICMP support for datagram V3

Closes TUN-8640

quic/v3/icmp.go

@@ -0,0 +1,52 @@
+package v3
+
+import (
+	"context"
+
+	"github.com/rs/zerolog"
+	"go.opentelemetry.io/otel/trace"
+
+	"github.com/cloudflare/cloudflared/ingress"
+	"github.com/cloudflare/cloudflared/packet"
+	"github.com/cloudflare/cloudflared/tracing"
+)
+
+// packetResponder is an implementation of the [ingress.ICMPResponder] which provides the ICMP Flow manager the
+// return path to return and ICMP Echo response back to the QUIC muxer.
+type packetResponder struct {
+	datagramMuxer DatagramICMPWriter
+	connID        uint8
+}
+
+func newPacketResponder(datagramMuxer DatagramICMPWriter, connID uint8) ingress.ICMPResponder {
+	return &packetResponder{
+		datagramMuxer,
+		connID,
+	}
+}
+
+func (pr *packetResponder) ConnectionIndex() uint8 {
+	return pr.connID
+}
+
+func (pr *packetResponder) ReturnPacket(pk *packet.ICMP) error {
+	return pr.datagramMuxer.SendICMPPacket(pk)
+}
+
+func (pr *packetResponder) AddTraceContext(tracedCtx *tracing.TracedContext, serializedIdentity []byte) {
+	// datagram v3 does not support tracing ICMP packets
+}
+
+func (pr *packetResponder) RequestSpan(ctx context.Context, pk *packet.ICMP) (context.Context, trace.Span) {
+	// datagram v3 does not support tracing ICMP packets
+	return ctx, tracing.NewNoopSpan()
+}
+
+func (pr *packetResponder) ReplySpan(ctx context.Context, logger *zerolog.Logger) (context.Context, trace.Span) {
+	// datagram v3 does not support tracing ICMP packets
+	return ctx, tracing.NewNoopSpan()
+}
+
+func (pr *packetResponder) ExportSpan() {
+	// datagram v3 does not support tracing ICMP packets
+}