TUN-6592: Decrement TTL and return ICMP time exceed if it's 0

packet/funnel_test.go

@@ -0,0 +1,16 @@
+package packet
+
+import "net/netip"
+
+type mockFunnelUniPipe struct {
+	uniPipe chan RawPacket
+}
+
+func (mfui *mockFunnelUniPipe) SendPacket(dst netip.Addr, pk RawPacket) error {
+	mfui.uniPipe <- pk
+	return nil
+}
+
+func (mfui *mockFunnelUniPipe) Close() error {
+	return nil
+}