TUN-6530: Implement ICMPv4 proxy

This proxy uses unprivileged datagram-oriented endpoint and is shared by all quic connections

ingress/origin_icmp_proxy_test.go

@@ -0,0 +1,150 @@
+package ingress
+
+import (
+	"context"
+	"fmt"
+	"net/netip"
+	"runtime"
+	"testing"
+
+	"github.com/google/gopacket/layers"
+	"github.com/rs/zerolog"
+	"github.com/stretchr/testify/require"
+	"golang.org/x/net/icmp"
+	"golang.org/x/net/ipv4"
+
+	"github.com/cloudflare/cloudflared/packet"
+)
+
+var (
+	noopLogger  = zerolog.Nop()
+	localhostIP = netip.MustParseAddr("127.0.0.1")
+)
+
+// TestICMPProxyEcho makes sure we can send ICMP echo via the Request method and receives response via the
+// ListenResponse method
+func TestICMPProxyEcho(t *testing.T) {
+	skipWindows(t)
+	const (
+		echoID = 36571
+		endSeq = 100
+	)
+	proxy, err := NewICMPProxy("udp4", localhostIP.AsSlice(), &noopLogger)
+	require.NoError(t, err)
+
+	proxyDone := make(chan struct{})
+	ctx, cancel := context.WithCancel(context.Background())
+	go func() {
+		proxy.ListenResponse(ctx)
+		close(proxyDone)
+	}()
+
+	responder := echoFlowResponder{
+		decoder:  packet.NewICMPDecoder(),
+		respChan: make(chan []byte),
+	}
+
+	ip := packet.IP{
+		Src:      localhostIP,
+		Dst:      localhostIP,
+		Protocol: layers.IPProtocolICMPv4,
+	}
+	for i := 0; i < endSeq; i++ {
+		pk := packet.ICMP{
+			IP: &ip,
+			Message: &icmp.Message{
+				Type: ipv4.ICMPTypeEcho,
+				Code: 0,
+				Body: &icmp.Echo{
+					ID:   echoID,
+					Seq:  i,
+					Data: []byte(fmt.Sprintf("icmp echo seq %d", i)),
+				},
+			},
+		}
+		require.NoError(t, proxy.Request(&pk, &responder))
+		responder.validate(t, &pk)
+	}
+	cancel()
+	<-proxyDone
+}
+
+// TestICMPProxyRejectNotEcho makes sure it rejects messages other than echo
+func TestICMPProxyRejectNotEcho(t *testing.T) {
+	skipWindows(t)
+	msgs := []icmp.Message{
+		{
+			Type: ipv4.ICMPTypeDestinationUnreachable,
+			Code: 1,
+			Body: &icmp.DstUnreach{
+				Data: []byte("original packet"),
+			},
+		},
+		{
+			Type: ipv4.ICMPTypeTimeExceeded,
+			Code: 1,
+			Body: &icmp.TimeExceeded{
+				Data: []byte("original packet"),
+			},
+		},
+		{
+			Type: ipv4.ICMPType(2),
+			Code: 0,
+			Body: &icmp.PacketTooBig{
+				MTU:  1280,
+				Data: []byte("original packet"),
+			},
+		},
+	}
+	proxy, err := NewICMPProxy("udp4", localhostIP.AsSlice(), &noopLogger)
+	require.NoError(t, err)
+
+	responder := echoFlowResponder{
+		decoder:  packet.NewICMPDecoder(),
+		respChan: make(chan []byte),
+	}
+	for _, m := range msgs {
+		pk := packet.ICMP{
+			IP: &packet.IP{
+				Src:      localhostIP,
+				Dst:      localhostIP,
+				Protocol: layers.IPProtocolICMPv4,
+			},
+			Message: &m,
+		}
+		require.Error(t, proxy.Request(&pk, &responder))
+	}
+}
+
+func skipWindows(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("Cannot create non-privileged datagram-oriented ICMP endpoint on Windows")
+	}
+}
+
+type echoFlowResponder struct {
+	decoder  *packet.ICMPDecoder
+	respChan chan []byte
+}
+
+func (efr *echoFlowResponder) SendPacket(pk packet.RawPacket) error {
+	copiedPacket := make([]byte, len(pk.Data))
+	copy(copiedPacket, pk.Data)
+	efr.respChan <- copiedPacket
+	return nil
+}
+
+func (efr *echoFlowResponder) validate(t *testing.T, echoReq *packet.ICMP) {
+	pk := <-efr.respChan
+	decoded, err := efr.decoder.Decode(packet.RawPacket{Data: pk})
+	require.NoError(t, err)
+	require.Equal(t, decoded.Src, echoReq.Dst)
+	require.Equal(t, decoded.Dst, echoReq.Src)
+	require.Equal(t, echoReq.Protocol, decoded.Protocol)
+
+	require.Equal(t, ipv4.ICMPTypeEchoReply, decoded.Type)
+	require.Equal(t, 0, decoded.Code)
+	require.NotZero(t, decoded.Checksum)
+	// TODO: TUN-6586: Enable this validation when ICMP echo ID matches on Linux
+	//require.Equal(t, echoReq.Body, decoded.Body)
+}