TUN-9882: Add buffers for UDP and ICMP datagrams in datagram v3

Instead of creating a go routine to process each incoming datagram from the tunnel, a single consumer (the demuxer) will
process each of the datagrams in serial.

Registration datagrams will still be spun out into separate go routines since they are responsible for managing the
lifetime of the session once started via the `Serve` method.

UDP payload datagrams will be handled in separate channels to allow for parallel writing inside of the scope of a
session via a new write loop. This channel will have a small buffer to help unblock the demuxer from dequeueing other
datagrams.

ICMP datagrams will be funneled into a single channel across all possible origins with a single consumer to write to
their respective destinations.

Each of these changes is to prevent datagram reordering from occurring when dequeuing from the tunnel connection. By
establishing a single demuxer that serializes the writes per session, each session will be able to write sequentially,
but in parallel to their respective origins.

Closes TUN-9882

quic/v3/session_test.go

@@ -31,60 +31,61 @@ func TestSessionNew(t *testing.T) {
 	}
 }
 
-func testSessionWrite(t *testing.T, payload []byte) {
+func testSessionWrite(t *testing.T, payloads [][]byte) {
 	log := zerolog.Nop()
 	origin, server := net.Pipe()
 	defer origin.Close()
 	defer server.Close()
-	// Start origin server read
-	serverRead := make(chan []byte, 1)
+	// Start origin server reads
+	serverRead := make(chan []byte, len(payloads))
 	go func() {
-		read := make([]byte, 1500)
-		_, _ = server.Read(read[:])
-		serverRead <- read
+		for range len(payloads) {
+			buf := make([]byte, 1500)
+			_, _ = server.Read(buf[:])
+			serverRead <- buf
+		}
+		close(serverRead)
 	}()
-	// Create session and write to origin
+
+	// Create a session
 	session := v3.NewSession(testRequestID, 5*time.Second, origin, testOriginAddr, testLocalAddr, &noopEyeball{}, &noopMetrics{}, &log)
-	n, err := session.Write(payload)
 	defer session.Close()
-	if err != nil {
-		t.Fatal(err)
-	}
-	if n != len(payload) {
-		t.Fatal("unable to write the whole payload")
+	// Start the Serve to begin the writeLoop
+	ctx, cancel := context.WithCancelCause(t.Context())
+	defer cancel(context.Canceled)
+	done := make(chan error)
+	go func() {
+		done <- session.Serve(ctx)
+	}()
+	// Write the payloads to the session
+	for _, payload := range payloads {
+		session.Write(payload)
 	}
 
-	read := <-serverRead
-	if !slices.Equal(payload, read[:len(payload)]) {
-		t.Fatal("payload provided from origin and read value are not the same")
+	// Read from the origin to ensure the payloads were received (in-order)
+	for i, payload := range payloads {
+		read := <-serverRead
+		if !slices.Equal(payload, read[:len(payload)]) {
+			t.Fatalf("payload[%d] provided from origin and read value are not the same (%x) and (%x)", i, payload[:16], read[:16])
+		}
+	}
+	_, more := <-serverRead
+	if more {
+		t.Fatalf("expected the session to have all of the origin payloads received: %d", len(serverRead))
+	}
+
+	assertContextClosed(t, ctx, done, cancel)
+}
+
+func TestSessionWrite(t *testing.T) {
+	defer leaktest.Check(t)()
+	for i := range 1280 {
+		payloads := makePayloads(i, 16)
+		testSessionWrite(t, payloads)
 	}
 }
 
-func TestSessionWrite_Max(t *testing.T) {
-	defer leaktest.Check(t)()
-	payload := makePayload(1280)
-	testSessionWrite(t, payload)
-}
-
-func TestSessionWrite_Min(t *testing.T) {
-	defer leaktest.Check(t)()
-	payload := makePayload(0)
-	testSessionWrite(t, payload)
-}
-
-func TestSessionServe_OriginMax(t *testing.T) {
-	defer leaktest.Check(t)()
-	payload := makePayload(1280)
-	testSessionServe_Origin(t, payload)
-}
-
-func TestSessionServe_OriginMin(t *testing.T) {
-	defer leaktest.Check(t)()
-	payload := makePayload(0)
-	testSessionServe_Origin(t, payload)
-}
-
-func testSessionServe_Origin(t *testing.T, payload []byte) {
+func testSessionRead(t *testing.T, payloads [][]byte) {
 	log := zerolog.Nop()
 	origin, server := net.Pipe()
 	defer origin.Close()
@@ -100,37 +101,42 @@ func testSessionServe_Origin(t *testing.T, payload []byte) {
 		done <- session.Serve(ctx)
 	}()
 
-	// Write from the origin server
-	_, err := server.Write(payload)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	select {
-	case data := <-eyeball.recvData:
-		// check received data matches provided from origin
-		expectedData := makePayload(1500)
-		_ = v3.MarshalPayloadHeaderTo(testRequestID, expectedData[:])
-		copy(expectedData[17:], payload)
-		if !slices.Equal(expectedData[:v3.DatagramPayloadHeaderLen+len(payload)], data) {
-			t.Fatal("expected datagram did not equal expected")
+	// Write from the origin server to the eyeball
+	go func() {
+		for _, payload := range payloads {
+			_, _ = server.Write(payload)
+		}
+	}()
+
+	// Read from the eyeball to ensure the payloads were received (in-order)
+	for i, payload := range payloads {
+		select {
+		case data := <-eyeball.recvData:
+			// check received data matches provided from origin
+			expectedData := makePayload(1500)
+			_ = v3.MarshalPayloadHeaderTo(testRequestID, expectedData[:])
+			copy(expectedData[17:], payload)
+			if !slices.Equal(expectedData[:v3.DatagramPayloadHeaderLen+len(payload)], data) {
+				t.Fatalf("expected datagram[%d] did not equal expected", i)
+			}
+		case err := <-ctx.Done():
+			// we expect the payload to return before the context to cancel on the session
+			t.Fatal(err)
 		}
-		cancel(errExpectedContextCanceled)
-	case err := <-ctx.Done():
-		// we expect the payload to return before the context to cancel on the session
-		t.Fatal(err)
 	}
 
-	err = <-done
-	if !errors.Is(err, context.Canceled) {
-		t.Fatal(err)
-	}
-	if !errors.Is(context.Cause(ctx), errExpectedContextCanceled) {
-		t.Fatal(err)
+	assertContextClosed(t, ctx, done, cancel)
+}
+
+func TestSessionRead(t *testing.T) {
+	defer leaktest.Check(t)()
+	for i := range 1280 {
+		payloads := makePayloads(i, 16)
+		testSessionRead(t, payloads)
 	}
 }
 
-func TestSessionServe_OriginTooLarge(t *testing.T) {
+func TestSessionRead_OriginTooLarge(t *testing.T) {
 	defer leaktest.Check(t)()
 	log := zerolog.Nop()
 	eyeball := newMockEyeball()
@@ -317,6 +323,8 @@ func TestSessionServe_IdleTimeout(t *testing.T) {
 	closeAfterIdle := 2 * time.Second
 	session := v3.NewSession(testRequestID, closeAfterIdle, origin, testOriginAddr, testLocalAddr, &noopEyeball{}, &noopMetrics{}, &log)
 	err := session.Serve(t.Context())
+
+	// Session should idle timeout if no reads or writes occur
 	if !errors.Is(err, v3.SessionIdleErr{}) {
 		t.Fatal(err)
 	}