XHTTP/3 client: Actively close underlying QUIC & UDP (#6332)

Fixes https://github.com/XTLS/Xray-core/issues/6328#issuecomment-4730379021

transport/internet/splithttp/client.go

@@ -9,6 +9,7 @@ import (
 	"net/http/httptrace"
 	"sync"
 
+	"github.com/apernet/quic-go/http3"
 	"github.com/xtls/xray-core/common"
 	"github.com/xtls/xray-core/common/buf"
 	"github.com/xtls/xray-core/common/errors"
@@ -176,6 +177,15 @@ func (c *DefaultDialerClient) PostPacket(ctx context.Context, url string, sessio
 	return nil
 }
 
+// HTTP/1.1 and HTTP/2 will close itself, we only handle HTTP/3 here
+func (c *DefaultDialerClient) Close() error {
+	transport := c.client.Transport
+	if h3Transport, ok := transport.(*http3.Transport); ok {
+		h3Transport.Close()
+	}
+	return nil
+}
+
 type WaitReadCloser struct {
 	Wait chan struct{}
 	io.ReadCloser

transport/internet/splithttp/dialer.go

@@ -259,6 +259,7 @@ func createHTTPClient(dest net.Destination, streamSettings *internet.MemoryStrea
 				if err != nil {
 					return nil, err
 				}
+				context.AfterFunc(conn.Context(), func() { pktConn.Close() })
 
 				switch quicParams.Congestion {
 				case "reno":
@@ -425,10 +426,10 @@ func Dial(ctx context.Context, dest net.Destination, streamSettings *internet.Me
 	}
 
 	if xmuxClient != nil {
-		xmuxClient.OpenUsage.Add(1)
+		xmuxClient.AddRunning()
 	}
 	if xmuxClient2 != nil && xmuxClient2 != xmuxClient {
-		xmuxClient2.OpenUsage.Add(1)
+		xmuxClient2.AddRunning()
 	}
 	var closed atomic.Int32
 
@@ -440,10 +441,10 @@ func Dial(ctx context.Context, dest net.Destination, streamSettings *internet.Me
 				return
 			}
 			if xmuxClient != nil {
-				xmuxClient.OpenUsage.Add(-1)
+				xmuxClient.DoneRunning()
 			}
 			if xmuxClient2 != nil && xmuxClient2 != xmuxClient {
-				xmuxClient2.OpenUsage.Add(-1)
+				xmuxClient2.DoneRunning()
 			}
 		},
 	}

transport/internet/splithttp/mux.go

@@ -8,6 +8,7 @@ import (
 	"sync/atomic"
 	"time"
 
+	"github.com/xtls/xray-core/common"
 	"github.com/xtls/xray-core/common/errors"
 )
 
@@ -17,10 +18,27 @@ type XmuxConn interface {
 
 type XmuxClient struct {
 	XmuxConn     XmuxConn
-	OpenUsage    atomic.Int32
+	Running      atomic.Int32
 	leftUsage    int32
 	LeftRequests atomic.Int32
 	UnreusableAt time.Time
+	NotUsed      atomic.Bool
+}
+
+func (c *XmuxClient) AddRunning() {
+	c.Running.Add(1)
+}
+
+func (c *XmuxClient) DoneRunning() {
+	c.Running.Add(-1)
+	c.maybeClose()
+}
+
+// close the XmuxConn if it is not used and has no running requests
+func (c *XmuxClient) maybeClose() {
+	if c.NotUsed.Load() && c.Running.Load() <= 0 {
+		common.Close(c.XmuxConn)
+	}
 }
 
 type XmuxManager struct {
@@ -68,10 +86,12 @@ func (m *XmuxManager) GetXmuxClient(ctx context.Context) *XmuxClient { // when l
 			xmuxClient.LeftRequests.Load() <= 0 ||
 			(xmuxClient.UnreusableAt != time.Time{} && time.Now().After(xmuxClient.UnreusableAt)) {
 			errors.LogDebug(ctx, "XMUX: removing xmuxClient, IsClosed() = ", xmuxClient.XmuxConn.IsClosed(),
-				", OpenUsage = ", xmuxClient.OpenUsage.Load(),
+				", Running = ", xmuxClient.Running.Load(),
 				", leftUsage = ", xmuxClient.leftUsage,
 				", LeftRequests = ", xmuxClient.LeftRequests.Load(),
 				", UnreusableAt = ", xmuxClient.UnreusableAt)
+			xmuxClient.NotUsed.Store(true)
+			xmuxClient.maybeClose()
 			m.xmuxClients = append(m.xmuxClients[:i], m.xmuxClients[i+1:]...)
 		} else {
 			i++
@@ -91,7 +111,7 @@ func (m *XmuxManager) GetXmuxClient(ctx context.Context) *XmuxClient { // when l
 	xmuxClients := make([]*XmuxClient, 0)
 	if m.concurrency > 0 {
 		for _, xmuxClient := range m.xmuxClients {
-			if xmuxClient.OpenUsage.Load() < m.concurrency {
+			if xmuxClient.Running.Load() < m.concurrency {
 				xmuxClients = append(xmuxClients, xmuxClient)
 			}
 		}

transport/internet/splithttp/mux_test.go

@@ -63,7 +63,7 @@ func TestMaxConcurrency(t *testing.T) {
 	xmuxClients := make(map[interface{}]struct{})
 	for i := 0; i < 64; i++ {
 		xmuxClient := xmuxManager.GetXmuxClient(context.Background())
-		xmuxClient.OpenUsage.Add(1)
+		xmuxClient.AddRunning()
 		xmuxClients[xmuxClient] = struct{}{}
 	}
 
@@ -82,7 +82,7 @@ func TestDefault(t *testing.T) {
 	xmuxClients := make(map[interface{}]struct{})
 	for i := 0; i < 64; i++ {
 		xmuxClient := xmuxManager.GetXmuxClient(context.Background())
-		xmuxClient.OpenUsage.Add(1)
+		xmuxClient.AddRunning()
 		xmuxClients[xmuxClient] = struct{}{}
 	}