Migrate to header-based network isolation key

Replace the C API-based SetConcurrencyIndex with the simpler
header-based approach from upstream naiveproxy.

Users now set network isolation via the `-network-isolation-key`
header instead of calling SetConcurrencyIndex().

naiveproxy changes:
- Revert 7ed35377ef (complex NAK C API)
- Cherry-pick 87b03cd9faad (header-based implementation)

Author: nekohasekai

bidirectional_conn.go

@@ -16,7 +16,6 @@ type BidirectionalConn struct {
 	stream           BidirectionalStream
 	readWaitHeaders  bool
 	writeWaitHeaders bool
-	concurrencyIndex int
 	access           sync.Mutex
 	close            chan struct{}
 	done             chan struct{}
@@ -28,11 +27,10 @@ type BidirectionalConn struct {
 	headers          map[string]string
 }
 
-func (e StreamEngine) CreateConn(readWaitHeaders bool, writeWaitHeaders bool, concurrencyIndex int) *BidirectionalConn {
+func (e StreamEngine) CreateConn(readWaitHeaders bool, writeWaitHeaders bool) *BidirectionalConn {
 	conn := &BidirectionalConn{
 		readWaitHeaders:  readWaitHeaders,
 		writeWaitHeaders: writeWaitHeaders,
-		concurrencyIndex: concurrencyIndex,
 		close:            make(chan struct{}),
 		done:             make(chan struct{}),
 		ready:            make(chan struct{}),
@@ -54,9 +52,6 @@ func (c *BidirectionalConn) Start(method string, url string, headers map[string]
 		return net.ErrClosed
 	default:
 	}
-	if c.concurrencyIndex >= 0 {
-		c.stream.SetConcurrencyIndex(c.concurrencyIndex)
-	}
 	if !c.stream.Start(method, url, headers, priority, endOfStream) {
 		return os.ErrInvalid
 	}

bidirectional_stream_cgo.go

@@ -156,11 +156,3 @@ func (c BidirectionalStream) Flush() {
 func (c BidirectionalStream) Cancel() {
 	C.bidirectional_stream_cancel((*C.bidirectional_stream)(unsafe.Pointer(c.ptr)))
 }
-
-// SetConcurrencyIndex sets the connection pool isolation index for insecure-concurrency feature.
-// index: 0 to N-1, consistent with naiveproxy's insecure-concurrency behavior.
-// Connections with the same index will reuse the same HTTP/2 connection.
-// Must be called before Start().
-func (c BidirectionalStream) SetConcurrencyIndex(index int) {
-	C.bidirectional_stream_set_concurrency_index((*C.bidirectional_stream)(unsafe.Pointer(c.ptr)), C.int(index))
-}

bidirectional_stream_purego.go

@@ -106,7 +106,3 @@ func (s BidirectionalStream) Flush() {
 func (s BidirectionalStream) Cancel() {
 	cronet.BidirectionalStreamCancel(s.ptr)
 }
-
-func (s BidirectionalStream) SetConcurrencyIndex(index int) {
-	cronet.BidirectionalStreamSetConcurrencyIndex(s.ptr, int32(index))
-}

internal/cronet/api_purego.go

@@ -1041,7 +1041,3 @@ func BidirectionalStreamFlush(stream uintptr) {
 func BidirectionalStreamCancel(stream uintptr) {
 	bidirectionalStreamCancel(stream)
 }
-
-func BidirectionalStreamSetConcurrencyIndex(stream uintptr, index int32) {
-	bidirectionalStreamSetConcurrencyIndex(stream, index)
-}

internal/cronet/loader_unix.go

@@ -920,9 +920,6 @@ func registerSymbols() error {
 	if err := registerFunc(&bidirectionalStreamCancel, "bidirectional_stream_cancel"); err != nil {
 		return err
 	}
-	if err := registerFunc(&bidirectionalStreamSetConcurrencyIndex, "bidirectional_stream_set_concurrency_index"); err != nil {
-		return err
-	}
 
 	return nil
 }

internal/cronet/loader_windows.go

@@ -945,9 +945,6 @@ func registerSymbols() error {
 	if err := registerFunc(&bidirectionalStreamCancel, "bidirectional_stream_cancel"); err != nil {
 		return err
 	}
-	if err := registerFunc(&bidirectionalStreamSetConcurrencyIndex, "bidirectional_stream_set_concurrency_index"); err != nil {
-		return err
-	}
 
 	// Register float functions (platform-specific, see loader_windows_float*.go)
 	if err := registerFloatFuncs(); err != nil {

internal/cronet/symbols_purego.go

@@ -308,7 +308,6 @@ var (
 	bidirectionalStreamWrite                         func(uintptr, uintptr, int32, bool) int32
 	bidirectionalStreamFlush                         func(uintptr)
 	bidirectionalStreamCancel                        func(uintptr)
-	bidirectionalStreamSetConcurrencyIndex           func(uintptr, int32)
 )
 
 // GoString converts a C string pointer to a Go string.

naive_client.go

@@ -161,8 +161,11 @@ func (c *NaiveClient) DialContext(ctx context.Context, destination M.Socksaddr)
 		headers[key] = value
 	}
 
-	concurrencyIndex := int(c.counter.Add(1) % uint64(c.concurrency))
-	conn := c.streamEngine.CreateConn(true, false, concurrencyIndex)
+	if c.concurrency > 1 {
+		concurrencyIndex := int(c.counter.Add(1) % uint64(c.concurrency))
+		headers["-network-isolation-key"] = F.ToString("https://pool-", concurrencyIndex, ":443")
+	}
+	conn := c.streamEngine.CreateConn(true, false)
 	err := conn.Start("CONNECT", c.serverURL, headers, 0, false)
 	if err != nil {
 		return nil, err