fix: 修复 dedicated bulk attach 竞态并优化 short write 补写路径

- 客户端 dedicated attach 回复改为精确读取单帧，避免 attach reply 与后续 NBR1 数据粘连后被误解析 - 服务端 accepted attach 改为先 detach transport，再直接回 attach reply，随后立即切入 dedicated bulk read loop - transport 读循环在 stop 或 transport ownership 失效后不再继续上推已读数据，避免 handoff 后首包被旧 reader 吃掉 - dedicated bulk record 写路径改为 full-write，消除 short write 导致的 invalid bulk fast payload - 优化 vectored write 补写策略：先尝试一次 writev，未写完时直接顺序补完剩余 buffers，减少重复 WriteTo 开销 - 放宽 vectored write 能力识别，支持通过 UnwrapConn/WriteBuffers 命中 fast path - 修复 dedicated batch 排队路径 payload 复用问题，改为深拷贝 queued items - 补齐 dedicated attach、short write、payload clone、transport stop/handoff 等回归测试
2026-04-16 17:27:48 +08:00 · 2026-04-16 17:27:48 +08:00 · 4f760f2807
commit 4f760f2807
parent 7ed3dd5b37
9 changed files with 690 additions and 47 deletions
--- a/bulk_dedicated.go
+++ b/bulk_dedicated.go
@ -3,11 +3,13 @@ package notify
 import (
 	"b612.me/notify/internal/transport"
 	"b612.me/stario"
+	"bytes"
 	"context"
 	cryptorand "crypto/rand"
 	"encoding/binary"
 	"encoding/hex"
 	"errors"
+	"fmt"
 	"io"
 	"net"
 	"sync/atomic"
@ -19,8 +21,17 @@ const (
 	bulkDedicatedRecordMagic     = "NBR1"
 	bulkDedicatedRecordHeaderLen = 8
 	bulkDedicatedAttachTimeout   = 5 * time.Second
+
+	bulkDedicatedAttachFrameMagicSize     = 8
+	bulkDedicatedAttachFrameHeaderLen     = 14
+	bulkDedicatedAttachFrameVersionOffset = 12
+	bulkDedicatedAttachFrameFlagsOffset   = 13
+	bulkDedicatedAttachFrameVersionV1     = 1
+	bulkDedicatedAttachFrameFlagsNone     = 0
 )

+var bulkDedicatedAttachFrameMagic = [bulkDedicatedAttachFrameMagicSize]byte{11, 27, 19, 96, 12, 25, 2, 20}
+
 type bulkAttachRequest struct {
 	PeerID      string
 	BulkID      string
@ -121,6 +132,35 @@ func decodeDirectSignalPayload(sequenceDe func([]byte) (interface{}, error), msg
 	return unwrapTransferMsgEnvelope(env, sequenceDe)
 }

+func readDirectSignalFramePayload(conn net.Conn) ([]byte, error) {
+	if conn == nil {
+		return nil, net.ErrClosed
+	}
+	var header [bulkDedicatedAttachFrameHeaderLen]byte
+	if _, err := io.ReadFull(conn, header[:]); err != nil {
+		return nil, err
+	}
+	if !bytes.Equal(header[:bulkDedicatedAttachFrameMagicSize], bulkDedicatedAttachFrameMagic[:]) {
+		return nil, stario.ErrQueueDataFormat
+	}
+	if got := header[bulkDedicatedAttachFrameVersionOffset]; got != bulkDedicatedAttachFrameVersionV1 {
+		return nil, stario.ErrQueueUnsupportedVersion
+	}
+	if got := header[bulkDedicatedAttachFrameFlagsOffset]; got != bulkDedicatedAttachFrameFlagsNone {
+		return nil, stario.ErrQueueUnsupportedFlags
+	}
+	length := binary.BigEndian.Uint32(header[bulkDedicatedAttachFrameMagicSize : bulkDedicatedAttachFrameMagicSize+4])
+	maxInt := int(^uint(0) >> 1)
+	if uint64(length) > uint64(maxInt) {
+		return nil, stario.ErrQueueMessageTooLarge
+	}
+	payload := make([]byte, int(length))
+	if _, err := io.ReadFull(conn, payload); err != nil {
+		return nil, err
+	}
+	return payload, nil
+}
+
 func writeBulkDedicatedRecord(conn net.Conn, payload []byte) error {
 	return writeBulkDedicatedRecordWithDeadline(conn, payload, time.Time{})
 }
@ -133,9 +173,7 @@ func writeBulkDedicatedRecordWithDeadline(conn net.Conn, payload []byte, deadlin
 		var header [bulkDedicatedRecordHeaderLen]byte
 		copy(header[:4], bulkDedicatedRecordMagic)
 		binary.BigEndian.PutUint32(header[4:8], uint32(len(payload)))
-		buffers := net.Buffers{header[:], payload}
-		_, err := buffers.WriteTo(conn)
-		return err
+		return writeNetBuffersFullUnlocked(conn, net.Buffers{header[:], payload})
 	})
 }

@ -148,7 +186,7 @@ func readBulkDedicatedRecord(conn net.Conn) ([]byte, error) {
 		return nil, err
 	}
 	if string(header[:4]) != bulkDedicatedRecordMagic {
-		return nil, errBulkFastPayloadInvalid
+		return nil, fmt.Errorf("%w: record magic=%x", errBulkFastPayloadInvalid, header[:4])
 	}
 	size := int(binary.BigEndian.Uint32(header[4:8]))
 	if size < 0 {
@ -224,51 +262,34 @@ func (c *ClientCommon) sendDedicatedBulkAttachRequest(ctx context.Context, conn
 	if err != nil {
 		return bulkAttachResponse{}, err
 	}
-	queue := stario.NewQueue()
 	msg := TransferMsg{
 		ID:    atomic.AddUint64(&c.msgID, 1),
 		Key:   systemBulkAttachKey,
 		Value: reqPayload,
 		Type:  MSG_SYS_WAIT,
 	}
-	frame, err := encodeDirectSignalFrame(queue, c.sequenceEn, c.msgEn, c.SecretKey, msg)
+	frame, err := encodeDirectSignalFrame(stario.NewQueue(), c.sequenceEn, c.msgEn, c.SecretKey, msg)
 	if err != nil {
 		return bulkAttachResponse{}, err
 	}
 	if err := writeFullToConn(conn, frame); err != nil {
 		return bulkAttachResponse{}, err
 	}
-	replyCh := make(chan Message, 1)
-	readBuf := streamReadBuffer()
-	for {
-		if deadline, ok := ctx.Deadline(); ok {
-			_ = conn.SetReadDeadline(deadline)
-		}
-		n, err := conn.Read(readBuf)
-		if err != nil {
-			return bulkAttachResponse{}, err
-		}
-		parseErr := queue.ParseMessageOwned(readBuf[:n], "bulk-attach", func(msgq stario.MsgQueue) error {
-			transfer, err := decodeDirectSignalPayload(c.sequenceDe, c.msgDe, c.SecretKey, msgq.Msg)
-			if err != nil {
-				return err
-			}
-			replyCh <- Message{
-				ServerConn:  c,
-				TransferMsg: transfer,
-				NetType:     NET_CLIENT,
-			}
-			return nil
-		})
-		if parseErr != nil {
-			return bulkAttachResponse{}, parseErr
-		}
-		select {
-		case reply := <-replyCh:
-			return decodeBulkAttachResponse(c.sequenceDe, reply.Value)
-		default:
-		}
+	if deadline, ok := ctx.Deadline(); ok {
+		_ = conn.SetReadDeadline(deadline)
 	}
+	replyPayload, err := readDirectSignalFramePayload(conn)
+	if err != nil {
+		return bulkAttachResponse{}, err
+	}
+	transfer, err := decodeDirectSignalPayload(c.sequenceDe, c.msgDe, c.SecretKey, replyPayload)
+	if err != nil {
+		return bulkAttachResponse{}, err
+	}
+	if transfer.Key != systemBulkAttachKey || transfer.Type != MSG_SYS_REPLY || transfer.ID != msg.ID {
+		return bulkAttachResponse{}, errors.New("invalid bulk attach reply")
+	}
+	return decodeBulkAttachResponse(c.sequenceDe, transfer.Value)
 }

 func (c *ClientCommon) readDedicatedBulkLoop(bulk *bulkHandle, conn net.Conn) {
@ -323,14 +344,13 @@ func (s *ServerCommon) handleBulkAttachSystemMessage(message Message) bool {
 	}
 	if err != nil {
 		resp.Error = err.Error()
-	} else {
-		resp.Accepted = true
+		if current != nil {
+			_ = s.replyDedicatedBulkAttach(current, message, resp)
+		}
+		return true
 	}
 	if current != nil {
-		_ = s.replyDedicatedBulkAttach(current, message, resp)
-	}
-	if err == nil {
-		if attachErr := s.finishInboundDedicatedBulkAttach(current, logical, bulk); attachErr != nil {
+		if attachErr := s.finishInboundDedicatedBulkAttach(current, logical, bulk, message); attachErr != nil {
 			bulk.markReset(attachErr)
 		}
 	}
@ -368,7 +388,7 @@ func (s *ServerCommon) resolveInboundDedicatedBulk(current *LogicalConn, req bul
 	return logical, bulk, nil
 }

-func (s *ServerCommon) finishInboundDedicatedBulkAttach(current *LogicalConn, logical *LogicalConn, bulk *bulkHandle) error {
+func (s *ServerCommon) finishInboundDedicatedBulkAttach(current *LogicalConn, logical *LogicalConn, bulk *bulkHandle, message Message) error {
 	if current == nil || logical == nil || bulk == nil {
 		return errBulkLogicalConnNil
 	}
@ -376,18 +396,56 @@ func (s *ServerCommon) finishInboundDedicatedBulkAttach(current *LogicalConn, lo
 	if err != nil {
 		return err
 	}
-	if err := bulk.attachDedicatedConn(conn); err != nil {
+	fail := func(reason string, err error) error {
 		if conn != nil {
 			_ = conn.Close()
 		}
+		current.markSessionStopped(reason, err)
+		s.removeLogical(current)
 		return err
 	}
+	if err := s.replyDedicatedBulkAttachDetached(current, conn, message, bulkAttachResponse{Accepted: true}); err != nil {
+		return fail("bulk dedicated attach reply failed", err)
+	}
+	if err := bulk.attachDedicatedConn(conn); err != nil {
+		return fail("bulk dedicated attach failed", err)
+	}
 	go s.readDedicatedBulkLoop(logical, bulk, conn)
 	current.markSessionStopped("bulk dedicated attach", nil)
 	s.removeLogical(current)
 	return nil
 }

+func (s *ServerCommon) replyDedicatedBulkAttachDetached(client *LogicalConn, conn net.Conn, message Message, resp bulkAttachResponse) error {
+	if s == nil || client == nil {
+		return errBulkServerNil
+	}
+	if conn == nil {
+		return net.ErrClosed
+	}
+	msgEn := client.msgEnSnapshot()
+	if msgEn == nil {
+		return errTransportPayloadEncryptFailed
+	}
+	encoded, err := s.sequenceEn(resp)
+	if err != nil {
+		return err
+	}
+	reply := TransferMsg{
+		ID:    message.ID,
+		Key:   systemBulkAttachKey,
+		Value: encoded,
+		Type:  MSG_SYS_REPLY,
+	}
+	frame, err := encodeDirectSignalFrame(stario.NewQueue(), s.sequenceEn, msgEn, client.secretKeySnapshot(), reply)
+	if err != nil {
+		return err
+	}
+	return withRawConnWriteLockDeadline(conn, writeDeadlineFromTimeout(client.maxWriteTimeoutSnapshot()), func(conn net.Conn) error {
+		return writeFullToConnUnlocked(conn, frame)
+	})
+}
+
 func (s *ServerCommon) replyDedicatedBulkAttach(client *LogicalConn, message Message, resp bulkAttachResponse) error {
 	if s == nil || client == nil {
 		return errBulkServerNil
--- a/bulk_dedicated_attach_test.go
+++ b/bulk_dedicated_attach_test.go
@ -0,0 +1,217 @@
+package notify
+
+import (
+	"bytes"
+	"context"
+	"encoding/binary"
+	"net"
+	"testing"
+	"time"
+
+	"b612.me/stario"
+)
+
+type bulkAttachScriptConn struct {
+	readBuf  *bytes.Reader
+	writeBuf bytes.Buffer
+}
+
+func newBulkAttachScriptConn(inbound []byte) *bulkAttachScriptConn {
+	return &bulkAttachScriptConn{
+		readBuf: bytes.NewReader(append([]byte(nil), inbound...)),
+	}
+}
+
+func (c *bulkAttachScriptConn) Read(p []byte) (int, error)  { return c.readBuf.Read(p) }
+func (c *bulkAttachScriptConn) Write(p []byte) (int, error) { return c.writeBuf.Write(p) }
+func (c *bulkAttachScriptConn) Close() error                { return nil }
+func (c *bulkAttachScriptConn) LocalAddr() net.Addr         { return bulkAttachTestAddr("local") }
+func (c *bulkAttachScriptConn) RemoteAddr() net.Addr        { return bulkAttachTestAddr("remote") }
+func (c *bulkAttachScriptConn) SetDeadline(time.Time) error { return nil }
+func (c *bulkAttachScriptConn) SetReadDeadline(time.Time) error {
+	return nil
+}
+func (c *bulkAttachScriptConn) SetWriteDeadline(time.Time) error {
+	return nil
+}
+
+func (c *bulkAttachScriptConn) writtenBytes() []byte {
+	return append([]byte(nil), c.writeBuf.Bytes()...)
+}
+
+type bulkAttachTestAddr string
+
+func (a bulkAttachTestAddr) Network() string { return "tcp" }
+func (a bulkAttachTestAddr) String() string  { return string(a) }
+
+func encodeDedicatedRecordForAttachTest(payload []byte) []byte {
+	out := make([]byte, bulkDedicatedRecordHeaderLen+len(payload))
+	copy(out[:4], bulkDedicatedRecordMagic)
+	binary.BigEndian.PutUint32(out[4:8], uint32(len(payload)))
+	copy(out[bulkDedicatedRecordHeaderLen:], payload)
+	return out
+}
+
+func TestSendDedicatedBulkAttachRequestKeepsCoalescedDedicatedPayloadUnread(t *testing.T) {
+	client := NewClient().(*ClientCommon)
+	UseLegacySecurityClient(client)
+	client.msgID = 100
+
+	bulk := newBulkHandle(context.Background(), newBulkRuntime("dedicated-attach-test"), clientFileScope(), BulkOpenRequest{
+		BulkID:      "bulk-attach-test",
+		DataID:      1,
+		Dedicated:   true,
+		AttachToken: "attach-token",
+	}, 0, nil, nil, 0, nil, nil, nil, nil, nil)
+
+	encodedResp, err := client.sequenceEn(bulkAttachResponse{Accepted: true})
+	if err != nil {
+		t.Fatalf("encode bulkAttachResponse failed: %v", err)
+	}
+	replyFrame, err := encodeDirectSignalFrame(stario.NewQueue(), client.sequenceEn, client.msgEn, client.SecretKey, TransferMsg{
+		ID:    101,
+		Key:   systemBulkAttachKey,
+		Value: encodedResp,
+		Type:  MSG_SYS_REPLY,
+	})
+	if err != nil {
+		t.Fatalf("encode attach reply frame failed: %v", err)
+	}
+	dedicatedPayload := []byte("dedicated-tail-bytes")
+	conn := newBulkAttachScriptConn(append(replyFrame, encodeDedicatedRecordForAttachTest(dedicatedPayload)...))
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+	defer cancel()
+	resp, err := client.sendDedicatedBulkAttachRequest(ctx, conn, bulk)
+	if err != nil {
+		t.Fatalf("sendDedicatedBulkAttachRequest failed: %v", err)
+	}
+	if !resp.Accepted {
+		t.Fatalf("bulk attach response = %+v, want accepted", resp)
+	}
+
+	parsedReq := stario.NewQueue()
+	var reqMsg TransferMsg
+	if err := parsedReq.ParseMessageOwned(conn.writtenBytes(), "attach-request", func(msgq stario.MsgQueue) error {
+		transfer, err := decodeDirectSignalPayload(client.sequenceDe, client.msgDe, client.SecretKey, msgq.Msg)
+		if err != nil {
+			return err
+		}
+		reqMsg = transfer
+		return nil
+	}); err != nil {
+		t.Fatalf("parse written attach request failed: %v", err)
+	}
+	if reqMsg.Key != systemBulkAttachKey || reqMsg.Type != MSG_SYS_WAIT {
+		t.Fatalf("attach request message mismatch: %+v", reqMsg)
+	}
+	readPayload, err := readBulkDedicatedRecord(conn)
+	if err != nil {
+		t.Fatalf("readBulkDedicatedRecord after attach failed: %v", err)
+	}
+	if !bytes.Equal(readPayload, dedicatedPayload) {
+		t.Fatalf("dedicated payload mismatch: got %q want %q", string(readPayload), string(dedicatedPayload))
+	}
+}
+
+func TestHandleBulkAttachSystemMessageAcceptedWritesDirectReplyBeforeDedicatedHandoff(t *testing.T) {
+	server := NewServer().(*ServerCommon)
+	UseLegacySecurityServer(server)
+
+	sidecarLeft, sidecarRight := net.Pipe()
+	defer sidecarRight.Close()
+
+	current := server.bootstrapAcceptedLogical("dedicated-attach-current", nil, sidecarLeft)
+	if current == nil {
+		t.Fatal("bootstrapAcceptedLogical(current) should return logical")
+	}
+	target := server.bootstrapAcceptedLogical("dedicated-attach-target", nil, nil)
+	if target == nil {
+		t.Fatal("bootstrapAcceptedLogical(target) should return logical")
+	}
+
+	bulk := newBulkHandle(context.Background(), server.getBulkRuntime(), serverFileScope(target), BulkOpenRequest{
+		BulkID:      "server-dedicated-attach-test",
+		DataID:      7,
+		Dedicated:   true,
+		AttachToken: "attach-token",
+	}, 0, target, nil, 0, nil, nil, nil, nil, nil)
+	if err := server.getBulkRuntime().register(serverFileScope(target), bulk); err != nil {
+		t.Fatalf("register bulk runtime failed: %v", err)
+	}
+
+	reqPayload, err := server.sequenceEn(bulkAttachRequest{
+		PeerID:      target.ID(),
+		BulkID:      bulk.ID(),
+		AttachToken: "attach-token",
+	})
+	if err != nil {
+		t.Fatalf("encode bulkAttachRequest failed: %v", err)
+	}
+	msg := Message{
+		NetType:     NET_SERVER,
+		LogicalConn: current,
+		ClientConn:  current.compatClientConn(),
+		TransferMsg: TransferMsg{
+			ID:    42,
+			Key:   systemBulkAttachKey,
+			Value: reqPayload,
+			Type:  MSG_SYS_WAIT,
+		},
+		inboundConn: sidecarLeft,
+		Time:        time.Now(),
+	}
+
+	type attachReplyResult struct {
+		transfer TransferMsg
+		resp     bulkAttachResponse
+		err      error
+	}
+	replyCh := make(chan attachReplyResult, 1)
+	go func() {
+		_ = sidecarRight.SetReadDeadline(time.Now().Add(time.Second))
+		replyPayload, err := readDirectSignalFramePayload(sidecarRight)
+		if err != nil {
+			replyCh <- attachReplyResult{err: err}
+			return
+		}
+		transfer, err := decodeDirectSignalPayload(server.sequenceDe, current.msgDeSnapshot(), current.secretKeySnapshot(), replyPayload)
+		if err != nil {
+			replyCh <- attachReplyResult{err: err}
+			return
+		}
+		resp, err := decodeBulkAttachResponse(server.sequenceDe, transfer.Value)
+		replyCh <- attachReplyResult{transfer: transfer, resp: resp, err: err}
+	}()
+
+	if !server.handleBulkAttachSystemMessage(msg) {
+		t.Fatal("handleBulkAttachSystemMessage should accept dedicated attach message")
+	}
+
+	var result attachReplyResult
+	select {
+	case result = <-replyCh:
+	case <-time.After(2 * time.Second):
+		t.Fatal("timed out waiting for direct attach reply")
+	}
+	if result.err != nil {
+		t.Fatalf("read direct attach reply failed: %v", result.err)
+	}
+	transfer := result.transfer
+	if transfer.ID != msg.ID || transfer.Key != systemBulkAttachKey || transfer.Type != MSG_SYS_REPLY {
+		t.Fatalf("attach reply mismatch: %+v", transfer)
+	}
+	resp := result.resp
+	if !resp.Accepted || resp.Error != "" {
+		t.Fatalf("bulk attach response = %+v, want accepted", resp)
+	}
+	if got := bulk.dedicatedConnSnapshot(); got != sidecarLeft {
+		t.Fatalf("dedicated conn mismatch: got %v want %v", got, sidecarLeft)
+	}
+	if current.transportAttachedSnapshot() {
+		t.Fatal("attach sidecar logical transport should be detached after handoff")
+	}
+	if got := server.GetLogicalConn(current.ID()); got != nil {
+		t.Fatalf("attach sidecar logical should be removed after handoff, got %+v", got)
+	}
+}
--- a/bulk_dedicated_batch.go
+++ b/bulk_dedicated_batch.go
@ -165,8 +165,7 @@ func (s *bulkDedicatedSender) submitWriteBatch(ctx context.Context, items []bulk
 	if submitted, err := s.tryDirectSubmitBatch(ctx, items); submitted {
 		return err
 	}
-	queuedItems := make([]bulkDedicatedSendRequest, len(items))
-	copy(queuedItems, items)
+	queuedItems := cloneBulkDedicatedSendRequests(items)
 	return s.submitBatch(ctx, queuedItems, true)
 }

@ -458,6 +457,20 @@ func (s *bulkDedicatedSender) stoppedErr() error {
 	return errTransportDetached
 }

+func cloneBulkDedicatedSendRequests(items []bulkDedicatedSendRequest) []bulkDedicatedSendRequest {
+	if len(items) == 0 {
+		return nil
+	}
+	cloned := make([]bulkDedicatedSendRequest, len(items))
+	for i, item := range items {
+		cloned[i] = item
+		if len(item.Payload) > 0 {
+			cloned[i].Payload = append([]byte(nil), item.Payload...)
+		}
+	}
+	return cloned
+}
+
 func bulkDedicatedSendRequestLen(req bulkDedicatedSendRequest) int {
 	return bulkDedicatedSendRequestLenFromPayloadLen(len(req.Payload))
 }
--- a/bulk_dedicated_batch_test.go
+++ b/bulk_dedicated_batch_test.go
@ -1,6 +1,7 @@
 package notify

 import (
+	"bytes"
 	"context"
 	"errors"
 	"net"
@ -8,6 +9,38 @@ import (
 	"time"
 )

+func TestCloneBulkDedicatedSendRequestsDeepCopiesPayload(t *testing.T) {
+	src := []bulkDedicatedSendRequest{
+		{
+			Type:    bulkFastPayloadTypeData,
+			Seq:     1,
+			Payload: []byte("payload-a"),
+		},
+		{
+			Type:    bulkFastPayloadTypeReset,
+			Seq:     2,
+			Payload: []byte("payload-b"),
+		},
+	}
+	cloned := cloneBulkDedicatedSendRequests(src)
+	if len(cloned) != len(src) {
+		t.Fatalf("clone length = %d, want %d", len(cloned), len(src))
+	}
+	if &cloned[0] == &src[0] {
+		t.Fatal("request clone should not alias source slice elements")
+	}
+	if len(cloned[0].Payload) == 0 || len(src[0].Payload) == 0 {
+		t.Fatal("payload should not be empty")
+	}
+	if &cloned[0].Payload[0] == &src[0].Payload[0] {
+		t.Fatal("payload clone should not alias source bytes")
+	}
+	src[0].Payload[0] = 'X'
+	if bytes.Equal(cloned[0].Payload, src[0].Payload) {
+		t.Fatal("mutating source payload should not affect cloned payload")
+	}
+}
+
 func TestBulkDedicatedBatchPlainRoundTrip(t *testing.T) {
 	releasePayload, err := encodeBulkDedicatedReleasePayload(4096, 2)
 	if err != nil {
--- a/bulk_dedicated_record_test.go
+++ b/bulk_dedicated_record_test.go
@ -0,0 +1,66 @@
+package notify
+
+import (
+	"bytes"
+	"encoding/binary"
+	"io"
+	"net"
+	"testing"
+	"time"
+)
+
+type shortWriteBulkRecordConn struct {
+	maxPerWrite int
+	buf         bytes.Buffer
+}
+
+func (c *shortWriteBulkRecordConn) Read([]byte) (int, error) { return 0, io.EOF }
+
+func (c *shortWriteBulkRecordConn) Write(p []byte) (int, error) {
+	if len(p) == 0 {
+		return 0, nil
+	}
+	n := c.maxPerWrite
+	if n <= 0 || n > len(p) {
+		n = len(p)
+	}
+	_, _ = c.buf.Write(p[:n])
+	return n, nil
+}
+
+func (c *shortWriteBulkRecordConn) Close() error                { return nil }
+func (c *shortWriteBulkRecordConn) LocalAddr() net.Addr         { return shortWriteBulkRecordAddr("local") }
+func (c *shortWriteBulkRecordConn) RemoteAddr() net.Addr        { return shortWriteBulkRecordAddr("remote") }
+func (c *shortWriteBulkRecordConn) SetDeadline(time.Time) error { return nil }
+func (c *shortWriteBulkRecordConn) SetReadDeadline(time.Time) error {
+	return nil
+}
+func (c *shortWriteBulkRecordConn) SetWriteDeadline(time.Time) error {
+	return nil
+}
+
+type shortWriteBulkRecordAddr string
+
+func (a shortWriteBulkRecordAddr) Network() string { return "tcp" }
+func (a shortWriteBulkRecordAddr) String() string  { return string(a) }
+
+func TestWriteBulkDedicatedRecordWithDeadlineHandlesShortWrite(t *testing.T) {
+	conn := &shortWriteBulkRecordConn{maxPerWrite: 3}
+	payload := []byte("abcdefghijklmnopqrstuvwxyz")
+	if err := writeBulkDedicatedRecordWithDeadline(conn, payload, time.Time{}); err != nil {
+		t.Fatalf("writeBulkDedicatedRecordWithDeadline failed: %v", err)
+	}
+	raw := conn.buf.Bytes()
+	if got, want := len(raw), bulkDedicatedRecordHeaderLen+len(payload); got != want {
+		t.Fatalf("record length = %d, want %d", got, want)
+	}
+	if got := string(raw[:4]); got != bulkDedicatedRecordMagic {
+		t.Fatalf("record magic = %q, want %q", got, bulkDedicatedRecordMagic)
+	}
+	if got, want := int(binary.BigEndian.Uint32(raw[4:8])), len(payload); got != want {
+		t.Fatalf("record payload length = %d, want %d", got, want)
+	}
+	if got := raw[bulkDedicatedRecordHeaderLen:]; !bytes.Equal(got, payload) {
+		t.Fatalf("record payload mismatch")
+	}
+}
--- a/client_conn_session_test.go
+++ b/client_conn_session_test.go
@ -332,6 +332,24 @@ func TestLogicalDetachTransportForTransferKeepsHandoffConnAlive(t *testing.T) {
 	}
 }

+func TestLogicalHandleTUTransportReadResultWithSessionDropsDataAfterTransportStop(t *testing.T) {
+	server := NewServer().(*ServerCommon)
+	left, right := net.Pipe()
+	defer right.Close()
+
+	stopCtx, stopFn := context.WithCancel(context.Background())
+	logical, _, _ := newRegisteredServerLogicalForTest(t, server, "logical-stop-read-drop", left, stopCtx, stopFn)
+	if logical == nil {
+		t.Fatal("logical should not be nil")
+	}
+	generation := logical.transportGenerationSnapshot()
+	stopFn()
+
+	if logical.handleTUTransportReadResultWithSession(stopCtx, left, generation, len([]byte("late-data")), []byte("late-data"), nil) {
+		t.Fatal("handleTUTransportReadResultWithSession should stop after transport stop")
+	}
+}
+
 func TestClientConnTransportBindingSnapshotUsesRuntimeBinding(t *testing.T) {
 	client := &ClientConn{}
 	left, right := net.Pipe()
--- a/client_conn_transport.go
+++ b/client_conn_transport.go
@ -69,6 +69,12 @@ func (c *LogicalConn) readFromTUTransportConnWithBuffer(conn net.Conn, data []by
 }

 func (c *LogicalConn) handleTUTransportReadResultWithSession(stopCtx context.Context, conn net.Conn, generation uint64, num int, data []byte, err error) bool {
+	if transportReadShouldStop(stopCtx) || !c.ownsTransportRead(conn, generation) {
+		if c.shouldCloseTransportOnStop(conn) {
+			_ = conn.Close()
+		}
+		return false
+	}
 	if err == os.ErrDeadlineExceeded {
 		if num != 0 {
 			c.pushServerOwnedTransportMessage(data[:num], conn, generation)
@ -95,6 +101,30 @@ func (c *LogicalConn) handleTUTransportReadResultWithSession(stopCtx context.Con
 	return true
 }

+func transportReadShouldStop(stopCtx context.Context) bool {
+	select {
+	case <-sessionStopChan(stopCtx):
+		return true
+	default:
+		return false
+	}
+}
+
+func (c *LogicalConn) ownsTransportRead(conn net.Conn, generation uint64) bool {
+	if c == nil {
+		return false
+	}
+	rt := c.clientConnSessionRuntimeSnapshot()
+	if rt == nil || !rt.transportAttached || rt.transportGeneration != generation {
+		return false
+	}
+	current := rt.tuConn
+	if rt.transport != nil && rt.transport.connSnapshot() != nil {
+		current = rt.transport.connSnapshot()
+	}
+	return current == conn
+}
+
 func (c *LogicalConn) pushServerOwnedTransportMessage(data []byte, conn net.Conn, generation uint64) {
 	if c == nil || len(data) == 0 {
 		return
@ -163,6 +193,12 @@ func (c *ClientConn) handleTUTransportReadResultWithSession(stopCtx context.Cont
 	if logical := c.LogicalConn(); logical != nil {
 		return logical.handleTUTransportReadResultWithSession(stopCtx, conn, generation, num, data, err)
 	}
+	if transportReadShouldStop(stopCtx) || !c.ownsTransportRead(conn, generation) {
+		if c.shouldCloseClientConnTransportOnStop(conn) {
+			_ = conn.Close()
+		}
+		return false
+	}
 	if err == os.ErrDeadlineExceeded {
 		if num != 0 {
 			c.pushServerOwnedTransportMessage(data[:num], conn, generation)
@ -189,6 +225,21 @@ func (c *ClientConn) handleTUTransportReadResultWithSession(stopCtx context.Cont
 	return true
 }

+func (c *ClientConn) ownsTransportRead(conn net.Conn, generation uint64) bool {
+	if c == nil {
+		return false
+	}
+	rt := c.clientConnSessionRuntimeSnapshot()
+	if rt == nil || !rt.transportAttached || rt.transportGeneration != generation {
+		return false
+	}
+	current := rt.tuConn
+	if rt.transport != nil && rt.transport.connSnapshot() != nil {
+		current = rt.transport.connSnapshot()
+	}
+	return current == conn
+}
+
 func (c *ClientConn) pushServerOwnedTransportMessage(data []byte, conn net.Conn, generation uint64) {
 	if logical := c.LogicalConn(); logical != nil {
 		logical.pushServerOwnedTransportMessage(data, conn, generation)
--- a/transport_write.go
+++ b/transport_write.go
@ -13,6 +13,14 @@ import (
 var transportConnWriteLocks sync.Map
 var errTransportFrameQueueUnavailable = errors.New("transport frame queue is unavailable")

+type vectoredBuffersWriter interface {
+	WriteBuffers(*net.Buffers) (int64, error)
+}
+
+type vectoredConnUnwrapper interface {
+	UnwrapConn() net.Conn
+}
+
 func writeFullToConn(conn net.Conn, data []byte) error {
 	if conn == nil {
 		return net.ErrClosed
@ -26,8 +34,15 @@ func writeFullToConnUnlocked(conn net.Conn, data []byte) error {
 	if conn == nil {
 		return net.ErrClosed
 	}
+	return writeFullToWriterUnlocked(conn, data)
+}
+
+func writeFullToWriterUnlocked(writer io.Writer, data []byte) error {
+	if writer == nil {
+		return io.ErrClosedPipe
+	}
 	for len(data) > 0 {
-		n, err := conn.Write(data)
+		n, err := writer.Write(data)
 		if n > 0 {
 			data = data[n:]
 		}
@ -41,6 +56,69 @@ func writeFullToConnUnlocked(conn net.Conn, data []byte) error {
 	return nil
 }

+func writeNetBuffersFullUnlocked(conn net.Conn, buffers net.Buffers) error {
+	if conn == nil {
+		return net.ErrClosed
+	}
+	writer, writeFn := vectoredWriteStrategy(conn)
+	if writeFn == nil {
+		return writeRemainingBuffersUnlocked(conn, buffers)
+	}
+	n, err := writeFn(&buffers)
+	if err != nil {
+		return err
+	}
+	if len(buffers) == 0 {
+		return nil
+	}
+	if n == 0 {
+		return io.ErrNoProgress
+	}
+	return writeRemainingBuffersUnlocked(writer, buffers)
+}
+
+func vectoredWriteStrategy(conn net.Conn) (io.Writer, func(*net.Buffers) (int64, error)) {
+	current := conn
+	for depth := 0; depth < 8 && current != nil; depth++ {
+		if writer, ok := current.(vectoredBuffersWriter); ok {
+			target := current
+			return target, writer.WriteBuffers
+		}
+		switch target := current.(type) {
+		case *net.TCPConn:
+			return target, func(bufs *net.Buffers) (int64, error) {
+				return bufs.WriteTo(target)
+			}
+		case *net.UnixConn:
+			return target, func(bufs *net.Buffers) (int64, error) {
+				return bufs.WriteTo(target)
+			}
+		}
+		unwrapper, ok := current.(vectoredConnUnwrapper)
+		if !ok {
+			break
+		}
+		next := unwrapper.UnwrapConn()
+		if next == nil || next == current {
+			break
+		}
+		current = next
+	}
+	return nil, nil
+}
+
+func writeRemainingBuffersUnlocked(writer io.Writer, buffers net.Buffers) error {
+	for _, part := range buffers {
+		if len(part) == 0 {
+			continue
+		}
+		if err := writeFullToWriterUnlocked(writer, part); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 func withRawConnWriteLock(conn net.Conn, fn func(net.Conn) error) error {
 	return withRawConnWriteLockDeadline(conn, time.Time{}, fn)
 }
--- a/transport_write_test.go
+++ b/transport_write_test.go
@ -2,8 +2,10 @@ package notify

 import (
 	"b612.me/stario"
+	"bytes"
 	"context"
 	"errors"
+	"io"
 	"net"
 	"sync"
 	"sync/atomic"
@ -146,6 +148,113 @@ func (c *blockingPacketWriteConn) Write(p []byte) (int, error) {
 	return len(p), nil
 }

+type vectoredShortWriteConn struct {
+	steps  []int64
+	idx    int
+	buf    bytes.Buffer
+	writes int
+	writev int
+}
+
+func (c *vectoredShortWriteConn) Read([]byte) (int, error) { return 0, io.EOF }
+func (c *vectoredShortWriteConn) Write(p []byte) (int, error) {
+	c.writes++
+	return c.buf.Write(p)
+}
+func (c *vectoredShortWriteConn) Close() error                     { return nil }
+func (c *vectoredShortWriteConn) LocalAddr() net.Addr              { return nil }
+func (c *vectoredShortWriteConn) RemoteAddr() net.Addr             { return nil }
+func (c *vectoredShortWriteConn) SetDeadline(time.Time) error      { return nil }
+func (c *vectoredShortWriteConn) SetReadDeadline(time.Time) error  { return nil }
+func (c *vectoredShortWriteConn) SetWriteDeadline(time.Time) error { return nil }
+
+func (c *vectoredShortWriteConn) WriteBuffers(bufs *net.Buffers) (int64, error) {
+	c.writev++
+	if c.idx >= len(c.steps) {
+		return 0, io.ErrNoProgress
+	}
+	remaining := c.steps[c.idx]
+	c.idx++
+	written := int64(0)
+	for len(*bufs) > 0 && remaining > 0 {
+		part := (*bufs)[0]
+		if len(part) == 0 {
+			(*bufs)[0] = nil
+			*bufs = (*bufs)[1:]
+			continue
+		}
+		n := int64(len(part))
+		if n > remaining {
+			n = remaining
+		}
+		_, _ = c.buf.Write(part[:n])
+		written += n
+		remaining -= n
+		if n == int64(len(part)) {
+			(*bufs)[0] = nil
+			*bufs = (*bufs)[1:]
+			continue
+		}
+		(*bufs)[0] = part[n:]
+		break
+	}
+	return written, nil
+}
+
+type unwrapVectoredConn struct {
+	inner net.Conn
+}
+
+func (c *unwrapVectoredConn) Read(p []byte) (int, error)         { return c.inner.Read(p) }
+func (c *unwrapVectoredConn) Write(p []byte) (int, error)        { return c.inner.Write(p) }
+func (c *unwrapVectoredConn) Close() error                       { return c.inner.Close() }
+func (c *unwrapVectoredConn) LocalAddr() net.Addr                { return c.inner.LocalAddr() }
+func (c *unwrapVectoredConn) RemoteAddr() net.Addr               { return c.inner.RemoteAddr() }
+func (c *unwrapVectoredConn) SetDeadline(t time.Time) error      { return c.inner.SetDeadline(t) }
+func (c *unwrapVectoredConn) SetReadDeadline(t time.Time) error  { return c.inner.SetReadDeadline(t) }
+func (c *unwrapVectoredConn) SetWriteDeadline(t time.Time) error { return c.inner.SetWriteDeadline(t) }
+func (c *unwrapVectoredConn) UnwrapConn() net.Conn               { return c.inner }
+
+func TestWriteNetBuffersFullUnlockedFallsBackToDirectWritesAfterFirstPartialVectoredWrite(t *testing.T) {
+	conn := &vectoredShortWriteConn{steps: []int64{3}}
+	header := []byte("head")
+	payload := []byte("payload")
+	if err := writeNetBuffersFullUnlocked(conn, net.Buffers{header, payload}); err != nil {
+		t.Fatalf("writeNetBuffersFullUnlocked failed: %v", err)
+	}
+	if got, want := conn.writev, 1; got != want {
+		t.Fatalf("vectored write calls = %d, want %d", got, want)
+	}
+	if got, want := conn.writes, 2; got != want {
+		t.Fatalf("fallback direct writes = %d, want %d", got, want)
+	}
+	if got, want := conn.buf.String(), "headpayload"; got != want {
+		t.Fatalf("written bytes = %q, want %q", got, want)
+	}
+}
+
+func TestWriteNetBuffersFullUnlockedReturnsNoProgressWhenVectoredWriteDoesNotAdvance(t *testing.T) {
+	conn := &vectoredShortWriteConn{steps: []int64{0}}
+	err := writeNetBuffersFullUnlocked(conn, net.Buffers{[]byte("head"), []byte("payload")})
+	if !errors.Is(err, io.ErrNoProgress) {
+		t.Fatalf("writeNetBuffersFullUnlocked error = %v, want %v", err, io.ErrNoProgress)
+	}
+}
+
+func TestWriteNetBuffersFullUnlockedUsesUnwrappedVectoredConn(t *testing.T) {
+	inner := &vectoredShortWriteConn{steps: []int64{100}}
+	conn := &unwrapVectoredConn{inner: inner}
+	if err := writeNetBuffersFullUnlocked(conn, net.Buffers{[]byte("head"), []byte("payload")}); err != nil {
+		t.Fatalf("writeNetBuffersFullUnlocked failed: %v", err)
+	}
+	if got, want := inner.writev, 1; got != want {
+		t.Fatalf("unwrapped vectored write calls = %d, want %d", got, want)
+	}
+	if got := inner.writes; got != 0 {
+		t.Fatalf("unexpected fallback direct writes = %d, want 0", got)
+	}
+}
+
 func TestBulkBatchSenderSkipsQueuedCanceledRequest(t *testing.T) {
 	conn := newBlockingPacketWriteConn()
 	binding := newTransportBinding(conn, stario.NewQueue())