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fix: guard snell pooled connection reuse state #2878

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fix: guard snell pooled connection reuse state #2878

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3 changes: 3 additions & 0 deletions adapter/outbound/snell.go
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Original file line number Diff line number Diff line change
Expand Up @@ -91,6 +91,9 @@ func (s *Snell) DialContext(ctx context.Context, metadata *C.Metadata) (_ C.Conn
_ = c.Close()
return nil, err
}
if pc, ok := c.(*snell.PoolConn); ok {
pc.MarkReusable()
}
return NewConn(c, s), err
}

Expand Down
31 changes: 30 additions & 1 deletion transport/snell/pool.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@ import (
"io"
"net"
"sync"
"sync/atomic"
"time"

"github.com/metacubex/mihomo/component/pool"
Expand All @@ -15,6 +16,12 @@ type Pool struct {
pool *pool.Pool[*Snell]
}

const (
poolConnNew int32 = iota
poolConnReusable
poolConnClosedBeforeReuse
)

func (p *Pool) Get() (net.Conn, error) {
return p.GetContext(context.Background())
}
Expand Down Expand Up @@ -48,6 +55,8 @@ type PoolConn struct {
closeWriteErr error
closeOnce sync.Once
closeErr error
requestStarted atomic.Bool
reusableState atomic.Int32
}

func (pc *PoolConn) Read(b []byte) (int, error) {
Expand All @@ -59,18 +68,38 @@ func (pc *PoolConn) Read(b []byte) (int, error) {
}

func (pc *PoolConn) Write(b []byte) (int, error) {
return pc.Snell.Write(b)
n, err := pc.Snell.Write(b)
if err == nil && n == len(b) && len(b) > 0 {
pc.requestStarted.Store(true)
}
return n, err
}

// MarkReusable allows Close to return this request to the pool after DialContext succeeds.
func (pc *PoolConn) MarkReusable() {
if pc.requestStarted.Load() {
pc.reusableState.CompareAndSwap(poolConnNew, poolConnReusable)
}
}

func (pc *PoolConn) CloseWrite() error {
pc.closeWriteOnce.Do(func() {
if pc.reusableState.Load() != poolConnReusable {
pc.reusableState.CompareAndSwap(poolConnNew, poolConnClosedBeforeReuse)
pc.closeWriteErr = pc.Snell.Close()
return
}
pc.closeWriteErr = writeZeroChunk(pc.Snell)
})
return pc.closeWriteErr
}

func (pc *PoolConn) Close() error {
pc.closeOnce.Do(func() {
if pc.reusableState.Load() != poolConnReusable {
pc.closeErr = pc.CloseWrite()
return
}
if err := pc.CloseWrite(); err != nil {
pc.closeErr = err
_ = pc.Snell.Close()
Expand Down
118 changes: 112 additions & 6 deletions transport/snell/pool_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -19,15 +19,19 @@ func TestPoolConnCloseIsIdempotent(t *testing.T) {
})
conn := &PoolConn{Snell: pooledConn, pool: pool}

if _, err := conn.Write([]byte{Version, CommandConnectV2, 0}); err != nil {
t.Fatal(err)
}
conn.MarkReusable()
if err := conn.Close(); err != nil {
t.Fatal(err)
}
if err := conn.Close(); err != nil {
t.Fatal(err)
}

if rawConn.writes != 1 {
t.Fatalf("close should send one half-close record, got %d", rawConn.writes)
if rawConn.writes != 2 {
t.Fatalf("close should send the request and one half-close record, got %d writes", rawConn.writes)
}

got, err := pool.pool.Get()
Expand All @@ -39,6 +43,104 @@ func TestPoolConnCloseIsIdempotent(t *testing.T) {
}
}

func TestPoolConnCloseBeforeRequestClosesRawConnection(t *testing.T) {
rawConn := &recordingConn{}
pooledConn := &Snell{Conn: rawConn}
factoryConn := &Snell{Conn: &recordingConn{}}
pool := NewPool(func(context.Context) (*Snell, error) {
return factoryConn, nil
})
conn := &PoolConn{Snell: pooledConn, pool: pool}

if err := conn.Close(); err != nil {
t.Fatal(err)
}
if err := conn.Close(); err != nil {
t.Fatal(err)
}

if rawConn.writes != 0 {
t.Fatalf("close before request should not send half-close record, got %d writes", rawConn.writes)
}
if !rawConn.closed {
t.Fatal("close before request should close the raw connection")
}

got, err := pool.pool.Get()
if err != nil {
t.Fatal(err)
}
if got != factoryConn {
t.Fatal("unstarted connection should not be returned to the pool")
}
}

func TestPoolConnCloseAfterRequestBeforeReusableClosesRawConnection(t *testing.T) {
rawConn := &recordingConn{}
pooledConn := &Snell{Conn: rawConn}
factoryConn := &Snell{Conn: &recordingConn{}}
pool := NewPool(func(context.Context) (*Snell, error) {
return factoryConn, nil
})
conn := &PoolConn{Snell: pooledConn, pool: pool}

if _, err := conn.Write([]byte{Version, CommandConnectV2, 0}); err != nil {
t.Fatal(err)
}
if err := conn.Close(); err != nil {
t.Fatal(err)
}

if rawConn.writes != 1 {
t.Fatalf("close before reusable should only send the request, got %d writes", rawConn.writes)
}
if !rawConn.closed {
t.Fatal("close before reusable should close the raw connection")
}

got, err := pool.pool.Get()
if err != nil {
t.Fatal(err)
}
if got != factoryConn {
t.Fatal("connection closed before reusable should not be returned to the pool")
}
}

func TestPoolConnCloseWriteBeforeRequestClosesRawConnection(t *testing.T) {
rawConn := &recordingConn{}
pooledConn := &Snell{Conn: rawConn}
factoryConn := &Snell{Conn: &recordingConn{}}
pool := NewPool(func(context.Context) (*Snell, error) {
return factoryConn, nil
})
conn := &PoolConn{Snell: pooledConn, pool: pool}

if err := conn.CloseWrite(); err != nil {
t.Fatal(err)
}
if rawConn.writes != 0 {
t.Fatalf("CloseWrite before request should not send half-close record, got %d writes", rawConn.writes)
}
if !rawConn.closed {
t.Fatal("CloseWrite before request should close the raw connection")
}

// Simulate a concurrent write reporting success after the unstarted close path won.
conn.requestStarted.Store(true)
conn.MarkReusable()
if err := conn.Close(); err != nil {
t.Fatal(err)
}
got, err := pool.pool.Get()
if err != nil {
t.Fatal(err)
}
if got != factoryConn {
t.Fatal("unstarted connection should not be returned to the pool")
}
}

func TestPoolConnCloseWriteDoesNotReturnConnectionToPool(t *testing.T) {
rawConn := &recordingConn{}
pooledConn := &Snell{Conn: rawConn, reply: true}
Expand All @@ -48,6 +150,10 @@ func TestPoolConnCloseWriteDoesNotReturnConnectionToPool(t *testing.T) {
})
conn := &PoolConn{Snell: pooledConn, pool: pool}

if _, err := conn.Write([]byte{Version, CommandConnectV2, 0}); err != nil {
t.Fatal(err)
}
conn.MarkReusable()
if err := conn.CloseWrite(); err != nil {
t.Fatal(err)
}
Expand All @@ -59,8 +165,8 @@ func TestPoolConnCloseWriteDoesNotReturnConnectionToPool(t *testing.T) {
if got != factoryConn {
t.Fatal("CloseWrite should not put the active connection back into the pool")
}
if rawConn.writes != 1 {
t.Fatalf("CloseWrite should send one half-close record, got %d", rawConn.writes)
if rawConn.writes != 2 {
t.Fatalf("CloseWrite should send the request and one half-close record, got %d writes", rawConn.writes)
}
if !pooledConn.reply {
t.Fatal("CloseWrite should not reset reply while the read side may still be active")
Expand All @@ -76,8 +182,8 @@ func TestPoolConnCloseWriteDoesNotReturnConnectionToPool(t *testing.T) {
if got != pooledConn {
t.Fatal("Close should return the connection to the pool after CloseWrite")
}
if rawConn.writes != 1 {
t.Fatalf("Close after CloseWrite should not send another half-close record, got %d", rawConn.writes)
if rawConn.writes != 2 {
t.Fatalf("Close after CloseWrite should not send another half-close record, got %d writes", rawConn.writes)
}
if pooledConn.reply {
t.Fatal("Close should reset reply before returning the connection to the pool")
Expand Down
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