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net: use context.AfterFunc in connect

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This saves a goroutine when ctx can be but is not canceled during
the connect call.

The redundant fd.Close() call is removed, because the caller closes
the fd on error.

Change-Id: I124d7e480294a48ef74d5650d8ef0489bdfc64d6
Reviewed-on: https://go-review.googlesource.com/c/go/+/699256
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Sean Liao <sean@liao.dev>
Reviewed-by: Damien Neil <dneil@google.com>
Auto-Submit: Sean Liao <sean@liao.dev>
Reviewed-by: Mark Freeman <markfreeman@google.com>
This commit is contained in:
database64128 2025-08-27 17:38:13 +08:00 • committed by Gopher Robot
parent ac803b5949
commit 080882a928
1 changed files with 22 additions and 36 deletions
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58
src/net/fd_unix.go
View file

@ -74,46 +74,32 @@ func (fd *netFD) connect(ctx context.Context, la, ra syscall.Sockaddr) (rsa sysc
if err := fd.pfd.Init(fd.net, true); err != nil {
return nil, err
}
if deadline, hasDeadline := ctx.Deadline(); hasDeadline {
fd.pfd.SetWriteDeadline(deadline)
defer fd.pfd.SetWriteDeadline(noDeadline)
}
// Start the "interrupter" goroutine, if this context might be canceled.
//
// The interrupter goroutine waits for the context to be done and
// interrupts the dial (by altering the fd's write deadline, which
// wakes up waitWrite).
ctxDone := ctx.Done()
if ctxDone != nil {
// Wait for the interrupter goroutine to exit before returning
// from connect.
done := make(chan struct{})
interruptRes := make(chan error)
if deadline, hasDeadline := ctx.Deadline(); hasDeadline {
fd.pfd.SetWriteDeadline(deadline)
defer fd.pfd.SetWriteDeadline(noDeadline)
}
stop := context.AfterFunc(ctx, func() {
// Force the runtime's poller to immediately give up
// waiting for writability, unblocking waitWrite
// below.
_ = fd.pfd.SetWriteDeadline(aLongTimeAgo)
testHookCanceledDial()
})
defer func() {
close(done)
if ctxErr := <-interruptRes; ctxErr != nil && ret == nil {
// The interrupter goroutine called SetWriteDeadline,
// but the connect code below had returned from
// waitWrite already and did a successful connect (ret
// == nil). Because we've now poisoned the connection
// by making it unwritable, don't return a successful
// dial. This was issue 16523.
ret = mapErr(ctxErr)
fd.Close() // prevent a leak
}
}()
go func() {
select {
case <-ctxDone:
// Force the runtime's poller to immediately give up
// waiting for writability, unblocking waitWrite
// below.
fd.pfd.SetWriteDeadline(aLongTimeAgo)
testHookCanceledDial()
interruptRes <- ctx.Err()
case <-done:
interruptRes <- nil
if !stop() && ret == nil {
// The context.AfterFunc has called or is about to call
// SetWriteDeadline, but the connect code below had
// returned from waitWrite already and did a successful
// connect (ret == nil). Because we've now poisoned the
// connection by making it unwritable, don't return a
// successful dial. This was issue 16523.
ret = mapErr(ctx.Err())
// The caller closes fd on error, so there's no need to
// wait for the SetWriteDeadline call to return.
}
}()
}