blob: 811c2e4e962ee76c13a56bb99c88d3b002b3095b [file] [log] [blame]
Scott Baker8487c5d2019-10-18 12:49:46 -07001// Copyright 2019 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package proxy
6
7import (
8 "context"
9 "net"
10)
11
12// A ContextDialer dials using a context.
13type ContextDialer interface {
14 DialContext(ctx context.Context, network, address string) (net.Conn, error)
15}
16
17// Dial works like DialContext on net.Dialer but using a dialer returned by FromEnvironment.
18//
19// The passed ctx is only used for returning the Conn, not the lifetime of the Conn.
20//
21// Custom dialers (registered via RegisterDialerType) that do not implement ContextDialer
22// can leak a goroutine for as long as it takes the underlying Dialer implementation to timeout.
23//
24// A Conn returned from a successful Dial after the context has been cancelled will be immediately closed.
25func Dial(ctx context.Context, network, address string) (net.Conn, error) {
26 d := FromEnvironment()
27 if xd, ok := d.(ContextDialer); ok {
28 return xd.DialContext(ctx, network, address)
29 }
30 return dialContext(ctx, d, network, address)
31}
32
33// WARNING: this can leak a goroutine for as long as the underlying Dialer implementation takes to timeout
34// A Conn returned from a successful Dial after the context has been cancelled will be immediately closed.
35func dialContext(ctx context.Context, d Dialer, network, address string) (net.Conn, error) {
36 var (
37 conn net.Conn
38 done = make(chan struct{}, 1)
39 err error
40 )
41 go func() {
42 conn, err = d.Dial(network, address)
43 close(done)
44 if conn != nil && ctx.Err() != nil {
45 conn.Close()
46 }
47 }()
48 select {
49 case <-ctx.Done():
50 err = ctx.Err()
51 case <-done:
52 }
53 return conn, err
54}