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// Copyright 2019 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package proxy
import (
"context"
"net"
)
// A ContextDialer dials using a context.
type ContextDialer interface {
DialContext(ctx context.Context, network, address string) (net.Conn, error)
}
// Dial works like DialContext on net.Dialer but using a dialer returned by FromEnvironment.
//
// The passed ctx is only used for returning the Conn, not the lifetime of the Conn.
//
// Custom dialers (registered via RegisterDialerType) that do not implement ContextDialer
// can leak a goroutine for as long as it takes the underlying Dialer implementation to timeout.
//
// A Conn returned from a successful Dial after the context has been cancelled will be immediately closed.
func Dial(ctx context.Context, network, address string) (net.Conn, error) {
d := FromEnvironment()
if xd, ok := d.(ContextDialer); ok {
return xd.DialContext(ctx, network, address)
}
return dialContext(ctx, d, network, address)
}
// WARNING: this can leak a goroutine for as long as the underlying Dialer implementation takes to timeout
// A Conn returned from a successful Dial after the context has been cancelled will be immediately closed.
func dialContext(ctx context.Context, d Dialer, network, address string) (net.Conn, error) {
var (
conn net.Conn
done = make(chan struct{}, 1)
err error
)
go func() {
conn, err = d.Dial(network, address)
close(done)
if conn != nil && ctx.Err() != nil {
conn.Close()
}
}()
select {
case <-ctx.Done():
err = ctx.Err()
case <-done:
}
return conn, err
}