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