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// Copyright 2011 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 provides support for a variety of protocols to proxy network
// data.
package proxy // import "golang.org/x/net/proxy"
import (
"errors"
"net"
"net/url"
"os"
"sync"
)
// A Dialer is a means to establish a connection.
type Dialer interface {
// Dial connects to the given address via the proxy.
Dial(network, addr string) (c net.Conn, err error)
}
// Auth contains authentication parameters that specific Dialers may require.
type Auth struct {
User, Password string
}
// FromEnvironment returns the dialer specified by the proxy related variables in
// the environment.
func FromEnvironment() Dialer {
allProxy := allProxyEnv.Get()
if len(allProxy) == 0 {
return Direct
}
proxyURL, err := url.Parse(allProxy)
if err != nil {
return Direct
}
proxy, err := FromURL(proxyURL, Direct)
if err != nil {
return Direct
}
noProxy := noProxyEnv.Get()
if len(noProxy) == 0 {
return proxy
}
perHost := NewPerHost(proxy, Direct)
perHost.AddFromString(noProxy)
return perHost
}
// proxySchemes is a map from URL schemes to a function that creates a Dialer
// from a URL with such a scheme.
var proxySchemes map[string]func(*url.URL, Dialer) (Dialer, error)
// RegisterDialerType takes a URL scheme and a function to generate Dialers from
// a URL with that scheme and a forwarding Dialer. Registered schemes are used
// by FromURL.
func RegisterDialerType(scheme string, f func(*url.URL, Dialer) (Dialer, error)) {
if proxySchemes == nil {
proxySchemes = make(map[string]func(*url.URL, Dialer) (Dialer, error))
}
proxySchemes[scheme] = f
}
// FromURL returns a Dialer given a URL specification and an underlying
// Dialer for it to make network requests.
func FromURL(u *url.URL, forward Dialer) (Dialer, error) {
var auth *Auth
if u.User != nil {
auth = new(Auth)
auth.User = u.User.Username()
if p, ok := u.User.Password(); ok {
auth.Password = p
}
}
switch u.Scheme {
case "socks5":
return SOCKS5("tcp", u.Host, auth, forward)
}
// If the scheme doesn't match any of the built-in schemes, see if it
// was registered by another package.
if proxySchemes != nil {
if f, ok := proxySchemes[u.Scheme]; ok {
return f(u, forward)
}
}
return nil, errors.New("proxy: unknown scheme: " + u.Scheme)
}
var (
allProxyEnv = &envOnce{
names: []string{"ALL_PROXY", "all_proxy"},
}
noProxyEnv = &envOnce{
names: []string{"NO_PROXY", "no_proxy"},
}
)
// envOnce looks up an environment variable (optionally by multiple
// names) once. It mitigates expensive lookups on some platforms
// (e.g. Windows).
// (Borrowed from net/http/transport.go)
type envOnce struct {
names []string
once sync.Once
val string
}
func (e *envOnce) Get() string {
e.once.Do(e.init)
return e.val
}
func (e *envOnce) init() {
for _, n := range e.names {
e.val = os.Getenv(n)
if e.val != "" {
return
}
}
}
// reset is used by tests
func (e *envOnce) reset() {
e.once = sync.Once{}
e.val = ""
}