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// Copyright 2010 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 net
import (
"errors"
"time"
)
// A Dialer contains options for connecting to an address.
//
// The zero value for each field is equivalent to dialing
// without that option. Dialing with the zero value of Dialer
// is therefore equivalent to just calling the Dial function.
type Dialer struct {
// Timeout is the maximum amount of time a dial will wait for
// a connect to complete. If Deadline is also set, it may fail
// earlier.
//
// The default is no timeout.
//
// With or without a timeout, the operating system may impose
// its own earlier timeout. For instance, TCP timeouts are
// often around 3 minutes.
Timeout time.Duration
// Deadline is the absolute point in time after which dials
// will fail. If Timeout is set, it may fail earlier.
// Zero means no deadline, or dependent on the operating system
// as with the Timeout option.
Deadline time.Time
// LocalAddr is the local address to use when dialing an
// address. The address must be of a compatible type for the
// network being dialed.
// If nil, a local address is automatically chosen.
LocalAddr Addr
// DualStack allows a single dial to attempt to establish
// multiple IPv4 and IPv6 connections and to return the first
// established connection when the network is "tcp" and the
// destination is a host name that has multiple address family
// DNS records.
DualStack bool
}
// Return either now+Timeout or Deadline, whichever comes first.
// Or zero, if neither is set.
func (d *Dialer) deadline() time.Time {
if d.Timeout == 0 {
return d.Deadline
}
timeoutDeadline := time.Now().Add(d.Timeout)
if d.Deadline.IsZero() || timeoutDeadline.Before(d.Deadline) {
return timeoutDeadline
} else {
return d.Deadline
}
}
func parseNetwork(net string) (afnet string, proto int, err error) {
i := last(net, ':')
if i < 0 { // no colon
switch net {
case "tcp", "tcp4", "tcp6":
case "udp", "udp4", "udp6":
case "ip", "ip4", "ip6":
case "unix", "unixgram", "unixpacket":
default:
return "", 0, UnknownNetworkError(net)
}
return net, 0, nil
}
afnet = net[:i]
switch afnet {
case "ip", "ip4", "ip6":
protostr := net[i+1:]
proto, i, ok := dtoi(protostr, 0)
if !ok || i != len(protostr) {
proto, err = lookupProtocol(protostr)
if err != nil {
return "", 0, err
}
}
return afnet, proto, nil
}
return "", 0, UnknownNetworkError(net)
}
func resolveAddr(op, net, addr string, deadline time.Time) (netaddr, error) {
afnet, _, err := parseNetwork(net)
if err != nil {
return nil, err
}
if op == "dial" && addr == "" {
return nil, errMissingAddress
}
switch afnet {
case "unix", "unixgram", "unixpacket":
return ResolveUnixAddr(afnet, addr)
}
return resolveInternetAddr(afnet, addr, deadline)
}
// Dial connects to the address on the named network.
//
// Known networks are "tcp", "tcp4" (IPv4-only), "tcp6" (IPv6-only),
// "udp", "udp4" (IPv4-only), "udp6" (IPv6-only), "ip", "ip4"
// (IPv4-only), "ip6" (IPv6-only), "unix", "unixgram" and
// "unixpacket".
//
// For TCP and UDP networks, addresses have the form host:port.
// If host is a literal IPv6 address or host name, it must be enclosed
// in square brackets as in "[::1]:80", "[ipv6-host]:http" or
// "[ipv6-host%zone]:80".
// The functions JoinHostPort and SplitHostPort manipulate addresses
// in this form.
//
// Examples:
// Dial("tcp", "12.34.56.78:80")
// Dial("tcp", "google.com:http")
// Dial("tcp", "[2001:db8::1]:http")
// Dial("tcp", "[fe80::1%lo0]:80")
//
// For IP networks, the network must be "ip", "ip4" or "ip6" followed
// by a colon and a protocol number or name and the addr must be a
// literal IP address.
//
// Examples:
// Dial("ip4:1", "127.0.0.1")
// Dial("ip6:ospf", "::1")
//
// For Unix networks, the address must be a file system path.
func Dial(network, address string) (Conn, error) {
var d Dialer
return d.Dial(network, address)
}
// DialTimeout acts like Dial but takes a timeout.
// The timeout includes name resolution, if required.
func DialTimeout(network, address string, timeout time.Duration) (Conn, error) {
d := Dialer{Timeout: timeout}
return d.Dial(network, address)
}
// Dial connects to the address on the named network.
//
// See func Dial for a description of the network and address
// parameters.
func (d *Dialer) Dial(network, address string) (Conn, error) {
ra, err := resolveAddr("dial", network, address, d.deadline())
if err != nil {
return nil, &OpError{Op: "dial", Net: network, Addr: nil, Err: err}
}
dialer := func(deadline time.Time) (Conn, error) {
return dialSingle(network, address, d.LocalAddr, ra.toAddr(), deadline)
}
if ras, ok := ra.(addrList); ok && d.DualStack && network == "tcp" {
dialer = func(deadline time.Time) (Conn, error) {
return dialMulti(network, address, d.LocalAddr, ras, deadline)
}
}
return dial(network, ra.toAddr(), dialer, d.deadline())
}
// dialMulti attempts to establish connections to each destination of
// the list of addresses. It will return the first established
// connection and close the other connections. Otherwise it returns
// error on the last attempt.
func dialMulti(net, addr string, la Addr, ras addrList, deadline time.Time) (Conn, error) {
type racer struct {
Conn
Addr
error
}
// Sig controls the flow of dial results on lane. It passes a
// token to the next racer and also indicates the end of flow
// by using closed channel.
sig := make(chan bool, 1)
lane := make(chan racer, 1)
for _, ra := range ras {
go func(ra Addr) {
c, err := dialSingle(net, addr, la, ra, deadline)
if _, ok := <-sig; ok {
lane <- racer{c, ra, err}
} else if err == nil {
// We have to return the resources
// that belong to the other
// connections here for avoiding
// unnecessary resource starvation.
c.Close()
}
}(ra.toAddr())
}
defer close(sig)
var failAddr Addr
lastErr := errTimeout
nracers := len(ras)
for nracers > 0 {
sig <- true
select {
case racer := <-lane:
if racer.error == nil {
return racer.Conn, nil
}
failAddr = racer.Addr
lastErr = racer.error
nracers--
}
}
return nil, &OpError{Op: "dial", Net: net, Addr: failAddr, Err: lastErr}
}
// dialSingle attempts to establish and returns a single connection to
// the destination address.
func dialSingle(net, addr string, la, ra Addr, deadline time.Time) (c Conn, err error) {
if la != nil && la.Network() != ra.Network() {
return nil, &OpError{Op: "dial", Net: net, Addr: ra, Err: errors.New("mismatched local address type " + la.Network())}
}
switch ra := ra.(type) {
case *TCPAddr:
la, _ := la.(*TCPAddr)
c, err = dialTCP(net, la, ra, deadline)
case *UDPAddr:
la, _ := la.(*UDPAddr)
c, err = dialUDP(net, la, ra, deadline)
case *IPAddr:
la, _ := la.(*IPAddr)
c, err = dialIP(net, la, ra, deadline)
case *UnixAddr:
la, _ := la.(*UnixAddr)
c, err = dialUnix(net, la, ra, deadline)
default:
return nil, &OpError{Op: "dial", Net: net, Addr: ra, Err: &AddrError{Err: "unexpected address type", Addr: addr}}
}
if err != nil {
return nil, err // c is non-nil interface containing nil pointer
}
return c, nil
}
// Listen announces on the local network address laddr.
// The network net must be a stream-oriented network: "tcp", "tcp4",
// "tcp6", "unix" or "unixpacket".
// See Dial for the syntax of laddr.
func Listen(net, laddr string) (Listener, error) {
la, err := resolveAddr("listen", net, laddr, noDeadline)
if err != nil {
return nil, &OpError{Op: "listen", Net: net, Addr: nil, Err: err}
}
var l Listener
switch la := la.toAddr().(type) {
case *TCPAddr:
l, err = ListenTCP(net, la)
case *UnixAddr:
l, err = ListenUnix(net, la)
default:
return nil, &OpError{Op: "listen", Net: net, Addr: la, Err: &AddrError{Err: "unexpected address type", Addr: laddr}}
}
if err != nil {
return nil, err // l is non-nil interface containing nil pointer
}
return l, nil
}
// ListenPacket announces on the local network address laddr.
// The network net must be a packet-oriented network: "udp", "udp4",
// "udp6", "ip", "ip4", "ip6" or "unixgram".
// See Dial for the syntax of laddr.
func ListenPacket(net, laddr string) (PacketConn, error) {
la, err := resolveAddr("listen", net, laddr, noDeadline)
if err != nil {
return nil, &OpError{Op: "listen", Net: net, Addr: nil, Err: err}
}
var l PacketConn
switch la := la.toAddr().(type) {
case *UDPAddr:
l, err = ListenUDP(net, la)
case *IPAddr:
l, err = ListenIP(net, la)
case *UnixAddr:
l, err = ListenUnixgram(net, la)
default:
return nil, &OpError{Op: "listen", Net: net, Addr: la, Err: &AddrError{Err: "unexpected address type", Addr: laddr}}
}
if err != nil {
return nil, err // l is non-nil interface containing nil pointer
}
return l, nil
}