src/net/dial.go - go - Git at Google

 // 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

 	// KeepAlive specifies the keep-alive period for an active
 	// network connection.
 	// If zero, keep-alives are not enabled. Network protocols
 	// that do not support keep-alives ignore this field.
 	KeepAlive time.Duration
 }

 // 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 resolveAddrList(op, net, addr string, deadline time.Time) (addrList, error) {
 	afnet, _, err := parseNetwork(net)
 	if err != nil {
 		return nil, err
 	}
 	if op == "dial" && addr == "" {
 		return nil, errMissingAddress
 	}
 	switch afnet {
 	case "unix", "unixgram", "unixpacket":
 		addr, err := ResolveUnixAddr(afnet, addr)
 		if err != nil {
 			return nil, err
 		}
 		return addrList{addr}, nil
 	}
 	return internetAddrList(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 it must be enclosed
 // in square brackets as in "[::1]:80" 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) {
 	addrs, err := resolveAddrList("dial", network, address, d.deadline())
 	if err != nil {
 		return nil, &OpError{Op: "dial", Net: network, Source: nil, Addr: nil, Err: err}
 	}
 	var dialer func(deadline time.Time) (Conn, error)
 	if d.DualStack && network == "tcp" {
 		primaries, fallbacks := addrs.partition(isIPv4)
 		if len(fallbacks) > 0 {
 			dialer = func(deadline time.Time) (Conn, error) {
 				return dialMulti(network, address, d.LocalAddr, addrList{primaries[0], fallbacks[0]}, deadline)
 			}
 		}
 	}
 	if dialer == nil {
 		dialer = func(deadline time.Time) (Conn, error) {
 			return dialSingle(network, address, d.LocalAddr, addrs.first(isIPv4), deadline)
 		}
 	}
 	c, err := dial(network, addrs.first(isIPv4), dialer, d.deadline())
 	if d.KeepAlive > 0 && err == nil {
 		if tc, ok := c.(*TCPConn); ok {
 			setKeepAlive(tc.fd, true)
 			setKeepAlivePeriod(tc.fd, d.KeepAlive)
 			testHookSetKeepAlive()
 		}
 	}
 	return c, err
 }

 // 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
 		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, 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)
 	}
 	defer close(sig)
 	lastErr := errTimeout
 	nracers := len(ras)
 	for nracers > 0 {
 		sig <- true
 		racer := <-lane
 		if racer.error == nil {
 			return racer.Conn, nil
 		}
 		lastErr = racer.error
 		nracers--
 	}
 	return nil, 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, Source: la, 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, Source: la, 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) {
 	addrs, err := resolveAddrList("listen", net, laddr, noDeadline)
 	if err != nil {
 		return nil, &OpError{Op: "listen", Net: net, Source: nil, Addr: nil, Err: err}
 	}
 	var l Listener
 	switch la := addrs.first(isIPv4).(type) {
 	case *TCPAddr:
 		l, err = ListenTCP(net, la)
 	case *UnixAddr:
 		l, err = ListenUnix(net, la)
 	default:
 		return nil, &OpError{Op: "listen", Net: net, Source: nil, 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) {
 	addrs, err := resolveAddrList("listen", net, laddr, noDeadline)
 	if err != nil {
 		return nil, &OpError{Op: "listen", Net: net, Source: nil, Addr: nil, Err: err}
 	}
 	var l PacketConn
 	switch la := addrs.first(isIPv4).(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, Source: nil, 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
 }
	// 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

	// KeepAlive specifies the keep-alive period for an active
	// network connection.
	// If zero, keep-alives are not enabled. Network protocols
	// that do not support keep-alives ignore this field.
	KeepAlive time.Duration
	}

	// 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 resolveAddrList(op, net, addr string, deadline time.Time) (addrList, error) {
	afnet, _, err := parseNetwork(net)
	if err != nil {
	return nil, err
	}
	if op == "dial" && addr == "" {
	return nil, errMissingAddress
	}
	switch afnet {
	case "unix", "unixgram", "unixpacket":
	addr, err := ResolveUnixAddr(afnet, addr)
	if err != nil {
	return nil, err
	}
	return addrList{addr}, nil
	}
	return internetAddrList(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 it must be enclosed
	// in square brackets as in "[::1]:80" 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) {
	addrs, err := resolveAddrList("dial", network, address, d.deadline())
	if err != nil {
	return nil, &OpError{Op: "dial", Net: network, Source: nil, Addr: nil, Err: err}
	}
	var dialer func(deadline time.Time) (Conn, error)
	if d.DualStack && network == "tcp" {
	primaries, fallbacks := addrs.partition(isIPv4)
	if len(fallbacks) > 0 {
	dialer = func(deadline time.Time) (Conn, error) {
	return dialMulti(network, address, d.LocalAddr, addrList{primaries[0], fallbacks[0]}, deadline)
	}
	}
	}
	if dialer == nil {
	dialer = func(deadline time.Time) (Conn, error) {
	return dialSingle(network, address, d.LocalAddr, addrs.first(isIPv4), deadline)
	}
	}
	c, err := dial(network, addrs.first(isIPv4), dialer, d.deadline())
	if d.KeepAlive > 0 && err == nil {
	if tc, ok := c.(*TCPConn); ok {
	setKeepAlive(tc.fd, true)
	setKeepAlivePeriod(tc.fd, d.KeepAlive)
	testHookSetKeepAlive()
	}
	}
	return c, err
	}

	// 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
	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, 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)
	}
	defer close(sig)
	lastErr := errTimeout
	nracers := len(ras)
	for nracers > 0 {
	sig <- true
	racer := <-lane
	if racer.error == nil {
	return racer.Conn, nil
	}
	lastErr = racer.error
	nracers--
	}
	return nil, 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, Source: la, 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, Source: la, 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) {
	addrs, err := resolveAddrList("listen", net, laddr, noDeadline)
	if err != nil {
	return nil, &OpError{Op: "listen", Net: net, Source: nil, Addr: nil, Err: err}
	}
	var l Listener
	switch la := addrs.first(isIPv4).(type) {
	case *TCPAddr:
	l, err = ListenTCP(net, la)
	case *UnixAddr:
	l, err = ListenUnix(net, la)
	default:
	return nil, &OpError{Op: "listen", Net: net, Source: nil, 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) {
	addrs, err := resolveAddrList("listen", net, laddr, noDeadline)
	if err != nil {
	return nil, &OpError{Op: "listen", Net: net, Source: nil, Addr: nil, Err: err}
	}
	var l PacketConn
	switch la := addrs.first(isIPv4).(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, Source: nil, 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
	}