1 files changed, 302 insertions, 0 deletions
diff --git a/src/net/dial.go b/src/net/dial.go
new file mode 100644
index 000000000..e6f0436cd
--- /dev/null
+++ b/src/net/dial.go
@@ -0,0 +1,302 @@
+// 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 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 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) {
+	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)
+		}
+	}
+	c, err := dial(network, ra.toAddr(), dialer, d.deadline())
+	if d.KeepAlive > 0 && err == nil {
+		if tc, ok := c.(*TCPConn); ok {
+			tc.SetKeepAlive(true)
+			tc.SetKeepAlivePeriod(d.KeepAlive)
+			testHookSetKeepAlive()
+		}
+	}
+	return c, err
+}
+
+var testHookSetKeepAlive = func() {} // changed by dial_test.go
+
+// 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.toAddr())
+	}
+	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, 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
+}