mirror of
https://github.com/autc04/Retro68.git
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293 lines
8.7 KiB
Go
293 lines
8.7 KiB
Go
// Copyright 2010 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 net
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import (
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"errors"
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"time"
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)
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// A Dialer contains options for connecting to an address.
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//
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// The zero value for each field is equivalent to dialing
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// without that option. Dialing with the zero value of Dialer
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// is therefore equivalent to just calling the Dial function.
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type Dialer struct {
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// Timeout is the maximum amount of time a dial will wait for
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// a connect to complete. If Deadline is also set, it may fail
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// earlier.
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//
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// The default is no timeout.
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//
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// With or without a timeout, the operating system may impose
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// its own earlier timeout. For instance, TCP timeouts are
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// often around 3 minutes.
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Timeout time.Duration
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// Deadline is the absolute point in time after which dials
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// will fail. If Timeout is set, it may fail earlier.
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// Zero means no deadline, or dependent on the operating system
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// as with the Timeout option.
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Deadline time.Time
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// LocalAddr is the local address to use when dialing an
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// address. The address must be of a compatible type for the
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// network being dialed.
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// If nil, a local address is automatically chosen.
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LocalAddr Addr
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// DualStack allows a single dial to attempt to establish
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// multiple IPv4 and IPv6 connections and to return the first
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// established connection when the network is "tcp" and the
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// destination is a host name that has multiple address family
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// DNS records.
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DualStack bool
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}
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// Return either now+Timeout or Deadline, whichever comes first.
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// Or zero, if neither is set.
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func (d *Dialer) deadline() time.Time {
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if d.Timeout == 0 {
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return d.Deadline
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}
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timeoutDeadline := time.Now().Add(d.Timeout)
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if d.Deadline.IsZero() || timeoutDeadline.Before(d.Deadline) {
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return timeoutDeadline
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} else {
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return d.Deadline
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}
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}
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func parseNetwork(net string) (afnet string, proto int, err error) {
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i := last(net, ':')
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if i < 0 { // no colon
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switch net {
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case "tcp", "tcp4", "tcp6":
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case "udp", "udp4", "udp6":
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case "ip", "ip4", "ip6":
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case "unix", "unixgram", "unixpacket":
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default:
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return "", 0, UnknownNetworkError(net)
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}
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return net, 0, nil
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}
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afnet = net[:i]
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switch afnet {
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case "ip", "ip4", "ip6":
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protostr := net[i+1:]
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proto, i, ok := dtoi(protostr, 0)
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if !ok || i != len(protostr) {
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proto, err = lookupProtocol(protostr)
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if err != nil {
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return "", 0, err
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}
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}
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return afnet, proto, nil
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}
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return "", 0, UnknownNetworkError(net)
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}
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func resolveAddr(op, net, addr string, deadline time.Time) (netaddr, error) {
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afnet, _, err := parseNetwork(net)
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if err != nil {
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return nil, err
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}
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if op == "dial" && addr == "" {
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return nil, errMissingAddress
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}
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switch afnet {
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case "unix", "unixgram", "unixpacket":
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return ResolveUnixAddr(afnet, addr)
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}
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return resolveInternetAddr(afnet, addr, deadline)
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}
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// Dial connects to the address on the named network.
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//
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// Known networks are "tcp", "tcp4" (IPv4-only), "tcp6" (IPv6-only),
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// "udp", "udp4" (IPv4-only), "udp6" (IPv6-only), "ip", "ip4"
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// (IPv4-only), "ip6" (IPv6-only), "unix", "unixgram" and
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// "unixpacket".
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//
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// For TCP and UDP networks, addresses have the form host:port.
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// If host is a literal IPv6 address or host name, it must be enclosed
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// in square brackets as in "[::1]:80", "[ipv6-host]:http" or
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// "[ipv6-host%zone]:80".
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// The functions JoinHostPort and SplitHostPort manipulate addresses
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// in this form.
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//
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// Examples:
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// Dial("tcp", "12.34.56.78:80")
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// Dial("tcp", "google.com:http")
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// Dial("tcp", "[2001:db8::1]:http")
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// Dial("tcp", "[fe80::1%lo0]:80")
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//
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// For IP networks, the network must be "ip", "ip4" or "ip6" followed
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// by a colon and a protocol number or name and the addr must be a
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// literal IP address.
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//
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// Examples:
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// Dial("ip4:1", "127.0.0.1")
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// Dial("ip6:ospf", "::1")
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//
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// For Unix networks, the address must be a file system path.
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func Dial(network, address string) (Conn, error) {
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var d Dialer
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return d.Dial(network, address)
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}
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// DialTimeout acts like Dial but takes a timeout.
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// The timeout includes name resolution, if required.
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func DialTimeout(network, address string, timeout time.Duration) (Conn, error) {
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d := Dialer{Timeout: timeout}
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return d.Dial(network, address)
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}
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// Dial connects to the address on the named network.
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//
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// See func Dial for a description of the network and address
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// parameters.
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func (d *Dialer) Dial(network, address string) (Conn, error) {
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ra, err := resolveAddr("dial", network, address, d.deadline())
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if err != nil {
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return nil, &OpError{Op: "dial", Net: network, Addr: nil, Err: err}
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}
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dialer := func(deadline time.Time) (Conn, error) {
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return dialSingle(network, address, d.LocalAddr, ra.toAddr(), deadline)
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}
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if ras, ok := ra.(addrList); ok && d.DualStack && network == "tcp" {
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dialer = func(deadline time.Time) (Conn, error) {
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return dialMulti(network, address, d.LocalAddr, ras, deadline)
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}
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}
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return dial(network, ra.toAddr(), dialer, d.deadline())
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}
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// dialMulti attempts to establish connections to each destination of
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// the list of addresses. It will return the first established
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// connection and close the other connections. Otherwise it returns
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// error on the last attempt.
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func dialMulti(net, addr string, la Addr, ras addrList, deadline time.Time) (Conn, error) {
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type racer struct {
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Conn
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Addr
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error
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}
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// Sig controls the flow of dial results on lane. It passes a
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// token to the next racer and also indicates the end of flow
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// by using closed channel.
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sig := make(chan bool, 1)
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lane := make(chan racer, 1)
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for _, ra := range ras {
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go func(ra Addr) {
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c, err := dialSingle(net, addr, la, ra, deadline)
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if _, ok := <-sig; ok {
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lane <- racer{c, ra, err}
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} else if err == nil {
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// We have to return the resources
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// that belong to the other
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// connections here for avoiding
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// unnecessary resource starvation.
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c.Close()
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}
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}(ra.toAddr())
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}
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defer close(sig)
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var failAddr Addr
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lastErr := errTimeout
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nracers := len(ras)
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for nracers > 0 {
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sig <- true
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select {
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case racer := <-lane:
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if racer.error == nil {
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return racer.Conn, nil
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}
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failAddr = racer.Addr
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lastErr = racer.error
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nracers--
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}
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}
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return nil, &OpError{Op: "dial", Net: net, Addr: failAddr, Err: lastErr}
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}
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// dialSingle attempts to establish and returns a single connection to
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// the destination address.
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func dialSingle(net, addr string, la, ra Addr, deadline time.Time) (c Conn, err error) {
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if la != nil && la.Network() != ra.Network() {
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return nil, &OpError{Op: "dial", Net: net, Addr: ra, Err: errors.New("mismatched local address type " + la.Network())}
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}
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switch ra := ra.(type) {
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case *TCPAddr:
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la, _ := la.(*TCPAddr)
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c, err = dialTCP(net, la, ra, deadline)
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case *UDPAddr:
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la, _ := la.(*UDPAddr)
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c, err = dialUDP(net, la, ra, deadline)
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case *IPAddr:
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la, _ := la.(*IPAddr)
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c, err = dialIP(net, la, ra, deadline)
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case *UnixAddr:
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la, _ := la.(*UnixAddr)
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c, err = dialUnix(net, la, ra, deadline)
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default:
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return nil, &OpError{Op: "dial", Net: net, Addr: ra, Err: &AddrError{Err: "unexpected address type", Addr: addr}}
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}
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if err != nil {
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return nil, err // c is non-nil interface containing nil pointer
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}
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return c, nil
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}
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// Listen announces on the local network address laddr.
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// The network net must be a stream-oriented network: "tcp", "tcp4",
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// "tcp6", "unix" or "unixpacket".
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// See Dial for the syntax of laddr.
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func Listen(net, laddr string) (Listener, error) {
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la, err := resolveAddr("listen", net, laddr, noDeadline)
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if err != nil {
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return nil, &OpError{Op: "listen", Net: net, Addr: nil, Err: err}
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}
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var l Listener
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switch la := la.toAddr().(type) {
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case *TCPAddr:
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l, err = ListenTCP(net, la)
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case *UnixAddr:
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l, err = ListenUnix(net, la)
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default:
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return nil, &OpError{Op: "listen", Net: net, Addr: la, Err: &AddrError{Err: "unexpected address type", Addr: laddr}}
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}
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if err != nil {
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return nil, err // l is non-nil interface containing nil pointer
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}
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return l, nil
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}
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// ListenPacket announces on the local network address laddr.
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// The network net must be a packet-oriented network: "udp", "udp4",
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// "udp6", "ip", "ip4", "ip6" or "unixgram".
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// See Dial for the syntax of laddr.
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func ListenPacket(net, laddr string) (PacketConn, error) {
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la, err := resolveAddr("listen", net, laddr, noDeadline)
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if err != nil {
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return nil, &OpError{Op: "listen", Net: net, Addr: nil, Err: err}
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}
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var l PacketConn
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switch la := la.toAddr().(type) {
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case *UDPAddr:
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l, err = ListenUDP(net, la)
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case *IPAddr:
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l, err = ListenIP(net, la)
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case *UnixAddr:
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l, err = ListenUnixgram(net, la)
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default:
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return nil, &OpError{Op: "listen", Net: net, Addr: la, Err: &AddrError{Err: "unexpected address type", Addr: laddr}}
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}
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if err != nil {
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return nil, err // l is non-nil interface containing nil pointer
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}
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return l, nil
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}
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