mirror of
https://github.com/autc04/Retro68.git
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445 lines
14 KiB
Go
445 lines
14 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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// When dialing a name with multiple IP addresses, the timeout
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// may be divided between them.
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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 enables RFC 6555-compliant "Happy Eyeballs" dialing
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// when the network is "tcp" and the destination is a host name
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// with both IPv4 and IPv6 addresses. This allows a client to
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// tolerate networks where one address family is silently broken.
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DualStack bool
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// FallbackDelay specifies the length of time to wait before
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// spawning a fallback connection, when DualStack is enabled.
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// If zero, a default delay of 300ms is used.
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FallbackDelay time.Duration
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// KeepAlive specifies the keep-alive period for an active
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// network connection.
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// If zero, keep-alives are not enabled. Network protocols
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// that do not support keep-alives ignore this field.
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KeepAlive time.Duration
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// Cancel is an optional channel whose closure indicates that
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// the dial should be canceled. Not all types of dials support
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// cancelation.
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Cancel <-chan struct{}
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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(now time.Time) 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 := 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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// partialDeadline returns the deadline to use for a single address,
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// when multiple addresses are pending.
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func partialDeadline(now, deadline time.Time, addrsRemaining int) (time.Time, error) {
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if deadline.IsZero() {
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return deadline, nil
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}
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timeRemaining := deadline.Sub(now)
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if timeRemaining <= 0 {
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return time.Time{}, errTimeout
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}
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// Tentatively allocate equal time to each remaining address.
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timeout := timeRemaining / time.Duration(addrsRemaining)
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// If the time per address is too short, steal from the end of the list.
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const saneMinimum = 2 * time.Second
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if timeout < saneMinimum {
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if timeRemaining < saneMinimum {
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timeout = timeRemaining
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} else {
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timeout = saneMinimum
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}
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}
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return now.Add(timeout), nil
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}
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func (d *Dialer) fallbackDelay() time.Duration {
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if d.FallbackDelay > 0 {
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return d.FallbackDelay
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} else {
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return 300 * time.Millisecond
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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 resolveAddrList(op, net, addr string, deadline time.Time) (addrList, 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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addr, err := ResolveUnixAddr(afnet, addr)
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if err != nil {
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return nil, err
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}
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return addrList{addr}, nil
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}
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return internetAddrList(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 it must be enclosed
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// in square brackets as in "[::1]:80" or "[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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// If the host is empty, as in ":80", the local system is assumed.
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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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// Dial("tcp", ":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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// dialContext holds common state for all dial operations.
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type dialContext struct {
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Dialer
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network, address string
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finalDeadline time.Time
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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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finalDeadline := d.deadline(time.Now())
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addrs, err := resolveAddrList("dial", network, address, finalDeadline)
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if err != nil {
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return nil, &OpError{Op: "dial", Net: network, Source: nil, Addr: nil, Err: err}
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}
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ctx := &dialContext{
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Dialer: *d,
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network: network,
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address: address,
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finalDeadline: finalDeadline,
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}
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var primaries, fallbacks addrList
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if d.DualStack && network == "tcp" {
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primaries, fallbacks = addrs.partition(isIPv4)
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} else {
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primaries = addrs
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}
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var c Conn
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if len(fallbacks) == 0 {
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// dialParallel can accept an empty fallbacks list,
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// but this shortcut avoids the goroutine/channel overhead.
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c, err = dialSerial(ctx, primaries, nil)
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} else {
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c, err = dialParallel(ctx, primaries, fallbacks)
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}
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if d.KeepAlive > 0 && err == nil {
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if tc, ok := c.(*TCPConn); ok {
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setKeepAlive(tc.fd, true)
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setKeepAlivePeriod(tc.fd, d.KeepAlive)
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testHookSetKeepAlive()
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}
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}
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return c, err
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}
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// dialParallel races two copies of dialSerial, giving the first a
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// head start. It returns the first established connection and
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// closes the others. Otherwise it returns an error from the first
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// primary address.
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func dialParallel(ctx *dialContext, primaries, fallbacks addrList) (Conn, error) {
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results := make(chan dialResult) // unbuffered, so dialSerialAsync can detect race loss & cleanup
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cancel := make(chan struct{})
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defer close(cancel)
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// Spawn the primary racer.
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go dialSerialAsync(ctx, primaries, nil, cancel, results)
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// Spawn the fallback racer.
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fallbackTimer := time.NewTimer(ctx.fallbackDelay())
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go dialSerialAsync(ctx, fallbacks, fallbackTimer, cancel, results)
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var primaryErr error
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for nracers := 2; nracers > 0; nracers-- {
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res := <-results
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// If we're still waiting for a connection, then hasten the delay.
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// Otherwise, disable the Timer and let cancel take over.
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if fallbackTimer.Stop() && res.error != nil {
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fallbackTimer.Reset(0)
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}
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if res.error == nil {
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return res.Conn, nil
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}
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if res.primary {
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primaryErr = res.error
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}
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}
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return nil, primaryErr
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}
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type dialResult struct {
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Conn
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error
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primary bool
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}
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// dialSerialAsync runs dialSerial after some delay, and returns the
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// resulting connection through a channel. When racing two connections,
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// the primary goroutine uses a nil timer to omit the delay.
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func dialSerialAsync(ctx *dialContext, ras addrList, timer *time.Timer, cancel <-chan struct{}, results chan<- dialResult) {
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if timer != nil {
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// We're in the fallback goroutine; sleep before connecting.
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select {
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case <-timer.C:
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case <-cancel:
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return
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}
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}
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c, err := dialSerial(ctx, ras, cancel)
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select {
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case results <- dialResult{c, err, timer == nil}:
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// We won the race.
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case <-cancel:
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// The other goroutine won the race.
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if c != nil {
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c.Close()
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}
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}
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}
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// dialSerial connects to a list of addresses in sequence, returning
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// either the first successful connection, or the first error.
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func dialSerial(ctx *dialContext, ras addrList, cancel <-chan struct{}) (Conn, error) {
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var firstErr error // The error from the first address is most relevant.
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for i, ra := range ras {
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select {
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case <-cancel:
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return nil, &OpError{Op: "dial", Net: ctx.network, Source: ctx.LocalAddr, Addr: ra, Err: errCanceled}
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default:
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}
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partialDeadline, err := partialDeadline(time.Now(), ctx.finalDeadline, len(ras)-i)
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if err != nil {
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// Ran out of time.
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if firstErr == nil {
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firstErr = &OpError{Op: "dial", Net: ctx.network, Source: ctx.LocalAddr, Addr: ra, Err: err}
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}
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break
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}
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// dialTCP does not support cancelation (see golang.org/issue/11225),
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// so if cancel fires, we'll continue trying to connect until the next
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// timeout, or return a spurious connection for the caller to close.
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dialer := func(d time.Time) (Conn, error) {
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return dialSingle(ctx, ra, d)
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}
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c, err := dial(ctx.network, ra, dialer, partialDeadline)
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if err == nil {
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return c, nil
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}
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if firstErr == nil {
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firstErr = err
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}
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}
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if firstErr == nil {
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firstErr = &OpError{Op: "dial", Net: ctx.network, Source: nil, Addr: nil, Err: errMissingAddress}
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}
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return nil, firstErr
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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. This must be called through the OS-specific
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// dial function, because some OSes don't implement the deadline feature.
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func dialSingle(ctx *dialContext, ra Addr, deadline time.Time) (c Conn, err error) {
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la := ctx.LocalAddr
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if la != nil && la.Network() != ra.Network() {
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return nil, &OpError{Op: "dial", Net: ctx.network, Source: la, 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 = testHookDialTCP(ctx.network, la, ra, deadline, ctx.Cancel)
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case *UDPAddr:
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la, _ := la.(*UDPAddr)
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c, err = dialUDP(ctx.network, la, ra, deadline)
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case *IPAddr:
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la, _ := la.(*IPAddr)
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c, err = dialIP(ctx.network, la, ra, deadline)
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case *UnixAddr:
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la, _ := la.(*UnixAddr)
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c, err = dialUnix(ctx.network, la, ra, deadline)
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default:
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return nil, &OpError{Op: "dial", Net: ctx.network, Source: la, Addr: ra, Err: &AddrError{Err: "unexpected address type", Addr: ctx.address}}
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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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// For TCP and UDP, the syntax of laddr is "host:port", like "127.0.0.1:8080".
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// If host is omitted, as in ":8080", Listen listens on all available interfaces
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// instead of just the interface with the given host address.
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// See Dial for more details about address syntax.
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func Listen(net, laddr string) (Listener, error) {
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addrs, err := resolveAddrList("listen", net, laddr, noDeadline)
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if err != nil {
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return nil, &OpError{Op: "listen", Net: net, Source: nil, Addr: nil, Err: err}
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}
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var l Listener
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switch la := addrs.first(isIPv4).(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, Source: nil, 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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// For TCP and UDP, the syntax of laddr is "host:port", like "127.0.0.1:8080".
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// If host is omitted, as in ":8080", ListenPacket listens on all available interfaces
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// instead of just the interface with the given host address.
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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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addrs, err := resolveAddrList("listen", net, laddr, noDeadline)
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if err != nil {
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return nil, &OpError{Op: "listen", Net: net, Source: nil, Addr: nil, Err: err}
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}
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var l PacketConn
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switch la := addrs.first(isIPv4).(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, Source: nil, 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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