358 lines
10 KiB
Go
358 lines
10 KiB
Go
// Copyright 2009 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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// +build darwin freebsd linux netbsd openbsd windows
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// TCP sockets
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package net
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import (
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"fmt"
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"io"
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"os"
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"syscall"
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"time"
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)
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// BUG(rsc): On OpenBSD, listening on the "tcp" network does not listen for
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// both IPv4 and IPv6 connections. This is due to the fact that IPv4 traffic
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// will not be routed to an IPv6 socket - two separate sockets are required
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// if both AFs are to be supported. See inet6(4) on OpenBSD for details.
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func sockaddrToTCP(sa syscall.Sockaddr) Addr {
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switch sa := sa.(type) {
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case *syscall.SockaddrInet4:
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return &TCPAddr{sa.Addr[0:], sa.Port}
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case *syscall.SockaddrInet6:
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return &TCPAddr{sa.Addr[0:], sa.Port}
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default:
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if sa != nil {
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// Diagnose when we will turn a non-nil sockaddr into a nil.
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panic(fmt.Sprintf("unexpected type in sockaddrToTCP: %T", sa))
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}
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}
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return nil
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}
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func (a *TCPAddr) family() int {
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if a == nil || len(a.IP) <= IPv4len {
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return syscall.AF_INET
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}
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if a.IP.To4() != nil {
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return syscall.AF_INET
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}
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return syscall.AF_INET6
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}
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func (a *TCPAddr) sockaddr(family int) (syscall.Sockaddr, error) {
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return ipToSockaddr(family, a.IP, a.Port)
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}
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func (a *TCPAddr) toAddr() sockaddr {
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if a == nil { // nil *TCPAddr
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return nil // nil interface
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}
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return a
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}
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// TCPConn is an implementation of the Conn interface
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// for TCP network connections.
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type TCPConn struct {
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fd *netFD
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}
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func newTCPConn(fd *netFD) *TCPConn {
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c := &TCPConn{fd}
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c.SetNoDelay(true)
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return c
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}
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func (c *TCPConn) ok() bool { return c != nil && c.fd != nil }
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// Implementation of the Conn interface - see Conn for documentation.
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// Read implements the Conn Read method.
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func (c *TCPConn) Read(b []byte) (n int, err error) {
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if !c.ok() {
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return 0, syscall.EINVAL
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}
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return c.fd.Read(b)
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}
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// ReadFrom implements the io.ReaderFrom ReadFrom method.
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func (c *TCPConn) ReadFrom(r io.Reader) (int64, error) {
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if n, err, handled := sendFile(c.fd, r); handled {
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return n, err
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}
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return genericReadFrom(c, r)
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}
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// Write implements the Conn Write method.
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func (c *TCPConn) Write(b []byte) (n int, err error) {
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if !c.ok() {
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return 0, syscall.EINVAL
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}
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return c.fd.Write(b)
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}
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// Close closes the TCP connection.
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func (c *TCPConn) Close() error {
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if !c.ok() {
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return syscall.EINVAL
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}
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err := c.fd.Close()
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c.fd = nil
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return err
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}
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// CloseRead shuts down the reading side of the TCP connection.
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// Most callers should just use Close.
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func (c *TCPConn) CloseRead() error {
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if !c.ok() {
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return syscall.EINVAL
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}
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return c.fd.CloseRead()
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}
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// CloseWrite shuts down the writing side of the TCP connection.
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// Most callers should just use Close.
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func (c *TCPConn) CloseWrite() error {
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if !c.ok() {
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return syscall.EINVAL
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}
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return c.fd.CloseWrite()
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}
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// LocalAddr returns the local network address, a *TCPAddr.
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func (c *TCPConn) LocalAddr() Addr {
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if !c.ok() {
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return nil
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}
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return c.fd.laddr
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}
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// RemoteAddr returns the remote network address, a *TCPAddr.
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func (c *TCPConn) RemoteAddr() Addr {
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if !c.ok() {
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return nil
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}
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return c.fd.raddr
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}
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// SetDeadline implements the Conn SetDeadline method.
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func (c *TCPConn) SetDeadline(t time.Time) error {
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if !c.ok() {
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return syscall.EINVAL
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}
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return setDeadline(c.fd, t)
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}
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// SetReadDeadline implements the Conn SetReadDeadline method.
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func (c *TCPConn) SetReadDeadline(t time.Time) error {
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if !c.ok() {
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return syscall.EINVAL
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}
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return setReadDeadline(c.fd, t)
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}
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// SetWriteDeadline implements the Conn SetWriteDeadline method.
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func (c *TCPConn) SetWriteDeadline(t time.Time) error {
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if !c.ok() {
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return syscall.EINVAL
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}
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return setWriteDeadline(c.fd, t)
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}
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// SetReadBuffer sets the size of the operating system's
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// receive buffer associated with the connection.
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func (c *TCPConn) SetReadBuffer(bytes int) error {
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if !c.ok() {
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return syscall.EINVAL
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}
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return setReadBuffer(c.fd, bytes)
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}
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// SetWriteBuffer sets the size of the operating system's
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// transmit buffer associated with the connection.
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func (c *TCPConn) SetWriteBuffer(bytes int) error {
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if !c.ok() {
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return syscall.EINVAL
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}
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return setWriteBuffer(c.fd, bytes)
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}
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// SetLinger sets the behavior of Close() on a connection
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// which still has data waiting to be sent or to be acknowledged.
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//
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// If sec < 0 (the default), Close returns immediately and
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// the operating system finishes sending the data in the background.
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//
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// If sec == 0, Close returns immediately and the operating system
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// discards any unsent or unacknowledged data.
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//
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// If sec > 0, Close blocks for at most sec seconds waiting for
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// data to be sent and acknowledged.
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func (c *TCPConn) SetLinger(sec int) error {
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if !c.ok() {
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return syscall.EINVAL
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}
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return setLinger(c.fd, sec)
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}
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// SetKeepAlive sets whether the operating system should send
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// keepalive messages on the connection.
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func (c *TCPConn) SetKeepAlive(keepalive bool) error {
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if !c.ok() {
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return syscall.EINVAL
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}
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return setKeepAlive(c.fd, keepalive)
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}
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// SetNoDelay controls whether the operating system should delay
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// packet transmission in hopes of sending fewer packets
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// (Nagle's algorithm). The default is true (no delay), meaning
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// that data is sent as soon as possible after a Write.
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func (c *TCPConn) SetNoDelay(noDelay bool) error {
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if !c.ok() {
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return syscall.EINVAL
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}
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return setNoDelay(c.fd, noDelay)
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}
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// File returns a copy of the underlying os.File, set to blocking mode.
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// It is the caller's responsibility to close f when finished.
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// Closing c does not affect f, and closing f does not affect c.
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func (c *TCPConn) File() (f *os.File, err error) { return c.fd.dup() }
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// DialTCP connects to the remote address raddr on the network net,
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// which must be "tcp", "tcp4", or "tcp6". If laddr is not nil, it is used
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// as the local address for the connection.
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func DialTCP(net string, laddr, raddr *TCPAddr) (*TCPConn, error) {
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if raddr == nil {
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return nil, &OpError{"dial", net, nil, errMissingAddress}
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}
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fd, err := internetSocket(net, laddr.toAddr(), raddr.toAddr(), syscall.SOCK_STREAM, 0, "dial", sockaddrToTCP)
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// TCP has a rarely used mechanism called a 'simultaneous connection' in
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// which Dial("tcp", addr1, addr2) run on the machine at addr1 can
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// connect to a simultaneous Dial("tcp", addr2, addr1) run on the machine
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// at addr2, without either machine executing Listen. If laddr == nil,
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// it means we want the kernel to pick an appropriate originating local
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// address. Some Linux kernels cycle blindly through a fixed range of
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// local ports, regardless of destination port. If a kernel happens to
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// pick local port 50001 as the source for a Dial("tcp", "", "localhost:50001"),
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// then the Dial will succeed, having simultaneously connected to itself.
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// This can only happen when we are letting the kernel pick a port (laddr == nil)
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// and when there is no listener for the destination address.
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// It's hard to argue this is anything other than a kernel bug. If we
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// see this happen, rather than expose the buggy effect to users, we
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// close the fd and try again. If it happens twice more, we relent and
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// use the result. See also:
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// http://golang.org/issue/2690
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// http://stackoverflow.com/questions/4949858/
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for i := 0; i < 2 && err == nil && laddr == nil && selfConnect(fd); i++ {
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fd.Close()
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fd, err = internetSocket(net, laddr.toAddr(), raddr.toAddr(), syscall.SOCK_STREAM, 0, "dial", sockaddrToTCP)
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}
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if err != nil {
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return nil, err
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}
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return newTCPConn(fd), nil
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}
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func selfConnect(fd *netFD) bool {
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// The socket constructor can return an fd with raddr nil under certain
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// unknown conditions. The errors in the calls there to Getpeername
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// are discarded, but we can't catch the problem there because those
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// calls are sometimes legally erroneous with a "socket not connected".
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// Since this code (selfConnect) is already trying to work around
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// a problem, we make sure if this happens we recognize trouble and
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// ask the DialTCP routine to try again.
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// TODO: try to understand what's really going on.
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if fd.laddr == nil || fd.raddr == nil {
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return true
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}
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l := fd.laddr.(*TCPAddr)
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r := fd.raddr.(*TCPAddr)
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return l.Port == r.Port && l.IP.Equal(r.IP)
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}
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// TCPListener is a TCP network listener.
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// Clients should typically use variables of type Listener
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// instead of assuming TCP.
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type TCPListener struct {
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fd *netFD
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}
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// ListenTCP announces on the TCP address laddr and returns a TCP listener.
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// Net must be "tcp", "tcp4", or "tcp6".
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// If laddr has a port of 0, it means to listen on some available port.
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// The caller can use l.Addr() to retrieve the chosen address.
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func ListenTCP(net string, laddr *TCPAddr) (*TCPListener, error) {
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fd, err := internetSocket(net, laddr.toAddr(), nil, syscall.SOCK_STREAM, 0, "listen", sockaddrToTCP)
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if err != nil {
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return nil, err
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}
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err = syscall.Listen(fd.sysfd, listenerBacklog)
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if err != nil {
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closesocket(fd.sysfd)
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return nil, &OpError{"listen", net, laddr, err}
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}
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l := new(TCPListener)
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l.fd = fd
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return l, nil
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}
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// AcceptTCP accepts the next incoming call and returns the new connection
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// and the remote address.
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func (l *TCPListener) AcceptTCP() (c *TCPConn, err error) {
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if l == nil || l.fd == nil || l.fd.sysfd < 0 {
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return nil, syscall.EINVAL
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}
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fd, err := l.fd.accept(sockaddrToTCP)
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if err != nil {
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return nil, err
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}
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return newTCPConn(fd), nil
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}
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// Accept implements the Accept method in the Listener interface;
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// it waits for the next call and returns a generic Conn.
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func (l *TCPListener) Accept() (c Conn, err error) {
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c1, err := l.AcceptTCP()
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if err != nil {
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return nil, err
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}
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return c1, nil
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}
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// Close stops listening on the TCP address.
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// Already Accepted connections are not closed.
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func (l *TCPListener) Close() error {
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if l == nil || l.fd == nil {
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return syscall.EINVAL
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}
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return l.fd.Close()
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}
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// Addr returns the listener's network address, a *TCPAddr.
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func (l *TCPListener) Addr() Addr { return l.fd.laddr }
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// SetDeadline sets the deadline associated with the listener.
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// A zero time value disables the deadline.
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func (l *TCPListener) SetDeadline(t time.Time) error {
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if l == nil || l.fd == nil {
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return syscall.EINVAL
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}
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return setDeadline(l.fd, t)
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}
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// File returns a copy of the underlying os.File, set to blocking mode.
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// It is the caller's responsibility to close f when finished.
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// Closing c does not affect f, and closing f does not affect c.
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func (l *TCPListener) File() (f *os.File, err error) { return l.fd.dup() }
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