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