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tcpsock_posix.go
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tcpsock_posix.go
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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 dragonfly freebsd linux nacl netbsd openbsd solaris windows
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{IP: sa.Addr[0:], Port: sa.Port}
case *syscall.SockaddrInet6:
return &TCPAddr{IP: sa.Addr[0:], Port: sa.Port, Zone: zoneToString(int(sa.ZoneId))}
}
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) isWildcard() bool {
if a == nil || a.IP == nil {
return true
}
return a.IP.IsUnspecified()
}
func (a *TCPAddr) sockaddr(family int) (syscall.Sockaddr, error) {
if a == nil {
return nil, nil
}
return ipToSockaddr(family, a.IP, a.Port, a.Zone)
}
// TCPConn is an implementation of the Conn interface for TCP network
// connections.
type TCPConn struct {
conn
}
func newTCPConn(fd *netFD) *TCPConn {
c := &TCPConn{conn{fd}}
c.SetNoDelay(true)
return c
}
// 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)
}
// 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 syscall.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 syscall.EINVAL
}
return c.fd.closeWrite()
}
// 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), the operating system finishes sending the
// data in the background.
//
// If sec == 0, the operating system discards any unsent or
// unacknowledged data.
//
// If sec > 0, the data is sent in the background as with sec < 0. On
// some operating systems after sec seconds have elapsed any remaining
// unsent data may be discarded.
func (c *TCPConn) SetLinger(sec int) error {
if !c.ok() {
return syscall.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 syscall.EINVAL
}
return setKeepAlive(c.fd, keepalive)
}
// SetKeepAlivePeriod sets period between keep alives.
func (c *TCPConn) SetKeepAlivePeriod(d time.Duration) error {
if !c.ok() {
return syscall.EINVAL
}
return setKeepAlivePeriod(c.fd, d)
}
// 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 syscall.EINVAL
}
return setNoDelay(c.fd, noDelay)
}
// 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) {
switch net {
case "tcp", "tcp4", "tcp6":
default:
return nil, &OpError{Op: "dial", Net: net, Addr: raddr, Err: UnknownNetworkError(net)}
}
if raddr == nil {
return nil, &OpError{Op: "dial", Net: net, Addr: nil, Err: errMissingAddress}
}
return dialTCP(net, laddr, raddr, noDeadline)
}
func dialTCP(net string, laddr, raddr *TCPAddr, deadline time.Time) (*TCPConn, error) {
fd, err := internetSocket(net, laddr, raddr, deadline, syscall.SOCK_STREAM, 0, "dial")
// 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/
//
// The opposite can also happen: if we ask the kernel to pick an appropriate
// originating local address, sometimes it picks one that is already in use.
// So if the error is EADDRNOTAVAIL, we have to try again too, just for
// a different reason.
//
// The kernel socket code is no doubt enjoying watching us squirm.
for i := 0; i < 2 && (laddr == nil || laddr.Port == 0) && (selfConnect(fd, err) || spuriousENOTAVAIL(err)); i++ {
if err == nil {
fd.Close()
}
fd, err = internetSocket(net, laddr, raddr, deadline, syscall.SOCK_STREAM, 0, "dial")
}
if err != nil {
return nil, &OpError{Op: "dial", Net: net, Addr: raddr, Err: err}
}
return newTCPConn(fd), nil
}
func selfConnect(fd *netFD, err error) bool {
// If the connect failed, we clearly didn't connect to ourselves.
if err != nil {
return false
}
// The socket constructor can return an fd with raddr nil under certain
// unknown conditions. The errors in the calls there to Getpeername
// are discarded, but we can't catch the problem there because those
// calls are sometimes legally erroneous with a "socket not connected".
// Since this code (selfConnect) is already trying to work around
// a problem, we make sure if this happens we recognize trouble and
// ask the DialTCP routine to try again.
// TODO: try to understand what's really going on.
if fd.laddr == nil || fd.raddr == nil {
return true
}
l := fd.laddr.(*TCPAddr)
r := fd.raddr.(*TCPAddr)
return l.Port == r.Port && l.IP.Equal(r.IP)
}
func spuriousENOTAVAIL(err error) bool {
e, ok := err.(*OpError)
return ok && e.Err == syscall.EADDRNOTAVAIL
}
// TCPListener is a TCP network listener. Clients should typically
// use variables of type Listener instead of assuming TCP.
type TCPListener struct {
fd *netFD
}
// AcceptTCP accepts the next incoming call and returns the new
// connection.
func (l *TCPListener) AcceptTCP() (*TCPConn, error) {
if l == nil || l.fd == nil {
return nil, syscall.EINVAL
}
fd, err := l.fd.accept()
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() (Conn, error) {
c, err := l.AcceptTCP()
if err != nil {
return nil, err
}
return c, 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 syscall.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 syscall.EINVAL
}
return l.fd.setDeadline(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 l does not affect f, and closing f does not affect l.
//
// The returned os.File's file descriptor is different from the
// connection's. Attempting to change properties of the original
// using this duplicate may or may not have the desired effect.
func (l *TCPListener) File() (f *os.File, err error) { return l.fd.dup() }
// 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, ListenTCP will choose an available port. The caller can
// use the Addr method of TCPListener to retrieve the chosen address.
func ListenTCP(net string, laddr *TCPAddr) (*TCPListener, error) {
switch net {
case "tcp", "tcp4", "tcp6":
default:
return nil, &OpError{Op: "listen", Net: net, Addr: laddr, Err: UnknownNetworkError(net)}
}
if laddr == nil {
laddr = &TCPAddr{}
}
fd, err := internetSocket(net, laddr, nil, noDeadline, syscall.SOCK_STREAM, 0, "listen")
if err != nil {
return nil, &OpError{Op: "listen", Net: net, Addr: laddr, Err: err}
}
return &TCPListener{fd}, nil
}