2013-02-11 Sebastian Huber <sebastian.huber@embedded-brains.de>

[official-gcc.git] / libgo / go / net / tcpsock_posix.go

// 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{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) {
        return ipToSockaddr(family, a.IP, a.Port, a.Zone)
}

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 {
        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), 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 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)
}

// 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, UnknownNetworkError(net)
        }
        if raddr == nil {
                return nil, &OpError{"dial", net, nil, errMissingAddress}
        }
        return dialTCP(net, laddr, raddr, noDeadline)
}

func dialTCP(net string, laddr, raddr *TCPAddr, deadline time.Time) (*TCPConn, error) {
        fd, err := internetSocket(net, laddr.toAddr(), raddr.toAddr(), deadline, 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/
        //
        // 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.toAddr(), raddr.toAddr(), deadline, syscall.SOCK_STREAM, 0, "dial", sockaddrToTCP)
        }

        if err != nil {
                return nil, 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
// and the remote address.
func (l *TCPListener) AcceptTCP() (c *TCPConn, err error) {
        if l == nil || l.fd == nil {
                return nil, syscall.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 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 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 l does not affect f, and closing f does not affect l.
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, 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) {
        switch net {
        case "tcp", "tcp4", "tcp6":
        default:
                return nil, UnknownNetworkError(net)
        }
        if laddr == nil {
                laddr = &TCPAddr{}
        }
        fd, err := internetSocket(net, laddr.toAddr(), nil, noDeadline, 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}
        }
        return &TCPListener{fd}, nil
}