src/syscall/net_nacl.go - go - Git at Google

 // Copyright 2013 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.

 // A simulated network for use within NaCl.
 // The simulation is not particularly tied to NaCl,
 // but other systems have real networks.

 package syscall

 import (
 	"sync"
 	"sync/atomic"
 )

 // Interface to timers implemented in package runtime.
 // Must be in sync with ../runtime/runtime.h:/^struct.Timer$
 // Really for use by package time, but we cannot import time here.

 type runtimeTimer struct {
 	i      int
 	when   int64
 	period int64
 	f      func(interface{}, uintptr) // NOTE: must not be closure
 	arg    interface{}
 	seq    uintptr
 }

 func startTimer(*runtimeTimer)
 func stopTimer(*runtimeTimer) bool

 type timer struct {
 	expired bool
 	q       *queue
 	r       runtimeTimer
 }

 func (t *timer) start(q *queue, deadline int64) {
 	if deadline == 0 {
 		return
 	}
 	t.q = q
 	t.r.when = deadline
 	t.r.f = timerExpired
 	t.r.arg = t
 	startTimer(&t.r)
 }

 func (t *timer) stop() {
 	stopTimer(&t.r)
 }

 func timerExpired(i interface{}, seq uintptr) {
 	t := i.(*timer)
 	go func() {
 		t.q.Lock()
 		defer t.q.Unlock()
 		t.expired = true
 		t.q.canRead.Broadcast()
 		t.q.canWrite.Broadcast()
 	}()
 }

 // Network constants and data structures. These match the traditional values.

 const (
 	AF_UNSPEC = iota
 	AF_UNIX
 	AF_INET
 	AF_INET6
 )

 const (
 	SHUT_RD = iota
 	SHUT_WR
 	SHUT_RDWR
 )

 const (
 	SOCK_STREAM = 1 + iota
 	SOCK_DGRAM
 	SOCK_RAW
 	SOCK_SEQPACKET
 )

 const (
 	IPPROTO_IP   = 0
 	IPPROTO_IPV4 = 4
 	IPPROTO_IPV6 = 0x29
 	IPPROTO_TCP  = 6
 	IPPROTO_UDP  = 0x11
 )

 // Misc constants expected by package net but not supported.
 const (
 	_ = iota
 	SOL_SOCKET
 	SO_TYPE
 	NET_RT_IFLIST
 	IFNAMSIZ
 	IFF_UP
 	IFF_BROADCAST
 	IFF_LOOPBACK
 	IFF_POINTOPOINT
 	IFF_MULTICAST
 	IPV6_V6ONLY
 	SOMAXCONN
 	F_DUPFD_CLOEXEC
 	SO_BROADCAST
 	SO_REUSEADDR
 	SO_REUSEPORT
 	SO_RCVBUF
 	SO_SNDBUF
 	SO_KEEPALIVE
 	SO_LINGER
 	SO_ERROR
 	IP_PORTRANGE
 	IP_PORTRANGE_DEFAULT
 	IP_PORTRANGE_LOW
 	IP_PORTRANGE_HIGH
 	IP_MULTICAST_IF
 	IP_MULTICAST_LOOP
 	IP_ADD_MEMBERSHIP
 	IPV6_PORTRANGE
 	IPV6_PORTRANGE_DEFAULT
 	IPV6_PORTRANGE_LOW
 	IPV6_PORTRANGE_HIGH
 	IPV6_MULTICAST_IF
 	IPV6_MULTICAST_LOOP
 	IPV6_JOIN_GROUP
 	TCP_NODELAY
 	TCP_KEEPINTVL
 	TCP_KEEPIDLE

 	SYS_FCNTL = 500 // unsupported
 )

 var SocketDisableIPv6 bool

 // A Sockaddr is one of the SockaddrXxx structs.
 type Sockaddr interface {
 	// copy returns a copy of the underlying data.
 	copy() Sockaddr

 	// key returns the value of the underlying data,
 	// for comparison as a map key.
 	key() interface{}
 }

 type SockaddrInet4 struct {
 	Port int
 	Addr [4]byte
 }

 func (sa *SockaddrInet4) copy() Sockaddr {
 	sa1 := *sa
 	return &sa1
 }

 func (sa *SockaddrInet4) key() interface{} { return *sa }

 type SockaddrInet6 struct {
 	Port   int
 	ZoneId uint32
 	Addr   [16]byte
 }

 func (sa *SockaddrInet6) copy() Sockaddr {
 	sa1 := *sa
 	return &sa1
 }

 func (sa *SockaddrInet6) key() interface{} { return *sa }

 type SockaddrUnix struct {
 	Name string
 }

 func (sa *SockaddrUnix) copy() Sockaddr {
 	sa1 := *sa
 	return &sa1
 }

 func (sa *SockaddrUnix) key() interface{} { return *sa }

 type SockaddrDatalink struct {
 	Len    uint8
 	Family uint8
 	Index  uint16
 	Type   uint8
 	Nlen   uint8
 	Alen   uint8
 	Slen   uint8
 	Data   [12]int8
 }

 func (sa *SockaddrDatalink) copy() Sockaddr {
 	sa1 := *sa
 	return &sa1
 }

 func (sa *SockaddrDatalink) key() interface{} { return *sa }

 // RoutingMessage represents a routing message.
 type RoutingMessage interface {
 	unimplemented()
 }

 type IPMreq struct {
 	Multiaddr [4]byte /* in_addr */
 	Interface [4]byte /* in_addr */
 }

 type IPv6Mreq struct {
 	Multiaddr [16]byte /* in6_addr */
 	Interface uint32
 }

 type Linger struct {
 	Onoff  int32
 	Linger int32
 }

 type ICMPv6Filter struct {
 	Filt [8]uint32
 }

 // A queue is the bookkeeping for a synchronized buffered queue.
 // We do not use channels because we need to be able to handle
 // writes after and during close, and because a chan byte would
 // require too many send and receive operations in real use.
 type queue struct {
 	sync.Mutex
 	canRead  sync.Cond
 	canWrite sync.Cond
 	r        int // total read index
 	w        int // total write index
 	m        int // index mask
 	closed   bool
 }

 func (q *queue) init(size int) {
 	if size&(size-1) != 0 {
 		panic("invalid queue size - must be power of two")
 	}
 	q.canRead.L = &q.Mutex
 	q.canWrite.L = &q.Mutex
 	q.m = size - 1
 }

 func past(deadline int64) bool {
 	sec, nsec := now()
 	return deadline > 0 && deadline < sec*1e9+int64(nsec)
 }

 func (q *queue) waitRead(n int, deadline int64) (int, error) {
 	if past(deadline) {
 		return 0, EAGAIN
 	}
 	var t timer
 	t.start(q, deadline)
 	for q.w-q.r == 0 && !q.closed && !t.expired {
 		q.canRead.Wait()
 	}
 	t.stop()
 	m := q.w - q.r
 	if m == 0 && t.expired {
 		return 0, EAGAIN
 	}
 	if m > n {
 		m = n
 		q.canRead.Signal() // wake up next reader too
 	}
 	q.canWrite.Signal()
 	return m, nil
 }

 func (q *queue) waitWrite(n int, deadline int64) (int, error) {
 	if past(deadline) {
 		return 0, EAGAIN
 	}
 	var t timer
 	t.start(q, deadline)
 	for q.w-q.r > q.m && !q.closed && !t.expired {
 		q.canWrite.Wait()
 	}
 	t.stop()
 	m := q.m + 1 - (q.w - q.r)
 	if m == 0 && t.expired {
 		return 0, EAGAIN
 	}
 	if m == 0 {
 		return 0, EAGAIN
 	}
 	if m > n {
 		m = n
 		q.canWrite.Signal() // wake up next writer too
 	}
 	q.canRead.Signal()
 	return m, nil
 }

 func (q *queue) close() {
 	q.Lock()
 	defer q.Unlock()
 	q.closed = true
 	q.canRead.Broadcast()
 	q.canWrite.Broadcast()
 }

 // A byteq is a byte queue.
 type byteq struct {
 	queue
 	data []byte
 }

 func newByteq() *byteq {
 	q := &byteq{
 		data: make([]byte, 4096),
 	}
 	q.init(len(q.data))
 	return q
 }

 func (q *byteq) read(b []byte, deadline int64) (int, error) {
 	q.Lock()
 	defer q.Unlock()
 	n, err := q.waitRead(len(b), deadline)
 	if err != nil {
 		return 0, err
 	}
 	b = b[:n]
 	for len(b) > 0 {
 		m := copy(b, q.data[q.r&q.m:])
 		q.r += m
 		b = b[m:]
 	}
 	return n, nil
 }

 func (q *byteq) write(b []byte, deadline int64) (n int, err error) {
 	q.Lock()
 	defer q.Unlock()
 	for n < len(b) {
 		nn, err := q.waitWrite(len(b[n:]), deadline)
 		if err != nil {
 			return n, err
 		}
 		bb := b[n : n+nn]
 		n += nn
 		for len(bb) > 0 {
 			m := copy(q.data[q.w&q.m:], bb)
 			q.w += m
 			bb = bb[m:]
 		}
 	}
 	return n, nil
 }

 // A msgq is a queue of messages.
 type msgq struct {
 	queue
 	data []interface{}
 }

 func newMsgq() *msgq {
 	q := &msgq{
 		data: make([]interface{}, 32),
 	}
 	q.init(len(q.data))
 	return q
 }

 func (q *msgq) read(deadline int64) (interface{}, error) {
 	q.Lock()
 	defer q.Unlock()
 	n, err := q.waitRead(1, deadline)
 	if err != nil {
 		return nil, err
 	}
 	if n == 0 {
 		return nil, nil
 	}
 	m := q.data[q.r&q.m]
 	q.r++
 	return m, nil
 }

 func (q *msgq) write(m interface{}, deadline int64) error {
 	q.Lock()
 	defer q.Unlock()
 	_, err := q.waitWrite(1, deadline)
 	if err != nil {
 		return err
 	}
 	q.data[q.w&q.m] = m
 	q.w++
 	return nil
 }

 // An addr is a sequence of bytes uniquely identifying a network address.
 // It is not human-readable.
 type addr string

 // A conn is one side of a stream-based network connection.
 // That is, a stream-based network connection is a pair of cross-connected conns.
 type conn struct {
 	rd     *byteq
 	wr     *byteq
 	local  addr
 	remote addr
 }

 // A pktconn is one side of a packet-based network connection.
 // That is, a packet-based network connection is a pair of cross-connected pktconns.
 type pktconn struct {
 	rd     *msgq
 	wr     *msgq
 	local  addr
 	remote addr
 }

 // A listener accepts incoming stream-based network connections.
 type listener struct {
 	rd    *msgq
 	local addr
 }

 // A netFile is an open network file.
 type netFile struct {
 	defaultFileImpl
 	proto      *netproto
 	sotype     int
 	listener   *msgq
 	packet     *msgq
 	rd         *byteq
 	wr         *byteq
 	rddeadline int64
 	wrdeadline int64
 	addr       Sockaddr
 	raddr      Sockaddr
 }

 // A netAddr is a network address in the global listener map.
 // All the fields must have defined == operations.
 type netAddr struct {
 	proto  *netproto
 	sotype int
 	addr   interface{}
 }

 // net records the state of the network.
 // It maps a network address to the listener on that address.
 var net = struct {
 	sync.Mutex
 	listener map[netAddr]*netFile
 }{
 	listener: make(map[netAddr]*netFile),
 }

 // TODO(rsc): Some day, do a better job with port allocation.
 // For playground programs, incrementing is fine.
 var nextport = 2

 // A netproto contains protocol-specific functionality
 // (one for AF_INET, one for AF_INET6 and so on).
 // It is a struct instead of an interface because the
 // implementation needs no state, and I expect to
 // add some data fields at some point.
 type netproto struct {
 	bind func(*netFile, Sockaddr) error
 }

 var netprotoAF_INET = &netproto{
 	bind: func(f *netFile, sa Sockaddr) error {
 		if sa == nil {
 			f.addr = &SockaddrInet4{
 				Port: nextport,
 				Addr: [4]byte{127, 0, 0, 1},
 			}
 			nextport++
 			return nil
 		}
 		addr, ok := sa.(*SockaddrInet4)
 		if !ok {
 			return EINVAL
 		}
 		addr = addr.copy().(*SockaddrInet4)
 		if addr.Port == 0 {
 			addr.Port = nextport
 			nextport++
 		}
 		f.addr = addr
 		return nil
 	},
 }

 var netprotos = map[int]*netproto{
 	AF_INET: netprotoAF_INET,
 }

 // These functions implement the usual BSD socket operations.

 func (f *netFile) bind(sa Sockaddr) error {
 	if f.addr != nil {
 		return EISCONN
 	}
 	if err := f.proto.bind(f, sa); err != nil {
 		return err
 	}
 	if f.sotype == SOCK_DGRAM {
 		_, ok := net.listener[netAddr{f.proto, f.sotype, f.addr.key()}]
 		if ok {
 			f.addr = nil
 			return EADDRINUSE
 		}
 		net.listener[netAddr{f.proto, f.sotype, f.addr.key()}] = f
 		f.packet = newMsgq()
 	}
 	return nil
 }

 func (f *netFile) listen(backlog int) error {
 	net.Lock()
 	defer net.Unlock()
 	if f.listener != nil {
 		return EINVAL
 	}
 	old, ok := net.listener[netAddr{f.proto, f.sotype, f.addr.key()}]
 	if ok && !old.listenerClosed() {
 		return EADDRINUSE
 	}
 	net.listener[netAddr{f.proto, f.sotype, f.addr.key()}] = f
 	f.listener = newMsgq()
 	return nil
 }

 func (f *netFile) accept() (fd int, sa Sockaddr, err error) {
 	msg, err := f.listener.read(f.readDeadline())
 	if err != nil {
 		return -1, nil, err
 	}
 	newf, ok := msg.(*netFile)
 	if !ok {
 		// must be eof
 		return -1, nil, EAGAIN
 	}
 	return newFD(newf), newf.raddr.copy(), nil
 }

 func (f *netFile) connect(sa Sockaddr) error {
 	if past(f.writeDeadline()) {
 		return EAGAIN
 	}
 	if f.addr == nil {
 		if err := f.bind(nil); err != nil {
 			return err
 		}
 	}
 	net.Lock()
 	if sa == nil {
 		net.Unlock()
 		return EINVAL
 	}
 	sa = sa.copy()
 	if f.raddr != nil {
 		net.Unlock()
 		return EISCONN
 	}
 	if f.sotype == SOCK_DGRAM {
 		net.Unlock()
 		f.raddr = sa
 		return nil
 	}
 	if f.listener != nil {
 		net.Unlock()
 		return EISCONN
 	}
 	l, ok := net.listener[netAddr{f.proto, f.sotype, sa.key()}]
 	if !ok || l.listenerClosed() {
 		net.Unlock()
 		return ECONNREFUSED
 	}
 	f.raddr = sa
 	f.rd = newByteq()
 	f.wr = newByteq()
 	newf := &netFile{
 		proto:  f.proto,
 		sotype: f.sotype,
 		addr:   f.raddr,
 		raddr:  f.addr,
 		rd:     f.wr,
 		wr:     f.rd,
 	}
 	net.Unlock()
 	l.listener.write(newf, f.writeDeadline())
 	return nil
 }

 func (f *netFile) read(b []byte) (int, error) {
 	if f.rd == nil {
 		if f.raddr != nil {
 			n, _, err := f.recvfrom(b, 0)
 			return n, err
 		}
 		return 0, ENOTCONN
 	}
 	return f.rd.read(b, f.readDeadline())
 }

 func (f *netFile) write(b []byte) (int, error) {
 	if f.wr == nil {
 		if f.raddr != nil {
 			err := f.sendto(b, 0, f.raddr)
 			var n int
 			if err == nil {
 				n = len(b)
 			}
 			return n, err
 		}
 		return 0, ENOTCONN
 	}
 	return f.wr.write(b, f.writeDeadline())
 }

 type pktmsg struct {
 	buf  []byte
 	addr Sockaddr
 }

 func (f *netFile) recvfrom(p []byte, flags int) (n int, from Sockaddr, err error) {
 	if f.sotype != SOCK_DGRAM {
 		return 0, nil, EINVAL
 	}
 	if f.packet == nil {
 		return 0, nil, ENOTCONN
 	}
 	msg1, err := f.packet.read(f.readDeadline())
 	if err != nil {
 		return 0, nil, err
 	}
 	msg, ok := msg1.(*pktmsg)
 	if !ok {
 		return 0, nil, EAGAIN
 	}
 	return copy(p, msg.buf), msg.addr, nil
 }

 func (f *netFile) sendto(p []byte, flags int, to Sockaddr) error {
 	if f.sotype != SOCK_DGRAM {
 		return EINVAL
 	}
 	if f.packet == nil {
 		if err := f.bind(nil); err != nil {
 			return err
 		}
 	}
 	net.Lock()
 	if to == nil {
 		net.Unlock()
 		return EINVAL
 	}
 	to = to.copy()
 	l, ok := net.listener[netAddr{f.proto, f.sotype, to.key()}]
 	if !ok || l.packet == nil {
 		net.Unlock()
 		return ECONNREFUSED
 	}
 	net.Unlock()
 	msg := &pktmsg{
 		buf:  make([]byte, len(p)),
 		addr: f.addr,
 	}
 	copy(msg.buf, p)
 	l.packet.write(msg, f.writeDeadline())
 	return nil
 }

 func (f *netFile) listenerClosed() bool {
 	f.listener.Lock()
 	defer f.listener.Unlock()
 	return f.listener.closed
 }

 func (f *netFile) close() error {
 	if f.listener != nil {
 		f.listener.close()
 	}
 	if f.packet != nil {
 		f.packet.close()
 	}
 	if f.rd != nil {
 		f.rd.close()
 	}
 	if f.wr != nil {
 		f.wr.close()
 	}
 	return nil
 }

 func fdToNetFile(fd int) (*netFile, error) {
 	f, err := fdToFile(fd)
 	if err != nil {
 		return nil, err
 	}
 	impl := f.impl
 	netf, ok := impl.(*netFile)
 	if !ok {
 		return nil, EINVAL
 	}
 	return netf, nil
 }

 func Socket(proto, sotype, unused int) (fd int, err error) {
 	p := netprotos[proto]
 	if p == nil {
 		return -1, EPROTONOSUPPORT
 	}
 	if sotype != SOCK_STREAM && sotype != SOCK_DGRAM {
 		return -1, ESOCKTNOSUPPORT
 	}
 	f := &netFile{
 		proto:  p,
 		sotype: sotype,
 	}
 	return newFD(f), nil
 }

 func Bind(fd int, sa Sockaddr) error {
 	f, err := fdToNetFile(fd)
 	if err != nil {
 		return err
 	}
 	return f.bind(sa)
 }

 func StopIO(fd int) error {
 	f, err := fdToNetFile(fd)
 	if err != nil {
 		return err
 	}
 	f.close()
 	return nil
 }

 func Listen(fd int, backlog int) error {
 	f, err := fdToNetFile(fd)
 	if err != nil {
 		return err
 	}
 	return f.listen(backlog)
 }

 func Accept(fd int) (newfd int, sa Sockaddr, err error) {
 	f, err := fdToNetFile(fd)
 	if err != nil {
 		return 0, nil, err
 	}
 	return f.accept()
 }

 func Getsockname(fd int) (sa Sockaddr, err error) {
 	f, err := fdToNetFile(fd)
 	if err != nil {
 		return nil, err
 	}
 	if f.addr == nil {
 		return nil, ENOTCONN
 	}
 	return f.addr.copy(), nil
 }

 func Getpeername(fd int) (sa Sockaddr, err error) {
 	f, err := fdToNetFile(fd)
 	if err != nil {
 		return nil, err
 	}
 	if f.raddr == nil {
 		return nil, ENOTCONN
 	}
 	return f.raddr.copy(), nil
 }

 func Connect(fd int, sa Sockaddr) error {
 	f, err := fdToNetFile(fd)
 	if err != nil {
 		return err
 	}
 	return f.connect(sa)
 }

 func Recvfrom(fd int, p []byte, flags int) (n int, from Sockaddr, err error) {
 	f, err := fdToNetFile(fd)
 	if err != nil {
 		return 0, nil, err
 	}
 	return f.recvfrom(p, flags)
 }

 func Sendto(fd int, p []byte, flags int, to Sockaddr) error {
 	f, err := fdToNetFile(fd)
 	if err != nil {
 		return err
 	}
 	return f.sendto(p, flags, to)
 }

 func Recvmsg(fd int, p, oob []byte, flags int) (n, oobn, recvflags int, from Sockaddr, err error) {
 	f, err := fdToNetFile(fd)
 	if err != nil {
 		return
 	}
 	n, from, err = f.recvfrom(p, flags)
 	return
 }

 func Sendmsg(fd int, p, oob []byte, to Sockaddr, flags int) error {
 	_, err := SendmsgN(fd, p, oob, to, flags)
 	return err
 }

 func SendmsgN(fd int, p, oob []byte, to Sockaddr, flags int) (n int, err error) {
 	f, err := fdToNetFile(fd)
 	if err != nil {
 		return 0, err
 	}
 	switch f.sotype {
 	case SOCK_STREAM:
 		n, err = f.write(p)
 	case SOCK_DGRAM:
 		n = len(p)
 		err = f.sendto(p, flags, to)
 	}
 	if err != nil {
 		return 0, err
 	}
 	return n, nil
 }

 func GetsockoptInt(fd, level, opt int) (value int, err error) {
 	f, err := fdToNetFile(fd)
 	if err != nil {
 		return 0, err
 	}
 	switch {
 	case level == SOL_SOCKET && opt == SO_TYPE:
 		return f.sotype, nil
 	}
 	return 0, ENOTSUP
 }

 func SetsockoptInt(fd, level, opt int, value int) error {
 	return nil
 }

 func SetsockoptByte(fd, level, opt int, value byte) error {
 	_, err := fdToNetFile(fd)
 	if err != nil {
 		return err
 	}
 	return ENOTSUP
 }

 func SetsockoptLinger(fd, level, opt int, l *Linger) error {
 	return nil
 }

 func SetReadDeadline(fd int, t int64) error {
 	f, err := fdToNetFile(fd)
 	if err != nil {
 		return err
 	}
 	atomic.StoreInt64(&f.rddeadline, t)
 	return nil
 }

 func (f *netFile) readDeadline() int64 {
 	return atomic.LoadInt64(&f.rddeadline)
 }

 func SetWriteDeadline(fd int, t int64) error {
 	f, err := fdToNetFile(fd)
 	if err != nil {
 		return err
 	}
 	atomic.StoreInt64(&f.wrdeadline, t)
 	return nil
 }

 func (f *netFile) writeDeadline() int64 {
 	return atomic.LoadInt64(&f.wrdeadline)
 }

 func Shutdown(fd int, how int) error {
 	f, err := fdToNetFile(fd)
 	if err != nil {
 		return err
 	}
 	switch how {
 	case SHUT_RD:
 		f.rd.close()
 	case SHUT_WR:
 		f.wr.close()
 	case SHUT_RDWR:
 		f.rd.close()
 		f.wr.close()
 	}
 	return nil
 }

 func SetsockoptICMPv6Filter(fd, level, opt int, filter *ICMPv6Filter) error { panic("SetsockoptICMPv") }
 func SetsockoptIPMreq(fd, level, opt int, mreq *IPMreq) error               { panic("SetsockoptIPMreq") }
 func SetsockoptIPv6Mreq(fd, level, opt int, mreq *IPv6Mreq) error           { panic("SetsockoptIPv") }
 func SetsockoptInet4Addr(fd, level, opt int, value [4]byte) error           { panic("SetsockoptInet") }
 func SetsockoptString(fd, level, opt int, s string) error                   { panic("SetsockoptString") }
 func SetsockoptTimeval(fd, level, opt int, tv *Timeval) error               { panic("SetsockoptTimeval") }
 func Socketpair(domain, typ, proto int) (fd [2]int, err error)              { panic("Socketpair") }

 func SetNonblock(fd int, nonblocking bool) error { return nil }
	// Copyright 2013 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.

	// A simulated network for use within NaCl.
	// The simulation is not particularly tied to NaCl,
	// but other systems have real networks.

	package syscall

	import (
	"sync"
	"sync/atomic"
	)

	// Interface to timers implemented in package runtime.
	// Must be in sync with ../runtime/runtime.h:/^struct.Timer$
	// Really for use by package time, but we cannot import time here.

	type runtimeTimer struct {
	i int
	when int64
	period int64
	f func(interface{}, uintptr) // NOTE: must not be closure
	arg interface{}
	seq uintptr
	}

	func startTimer(*runtimeTimer)
	func stopTimer(*runtimeTimer) bool

	type timer struct {
	expired bool
	q *queue
	r runtimeTimer
	}

	func (t timer) start(q queue, deadline int64) {
	if deadline == 0 {
	return
	}
	t.q = q
	t.r.when = deadline
	t.r.f = timerExpired
	t.r.arg = t
	startTimer(&t.r)
	}

	func (t *timer) stop() {
	stopTimer(&t.r)
	}

	func timerExpired(i interface{}, seq uintptr) {
	t := i.(*timer)
	go func() {
	t.q.Lock()
	defer t.q.Unlock()
	t.expired = true
	t.q.canRead.Broadcast()
	t.q.canWrite.Broadcast()
	}()
	}

	// Network constants and data structures. These match the traditional values.

	const (
	AF_UNSPEC = iota
	AF_UNIX
	AF_INET
	AF_INET6
	)

	const (
	SHUT_RD = iota
	SHUT_WR
	SHUT_RDWR
	)

	const (
	SOCK_STREAM = 1 + iota
	SOCK_DGRAM
	SOCK_RAW
	SOCK_SEQPACKET
	)

	const (
	IPPROTO_IP = 0
	IPPROTO_IPV4 = 4
	IPPROTO_IPV6 = 0x29
	IPPROTO_TCP = 6
	IPPROTO_UDP = 0x11
	)

	// Misc constants expected by package net but not supported.
	const (
	_ = iota
	SOL_SOCKET
	SO_TYPE
	NET_RT_IFLIST
	IFNAMSIZ
	IFF_UP
	IFF_BROADCAST
	IFF_LOOPBACK
	IFF_POINTOPOINT
	IFF_MULTICAST
	IPV6_V6ONLY
	SOMAXCONN
	F_DUPFD_CLOEXEC
	SO_BROADCAST
	SO_REUSEADDR
	SO_REUSEPORT
	SO_RCVBUF
	SO_SNDBUF
	SO_KEEPALIVE
	SO_LINGER
	SO_ERROR
	IP_PORTRANGE
	IP_PORTRANGE_DEFAULT
	IP_PORTRANGE_LOW
	IP_PORTRANGE_HIGH
	IP_MULTICAST_IF
	IP_MULTICAST_LOOP
	IP_ADD_MEMBERSHIP
	IPV6_PORTRANGE
	IPV6_PORTRANGE_DEFAULT
	IPV6_PORTRANGE_LOW
	IPV6_PORTRANGE_HIGH
	IPV6_MULTICAST_IF
	IPV6_MULTICAST_LOOP
	IPV6_JOIN_GROUP
	TCP_NODELAY
	TCP_KEEPINTVL
	TCP_KEEPIDLE

	SYS_FCNTL = 500 // unsupported
	)

	var SocketDisableIPv6 bool

	// A Sockaddr is one of the SockaddrXxx structs.
	type Sockaddr interface {
	// copy returns a copy of the underlying data.
	copy() Sockaddr

	// key returns the value of the underlying data,
	// for comparison as a map key.
	key() interface{}
	}

	type SockaddrInet4 struct {
	Port int
	Addr [4]byte
	}

	func (sa *SockaddrInet4) copy() Sockaddr {
	sa1 := *sa
	return &sa1
	}

	func (sa SockaddrInet4) key() interface{} { return sa }

	type SockaddrInet6 struct {
	Port int
	ZoneId uint32
	Addr [16]byte
	}

	func (sa *SockaddrInet6) copy() Sockaddr {
	sa1 := *sa
	return &sa1
	}

	func (sa SockaddrInet6) key() interface{} { return sa }

	type SockaddrUnix struct {
	Name string
	}

	func (sa *SockaddrUnix) copy() Sockaddr {
	sa1 := *sa
	return &sa1
	}

	func (sa SockaddrUnix) key() interface{} { return sa }

	type SockaddrDatalink struct {
	Len uint8
	Family uint8
	Index uint16
	Type uint8
	Nlen uint8
	Alen uint8
	Slen uint8
	Data [12]int8
	}

	func (sa *SockaddrDatalink) copy() Sockaddr {
	sa1 := *sa
	return &sa1
	}

	func (sa SockaddrDatalink) key() interface{} { return sa }

	// RoutingMessage represents a routing message.
	type RoutingMessage interface {
	unimplemented()
	}

	type IPMreq struct {
	Multiaddr [4]byte /* in_addr */
	Interface [4]byte /* in_addr */
	}

	type IPv6Mreq struct {
	Multiaddr [16]byte /* in6_addr */
	Interface uint32
	}

	type Linger struct {
	Onoff int32
	Linger int32
	}

	type ICMPv6Filter struct {
	Filt [8]uint32
	}

	// A queue is the bookkeeping for a synchronized buffered queue.
	// We do not use channels because we need to be able to handle
	// writes after and during close, and because a chan byte would
	// require too many send and receive operations in real use.
	type queue struct {
	sync.Mutex
	canRead sync.Cond
	canWrite sync.Cond
	r int // total read index
	w int // total write index
	m int // index mask
	closed bool
	}

	func (q *queue) init(size int) {
	if size&(size-1) != 0 {
	panic("invalid queue size - must be power of two")
	}
	q.canRead.L = &q.Mutex
	q.canWrite.L = &q.Mutex
	q.m = size - 1
	}

	func past(deadline int64) bool {
	sec, nsec := now()
	return deadline > 0 && deadline < sec*1e9+int64(nsec)
	}

	func (q *queue) waitRead(n int, deadline int64) (int, error) {
	if past(deadline) {
	return 0, EAGAIN
	}
	var t timer
	t.start(q, deadline)
	for q.w-q.r == 0 && !q.closed && !t.expired {
	q.canRead.Wait()
	}
	t.stop()
	m := q.w - q.r
	if m == 0 && t.expired {
	return 0, EAGAIN
	}
	if m > n {
	m = n
	q.canRead.Signal() // wake up next reader too
	}
	q.canWrite.Signal()
	return m, nil
	}

	func (q *queue) waitWrite(n int, deadline int64) (int, error) {
	if past(deadline) {
	return 0, EAGAIN
	}
	var t timer
	t.start(q, deadline)
	for q.w-q.r > q.m && !q.closed && !t.expired {
	q.canWrite.Wait()
	}
	t.stop()
	m := q.m + 1 - (q.w - q.r)
	if m == 0 && t.expired {
	return 0, EAGAIN
	}
	if m == 0 {
	return 0, EAGAIN
	}
	if m > n {
	m = n
	q.canWrite.Signal() // wake up next writer too
	}
	q.canRead.Signal()
	return m, nil
	}

	func (q *queue) close() {
	q.Lock()
	defer q.Unlock()
	q.closed = true
	q.canRead.Broadcast()
	q.canWrite.Broadcast()
	}

	// A byteq is a byte queue.
	type byteq struct {
	queue
	data []byte
	}

	func newByteq() *byteq {
	q := &byteq{
	data: make([]byte, 4096),
	}
	q.init(len(q.data))
	return q
	}

	func (q *byteq) read(b []byte, deadline int64) (int, error) {
	q.Lock()
	defer q.Unlock()
	n, err := q.waitRead(len(b), deadline)
	if err != nil {
	return 0, err
	}
	b = b[:n]
	for len(b) > 0 {
	m := copy(b, q.data[q.r&q.m:])
	q.r += m
	b = b[m:]
	}
	return n, nil
	}

	func (q *byteq) write(b []byte, deadline int64) (n int, err error) {
	q.Lock()
	defer q.Unlock()
	for n < len(b) {
	nn, err := q.waitWrite(len(b[n:]), deadline)
	if err != nil {
	return n, err
	}
	bb := b[n : n+nn]
	n += nn
	for len(bb) > 0 {
	m := copy(q.data[q.w&q.m:], bb)
	q.w += m
	bb = bb[m:]
	}
	}
	return n, nil
	}

	// A msgq is a queue of messages.
	type msgq struct {
	queue
	data []interface{}
	}

	func newMsgq() *msgq {
	q := &msgq{
	data: make([]interface{}, 32),
	}
	q.init(len(q.data))
	return q
	}

	func (q *msgq) read(deadline int64) (interface{}, error) {
	q.Lock()
	defer q.Unlock()
	n, err := q.waitRead(1, deadline)
	if err != nil {
	return nil, err
	}
	if n == 0 {
	return nil, nil
	}
	m := q.data[q.r&q.m]
	q.r++
	return m, nil
	}

	func (q *msgq) write(m interface{}, deadline int64) error {
	q.Lock()
	defer q.Unlock()
	_, err := q.waitWrite(1, deadline)
	if err != nil {
	return err
	}
	q.data[q.w&q.m] = m
	q.w++
	return nil
	}

	// An addr is a sequence of bytes uniquely identifying a network address.
	// It is not human-readable.
	type addr string

	// A conn is one side of a stream-based network connection.
	// That is, a stream-based network connection is a pair of cross-connected conns.
	type conn struct {
	rd *byteq
	wr *byteq
	local addr
	remote addr
	}

	// A pktconn is one side of a packet-based network connection.
	// That is, a packet-based network connection is a pair of cross-connected pktconns.
	type pktconn struct {
	rd *msgq
	wr *msgq
	local addr
	remote addr
	}

	// A listener accepts incoming stream-based network connections.
	type listener struct {
	rd *msgq
	local addr
	}

	// A netFile is an open network file.
	type netFile struct {
	defaultFileImpl
	proto *netproto
	sotype int
	listener *msgq
	packet *msgq
	rd *byteq
	wr *byteq
	rddeadline int64
	wrdeadline int64
	addr Sockaddr
	raddr Sockaddr
	}

	// A netAddr is a network address in the global listener map.
	// All the fields must have defined == operations.
	type netAddr struct {
	proto *netproto
	sotype int
	addr interface{}
	}

	// net records the state of the network.
	// It maps a network address to the listener on that address.
	var net = struct {
	sync.Mutex
	listener map[netAddr]*netFile
	}{
	listener: make(map[netAddr]*netFile),
	}

	// TODO(rsc): Some day, do a better job with port allocation.
	// For playground programs, incrementing is fine.
	var nextport = 2

	// A netproto contains protocol-specific functionality
	// (one for AF_INET, one for AF_INET6 and so on).
	// It is a struct instead of an interface because the
	// implementation needs no state, and I expect to
	// add some data fields at some point.
	type netproto struct {
	bind func(*netFile, Sockaddr) error
	}

	var netprotoAF_INET = &netproto{
	bind: func(f *netFile, sa Sockaddr) error {
	if sa == nil {
	f.addr = &SockaddrInet4{
	Port: nextport,
	Addr: [4]byte{127, 0, 0, 1},
	}
	nextport++
	return nil
	}
	addr, ok := sa.(*SockaddrInet4)
	if !ok {
	return EINVAL
	}
	addr = addr.copy().(*SockaddrInet4)
	if addr.Port == 0 {
	addr.Port = nextport
	nextport++
	}
	f.addr = addr
	return nil
	},
	}

	var netprotos = map[int]*netproto{
	AF_INET: netprotoAF_INET,
	}

	// These functions implement the usual BSD socket operations.

	func (f *netFile) bind(sa Sockaddr) error {
	if f.addr != nil {
	return EISCONN
	}
	if err := f.proto.bind(f, sa); err != nil {
	return err
	}
	if f.sotype == SOCK_DGRAM {
	_, ok := net.listener[netAddr{f.proto, f.sotype, f.addr.key()}]
	if ok {
	f.addr = nil
	return EADDRINUSE
	}
	net.listener[netAddr{f.proto, f.sotype, f.addr.key()}] = f
	f.packet = newMsgq()
	}
	return nil
	}

	func (f *netFile) listen(backlog int) error {
	net.Lock()
	defer net.Unlock()
	if f.listener != nil {
	return EINVAL
	}
	old, ok := net.listener[netAddr{f.proto, f.sotype, f.addr.key()}]
	if ok && !old.listenerClosed() {
	return EADDRINUSE
	}
	net.listener[netAddr{f.proto, f.sotype, f.addr.key()}] = f
	f.listener = newMsgq()
	return nil
	}

	func (f *netFile) accept() (fd int, sa Sockaddr, err error) {
	msg, err := f.listener.read(f.readDeadline())
	if err != nil {
	return -1, nil, err
	}
	newf, ok := msg.(*netFile)
	if !ok {
	// must be eof
	return -1, nil, EAGAIN
	}
	return newFD(newf), newf.raddr.copy(), nil
	}

	func (f *netFile) connect(sa Sockaddr) error {
	if past(f.writeDeadline()) {
	return EAGAIN
	}
	if f.addr == nil {
	if err := f.bind(nil); err != nil {
	return err
	}
	}
	net.Lock()
	if sa == nil {
	net.Unlock()
	return EINVAL
	}
	sa = sa.copy()
	if f.raddr != nil {
	net.Unlock()
	return EISCONN
	}
	if f.sotype == SOCK_DGRAM {
	net.Unlock()
	f.raddr = sa
	return nil
	}
	if f.listener != nil {
	net.Unlock()
	return EISCONN
	}
	l, ok := net.listener[netAddr{f.proto, f.sotype, sa.key()}]
	if !ok \|\| l.listenerClosed() {
	net.Unlock()
	return ECONNREFUSED
	}
	f.raddr = sa
	f.rd = newByteq()
	f.wr = newByteq()
	newf := &netFile{
	proto: f.proto,
	sotype: f.sotype,
	addr: f.raddr,
	raddr: f.addr,
	rd: f.wr,
	wr: f.rd,
	}
	net.Unlock()
	l.listener.write(newf, f.writeDeadline())
	return nil
	}

	func (f *netFile) read(b []byte) (int, error) {
	if f.rd == nil {
	if f.raddr != nil {
	n, _, err := f.recvfrom(b, 0)
	return n, err
	}
	return 0, ENOTCONN
	}
	return f.rd.read(b, f.readDeadline())
	}

	func (f *netFile) write(b []byte) (int, error) {
	if f.wr == nil {
	if f.raddr != nil {
	err := f.sendto(b, 0, f.raddr)
	var n int
	if err == nil {
	n = len(b)
	}
	return n, err
	}
	return 0, ENOTCONN
	}
	return f.wr.write(b, f.writeDeadline())
	}

	type pktmsg struct {
	buf []byte
	addr Sockaddr
	}

	func (f *netFile) recvfrom(p []byte, flags int) (n int, from Sockaddr, err error) {
	if f.sotype != SOCK_DGRAM {
	return 0, nil, EINVAL
	}
	if f.packet == nil {
	return 0, nil, ENOTCONN
	}
	msg1, err := f.packet.read(f.readDeadline())
	if err != nil {
	return 0, nil, err
	}
	msg, ok := msg1.(*pktmsg)
	if !ok {
	return 0, nil, EAGAIN
	}
	return copy(p, msg.buf), msg.addr, nil
	}

	func (f *netFile) sendto(p []byte, flags int, to Sockaddr) error {
	if f.sotype != SOCK_DGRAM {
	return EINVAL
	}
	if f.packet == nil {
	if err := f.bind(nil); err != nil {
	return err
	}
	}
	net.Lock()
	if to == nil {
	net.Unlock()
	return EINVAL
	}
	to = to.copy()
	l, ok := net.listener[netAddr{f.proto, f.sotype, to.key()}]
	if !ok \|\| l.packet == nil {
	net.Unlock()
	return ECONNREFUSED
	}
	net.Unlock()
	msg := &pktmsg{
	buf: make([]byte, len(p)),
	addr: f.addr,
	}
	copy(msg.buf, p)
	l.packet.write(msg, f.writeDeadline())
	return nil
	}

	func (f *netFile) listenerClosed() bool {
	f.listener.Lock()
	defer f.listener.Unlock()
	return f.listener.closed
	}

	func (f *netFile) close() error {
	if f.listener != nil {
	f.listener.close()
	}
	if f.packet != nil {
	f.packet.close()
	}
	if f.rd != nil {
	f.rd.close()
	}
	if f.wr != nil {
	f.wr.close()
	}
	return nil
	}

	func fdToNetFile(fd int) (*netFile, error) {
	f, err := fdToFile(fd)
	if err != nil {
	return nil, err
	}
	impl := f.impl
	netf, ok := impl.(*netFile)
	if !ok {
	return nil, EINVAL
	}
	return netf, nil
	}

	func Socket(proto, sotype, unused int) (fd int, err error) {
	p := netprotos[proto]
	if p == nil {
	return -1, EPROTONOSUPPORT
	}
	if sotype != SOCK_STREAM && sotype != SOCK_DGRAM {
	return -1, ESOCKTNOSUPPORT
	}
	f := &netFile{
	proto: p,
	sotype: sotype,
	}
	return newFD(f), nil
	}

	func Bind(fd int, sa Sockaddr) error {
	f, err := fdToNetFile(fd)
	if err != nil {
	return err
	}
	return f.bind(sa)
	}

	func StopIO(fd int) error {
	f, err := fdToNetFile(fd)
	if err != nil {
	return err
	}
	f.close()
	return nil
	}

	func Listen(fd int, backlog int) error {
	f, err := fdToNetFile(fd)
	if err != nil {
	return err
	}
	return f.listen(backlog)
	}

	func Accept(fd int) (newfd int, sa Sockaddr, err error) {
	f, err := fdToNetFile(fd)
	if err != nil {
	return 0, nil, err
	}
	return f.accept()
	}

	func Getsockname(fd int) (sa Sockaddr, err error) {
	f, err := fdToNetFile(fd)
	if err != nil {
	return nil, err
	}
	if f.addr == nil {
	return nil, ENOTCONN
	}
	return f.addr.copy(), nil
	}

	func Getpeername(fd int) (sa Sockaddr, err error) {
	f, err := fdToNetFile(fd)
	if err != nil {
	return nil, err
	}
	if f.raddr == nil {
	return nil, ENOTCONN
	}
	return f.raddr.copy(), nil
	}

	func Connect(fd int, sa Sockaddr) error {
	f, err := fdToNetFile(fd)
	if err != nil {
	return err
	}
	return f.connect(sa)
	}

	func Recvfrom(fd int, p []byte, flags int) (n int, from Sockaddr, err error) {
	f, err := fdToNetFile(fd)
	if err != nil {
	return 0, nil, err
	}
	return f.recvfrom(p, flags)
	}

	func Sendto(fd int, p []byte, flags int, to Sockaddr) error {
	f, err := fdToNetFile(fd)
	if err != nil {
	return err
	}
	return f.sendto(p, flags, to)
	}

	func Recvmsg(fd int, p, oob []byte, flags int) (n, oobn, recvflags int, from Sockaddr, err error) {
	f, err := fdToNetFile(fd)
	if err != nil {
	return
	}
	n, from, err = f.recvfrom(p, flags)
	return
	}

	func Sendmsg(fd int, p, oob []byte, to Sockaddr, flags int) error {
	_, err := SendmsgN(fd, p, oob, to, flags)
	return err
	}

	func SendmsgN(fd int, p, oob []byte, to Sockaddr, flags int) (n int, err error) {
	f, err := fdToNetFile(fd)
	if err != nil {
	return 0, err
	}
	switch f.sotype {
	case SOCK_STREAM:
	n, err = f.write(p)
	case SOCK_DGRAM:
	n = len(p)
	err = f.sendto(p, flags, to)
	}
	if err != nil {
	return 0, err
	}
	return n, nil
	}

	func GetsockoptInt(fd, level, opt int) (value int, err error) {
	f, err := fdToNetFile(fd)
	if err != nil {
	return 0, err
	}
	switch {
	case level == SOL_SOCKET && opt == SO_TYPE:
	return f.sotype, nil
	}
	return 0, ENOTSUP
	}

	func SetsockoptInt(fd, level, opt int, value int) error {
	return nil
	}

	func SetsockoptByte(fd, level, opt int, value byte) error {
	_, err := fdToNetFile(fd)
	if err != nil {
	return err
	}
	return ENOTSUP
	}

	func SetsockoptLinger(fd, level, opt int, l *Linger) error {
	return nil
	}

	func SetReadDeadline(fd int, t int64) error {
	f, err := fdToNetFile(fd)
	if err != nil {
	return err
	}
	atomic.StoreInt64(&f.rddeadline, t)
	return nil
	}

	func (f *netFile) readDeadline() int64 {
	return atomic.LoadInt64(&f.rddeadline)
	}

	func SetWriteDeadline(fd int, t int64) error {
	f, err := fdToNetFile(fd)
	if err != nil {
	return err
	}
	atomic.StoreInt64(&f.wrdeadline, t)
	return nil
	}

	func (f *netFile) writeDeadline() int64 {
	return atomic.LoadInt64(&f.wrdeadline)
	}

	func Shutdown(fd int, how int) error {
	f, err := fdToNetFile(fd)
	if err != nil {
	return err
	}
	switch how {
	case SHUT_RD:
	f.rd.close()
	case SHUT_WR:
	f.wr.close()
	case SHUT_RDWR:
	f.rd.close()
	f.wr.close()
	}
	return nil
	}

	func SetsockoptICMPv6Filter(fd, level, opt int, filter *ICMPv6Filter) error { panic("SetsockoptICMPv") }
	func SetsockoptIPMreq(fd, level, opt int, mreq *IPMreq) error { panic("SetsockoptIPMreq") }
	func SetsockoptIPv6Mreq(fd, level, opt int, mreq *IPv6Mreq) error { panic("SetsockoptIPv") }
	func SetsockoptInet4Addr(fd, level, opt int, value [4]byte) error { panic("SetsockoptInet") }
	func SetsockoptString(fd, level, opt int, s string) error { panic("SetsockoptString") }
	func SetsockoptTimeval(fd, level, opt int, tv *Timeval) error { panic("SetsockoptTimeval") }
	func Socketpair(domain, typ, proto int) (fd [2]int, err error) { panic("Socketpair") }

	func SetNonblock(fd int, nonblocking bool) error { return nil }