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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.
//go:build unix || (js && wasm) || windows
package net
import (
"context"
"io"
"os"
"syscall"
)
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: zoneCache.name(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) sockaddr(family int) (syscall.Sockaddr, error) {
if a == nil {
return nil, nil
}
return ipToSockaddr(family, a.IP, a.Port, a.Zone)
}
func (a *TCPAddr) toLocal(net string) sockaddr {
return &TCPAddr{loopbackIP(net), a.Port, a.Zone}
}
func (c *TCPConn) readFrom(r io.Reader) (int64, error) {
if n, err, handled := splice(c.fd, r); handled {
return n, err
}
if n, err, handled := sendFile(c.fd, r); handled {
return n, err
}
return genericReadFrom(c, r)
}
func (sd *sysDialer) dialTCP(ctx context.Context, laddr, raddr *TCPAddr) (*TCPConn, error) {
if h := sd.testHookDialTCP; h != nil {
return h(ctx, sd.network, laddr, raddr)
}
if h := testHookDialTCP; h != nil {
return h(ctx, sd.network, laddr, raddr)
}
return sd.doDialTCP(ctx, laddr, raddr)
}
func (sd *sysDialer) doDialTCP(ctx context.Context, laddr, raddr *TCPAddr) (*TCPConn, error) {
ctrlCtxFn := sd.Dialer.ControlContext
if ctrlCtxFn == nil && sd.Dialer.Control != nil {
ctrlCtxFn = func(cxt context.Context, network, address string, c syscall.RawConn) error {
return sd.Dialer.Control(network, address, c)
}
}
fd, err := internetSocket(ctx, sd.network, laddr, raddr, syscall.SOCK_STREAM, 0, "dial", ctrlCtxFn)
// 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:
// https://golang.org/issue/2690
// https://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(ctx, sd.network, laddr, raddr, syscall.SOCK_STREAM, 0, "dial", ctrlCtxFn)
}
if err != nil {
return nil, err
}
return newTCPConn(fd, sd.Dialer.KeepAlive, testHookSetKeepAlive), 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 {
if op, ok := err.(*OpError); ok {
err = op.Err
}
if sys, ok := err.(*os.SyscallError); ok {
err = sys.Err
}
return err == syscall.EADDRNOTAVAIL
}
func (ln *TCPListener) ok() bool { return ln != nil && ln.fd != nil }
func (ln *TCPListener) accept() (*TCPConn, error) {
fd, err := ln.fd.accept()
if err != nil {
return nil, err
}
return newTCPConn(fd, ln.lc.KeepAlive, nil), nil
}
func (ln *TCPListener) close() error {
return ln.fd.Close()
}
func (ln *TCPListener) file() (*os.File, error) {
f, err := ln.fd.dup()
if err != nil {
return nil, err
}
return f, nil
}
func (sl *sysListener) listenTCP(ctx context.Context, laddr *TCPAddr) (*TCPListener, error) {
var ctrlCtxFn func(cxt context.Context, network, address string, c syscall.RawConn) error
if sl.ListenConfig.Control != nil {
ctrlCtxFn = func(cxt context.Context, network, address string, c syscall.RawConn) error {
return sl.ListenConfig.Control(network, address, c)
}
}
fd, err := internetSocket(ctx, sl.network, laddr, nil, syscall.SOCK_STREAM, 0, "listen", ctrlCtxFn)
if err != nil {
return nil, err
}
return &TCPListener{fd: fd, lc: sl.ListenConfig}, nil
}
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