mirror of
https://github.com/autc04/Retro68.git
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165 lines
5.1 KiB
Go
165 lines
5.1 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// +build aix darwin dragonfly freebsd hurd js,wasm linux nacl netbsd openbsd solaris windows
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package net
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import (
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"context"
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"io"
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"os"
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"syscall"
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)
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func sockaddrToTCP(sa syscall.Sockaddr) Addr {
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switch sa := sa.(type) {
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case *syscall.SockaddrInet4:
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return &TCPAddr{IP: sa.Addr[0:], Port: sa.Port}
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case *syscall.SockaddrInet6:
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return &TCPAddr{IP: sa.Addr[0:], Port: sa.Port, Zone: zoneCache.name(int(sa.ZoneId))}
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}
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return nil
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}
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func (a *TCPAddr) family() int {
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if a == nil || len(a.IP) <= IPv4len {
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return syscall.AF_INET
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}
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if a.IP.To4() != nil {
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return syscall.AF_INET
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}
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return syscall.AF_INET6
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}
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func (a *TCPAddr) sockaddr(family int) (syscall.Sockaddr, error) {
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if a == nil {
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return nil, nil
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}
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return ipToSockaddr(family, a.IP, a.Port, a.Zone)
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}
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func (a *TCPAddr) toLocal(net string) sockaddr {
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return &TCPAddr{loopbackIP(net), a.Port, a.Zone}
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}
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func (c *TCPConn) readFrom(r io.Reader) (int64, error) {
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if n, err, handled := splice(c.fd, r); handled {
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return n, err
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}
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if n, err, handled := sendFile(c.fd, r); handled {
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return n, err
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}
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return genericReadFrom(c, r)
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}
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func (sd *sysDialer) dialTCP(ctx context.Context, laddr, raddr *TCPAddr) (*TCPConn, error) {
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if testHookDialTCP != nil {
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return testHookDialTCP(ctx, sd.network, laddr, raddr)
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}
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return sd.doDialTCP(ctx, laddr, raddr)
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}
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func (sd *sysDialer) doDialTCP(ctx context.Context, laddr, raddr *TCPAddr) (*TCPConn, error) {
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fd, err := internetSocket(ctx, sd.network, laddr, raddr, syscall.SOCK_STREAM, 0, "dial", sd.Dialer.Control)
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// TCP has a rarely used mechanism called a 'simultaneous connection' in
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// which Dial("tcp", addr1, addr2) run on the machine at addr1 can
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// connect to a simultaneous Dial("tcp", addr2, addr1) run on the machine
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// at addr2, without either machine executing Listen. If laddr == nil,
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// it means we want the kernel to pick an appropriate originating local
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// address. Some Linux kernels cycle blindly through a fixed range of
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// local ports, regardless of destination port. If a kernel happens to
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// pick local port 50001 as the source for a Dial("tcp", "", "localhost:50001"),
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// then the Dial will succeed, having simultaneously connected to itself.
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// This can only happen when we are letting the kernel pick a port (laddr == nil)
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// and when there is no listener for the destination address.
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// It's hard to argue this is anything other than a kernel bug. If we
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// see this happen, rather than expose the buggy effect to users, we
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// close the fd and try again. If it happens twice more, we relent and
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// use the result. See also:
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// https://golang.org/issue/2690
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// https://stackoverflow.com/questions/4949858/
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//
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// The opposite can also happen: if we ask the kernel to pick an appropriate
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// originating local address, sometimes it picks one that is already in use.
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// So if the error is EADDRNOTAVAIL, we have to try again too, just for
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// a different reason.
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//
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// The kernel socket code is no doubt enjoying watching us squirm.
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for i := 0; i < 2 && (laddr == nil || laddr.Port == 0) && (selfConnect(fd, err) || spuriousENOTAVAIL(err)); i++ {
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if err == nil {
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fd.Close()
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}
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fd, err = internetSocket(ctx, sd.network, laddr, raddr, syscall.SOCK_STREAM, 0, "dial", sd.Dialer.Control)
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}
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if err != nil {
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return nil, err
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}
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return newTCPConn(fd), nil
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}
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func selfConnect(fd *netFD, err error) bool {
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// If the connect failed, we clearly didn't connect to ourselves.
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if err != nil {
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return false
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}
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// The socket constructor can return an fd with raddr nil under certain
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// unknown conditions. The errors in the calls there to Getpeername
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// are discarded, but we can't catch the problem there because those
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// calls are sometimes legally erroneous with a "socket not connected".
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// Since this code (selfConnect) is already trying to work around
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// a problem, we make sure if this happens we recognize trouble and
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// ask the DialTCP routine to try again.
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// TODO: try to understand what's really going on.
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if fd.laddr == nil || fd.raddr == nil {
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return true
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}
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l := fd.laddr.(*TCPAddr)
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r := fd.raddr.(*TCPAddr)
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return l.Port == r.Port && l.IP.Equal(r.IP)
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}
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func spuriousENOTAVAIL(err error) bool {
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if op, ok := err.(*OpError); ok {
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err = op.Err
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}
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if sys, ok := err.(*os.SyscallError); ok {
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err = sys.Err
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}
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return err == syscall.EADDRNOTAVAIL
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}
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func (ln *TCPListener) ok() bool { return ln != nil && ln.fd != nil }
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func (ln *TCPListener) accept() (*TCPConn, error) {
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fd, err := ln.fd.accept()
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if err != nil {
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return nil, err
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}
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return newTCPConn(fd), nil
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}
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func (ln *TCPListener) close() error {
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return ln.fd.Close()
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}
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func (ln *TCPListener) file() (*os.File, error) {
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f, err := ln.fd.dup()
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if err != nil {
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return nil, err
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}
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return f, nil
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}
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func (sl *sysListener) listenTCP(ctx context.Context, laddr *TCPAddr) (*TCPListener, error) {
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fd, err := internetSocket(ctx, sl.network, laddr, nil, syscall.SOCK_STREAM, 0, "listen", sl.ListenConfig.Control)
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if err != nil {
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return nil, err
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}
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return &TCPListener{fd}, nil
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}
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