libgo/go/net/tcpsock_posix.go

   1 // Copyright 2009 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // +build aix darwin dragonfly freebsd hurd js,wasm linux nacl netbsd openbsd solaris windows
   6
   7 package net
   8
   9 import (
  10         "context"
  11         "io"
  12         "os"
  13         "syscall"
  14 )
  15
  16 func sockaddrToTCP(sa syscall.Sockaddr) Addr {
  17         switch sa := sa.(type) {
  18         case *syscall.SockaddrInet4:
  19                 return &TCPAddr{IP: sa.Addr[0:], Port: sa.Port}
  20         case *syscall.SockaddrInet6:
  21                 return &TCPAddr{IP: sa.Addr[0:], Port: sa.Port, Zone: zoneCache.name(int(sa.ZoneId))}
  22         }
  23         return nil
  24 }
  25
  26 func (a *TCPAddr) family() int {
  27         if a == nil || len(a.IP) <= IPv4len {
  28                 return syscall.AF_INET
  29         }
  30         if a.IP.To4() != nil {
  31                 return syscall.AF_INET
  32         }
  33         return syscall.AF_INET6
  34 }
  35
  36 func (a *TCPAddr) sockaddr(family int) (syscall.Sockaddr, error) {
  37         if a == nil {
  38                 return nil, nil
  39         }
  40         return ipToSockaddr(family, a.IP, a.Port, a.Zone)
  41 }
  42
  43 func (a *TCPAddr) toLocal(net string) sockaddr {
  44         return &TCPAddr{loopbackIP(net), a.Port, a.Zone}
  45 }
  46
  47 func (c *TCPConn) readFrom(r io.Reader) (int64, error) {
  48         if n, err, handled := splice(c.fd, r); handled {
  49                 return n, err
  50         }
  51         if n, err, handled := sendFile(c.fd, r); handled {
  52                 return n, err
  53         }
  54         return genericReadFrom(c, r)
  55 }
  56
  57 func (sd *sysDialer) dialTCP(ctx context.Context, laddr, raddr *TCPAddr) (*TCPConn, error) {
  58         if testHookDialTCP != nil {
  59                 return testHookDialTCP(ctx, sd.network, laddr, raddr)
  60         }
  61         return sd.doDialTCP(ctx, laddr, raddr)
  62 }
  63
  64 func (sd *sysDialer) doDialTCP(ctx context.Context, laddr, raddr *TCPAddr) (*TCPConn, error) {
  65         fd, err := internetSocket(ctx, sd.network, laddr, raddr, syscall.SOCK_STREAM, 0, "dial", sd.Dialer.Control)
  66
  67         // TCP has a rarely used mechanism called a 'simultaneous connection' in
  68         // which Dial("tcp", addr1, addr2) run on the machine at addr1 can
  69         // connect to a simultaneous Dial("tcp", addr2, addr1) run on the machine
  70         // at addr2, without either machine executing Listen. If laddr == nil,
  71         // it means we want the kernel to pick an appropriate originating local
  72         // address. Some Linux kernels cycle blindly through a fixed range of
  73         // local ports, regardless of destination port. If a kernel happens to
  74         // pick local port 50001 as the source for a Dial("tcp", "", "localhost:50001"),
  75         // then the Dial will succeed, having simultaneously connected to itself.
  76         // This can only happen when we are letting the kernel pick a port (laddr == nil)
  77         // and when there is no listener for the destination address.
  78         // It's hard to argue this is anything other than a kernel bug. If we
  79         // see this happen, rather than expose the buggy effect to users, we
  80         // close the fd and try again. If it happens twice more, we relent and
  81         // use the result. See also:
  82         //      https://golang.org/issue/2690
  83         //      https://stackoverflow.com/questions/4949858/
  84         //
  85         // The opposite can also happen: if we ask the kernel to pick an appropriate
  86         // originating local address, sometimes it picks one that is already in use.
  87         // So if the error is EADDRNOTAVAIL, we have to try again too, just for
  88         // a different reason.
  89         //
  90         // The kernel socket code is no doubt enjoying watching us squirm.
  91         for i := 0; i < 2 && (laddr == nil || laddr.Port == 0) && (selfConnect(fd, err) || spuriousENOTAVAIL(err)); i++ {
  92                 if err == nil {
  93                         fd.Close()
  94                 }
  95                 fd, err = internetSocket(ctx, sd.network, laddr, raddr, syscall.SOCK_STREAM, 0, "dial", sd.Dialer.Control)
  96         }
  97
  98         if err != nil {
  99                 return nil, err
 100         }
 101         return newTCPConn(fd), nil
 102 }
 103
 104 func selfConnect(fd *netFD, err error) bool {
 105         // If the connect failed, we clearly didn't connect to ourselves.
 106         if err != nil {
 107                 return false
 108         }
 109
 110         // The socket constructor can return an fd with raddr nil under certain
 111         // unknown conditions. The errors in the calls there to Getpeername
 112         // are discarded, but we can't catch the problem there because those
 113         // calls are sometimes legally erroneous with a "socket not connected".
 114         // Since this code (selfConnect) is already trying to work around
 115         // a problem, we make sure if this happens we recognize trouble and
 116         // ask the DialTCP routine to try again.
 117         // TODO: try to understand what's really going on.
 118         if fd.laddr == nil || fd.raddr == nil {
 119                 return true
 120         }
 121         l := fd.laddr.(*TCPAddr)
 122         r := fd.raddr.(*TCPAddr)
 123         return l.Port == r.Port && l.IP.Equal(r.IP)
 124 }
 125
 126 func spuriousENOTAVAIL(err error) bool {
 127         if op, ok := err.(*OpError); ok {
 128                 err = op.Err
 129         }
 130         if sys, ok := err.(*os.SyscallError); ok {
 131                 err = sys.Err
 132         }
 133         return err == syscall.EADDRNOTAVAIL
 134 }
 135
 136 func (ln *TCPListener) ok() bool { return ln != nil && ln.fd != nil }
 137
 138 func (ln *TCPListener) accept() (*TCPConn, error) {
 139         fd, err := ln.fd.accept()
 140         if err != nil {
 141                 return nil, err
 142         }
 143         tc := newTCPConn(fd)
 144         if ln.lc.KeepAlive >= 0 {
 145                 setKeepAlive(fd, true)
 146                 ka := ln.lc.KeepAlive
 147                 if ln.lc.KeepAlive == 0 {
 148                         ka = defaultTCPKeepAlive
 149                 }
 150                 setKeepAlivePeriod(fd, ka)
 151         }
 152         return tc, nil
 153 }
 154
 155 func (ln *TCPListener) close() error {
 156         return ln.fd.Close()
 157 }
 158
 159 func (ln *TCPListener) file() (*os.File, error) {
 160         f, err := ln.fd.dup()
 161         if err != nil {
 162                 return nil, err
 163         }
 164         return f, nil
 165 }
 166
 167 func (sl *sysListener) listenTCP(ctx context.Context, laddr *TCPAddr) (*TCPListener, error) {
 168         fd, err := internetSocket(ctx, sl.network, laddr, nil, syscall.SOCK_STREAM, 0, "listen", sl.ListenConfig.Control)
 169         if err != nil {
 170                 return nil, err
 171         }
 172         return &TCPListener{fd: fd, lc: sl.ListenConfig}, nil
 173 }