Source file src/pkg/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 darwin freebsd linux netbsd openbsd windows 6 7 // TCP sockets 8 9 package net 10 11 import ( 12 "io" 13 "os" 14 "syscall" 15 "time" 16 ) 17 18 // BUG(rsc): On OpenBSD, listening on the "tcp" network does not listen for 19 // both IPv4 and IPv6 connections. This is due to the fact that IPv4 traffic 20 // will not be routed to an IPv6 socket - two separate sockets are required 21 // if both AFs are to be supported. See inet6(4) on OpenBSD for details. 22 23 func sockaddrToTCP(sa syscall.Sockaddr) Addr { 24 switch sa := sa.(type) { 25 case *syscall.SockaddrInet4: 26 return &TCPAddr{sa.Addr[0:], sa.Port} 27 case *syscall.SockaddrInet6: 28 return &TCPAddr{sa.Addr[0:], sa.Port} 29 default: 30 if sa != nil { 31 // Diagnose when we will turn a non-nil sockaddr into a nil. 32 panic("unexpected type in sockaddrToTCP") 33 } 34 } 35 return nil 36 } 37 38 func (a *TCPAddr) family() int { 39 if a == nil || len(a.IP) <= IPv4len { 40 return syscall.AF_INET 41 } 42 if a.IP.To4() != nil { 43 return syscall.AF_INET 44 } 45 return syscall.AF_INET6 46 } 47 48 func (a *TCPAddr) isWildcard() bool { 49 if a == nil || a.IP == nil { 50 return true 51 } 52 return a.IP.IsUnspecified() 53 } 54 55 func (a *TCPAddr) sockaddr(family int) (syscall.Sockaddr, error) { 56 return ipToSockaddr(family, a.IP, a.Port) 57 } 58 59 func (a *TCPAddr) toAddr() sockaddr { 60 if a == nil { // nil *TCPAddr 61 return nil // nil interface 62 } 63 return a 64 } 65 66 // TCPConn is an implementation of the Conn interface 67 // for TCP network connections. 68 type TCPConn struct { 69 fd *netFD 70 } 71 72 func newTCPConn(fd *netFD) *TCPConn { 73 c := &TCPConn{fd} 74 c.SetNoDelay(true) 75 return c 76 } 77 78 func (c *TCPConn) ok() bool { return c != nil && c.fd != nil } 79 80 // Implementation of the Conn interface - see Conn for documentation. 81 82 // Read implements the Conn Read method. 83 func (c *TCPConn) Read(b []byte) (n int, err error) { 84 if !c.ok() { 85 return 0, syscall.EINVAL 86 } 87 return c.fd.Read(b) 88 } 89 90 // ReadFrom implements the io.ReaderFrom ReadFrom method. 91 func (c *TCPConn) ReadFrom(r io.Reader) (int64, error) { 92 if n, err, handled := sendFile(c.fd, r); handled { 93 return n, err 94 } 95 return genericReadFrom(c, r) 96 } 97 98 // Write implements the Conn Write method. 99 func (c *TCPConn) Write(b []byte) (n int, err error) { 100 if !c.ok() { 101 return 0, syscall.EINVAL 102 } 103 return c.fd.Write(b) 104 } 105 106 // Close closes the TCP connection. 107 func (c *TCPConn) Close() error { 108 if !c.ok() { 109 return syscall.EINVAL 110 } 111 return c.fd.Close() 112 } 113 114 // CloseRead shuts down the reading side of the TCP connection. 115 // Most callers should just use Close. 116 func (c *TCPConn) CloseRead() error { 117 if !c.ok() { 118 return syscall.EINVAL 119 } 120 return c.fd.CloseRead() 121 } 122 123 // CloseWrite shuts down the writing side of the TCP connection. 124 // Most callers should just use Close. 125 func (c *TCPConn) CloseWrite() error { 126 if !c.ok() { 127 return syscall.EINVAL 128 } 129 return c.fd.CloseWrite() 130 } 131 132 // LocalAddr returns the local network address, a *TCPAddr. 133 func (c *TCPConn) LocalAddr() Addr { 134 if !c.ok() { 135 return nil 136 } 137 return c.fd.laddr 138 } 139 140 // RemoteAddr returns the remote network address, a *TCPAddr. 141 func (c *TCPConn) RemoteAddr() Addr { 142 if !c.ok() { 143 return nil 144 } 145 return c.fd.raddr 146 } 147 148 // SetDeadline implements the Conn SetDeadline method. 149 func (c *TCPConn) SetDeadline(t time.Time) error { 150 if !c.ok() { 151 return syscall.EINVAL 152 } 153 return setDeadline(c.fd, t) 154 } 155 156 // SetReadDeadline implements the Conn SetReadDeadline method. 157 func (c *TCPConn) SetReadDeadline(t time.Time) error { 158 if !c.ok() { 159 return syscall.EINVAL 160 } 161 return setReadDeadline(c.fd, t) 162 } 163 164 // SetWriteDeadline implements the Conn SetWriteDeadline method. 165 func (c *TCPConn) SetWriteDeadline(t time.Time) error { 166 if !c.ok() { 167 return syscall.EINVAL 168 } 169 return setWriteDeadline(c.fd, t) 170 } 171 172 // SetReadBuffer sets the size of the operating system's 173 // receive buffer associated with the connection. 174 func (c *TCPConn) SetReadBuffer(bytes int) error { 175 if !c.ok() { 176 return syscall.EINVAL 177 } 178 return setReadBuffer(c.fd, bytes) 179 } 180 181 // SetWriteBuffer sets the size of the operating system's 182 // transmit buffer associated with the connection. 183 func (c *TCPConn) SetWriteBuffer(bytes int) error { 184 if !c.ok() { 185 return syscall.EINVAL 186 } 187 return setWriteBuffer(c.fd, bytes) 188 } 189 190 // SetLinger sets the behavior of Close() on a connection 191 // which still has data waiting to be sent or to be acknowledged. 192 // 193 // If sec < 0 (the default), Close returns immediately and 194 // the operating system finishes sending the data in the background. 195 // 196 // If sec == 0, Close returns immediately and the operating system 197 // discards any unsent or unacknowledged data. 198 // 199 // If sec > 0, Close blocks for at most sec seconds waiting for 200 // data to be sent and acknowledged. 201 func (c *TCPConn) SetLinger(sec int) error { 202 if !c.ok() { 203 return syscall.EINVAL 204 } 205 return setLinger(c.fd, sec) 206 } 207 208 // SetKeepAlive sets whether the operating system should send 209 // keepalive messages on the connection. 210 func (c *TCPConn) SetKeepAlive(keepalive bool) error { 211 if !c.ok() { 212 return syscall.EINVAL 213 } 214 return setKeepAlive(c.fd, keepalive) 215 } 216 217 // SetNoDelay controls whether the operating system should delay 218 // packet transmission in hopes of sending fewer packets 219 // (Nagle's algorithm). The default is true (no delay), meaning 220 // that data is sent as soon as possible after a Write. 221 func (c *TCPConn) SetNoDelay(noDelay bool) error { 222 if !c.ok() { 223 return syscall.EINVAL 224 } 225 return setNoDelay(c.fd, noDelay) 226 } 227 228 // File returns a copy of the underlying os.File, set to blocking mode. 229 // It is the caller's responsibility to close f when finished. 230 // Closing c does not affect f, and closing f does not affect c. 231 func (c *TCPConn) File() (f *os.File, err error) { return c.fd.dup() } 232 233 // DialTCP connects to the remote address raddr on the network net, 234 // which must be "tcp", "tcp4", or "tcp6". If laddr is not nil, it is used 235 // as the local address for the connection. 236 func DialTCP(net string, laddr, raddr *TCPAddr) (*TCPConn, error) { 237 if raddr == nil { 238 return nil, &OpError{"dial", net, nil, errMissingAddress} 239 } 240 241 fd, err := internetSocket(net, laddr.toAddr(), raddr.toAddr(), syscall.SOCK_STREAM, 0, "dial", sockaddrToTCP) 242 243 // TCP has a rarely used mechanism called a 'simultaneous connection' in 244 // which Dial("tcp", addr1, addr2) run on the machine at addr1 can 245 // connect to a simultaneous Dial("tcp", addr2, addr1) run on the machine 246 // at addr2, without either machine executing Listen. If laddr == nil, 247 // it means we want the kernel to pick an appropriate originating local 248 // address. Some Linux kernels cycle blindly through a fixed range of 249 // local ports, regardless of destination port. If a kernel happens to 250 // pick local port 50001 as the source for a Dial("tcp", "", "localhost:50001"), 251 // then the Dial will succeed, having simultaneously connected to itself. 252 // This can only happen when we are letting the kernel pick a port (laddr == nil) 253 // and when there is no listener for the destination address. 254 // It's hard to argue this is anything other than a kernel bug. If we 255 // see this happen, rather than expose the buggy effect to users, we 256 // close the fd and try again. If it happens twice more, we relent and 257 // use the result. See also: 258 // http://golang.org/issue/2690 259 // http://stackoverflow.com/questions/4949858/ 260 for i := 0; i < 2 && err == nil && laddr == nil && selfConnect(fd); i++ { 261 fd.Close() 262 fd, err = internetSocket(net, laddr.toAddr(), raddr.toAddr(), syscall.SOCK_STREAM, 0, "dial", sockaddrToTCP) 263 } 264 265 if err != nil { 266 return nil, err 267 } 268 return newTCPConn(fd), nil 269 } 270 271 func selfConnect(fd *netFD) bool { 272 // The socket constructor can return an fd with raddr nil under certain 273 // unknown conditions. The errors in the calls there to Getpeername 274 // are discarded, but we can't catch the problem there because those 275 // calls are sometimes legally erroneous with a "socket not connected". 276 // Since this code (selfConnect) is already trying to work around 277 // a problem, we make sure if this happens we recognize trouble and 278 // ask the DialTCP routine to try again. 279 // TODO: try to understand what's really going on. 280 if fd.laddr == nil || fd.raddr == nil { 281 return true 282 } 283 l := fd.laddr.(*TCPAddr) 284 r := fd.raddr.(*TCPAddr) 285 return l.Port == r.Port && l.IP.Equal(r.IP) 286 } 287 288 // TCPListener is a TCP network listener. 289 // Clients should typically use variables of type Listener 290 // instead of assuming TCP. 291 type TCPListener struct { 292 fd *netFD 293 } 294 295 // ListenTCP announces on the TCP address laddr and returns a TCP listener. 296 // Net must be "tcp", "tcp4", or "tcp6". 297 // If laddr has a port of 0, it means to listen on some available port. 298 // The caller can use l.Addr() to retrieve the chosen address. 299 func ListenTCP(net string, laddr *TCPAddr) (*TCPListener, error) { 300 fd, err := internetSocket(net, laddr.toAddr(), nil, syscall.SOCK_STREAM, 0, "listen", sockaddrToTCP) 301 if err != nil { 302 return nil, err 303 } 304 err = syscall.Listen(fd.sysfd, listenerBacklog) 305 if err != nil { 306 closesocket(fd.sysfd) 307 return nil, &OpError{"listen", net, laddr, err} 308 } 309 l := new(TCPListener) 310 l.fd = fd 311 return l, nil 312 } 313 314 // AcceptTCP accepts the next incoming call and returns the new connection 315 // and the remote address. 316 func (l *TCPListener) AcceptTCP() (c *TCPConn, err error) { 317 if l == nil || l.fd == nil || l.fd.sysfd < 0 { 318 return nil, syscall.EINVAL 319 } 320 fd, err := l.fd.accept(sockaddrToTCP) 321 if err != nil { 322 return nil, err 323 } 324 return newTCPConn(fd), nil 325 } 326 327 // Accept implements the Accept method in the Listener interface; 328 // it waits for the next call and returns a generic Conn. 329 func (l *TCPListener) Accept() (c Conn, err error) { 330 c1, err := l.AcceptTCP() 331 if err != nil { 332 return nil, err 333 } 334 return c1, nil 335 } 336 337 // Close stops listening on the TCP address. 338 // Already Accepted connections are not closed. 339 func (l *TCPListener) Close() error { 340 if l == nil || l.fd == nil { 341 return syscall.EINVAL 342 } 343 return l.fd.Close() 344 } 345 346 // Addr returns the listener's network address, a *TCPAddr. 347 func (l *TCPListener) Addr() Addr { return l.fd.laddr } 348 349 // SetDeadline sets the deadline associated with the listener. 350 // A zero time value disables the deadline. 351 func (l *TCPListener) SetDeadline(t time.Time) error { 352 if l == nil || l.fd == nil { 353 return syscall.EINVAL 354 } 355 return setDeadline(l.fd, t) 356 } 357 358 // File returns a copy of the underlying os.File, set to blocking mode. 359 // It is the caller's responsibility to close f when finished. 360 // Closing l does not affect f, and closing f does not affect l. 361 func (l *TCPListener) File() (f *os.File, err error) { return l.fd.dup() }