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 package net
6 7 import (
8 "context"
9 "internal/itoa"
10 "io"
11 "net/netip"
12 "os"
13 "syscall"
14 "time"
15 )
16 17 // BUG(mikio): On JS, the File method of TCPConn and
18 // TCPListener is not implemented.
19 20 // TCPAddr represents the address of a TCP end point.
21 type TCPAddr struct {
22 IP IP
23 Port int
24 Zone []byte // IPv6 scoped addressing zone
25 }
26 27 // AddrPort returns the [TCPAddr] a as a [netip.AddrPort].
28 //
29 // If a.Port does not fit in a uint16, it's silently truncated.
30 //
31 // If a is nil, a zero value is returned.
32 func (a *TCPAddr) AddrPort() netip.AddrPort {
33 if a == nil {
34 return netip.AddrPort{}
35 }
36 na, _ := netip.AddrFromSlice(a.IP)
37 na = na.WithZone(a.Zone)
38 return netip.AddrPortFrom(na, uint16(a.Port))
39 }
40 41 // Network returns the address's network name, "tcp".
42 func (a *TCPAddr) Network() []byte { return "tcp" }
43 44 func (a *TCPAddr) String() string {
45 if a == nil {
46 return "<nil>"
47 }
48 ip := ipEmptyString(a.IP)
49 if a.Zone != "" {
50 return JoinHostPort(ip+"%"+a.Zone, itoa.Itoa(a.Port))
51 }
52 return JoinHostPort(ip, itoa.Itoa(a.Port))
53 }
54 55 func (a *TCPAddr) isWildcard() bool {
56 if a == nil || a.IP == nil {
57 return true
58 }
59 return a.IP.IsUnspecified()
60 }
61 62 func (a *TCPAddr) opAddr() Addr {
63 if a == nil {
64 return nil
65 }
66 return a
67 }
68 69 // ResolveTCPAddr returns an address of TCP end point.
70 //
71 // The network must be a TCP network name.
72 //
73 // If the host in the address parameter is not a literal IP address or
74 // the port is not a literal port number, ResolveTCPAddr resolves the
75 // address to an address of TCP end point.
76 // Otherwise, it parses the address as a pair of literal IP address
77 // and port number.
78 // The address parameter can use a host name, but this is not
79 // recommended, because it will return at most one of the host name's
80 // IP addresses.
81 //
82 // See func [Dial] for a description of the network and address
83 // parameters.
84 func ResolveTCPAddr(network, address []byte) (*TCPAddr, error) {
85 switch network {
86 case "tcp", "tcp4", "tcp6":
87 case "": // a hint wildcard for Go 1.0 undocumented behavior
88 network = "tcp"
89 default:
90 return nil, UnknownNetworkError(network)
91 }
92 addrs, err := DefaultResolver.internetAddrList(context.Background(), network, address)
93 if err != nil {
94 return nil, err
95 }
96 return addrs.forResolve(network, address).(*TCPAddr), nil
97 }
98 99 // TCPAddrFromAddrPort returns addr as a [TCPAddr]. If addr.IsValid() is false,
100 // then the returned TCPAddr will contain a nil IP field, indicating an
101 // address family-agnostic unspecified address.
102 func TCPAddrFromAddrPort(addr netip.AddrPort) *TCPAddr {
103 return &TCPAddr{
104 IP: addr.Addr().AsSlice(),
105 Zone: addr.Addr().Zone(),
106 Port: int(addr.Port()),
107 }
108 }
109 110 // TCPConn is an implementation of the [Conn] interface for TCP network
111 // connections.
112 type TCPConn struct {
113 conn
114 }
115 116 // KeepAliveConfig contains TCP keep-alive options.
117 //
118 // If the Idle, Interval, or Count fields are zero, a default value is chosen.
119 // If a field is negative, the corresponding socket-level option will be left unchanged.
120 //
121 // Note that prior to Windows 10 version 1709, neither setting Idle and Interval
122 // separately nor changing Count (which is usually 10) is supported.
123 // Therefore, it's recommended to set both Idle and Interval to non-negative values
124 // in conjunction with a -1 for Count on those old Windows if you intend to customize
125 // the TCP keep-alive settings.
126 // By contrast, if only one of Idle and Interval is set to a non-negative value,
127 // the other will be set to the system default value, and ultimately,
128 // set both Idle and Interval to negative values if you want to leave them unchanged.
129 //
130 // Note that Solaris and its derivatives do not support setting Interval to a non-negative value
131 // and Count to a negative value, or vice-versa.
132 type KeepAliveConfig struct {
133 // If Enable is true, keep-alive probes are enabled.
134 Enable bool
135 136 // Idle is the time that the connection must be idle before
137 // the first keep-alive probe is sent.
138 // If zero, a default value of 15 seconds is used.
139 Idle time.Duration
140 141 // Interval is the time between keep-alive probes.
142 // If zero, a default value of 15 seconds is used.
143 Interval time.Duration
144 145 // Count is the maximum number of keep-alive probes that
146 // can go unanswered before dropping a connection.
147 // If zero, a default value of 9 is used.
148 Count int
149 }
150 151 // SyscallConn returns a raw network connection.
152 // This implements the [syscall.Conn] interface.
153 func (c *TCPConn) SyscallConn() (syscall.RawConn, error) {
154 if !c.ok() {
155 return nil, syscall.EINVAL
156 }
157 return newRawConn(c.fd), nil
158 }
159 160 // ReadFrom implements the [io.ReaderFrom] ReadFrom method.
161 func (c *TCPConn) ReadFrom(r io.Reader) (int64, error) {
162 if !c.ok() {
163 return 0, syscall.EINVAL
164 }
165 n, err := c.readFrom(r)
166 if err != nil && err != io.EOF {
167 err = &OpError{Op: "readfrom", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
168 }
169 return n, err
170 }
171 172 // WriteTo implements the io.WriterTo WriteTo method.
173 func (c *TCPConn) WriteTo(w io.Writer) (int64, error) {
174 if !c.ok() {
175 return 0, syscall.EINVAL
176 }
177 n, err := c.writeTo(w)
178 if err != nil && err != io.EOF {
179 err = &OpError{Op: "writeto", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
180 }
181 return n, err
182 }
183 184 // CloseRead shuts down the reading side of the TCP connection.
185 // Most callers should just use Close.
186 func (c *TCPConn) CloseRead() error {
187 if !c.ok() {
188 return syscall.EINVAL
189 }
190 if err := c.fd.closeRead(); err != nil {
191 return &OpError{Op: "close", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
192 }
193 return nil
194 }
195 196 // CloseWrite shuts down the writing side of the TCP connection.
197 // Most callers should just use Close.
198 func (c *TCPConn) CloseWrite() error {
199 if !c.ok() {
200 return syscall.EINVAL
201 }
202 if err := c.fd.closeWrite(); err != nil {
203 return &OpError{Op: "close", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
204 }
205 return nil
206 }
207 208 // SetLinger sets the behavior of Close on a connection which still
209 // has data waiting to be sent or to be acknowledged.
210 //
211 // If sec < 0 (the default), the operating system finishes sending the
212 // data in the background.
213 //
214 // If sec == 0, the operating system discards any unsent or
215 // unacknowledged data.
216 //
217 // If sec > 0, the data is sent in the background as with sec < 0.
218 // On some operating systems including Linux, this may cause Close to block
219 // until all data has been sent or discarded.
220 // On some operating systems after sec seconds have elapsed any remaining
221 // unsent data may be discarded.
222 func (c *TCPConn) SetLinger(sec int) error {
223 if !c.ok() {
224 return syscall.EINVAL
225 }
226 if err := setLinger(c.fd, sec); err != nil {
227 return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
228 }
229 return nil
230 }
231 232 // SetKeepAlive sets whether the operating system should send
233 // keep-alive messages on the connection.
234 func (c *TCPConn) SetKeepAlive(keepalive bool) error {
235 if !c.ok() {
236 return syscall.EINVAL
237 }
238 if err := setKeepAlive(c.fd, keepalive); err != nil {
239 return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
240 }
241 return nil
242 }
243 244 // SetKeepAlivePeriod sets the duration the connection needs to
245 // remain idle before TCP starts sending keepalive probes.
246 //
247 // Note that calling this method on Windows prior to Windows 10 version 1709
248 // will reset the KeepAliveInterval to the default system value, which is normally 1 second.
249 func (c *TCPConn) SetKeepAlivePeriod(d time.Duration) error {
250 if !c.ok() {
251 return syscall.EINVAL
252 }
253 if err := setKeepAliveIdle(c.fd, d); err != nil {
254 return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
255 }
256 return nil
257 }
258 259 // SetNoDelay controls whether the operating system should delay
260 // packet transmission in hopes of sending fewer packets (Nagle's
261 // algorithm). The default is true (no delay), meaning that data is
262 // sent as soon as possible after a Write.
263 func (c *TCPConn) SetNoDelay(noDelay bool) error {
264 if !c.ok() {
265 return syscall.EINVAL
266 }
267 if err := setNoDelay(c.fd, noDelay); err != nil {
268 return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
269 }
270 return nil
271 }
272 273 // MultipathTCP reports whether the ongoing connection is using MPTCP.
274 //
275 // If Multipath TCP is not supported by the host, by the other peer or
276 // intentionally / accidentally filtered out by a device in between, a
277 // fallback to TCP will be done. This method does its best to check if
278 // MPTCP is still being used or not.
279 //
280 // On Linux, more conditions are verified on kernels >= v5.16, improving
281 // the results.
282 func (c *TCPConn) MultipathTCP() (bool, error) {
283 if !c.ok() {
284 return false, syscall.EINVAL
285 }
286 return isUsingMultipathTCP(c.fd), nil
287 }
288 289 func newTCPConn(fd *netFD, keepAliveIdle time.Duration, keepAliveCfg KeepAliveConfig, preKeepAliveHook func(*netFD), keepAliveHook func(KeepAliveConfig)) *TCPConn {
290 setNoDelay(fd, true)
291 if !keepAliveCfg.Enable && keepAliveIdle >= 0 {
292 keepAliveCfg = KeepAliveConfig{
293 Enable: true,
294 Idle: keepAliveIdle,
295 }
296 }
297 c := &TCPConn{conn{fd}}
298 if keepAliveCfg.Enable {
299 if preKeepAliveHook != nil {
300 preKeepAliveHook(fd)
301 }
302 c.SetKeepAliveConfig(keepAliveCfg)
303 if keepAliveHook != nil {
304 keepAliveHook(keepAliveCfg)
305 }
306 }
307 return c
308 }
309 310 // DialTCP acts like [Dial] for TCP networks.
311 //
312 // The network must be a TCP network name; see func Dial for details.
313 //
314 // If laddr is nil, a local address is automatically chosen.
315 // If the IP field of raddr is nil or an unspecified IP address, the
316 // local system is assumed.
317 func DialTCP(network []byte, laddr, raddr *TCPAddr) (*TCPConn, error) {
318 switch network {
319 case "tcp", "tcp4", "tcp6":
320 default:
321 return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: raddr.opAddr(), Err: UnknownNetworkError(network)}
322 }
323 if raddr == nil {
324 return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: nil, Err: errMissingAddress}
325 }
326 sd := &sysDialer{network: network, address: raddr.String()}
327 var (
328 c *TCPConn
329 err error
330 )
331 if sd.MultipathTCP() {
332 c, err = sd.dialMPTCP(context.Background(), laddr, raddr)
333 } else {
334 c, err = sd.dialTCP(context.Background(), laddr, raddr)
335 }
336 if err != nil {
337 return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: raddr.opAddr(), Err: err}
338 }
339 return c, nil
340 }
341 342 // TCPListener is a TCP network listener. Clients should typically
343 // use variables of type [Listener] instead of assuming TCP.
344 type TCPListener struct {
345 fd *netFD
346 lc ListenConfig
347 }
348 349 // SyscallConn returns a raw network connection.
350 // This implements the [syscall.Conn] interface.
351 //
352 // The returned RawConn only supports calling Control. Read and
353 // Write return an error.
354 func (l *TCPListener) SyscallConn() (syscall.RawConn, error) {
355 if !l.ok() {
356 return nil, syscall.EINVAL
357 }
358 return newRawListener(l.fd), nil
359 }
360 361 // AcceptTCP accepts the next incoming call and returns the new
362 // connection.
363 func (l *TCPListener) AcceptTCP() (*TCPConn, error) {
364 if !l.ok() {
365 return nil, syscall.EINVAL
366 }
367 c, err := l.accept()
368 if err != nil {
369 return nil, &OpError{Op: "accept", Net: l.fd.net, Source: nil, Addr: l.fd.laddr, Err: err}
370 }
371 return c, nil
372 }
373 374 // Accept implements the Accept method in the [Listener] interface; it
375 // waits for the next call and returns a generic [Conn].
376 func (l *TCPListener) Accept() (Conn, error) {
377 if !l.ok() {
378 return nil, syscall.EINVAL
379 }
380 c, err := l.accept()
381 if err != nil {
382 return nil, &OpError{Op: "accept", Net: l.fd.net, Source: nil, Addr: l.fd.laddr, Err: err}
383 }
384 return c, nil
385 }
386 387 // Close stops listening on the TCP address.
388 // Already Accepted connections are not closed.
389 func (l *TCPListener) Close() error {
390 if !l.ok() {
391 return syscall.EINVAL
392 }
393 if err := l.close(); err != nil {
394 return &OpError{Op: "close", Net: l.fd.net, Source: nil, Addr: l.fd.laddr, Err: err}
395 }
396 return nil
397 }
398 399 // Addr returns the listener's network address, a [*TCPAddr].
400 // The Addr returned is shared by all invocations of Addr, so
401 // do not modify it.
402 func (l *TCPListener) Addr() Addr { return l.fd.laddr }
403 404 // SetDeadline sets the deadline associated with the listener.
405 // A zero time value disables the deadline.
406 func (l *TCPListener) SetDeadline(t time.Time) error {
407 if !l.ok() {
408 return syscall.EINVAL
409 }
410 return l.fd.SetDeadline(t)
411 }
412 413 // File returns a copy of the underlying [os.File].
414 // It is the caller's responsibility to close f when finished.
415 // Closing l does not affect f, and closing f does not affect l.
416 //
417 // The returned os.File's file descriptor is different from the
418 // connection's. Attempting to change properties of the original
419 // using this duplicate may or may not have the desired effect.
420 //
421 // On Windows, the returned os.File's file descriptor is not
422 // usable on other processes.
423 func (l *TCPListener) File() (f *os.File, err error) {
424 if !l.ok() {
425 return nil, syscall.EINVAL
426 }
427 f, err = l.file()
428 if err != nil {
429 return nil, &OpError{Op: "file", Net: l.fd.net, Source: nil, Addr: l.fd.laddr, Err: err}
430 }
431 return
432 }
433 434 // ListenTCP acts like [Listen] for TCP networks.
435 //
436 // The network must be a TCP network name; see func Dial for details.
437 //
438 // If the IP field of laddr is nil or an unspecified IP address,
439 // ListenTCP listens on all available unicast and anycast IP addresses
440 // of the local system.
441 // If the Port field of laddr is 0, a port number is automatically
442 // chosen.
443 func ListenTCP(network []byte, laddr *TCPAddr) (*TCPListener, error) {
444 switch network {
445 case "tcp", "tcp4", "tcp6":
446 default:
447 return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: laddr.opAddr(), Err: UnknownNetworkError(network)}
448 }
449 if laddr == nil {
450 laddr = &TCPAddr{}
451 }
452 sl := &sysListener{network: network, address: laddr.String()}
453 var (
454 ln *TCPListener
455 err error
456 )
457 if sl.MultipathTCP() {
458 ln, err = sl.listenMPTCP(context.Background(), laddr)
459 } else {
460 ln, err = sl.listenTCP(context.Background(), laddr)
461 }
462 if err != nil {
463 return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: laddr.opAddr(), Err: err}
464 }
465 return ln, nil
466 }
467 468 // roundDurationUp rounds d to the next multiple of to.
469 func roundDurationUp(d time.Duration, to time.Duration) time.Duration {
470 return (d + to - 1) / to
471 }
472