tcpsock.go

Documentation: net

     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 and Windows, 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 string // 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() string { 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 string) (*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  // SyscallConn returns a raw network connection.
   117  // This implements the [syscall.Conn] interface.
   118  func (c *TCPConn) SyscallConn() (syscall.RawConn, error) {
   119  	if !c.ok() {
   120  		return nil, syscall.EINVAL
   121  	}
   122  	return newRawConn(c.fd), nil
   123  }
   124  
   125  // ReadFrom implements the [io.ReaderFrom] ReadFrom method.
   126  func (c *TCPConn) ReadFrom(r io.Reader) (int64, error) {
   127  	if !c.ok() {
   128  		return 0, syscall.EINVAL
   129  	}
   130  	n, err := c.readFrom(r)
   131  	if err != nil && err != io.EOF {
   132  		err = &OpError{Op: "readfrom", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
   133  	}
   134  	return n, err
   135  }
   136  
   137  // WriteTo implements the io.WriterTo WriteTo method.
   138  func (c *TCPConn) WriteTo(w io.Writer) (int64, error) {
   139  	if !c.ok() {
   140  		return 0, syscall.EINVAL
   141  	}
   142  	n, err := c.writeTo(w)
   143  	if err != nil && err != io.EOF {
   144  		err = &OpError{Op: "writeto", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
   145  	}
   146  	return n, err
   147  }
   148  
   149  // CloseRead shuts down the reading side of the TCP connection.
   150  // Most callers should just use Close.
   151  func (c *TCPConn) CloseRead() error {
   152  	if !c.ok() {
   153  		return syscall.EINVAL
   154  	}
   155  	if err := c.fd.closeRead(); err != nil {
   156  		return &OpError{Op: "close", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
   157  	}
   158  	return nil
   159  }
   160  
   161  // CloseWrite shuts down the writing side of the TCP connection.
   162  // Most callers should just use Close.
   163  func (c *TCPConn) CloseWrite() error {
   164  	if !c.ok() {
   165  		return syscall.EINVAL
   166  	}
   167  	if err := c.fd.closeWrite(); err != nil {
   168  		return &OpError{Op: "close", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
   169  	}
   170  	return nil
   171  }
   172  
   173  // SetLinger sets the behavior of Close on a connection which still
   174  // has data waiting to be sent or to be acknowledged.
   175  //
   176  // If sec < 0 (the default), the operating system finishes sending the
   177  // data in the background.
   178  //
   179  // If sec == 0, the operating system discards any unsent or
   180  // unacknowledged data.
   181  //
   182  // If sec > 0, the data is sent in the background as with sec < 0.
   183  // On some operating systems including Linux, this may cause Close to block
   184  // until all data has been sent or discarded.
   185  // On some operating systems after sec seconds have elapsed any remaining
   186  // unsent data may be discarded.
   187  func (c *TCPConn) SetLinger(sec int) error {
   188  	if !c.ok() {
   189  		return syscall.EINVAL
   190  	}
   191  	if err := setLinger(c.fd, sec); err != nil {
   192  		return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
   193  	}
   194  	return nil
   195  }
   196  
   197  // SetKeepAlive sets whether the operating system should send
   198  // keep-alive messages on the connection.
   199  func (c *TCPConn) SetKeepAlive(keepalive bool) error {
   200  	if !c.ok() {
   201  		return syscall.EINVAL
   202  	}
   203  	if err := setKeepAlive(c.fd, keepalive); err != nil {
   204  		return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
   205  	}
   206  	return nil
   207  }
   208  
   209  // SetKeepAlivePeriod sets period between keep-alives.
   210  func (c *TCPConn) SetKeepAlivePeriod(d time.Duration) error {
   211  	if !c.ok() {
   212  		return syscall.EINVAL
   213  	}
   214  	if err := setKeepAlivePeriod(c.fd, d); err != nil {
   215  		return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
   216  	}
   217  	return nil
   218  }
   219  
   220  // SetNoDelay controls whether the operating system should delay
   221  // packet transmission in hopes of sending fewer packets (Nagle's
   222  // algorithm).  The default is true (no delay), meaning that data is
   223  // sent as soon as possible after a Write.
   224  func (c *TCPConn) SetNoDelay(noDelay bool) error {
   225  	if !c.ok() {
   226  		return syscall.EINVAL
   227  	}
   228  	if err := setNoDelay(c.fd, noDelay); err != nil {
   229  		return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
   230  	}
   231  	return nil
   232  }
   233  
   234  // MultipathTCP reports whether the ongoing connection is using MPTCP.
   235  //
   236  // If Multipath TCP is not supported by the host, by the other peer or
   237  // intentionally / accidentally filtered out by a device in between, a
   238  // fallback to TCP will be done. This method does its best to check if
   239  // MPTCP is still being used or not.
   240  //
   241  // On Linux, more conditions are verified on kernels >= v5.16, improving
   242  // the results.
   243  func (c *TCPConn) MultipathTCP() (bool, error) {
   244  	if !c.ok() {
   245  		return false, syscall.EINVAL
   246  	}
   247  	return isUsingMultipathTCP(c.fd), nil
   248  }
   249  
   250  func newTCPConn(fd *netFD, keepAlive time.Duration, keepAliveHook func(time.Duration)) *TCPConn {
   251  	setNoDelay(fd, true)
   252  	if keepAlive == 0 {
   253  		keepAlive = defaultTCPKeepAlive
   254  	}
   255  	if keepAlive > 0 {
   256  		setKeepAlive(fd, true)
   257  		setKeepAlivePeriod(fd, keepAlive)
   258  		if keepAliveHook != nil {
   259  			keepAliveHook(keepAlive)
   260  		}
   261  	}
   262  	return &TCPConn{conn{fd}}
   263  }
   264  
   265  // DialTCP acts like [Dial] for TCP networks.
   266  //
   267  // The network must be a TCP network name; see func Dial for details.
   268  //
   269  // If laddr is nil, a local address is automatically chosen.
   270  // If the IP field of raddr is nil or an unspecified IP address, the
   271  // local system is assumed.
   272  func DialTCP(network string, laddr, raddr *TCPAddr) (*TCPConn, error) {
   273  	switch network {
   274  	case "tcp", "tcp4", "tcp6":
   275  	default:
   276  		return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: raddr.opAddr(), Err: UnknownNetworkError(network)}
   277  	}
   278  	if raddr == nil {
   279  		return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: nil, Err: errMissingAddress}
   280  	}
   281  	sd := &sysDialer{network: network, address: raddr.String()}
   282  	c, err := sd.dialTCP(context.Background(), laddr, raddr)
   283  	if err != nil {
   284  		return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: raddr.opAddr(), Err: err}
   285  	}
   286  	return c, nil
   287  }
   288  
   289  // TCPListener is a TCP network listener. Clients should typically
   290  // use variables of type [Listener] instead of assuming TCP.
   291  type TCPListener struct {
   292  	fd *netFD
   293  	lc ListenConfig
   294  }
   295  
   296  // SyscallConn returns a raw network connection.
   297  // This implements the [syscall.Conn] interface.
   298  //
   299  // The returned RawConn only supports calling Control. Read and
   300  // Write return an error.
   301  func (l *TCPListener) SyscallConn() (syscall.RawConn, error) {
   302  	if !l.ok() {
   303  		return nil, syscall.EINVAL
   304  	}
   305  	return newRawListener(l.fd), nil
   306  }
   307  
   308  // AcceptTCP accepts the next incoming call and returns the new
   309  // connection.
   310  func (l *TCPListener) AcceptTCP() (*TCPConn, error) {
   311  	if !l.ok() {
   312  		return nil, syscall.EINVAL
   313  	}
   314  	c, err := l.accept()
   315  	if err != nil {
   316  		return nil, &OpError{Op: "accept", Net: l.fd.net, Source: nil, Addr: l.fd.laddr, Err: err}
   317  	}
   318  	return c, nil
   319  }
   320  
   321  // Accept implements the Accept method in the [Listener] interface; it
   322  // waits for the next call and returns a generic [Conn].
   323  func (l *TCPListener) Accept() (Conn, error) {
   324  	if !l.ok() {
   325  		return nil, syscall.EINVAL
   326  	}
   327  	c, err := l.accept()
   328  	if err != nil {
   329  		return nil, &OpError{Op: "accept", Net: l.fd.net, Source: nil, Addr: l.fd.laddr, Err: err}
   330  	}
   331  	return c, nil
   332  }
   333  
   334  // Close stops listening on the TCP address.
   335  // Already Accepted connections are not closed.
   336  func (l *TCPListener) Close() error {
   337  	if !l.ok() {
   338  		return syscall.EINVAL
   339  	}
   340  	if err := l.close(); err != nil {
   341  		return &OpError{Op: "close", Net: l.fd.net, Source: nil, Addr: l.fd.laddr, Err: err}
   342  	}
   343  	return nil
   344  }
   345  
   346  // Addr returns the listener's network address, a [*TCPAddr].
   347  // The Addr returned is shared by all invocations of Addr, so
   348  // do not modify it.
   349  func (l *TCPListener) Addr() Addr { return l.fd.laddr }
   350  
   351  // SetDeadline sets the deadline associated with the listener.
   352  // A zero time value disables the deadline.
   353  func (l *TCPListener) SetDeadline(t time.Time) error {
   354  	if !l.ok() {
   355  		return syscall.EINVAL
   356  	}
   357  	return l.fd.SetDeadline(t)
   358  }
   359  
   360  // File returns a copy of the underlying [os.File].
   361  // It is the caller's responsibility to close f when finished.
   362  // Closing l does not affect f, and closing f does not affect l.
   363  //
   364  // The returned os.File's file descriptor is different from the
   365  // connection's. Attempting to change properties of the original
   366  // using this duplicate may or may not have the desired effect.
   367  func (l *TCPListener) File() (f *os.File, err error) {
   368  	if !l.ok() {
   369  		return nil, syscall.EINVAL
   370  	}
   371  	f, err = l.file()
   372  	if err != nil {
   373  		return nil, &OpError{Op: "file", Net: l.fd.net, Source: nil, Addr: l.fd.laddr, Err: err}
   374  	}
   375  	return
   376  }
   377  
   378  // ListenTCP acts like [Listen] for TCP networks.
   379  //
   380  // The network must be a TCP network name; see func Dial for details.
   381  //
   382  // If the IP field of laddr is nil or an unspecified IP address,
   383  // ListenTCP listens on all available unicast and anycast IP addresses
   384  // of the local system.
   385  // If the Port field of laddr is 0, a port number is automatically
   386  // chosen.
   387  func ListenTCP(network string, laddr *TCPAddr) (*TCPListener, error) {
   388  	switch network {
   389  	case "tcp", "tcp4", "tcp6":
   390  	default:
   391  		return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: laddr.opAddr(), Err: UnknownNetworkError(network)}
   392  	}
   393  	if laddr == nil {
   394  		laddr = &TCPAddr{}
   395  	}
   396  	sl := &sysListener{network: network, address: laddr.String()}
   397  	ln, err := sl.listenTCP(context.Background(), laddr)
   398  	if err != nil {
   399  		return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: laddr.opAddr(), Err: err}
   400  	}
   401  	return ln, nil
   402  }
   403  
   404  // roundDurationUp rounds d to the next multiple of to.
   405  func roundDurationUp(d time.Duration, to time.Duration) time.Duration {
   406  	return (d + to - 1) / to
   407  }
   408
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