// Copyright 2009 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. package net import ( "context" "internal/itoa" "io" "net/netip" "os" "syscall" "time" ) // BUG(mikio): On JS and Windows, the File method of TCPConn and // TCPListener is not implemented. // TCPAddr represents the address of a TCP end point. type TCPAddr struct { IP IP Port int Zone string // IPv6 scoped addressing zone } // AddrPort returns the [TCPAddr] a as a [netip.AddrPort]. // // If a.Port does not fit in a uint16, it's silently truncated. // // If a is nil, a zero value is returned. func (a *TCPAddr) AddrPort() netip.AddrPort { if a == nil { return netip.AddrPort{} } na, _ := netip.AddrFromSlice(a.IP) na = na.WithZone(a.Zone) return netip.AddrPortFrom(na, uint16(a.Port)) } // Network returns the address's network name, "tcp". func (a *TCPAddr) Network() string { return "tcp" } func (a *TCPAddr) String() string { if a == nil { return "" } ip := ipEmptyString(a.IP) if a.Zone != "" { return JoinHostPort(ip+"%"+a.Zone, itoa.Itoa(a.Port)) } return JoinHostPort(ip, itoa.Itoa(a.Port)) } func (a *TCPAddr) isWildcard() bool { if a == nil || a.IP == nil { return true } return a.IP.IsUnspecified() } func (a *TCPAddr) opAddr() Addr { if a == nil { return nil } return a } // ResolveTCPAddr returns an address of TCP end point. // // The network must be a TCP network name. // // If the host in the address parameter is not a literal IP address or // the port is not a literal port number, ResolveTCPAddr resolves the // address to an address of TCP end point. // Otherwise, it parses the address as a pair of literal IP address // and port number. // The address parameter can use a host name, but this is not // recommended, because it will return at most one of the host name's // IP addresses. // // See func [Dial] for a description of the network and address // parameters. func ResolveTCPAddr(network, address string) (*TCPAddr, error) { switch network { case "tcp", "tcp4", "tcp6": case "": // a hint wildcard for Go 1.0 undocumented behavior network = "tcp" default: return nil, UnknownNetworkError(network) } addrs, err := DefaultResolver.internetAddrList(context.Background(), network, address) if err != nil { return nil, err } return addrs.forResolve(network, address).(*TCPAddr), nil } // TCPAddrFromAddrPort returns addr as a [TCPAddr]. If addr.IsValid() is false, // then the returned TCPAddr will contain a nil IP field, indicating an // address family-agnostic unspecified address. func TCPAddrFromAddrPort(addr netip.AddrPort) *TCPAddr { return &TCPAddr{ IP: addr.Addr().AsSlice(), Zone: addr.Addr().Zone(), Port: int(addr.Port()), } } // TCPConn is an implementation of the [Conn] interface for TCP network // connections. type TCPConn struct { conn } // SyscallConn returns a raw network connection. // This implements the [syscall.Conn] interface. func (c *TCPConn) SyscallConn() (syscall.RawConn, error) { if !c.ok() { return nil, syscall.EINVAL } return newRawConn(c.fd), nil } // ReadFrom implements the [io.ReaderFrom] ReadFrom method. func (c *TCPConn) ReadFrom(r io.Reader) (int64, error) { if !c.ok() { return 0, syscall.EINVAL } n, err := c.readFrom(r) if err != nil && err != io.EOF { err = &OpError{Op: "readfrom", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err} } return n, err } // WriteTo implements the io.WriterTo WriteTo method. func (c *TCPConn) WriteTo(w io.Writer) (int64, error) { if !c.ok() { return 0, syscall.EINVAL } n, err := c.writeTo(w) if err != nil && err != io.EOF { err = &OpError{Op: "writeto", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err} } return n, err } // CloseRead shuts down the reading side of the TCP connection. // Most callers should just use Close. func (c *TCPConn) CloseRead() error { if !c.ok() { return syscall.EINVAL } if err := c.fd.closeRead(); err != nil { return &OpError{Op: "close", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err} } return nil } // CloseWrite shuts down the writing side of the TCP connection. // Most callers should just use Close. func (c *TCPConn) CloseWrite() error { if !c.ok() { return syscall.EINVAL } if err := c.fd.closeWrite(); err != nil { return &OpError{Op: "close", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err} } return nil } // SetLinger sets the behavior of Close on a connection which still // has data waiting to be sent or to be acknowledged. // // If sec < 0 (the default), the operating system finishes sending the // data in the background. // // If sec == 0, the operating system discards any unsent or // unacknowledged data. // // If sec > 0, the data is sent in the background as with sec < 0. // On some operating systems including Linux, this may cause Close to block // until all data has been sent or discarded. // On some operating systems after sec seconds have elapsed any remaining // unsent data may be discarded. func (c *TCPConn) SetLinger(sec int) error { if !c.ok() { return syscall.EINVAL } if err := setLinger(c.fd, sec); err != nil { return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err} } return nil } // SetKeepAlive sets whether the operating system should send // keep-alive messages on the connection. func (c *TCPConn) SetKeepAlive(keepalive bool) error { if !c.ok() { return syscall.EINVAL } if err := setKeepAlive(c.fd, keepalive); err != nil { return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err} } return nil } // SetKeepAlivePeriod sets period between keep-alives. func (c *TCPConn) SetKeepAlivePeriod(d time.Duration) error { if !c.ok() { return syscall.EINVAL } if err := setKeepAlivePeriod(c.fd, d); err != nil { return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err} } return nil } // SetNoDelay controls whether the operating system should delay // packet transmission in hopes of sending fewer packets (Nagle's // algorithm). The default is true (no delay), meaning that data is // sent as soon as possible after a Write. func (c *TCPConn) SetNoDelay(noDelay bool) error { if !c.ok() { return syscall.EINVAL } if err := setNoDelay(c.fd, noDelay); err != nil { return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err} } return nil } // MultipathTCP reports whether the ongoing connection is using MPTCP. // // If Multipath TCP is not supported by the host, by the other peer or // intentionally / accidentally filtered out by a device in between, a // fallback to TCP will be done. This method does its best to check if // MPTCP is still being used or not. // // On Linux, more conditions are verified on kernels >= v5.16, improving // the results. func (c *TCPConn) MultipathTCP() (bool, error) { if !c.ok() { return false, syscall.EINVAL } return isUsingMultipathTCP(c.fd), nil } func newTCPConn(fd *netFD, keepAlive time.Duration, keepAliveHook func(time.Duration)) *TCPConn { setNoDelay(fd, true) if keepAlive == 0 { keepAlive = defaultTCPKeepAlive } if keepAlive > 0 { setKeepAlive(fd, true) setKeepAlivePeriod(fd, keepAlive) if keepAliveHook != nil { keepAliveHook(keepAlive) } } return &TCPConn{conn{fd}} } // DialTCP acts like [Dial] for TCP networks. // // The network must be a TCP network name; see func Dial for details. // // If laddr is nil, a local address is automatically chosen. // If the IP field of raddr is nil or an unspecified IP address, the // local system is assumed. func DialTCP(network string, laddr, raddr *TCPAddr) (*TCPConn, error) { switch network { case "tcp", "tcp4", "tcp6": default: return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: raddr.opAddr(), Err: UnknownNetworkError(network)} } if raddr == nil { return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: nil, Err: errMissingAddress} } sd := &sysDialer{network: network, address: raddr.String()} c, err := sd.dialTCP(context.Background(), laddr, raddr) if err != nil { return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: raddr.opAddr(), Err: err} } return c, nil } // TCPListener is a TCP network listener. Clients should typically // use variables of type [Listener] instead of assuming TCP. type TCPListener struct { fd *netFD lc ListenConfig } // SyscallConn returns a raw network connection. // This implements the [syscall.Conn] interface. // // The returned RawConn only supports calling Control. Read and // Write return an error. func (l *TCPListener) SyscallConn() (syscall.RawConn, error) { if !l.ok() { return nil, syscall.EINVAL } return newRawListener(l.fd), nil } // AcceptTCP accepts the next incoming call and returns the new // connection. func (l *TCPListener) AcceptTCP() (*TCPConn, error) { if !l.ok() { return nil, syscall.EINVAL } c, err := l.accept() if err != nil { return nil, &OpError{Op: "accept", Net: l.fd.net, Source: nil, Addr: l.fd.laddr, Err: err} } return c, nil } // Accept implements the Accept method in the [Listener] interface; it // waits for the next call and returns a generic [Conn]. func (l *TCPListener) Accept() (Conn, error) { if !l.ok() { return nil, syscall.EINVAL } c, err := l.accept() if err != nil { return nil, &OpError{Op: "accept", Net: l.fd.net, Source: nil, Addr: l.fd.laddr, Err: err} } return c, nil } // Close stops listening on the TCP address. // Already Accepted connections are not closed. func (l *TCPListener) Close() error { if !l.ok() { return syscall.EINVAL } if err := l.close(); err != nil { return &OpError{Op: "close", Net: l.fd.net, Source: nil, Addr: l.fd.laddr, Err: err} } return nil } // Addr returns the listener's network address, a [*TCPAddr]. // The Addr returned is shared by all invocations of Addr, so // do not modify it. func (l *TCPListener) Addr() Addr { return l.fd.laddr } // SetDeadline sets the deadline associated with the listener. // A zero time value disables the deadline. func (l *TCPListener) SetDeadline(t time.Time) error { if !l.ok() { return syscall.EINVAL } return l.fd.SetDeadline(t) } // File returns a copy of the underlying [os.File]. // It is the caller's responsibility to close f when finished. // Closing l does not affect f, and closing f does not affect l. // // The returned os.File's file descriptor is different from the // connection's. Attempting to change properties of the original // using this duplicate may or may not have the desired effect. func (l *TCPListener) File() (f *os.File, err error) { if !l.ok() { return nil, syscall.EINVAL } f, err = l.file() if err != nil { return nil, &OpError{Op: "file", Net: l.fd.net, Source: nil, Addr: l.fd.laddr, Err: err} } return } // ListenTCP acts like [Listen] for TCP networks. // // The network must be a TCP network name; see func Dial for details. // // If the IP field of laddr is nil or an unspecified IP address, // ListenTCP listens on all available unicast and anycast IP addresses // of the local system. // If the Port field of laddr is 0, a port number is automatically // chosen. func ListenTCP(network string, laddr *TCPAddr) (*TCPListener, error) { switch network { case "tcp", "tcp4", "tcp6": default: return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: laddr.opAddr(), Err: UnknownNetworkError(network)} } if laddr == nil { laddr = &TCPAddr{} } sl := &sysListener{network: network, address: laddr.String()} ln, err := sl.listenTCP(context.Background(), laddr) if err != nil { return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: laddr.opAddr(), Err: err} } return ln, nil } // roundDurationUp rounds d to the next multiple of to. func roundDurationUp(d time.Duration, to time.Duration) time.Duration { return (d + to - 1) / to }