Source file src/net/udpsock.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  package net
     6  
     7  import (
     8  	"context"
     9  	"internal/itoa"
    10  	"net/netip"
    11  	"syscall"
    12  )
    13  
    14  // BUG(mikio): On Plan 9, the ReadMsgUDP and
    15  // WriteMsgUDP methods of UDPConn are not implemented.
    16  
    17  // BUG(mikio): On Windows, the File method of UDPConn is not
    18  // implemented.
    19  
    20  // BUG(mikio): On JS, methods and functions related to UDPConn are not
    21  // implemented.
    22  
    23  // UDPAddr represents the address of a UDP end point.
    24  type UDPAddr struct {
    25  	IP   IP
    26  	Port int
    27  	Zone string // IPv6 scoped addressing zone
    28  }
    29  
    30  // AddrPort returns the [UDPAddr] a as a [netip.AddrPort].
    31  //
    32  // If a.Port does not fit in a uint16, it's silently truncated.
    33  //
    34  // If a is nil, a zero value is returned.
    35  func (a *UDPAddr) AddrPort() netip.AddrPort {
    36  	if a == nil {
    37  		return netip.AddrPort{}
    38  	}
    39  	na, _ := netip.AddrFromSlice(a.IP)
    40  	na = na.WithZone(a.Zone)
    41  	return netip.AddrPortFrom(na, uint16(a.Port))
    42  }
    43  
    44  // Network returns the address's network name, "udp".
    45  func (a *UDPAddr) Network() string { return "udp" }
    46  
    47  func (a *UDPAddr) String() string {
    48  	if a == nil {
    49  		return "<nil>"
    50  	}
    51  	ip := ipEmptyString(a.IP)
    52  	if a.Zone != "" {
    53  		return JoinHostPort(ip+"%"+a.Zone, itoa.Itoa(a.Port))
    54  	}
    55  	return JoinHostPort(ip, itoa.Itoa(a.Port))
    56  }
    57  
    58  func (a *UDPAddr) isWildcard() bool {
    59  	if a == nil || a.IP == nil {
    60  		return true
    61  	}
    62  	return a.IP.IsUnspecified()
    63  }
    64  
    65  func (a *UDPAddr) opAddr() Addr {
    66  	if a == nil {
    67  		return nil
    68  	}
    69  	return a
    70  }
    71  
    72  // ResolveUDPAddr returns an address of UDP end point.
    73  //
    74  // The network must be a UDP network name.
    75  //
    76  // If the host in the address parameter is not a literal IP address or
    77  // the port is not a literal port number, ResolveUDPAddr resolves the
    78  // address to an address of UDP end point.
    79  // Otherwise, it parses the address as a pair of literal IP address
    80  // and port number.
    81  // The address parameter can use a host name, but this is not
    82  // recommended, because it will return at most one of the host name's
    83  // IP addresses.
    84  //
    85  // See func [Dial] for a description of the network and address
    86  // parameters.
    87  func ResolveUDPAddr(network, address string) (*UDPAddr, error) {
    88  	switch network {
    89  	case "udp", "udp4", "udp6":
    90  	case "": // a hint wildcard for Go 1.0 undocumented behavior
    91  		network = "udp"
    92  	default:
    93  		return nil, UnknownNetworkError(network)
    94  	}
    95  	addrs, err := DefaultResolver.internetAddrList(context.Background(), network, address)
    96  	if err != nil {
    97  		return nil, err
    98  	}
    99  	return addrs.forResolve(network, address).(*UDPAddr), nil
   100  }
   101  
   102  // UDPAddrFromAddrPort returns addr as a [UDPAddr]. If addr.IsValid() is false,
   103  // then the returned UDPAddr will contain a nil IP field, indicating an
   104  // address family-agnostic unspecified address.
   105  func UDPAddrFromAddrPort(addr netip.AddrPort) *UDPAddr {
   106  	return &UDPAddr{
   107  		IP:   addr.Addr().AsSlice(),
   108  		Zone: addr.Addr().Zone(),
   109  		Port: int(addr.Port()),
   110  	}
   111  }
   112  
   113  // An addrPortUDPAddr is a netip.AddrPort-based UDP address that satisfies the Addr interface.
   114  type addrPortUDPAddr struct {
   115  	netip.AddrPort
   116  }
   117  
   118  func (addrPortUDPAddr) Network() string { return "udp" }
   119  
   120  // UDPConn is the implementation of the [Conn] and [PacketConn] interfaces
   121  // for UDP network connections.
   122  type UDPConn struct {
   123  	conn
   124  }
   125  
   126  // SyscallConn returns a raw network connection.
   127  // This implements the [syscall.Conn] interface.
   128  func (c *UDPConn) SyscallConn() (syscall.RawConn, error) {
   129  	if !c.ok() {
   130  		return nil, syscall.EINVAL
   131  	}
   132  	return newRawConn(c.fd), nil
   133  }
   134  
   135  // ReadFromUDP acts like [UDPConn.ReadFrom] but returns a UDPAddr.
   136  func (c *UDPConn) ReadFromUDP(b []byte) (n int, addr *UDPAddr, err error) {
   137  	// This function is designed to allow the caller to control the lifetime
   138  	// of the returned *UDPAddr and thereby prevent an allocation.
   139  	// See https://blog.filippo.io/efficient-go-apis-with-the-inliner/.
   140  	// The real work is done by readFromUDP, below.
   141  	return c.readFromUDP(b, &UDPAddr{})
   142  }
   143  
   144  // readFromUDP implements ReadFromUDP.
   145  func (c *UDPConn) readFromUDP(b []byte, addr *UDPAddr) (int, *UDPAddr, error) {
   146  	if !c.ok() {
   147  		return 0, nil, syscall.EINVAL
   148  	}
   149  	n, addr, err := c.readFrom(b, addr)
   150  	if err != nil {
   151  		err = &OpError{Op: "read", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
   152  	}
   153  	return n, addr, err
   154  }
   155  
   156  // ReadFrom implements the [PacketConn] ReadFrom method.
   157  func (c *UDPConn) ReadFrom(b []byte) (int, Addr, error) {
   158  	n, addr, err := c.readFromUDP(b, &UDPAddr{})
   159  	if addr == nil {
   160  		// Return Addr(nil), not Addr(*UDPConn(nil)).
   161  		return n, nil, err
   162  	}
   163  	return n, addr, err
   164  }
   165  
   166  // ReadFromUDPAddrPort acts like ReadFrom but returns a [netip.AddrPort].
   167  //
   168  // If c is bound to an unspecified address, the returned
   169  // netip.AddrPort's address might be an IPv4-mapped IPv6 address.
   170  // Use [netip.Addr.Unmap] to get the address without the IPv6 prefix.
   171  func (c *UDPConn) ReadFromUDPAddrPort(b []byte) (n int, addr netip.AddrPort, err error) {
   172  	if !c.ok() {
   173  		return 0, netip.AddrPort{}, syscall.EINVAL
   174  	}
   175  	n, addr, err = c.readFromAddrPort(b)
   176  	if err != nil {
   177  		err = &OpError{Op: "read", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
   178  	}
   179  	return n, addr, err
   180  }
   181  
   182  // ReadMsgUDP reads a message from c, copying the payload into b and
   183  // the associated out-of-band data into oob. It returns the number of
   184  // bytes copied into b, the number of bytes copied into oob, the flags
   185  // that were set on the message and the source address of the message.
   186  //
   187  // The packages [golang.org/x/net/ipv4] and [golang.org/x/net/ipv6] can be
   188  // used to manipulate IP-level socket options in oob.
   189  func (c *UDPConn) ReadMsgUDP(b, oob []byte) (n, oobn, flags int, addr *UDPAddr, err error) {
   190  	var ap netip.AddrPort
   191  	n, oobn, flags, ap, err = c.ReadMsgUDPAddrPort(b, oob)
   192  	if ap.IsValid() {
   193  		addr = UDPAddrFromAddrPort(ap)
   194  	}
   195  	return
   196  }
   197  
   198  // ReadMsgUDPAddrPort is like [UDPConn.ReadMsgUDP] but returns an [netip.AddrPort] instead of a [UDPAddr].
   199  func (c *UDPConn) ReadMsgUDPAddrPort(b, oob []byte) (n, oobn, flags int, addr netip.AddrPort, err error) {
   200  	if !c.ok() {
   201  		return 0, 0, 0, netip.AddrPort{}, syscall.EINVAL
   202  	}
   203  	n, oobn, flags, addr, err = c.readMsg(b, oob)
   204  	if err != nil {
   205  		err = &OpError{Op: "read", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
   206  	}
   207  	return
   208  }
   209  
   210  // WriteToUDP acts like [UDPConn.WriteTo] but takes a [UDPAddr].
   211  func (c *UDPConn) WriteToUDP(b []byte, addr *UDPAddr) (int, error) {
   212  	if !c.ok() {
   213  		return 0, syscall.EINVAL
   214  	}
   215  	n, err := c.writeTo(b, addr)
   216  	if err != nil {
   217  		err = &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: addr.opAddr(), Err: err}
   218  	}
   219  	return n, err
   220  }
   221  
   222  // WriteToUDPAddrPort acts like [UDPConn.WriteTo] but takes a [netip.AddrPort].
   223  func (c *UDPConn) WriteToUDPAddrPort(b []byte, addr netip.AddrPort) (int, error) {
   224  	if !c.ok() {
   225  		return 0, syscall.EINVAL
   226  	}
   227  	n, err := c.writeToAddrPort(b, addr)
   228  	if err != nil {
   229  		err = &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: addrPortUDPAddr{addr}, Err: err}
   230  	}
   231  	return n, err
   232  }
   233  
   234  // WriteTo implements the [PacketConn] WriteTo method.
   235  func (c *UDPConn) WriteTo(b []byte, addr Addr) (int, error) {
   236  	if !c.ok() {
   237  		return 0, syscall.EINVAL
   238  	}
   239  	a, ok := addr.(*UDPAddr)
   240  	if !ok {
   241  		return 0, &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: addr, Err: syscall.EINVAL}
   242  	}
   243  	n, err := c.writeTo(b, a)
   244  	if err != nil {
   245  		err = &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: a.opAddr(), Err: err}
   246  	}
   247  	return n, err
   248  }
   249  
   250  // WriteMsgUDP writes a message to addr via c if c isn't connected, or
   251  // to c's remote address if c is connected (in which case addr must be
   252  // nil). The payload is copied from b and the associated out-of-band
   253  // data is copied from oob. It returns the number of payload and
   254  // out-of-band bytes written.
   255  //
   256  // The packages [golang.org/x/net/ipv4] and [golang.org/x/net/ipv6] can be
   257  // used to manipulate IP-level socket options in oob.
   258  func (c *UDPConn) WriteMsgUDP(b, oob []byte, addr *UDPAddr) (n, oobn int, err error) {
   259  	if !c.ok() {
   260  		return 0, 0, syscall.EINVAL
   261  	}
   262  	n, oobn, err = c.writeMsg(b, oob, addr)
   263  	if err != nil {
   264  		err = &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: addr.opAddr(), Err: err}
   265  	}
   266  	return
   267  }
   268  
   269  // WriteMsgUDPAddrPort is like [UDPConn.WriteMsgUDP] but takes a [netip.AddrPort] instead of a [UDPAddr].
   270  func (c *UDPConn) WriteMsgUDPAddrPort(b, oob []byte, addr netip.AddrPort) (n, oobn int, err error) {
   271  	if !c.ok() {
   272  		return 0, 0, syscall.EINVAL
   273  	}
   274  	n, oobn, err = c.writeMsgAddrPort(b, oob, addr)
   275  	if err != nil {
   276  		err = &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: addrPortUDPAddr{addr}, Err: err}
   277  	}
   278  	return
   279  }
   280  
   281  func newUDPConn(fd *netFD) *UDPConn { return &UDPConn{conn{fd}} }
   282  
   283  // DialUDP acts like [Dial] for UDP networks.
   284  //
   285  // The network must be a UDP network name; see func [Dial] for details.
   286  //
   287  // If laddr is nil, a local address is automatically chosen.
   288  // If the IP field of raddr is nil or an unspecified IP address, the
   289  // local system is assumed.
   290  func DialUDP(network string, laddr, raddr *UDPAddr) (*UDPConn, error) {
   291  	switch network {
   292  	case "udp", "udp4", "udp6":
   293  	default:
   294  		return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: raddr.opAddr(), Err: UnknownNetworkError(network)}
   295  	}
   296  	if raddr == nil {
   297  		return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: nil, Err: errMissingAddress}
   298  	}
   299  	sd := &sysDialer{network: network, address: raddr.String()}
   300  	c, err := sd.dialUDP(context.Background(), laddr, raddr)
   301  	if err != nil {
   302  		return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: raddr.opAddr(), Err: err}
   303  	}
   304  	return c, nil
   305  }
   306  
   307  // ListenUDP acts like [ListenPacket] for UDP networks.
   308  //
   309  // The network must be a UDP network name; see func [Dial] for details.
   310  //
   311  // If the IP field of laddr is nil or an unspecified IP address,
   312  // ListenUDP listens on all available IP addresses of the local system
   313  // except multicast IP addresses.
   314  // If the Port field of laddr is 0, a port number is automatically
   315  // chosen.
   316  func ListenUDP(network string, laddr *UDPAddr) (*UDPConn, error) {
   317  	switch network {
   318  	case "udp", "udp4", "udp6":
   319  	default:
   320  		return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: laddr.opAddr(), Err: UnknownNetworkError(network)}
   321  	}
   322  	if laddr == nil {
   323  		laddr = &UDPAddr{}
   324  	}
   325  	sl := &sysListener{network: network, address: laddr.String()}
   326  	c, err := sl.listenUDP(context.Background(), laddr)
   327  	if err != nil {
   328  		return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: laddr.opAddr(), Err: err}
   329  	}
   330  	return c, nil
   331  }
   332  
   333  // ListenMulticastUDP acts like [ListenPacket] for UDP networks but
   334  // takes a group address on a specific network interface.
   335  //
   336  // The network must be a UDP network name; see func [Dial] for details.
   337  //
   338  // ListenMulticastUDP listens on all available IP addresses of the
   339  // local system including the group, multicast IP address.
   340  // If ifi is nil, ListenMulticastUDP uses the system-assigned
   341  // multicast interface, although this is not recommended because the
   342  // assignment depends on platforms and sometimes it might require
   343  // routing configuration.
   344  // If the Port field of gaddr is 0, a port number is automatically
   345  // chosen.
   346  //
   347  // ListenMulticastUDP is just for convenience of simple, small
   348  // applications. There are [golang.org/x/net/ipv4] and
   349  // [golang.org/x/net/ipv6] packages for general purpose uses.
   350  //
   351  // Note that ListenMulticastUDP will set the IP_MULTICAST_LOOP socket option
   352  // to 0 under IPPROTO_IP, to disable loopback of multicast packets.
   353  func ListenMulticastUDP(network string, ifi *Interface, gaddr *UDPAddr) (*UDPConn, error) {
   354  	switch network {
   355  	case "udp", "udp4", "udp6":
   356  	default:
   357  		return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: gaddr.opAddr(), Err: UnknownNetworkError(network)}
   358  	}
   359  	if gaddr == nil || gaddr.IP == nil {
   360  		return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: gaddr.opAddr(), Err: errMissingAddress}
   361  	}
   362  	sl := &sysListener{network: network, address: gaddr.String()}
   363  	c, err := sl.listenMulticastUDP(context.Background(), ifi, gaddr)
   364  	if err != nil {
   365  		return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: gaddr.opAddr(), Err: err}
   366  	}
   367  	return c, nil
   368  }
   369  

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