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