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Source file src/net/udpsock.go

  // 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"
  	"syscall"
  )
  
  // BUG(mikio): On NaCl, Plan 9 and Windows, the ReadMsgUDP and
  // WriteMsgUDP methods of UDPConn are not implemented.
  
  // BUG(mikio): On Windows, the File method of UDPConn is not
  // implemented.
  
  // BUG(mikio): On NaCl, the ListenMulticastUDP function is not
  // implemented.
  
  // UDPAddr represents the address of a UDP end point.
  type UDPAddr struct {
  	IP   IP
  	Port int
  	Zone string // IPv6 scoped addressing zone
  }
  
  // Network returns the address's network name, "udp".
  func (a *UDPAddr) Network() string { return "udp" }
  
  func (a *UDPAddr) String() string {
  	if a == nil {
  		return "<nil>"
  	}
  	ip := ipEmptyString(a.IP)
  	if a.Zone != "" {
  		return JoinHostPort(ip+"%"+a.Zone, itoa(a.Port))
  	}
  	return JoinHostPort(ip, itoa(a.Port))
  }
  
  func (a *UDPAddr) isWildcard() bool {
  	if a == nil || a.IP == nil {
  		return true
  	}
  	return a.IP.IsUnspecified()
  }
  
  func (a *UDPAddr) opAddr() Addr {
  	if a == nil {
  		return nil
  	}
  	return a
  }
  
  // ResolveUDPAddr parses addr as a UDP address of the form "host:port"
  // or "[ipv6-host%zone]:port" and resolves a pair of domain name and
  // port name on the network net, which must be "udp", "udp4" or
  // "udp6".  A literal address or host name for IPv6 must be enclosed
  // in square brackets, as in "[::1]:80", "[ipv6-host]:http" or
  // "[ipv6-host%zone]:80".
  //
  // Resolving a hostname is not recommended because this returns at most
  // one of its IP addresses.
  func ResolveUDPAddr(net, addr string) (*UDPAddr, error) {
  	switch net {
  	case "udp", "udp4", "udp6":
  	case "": // a hint wildcard for Go 1.0 undocumented behavior
  		net = "udp"
  	default:
  		return nil, UnknownNetworkError(net)
  	}
  	addrs, err := DefaultResolver.internetAddrList(context.Background(), net, addr)
  	if err != nil {
  		return nil, err
  	}
  	return addrs.first(isIPv4).(*UDPAddr), nil
  }
  
  // UDPConn is the implementation of the Conn and PacketConn interfaces
  // for UDP network connections.
  type UDPConn struct {
  	conn
  }
  
  // ReadFromUDP reads a UDP packet from c, copying the payload into b.
  // It returns the number of bytes copied into b and the return address
  // that was on the packet.
  //
  // ReadFromUDP can be made to time out and return an error with
  // Timeout() == true after a fixed time limit; see SetDeadline and
  // SetReadDeadline.
  func (c *UDPConn) ReadFromUDP(b []byte) (int, *UDPAddr, error) {
  	if !c.ok() {
  		return 0, nil, syscall.EINVAL
  	}
  	n, addr, err := c.readFrom(b)
  	if err != nil {
  		err = &OpError{Op: "read", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
  	}
  	return n, addr, err
  }
  
  // ReadFrom implements the PacketConn ReadFrom method.
  func (c *UDPConn) ReadFrom(b []byte) (int, Addr, error) {
  	if !c.ok() {
  		return 0, nil, syscall.EINVAL
  	}
  	n, addr, err := c.readFrom(b)
  	if err != nil {
  		err = &OpError{Op: "read", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
  	}
  	if addr == nil {
  		return n, nil, err
  	}
  	return n, addr, err
  }
  
  // ReadMsgUDP reads a packet from c, copying the payload into b and
  // the associated out-of-band data into oob. It returns the number
  // of bytes copied into b, the number of bytes copied into oob, the
  // flags that were set on the packet and the source address of the
  // packet.
  func (c *UDPConn) ReadMsgUDP(b, oob []byte) (n, oobn, flags int, addr *UDPAddr, err error) {
  	if !c.ok() {
  		return 0, 0, 0, nil, syscall.EINVAL
  	}
  	n, oobn, flags, addr, err = c.readMsg(b, oob)
  	if err != nil {
  		err = &OpError{Op: "read", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
  	}
  	return
  }
  
  // WriteToUDP writes a UDP packet to addr via c, copying the payload
  // from b.
  //
  // WriteToUDP can be made to time out and return an error with
  // Timeout() == true after a fixed time limit; see SetDeadline and
  // SetWriteDeadline. On packet-oriented connections, write timeouts
  // are rare.
  func (c *UDPConn) WriteToUDP(b []byte, addr *UDPAddr) (int, error) {
  	if !c.ok() {
  		return 0, syscall.EINVAL
  	}
  	n, err := c.writeTo(b, addr)
  	if err != nil {
  		err = &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: addr.opAddr(), Err: err}
  	}
  	return n, err
  }
  
  // WriteTo implements the PacketConn WriteTo method.
  func (c *UDPConn) WriteTo(b []byte, addr Addr) (int, error) {
  	if !c.ok() {
  		return 0, syscall.EINVAL
  	}
  	a, ok := addr.(*UDPAddr)
  	if !ok {
  		return 0, &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: addr, Err: syscall.EINVAL}
  	}
  	n, err := c.writeTo(b, a)
  	if err != nil {
  		err = &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: a.opAddr(), Err: err}
  	}
  	return n, err
  }
  
  // WriteMsgUDP writes a packet to addr via c if c isn't connected, or
  // to c's remote destination address if c is connected (in which case
  // addr must be nil).  The payload is copied from b and the associated
  // out-of-band data is copied from oob. It returns the number of
  // payload and out-of-band bytes written.
  func (c *UDPConn) WriteMsgUDP(b, oob []byte, addr *UDPAddr) (n, oobn int, err error) {
  	if !c.ok() {
  		return 0, 0, syscall.EINVAL
  	}
  	n, oobn, err = c.writeMsg(b, oob, addr)
  	if err != nil {
  		err = &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: addr.opAddr(), Err: err}
  	}
  	return
  }
  
  func newUDPConn(fd *netFD) *UDPConn { return &UDPConn{conn{fd}} }
  
  // DialUDP connects to the remote address raddr on the network net,
  // which must be "udp", "udp4", or "udp6".  If laddr is not nil, it is
  // used as the local address for the connection.
  func DialUDP(net string, laddr, raddr *UDPAddr) (*UDPConn, error) {
  	switch net {
  	case "udp", "udp4", "udp6":
  	default:
  		return nil, &OpError{Op: "dial", Net: net, Source: laddr.opAddr(), Addr: raddr.opAddr(), Err: UnknownNetworkError(net)}
  	}
  	if raddr == nil {
  		return nil, &OpError{Op: "dial", Net: net, Source: laddr.opAddr(), Addr: nil, Err: errMissingAddress}
  	}
  	c, err := dialUDP(context.Background(), net, laddr, raddr)
  	if err != nil {
  		return nil, &OpError{Op: "dial", Net: net, Source: laddr.opAddr(), Addr: raddr.opAddr(), Err: err}
  	}
  	return c, nil
  }
  
  // ListenUDP listens for incoming UDP packets addressed to the local
  // address laddr. Net must be "udp", "udp4", or "udp6".  If laddr has
  // a port of 0, ListenUDP will choose an available port.
  // The LocalAddr method of the returned UDPConn can be used to
  // discover the port. The returned connection's ReadFrom and WriteTo
  // methods can be used to receive and send UDP packets with per-packet
  // addressing.
  func ListenUDP(net string, laddr *UDPAddr) (*UDPConn, error) {
  	switch net {
  	case "udp", "udp4", "udp6":
  	default:
  		return nil, &OpError{Op: "listen", Net: net, Source: nil, Addr: laddr.opAddr(), Err: UnknownNetworkError(net)}
  	}
  	if laddr == nil {
  		laddr = &UDPAddr{}
  	}
  	c, err := listenUDP(context.Background(), net, laddr)
  	if err != nil {
  		return nil, &OpError{Op: "listen", Net: net, Source: nil, Addr: laddr.opAddr(), Err: err}
  	}
  	return c, nil
  }
  
  // ListenMulticastUDP listens for incoming multicast UDP packets
  // addressed to the group address gaddr on the interface ifi.
  // Network must be "udp", "udp4" or "udp6".
  // ListenMulticastUDP uses the system-assigned multicast interface
  // when ifi is nil, although this is not recommended because the
  // assignment depends on platforms and sometimes it might require
  // routing configuration.
  //
  // ListenMulticastUDP is just for convenience of simple, small
  // applications. There are golang.org/x/net/ipv4 and
  // golang.org/x/net/ipv6 packages for general purpose uses.
  func ListenMulticastUDP(network string, ifi *Interface, gaddr *UDPAddr) (*UDPConn, error) {
  	switch network {
  	case "udp", "udp4", "udp6":
  	default:
  		return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: gaddr.opAddr(), Err: UnknownNetworkError(network)}
  	}
  	if gaddr == nil || gaddr.IP == nil {
  		return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: gaddr.opAddr(), Err: errMissingAddress}
  	}
  	c, err := listenMulticastUDP(context.Background(), network, ifi, gaddr)
  	if err != nil {
  		return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: gaddr.opAddr(), Err: err}
  	}
  	return c, nil
  }
  

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