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// 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.
// UDP for Plan 9
package net
import (
"errors"
"os"
"syscall"
"time"
)
// UDPConn is the implementation of the Conn and PacketConn
// interfaces for UDP network connections.
type UDPConn struct {
plan9Conn
}
// SetDeadline implements the Conn SetDeadline method.
func (c *UDPConn) SetDeadline(t time.Time) error {
return syscall.EPLAN9
}
// SetReadDeadline implements the Conn SetReadDeadline method.
func (c *UDPConn) SetReadDeadline(t time.Time) error {
return syscall.EPLAN9
}
// SetWriteDeadline implements the Conn SetWriteDeadline method.
func (c *UDPConn) SetWriteDeadline(t time.Time) error {
return syscall.EPLAN9
}
// UDP-specific methods.
// 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) (n int, addr *UDPAddr, err error) {
if !c.ok() {
return 0, nil, syscall.EINVAL
}
if c.data == nil {
c.data, err = os.OpenFile(c.dir+"/data", os.O_RDWR, 0)
if err != nil {
return 0, nil, err
}
}
buf := make([]byte, udpHeaderSize+len(b))
m, err := c.data.Read(buf)
if err != nil {
return
}
if m < udpHeaderSize {
return 0, nil, errors.New("short read reading UDP header")
}
buf = buf[:m]
h, buf := unmarshalUDPHeader(buf)
n = copy(b, buf)
return n, &UDPAddr{h.raddr, int(h.rport)}, nil
}
// ReadFrom implements the PacketConn ReadFrom method.
func (c *UDPConn) ReadFrom(b []byte) (n int, addr Addr, err error) {
if !c.ok() {
return 0, nil, syscall.EINVAL
}
return c.ReadFromUDP(b)
}
// 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) (n int, err error) {
if !c.ok() {
return 0, syscall.EINVAL
}
if c.data == nil {
c.data, err = os.OpenFile(c.dir+"/data", os.O_RDWR, 0)
if err != nil {
return 0, err
}
}
h := new(udpHeader)
h.raddr = addr.IP.To16()
h.laddr = c.laddr.(*UDPAddr).IP.To16()
h.ifcaddr = IPv6zero // ignored (receive only)
h.rport = uint16(addr.Port)
h.lport = uint16(c.laddr.(*UDPAddr).Port)
buf := make([]byte, udpHeaderSize+len(b))
i := copy(buf, h.Bytes())
copy(buf[i:], b)
return c.data.Write(buf)
}
// WriteTo implements the PacketConn WriteTo method.
func (c *UDPConn) WriteTo(b []byte, addr Addr) (n int, err error) {
if !c.ok() {
return 0, syscall.EINVAL
}
a, ok := addr.(*UDPAddr)
if !ok {
return 0, &OpError{"write", c.dir, addr, syscall.EINVAL}
}
return c.WriteToUDP(b, a)
}
// 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) (c *UDPConn, err error) {
switch net {
case "udp", "udp4", "udp6":
default:
return nil, UnknownNetworkError(net)
}
if raddr == nil {
return nil, &OpError{"dial", net, nil, errMissingAddress}
}
c1, err := dialPlan9(net, laddr, raddr)
if err != nil {
return
}
return &UDPConn{*c1}, nil
}
const udpHeaderSize = 16*3 + 2*2
type udpHeader struct {
raddr, laddr, ifcaddr IP
rport, lport uint16
}
func (h *udpHeader) Bytes() []byte {
b := make([]byte, udpHeaderSize)
i := 0
i += copy(b[i:i+16], h.raddr)
i += copy(b[i:i+16], h.laddr)
i += copy(b[i:i+16], h.ifcaddr)
b[i], b[i+1], i = byte(h.rport>>8), byte(h.rport), i+2
b[i], b[i+1], i = byte(h.lport>>8), byte(h.lport), i+2
return b
}
func unmarshalUDPHeader(b []byte) (*udpHeader, []byte) {
h := new(udpHeader)
h.raddr, b = IP(b[:16]), b[16:]
h.laddr, b = IP(b[:16]), b[16:]
h.ifcaddr, b = IP(b[:16]), b[16:]
h.rport, b = uint16(b[0])<<8|uint16(b[1]), b[2:]
h.lport, b = uint16(b[0])<<8|uint16(b[1]), b[2:]
return h, b
}
// ListenUDP listens for incoming UDP packets addressed to the
// local address laddr. The returned connection c's ReadFrom
// and WriteTo methods can be used to receive and send UDP
// packets with per-packet addressing.
func ListenUDP(net string, laddr *UDPAddr) (c *UDPConn, err error) {
switch net {
case "udp", "udp4", "udp6":
default:
return nil, UnknownNetworkError(net)
}
if laddr == nil {
return nil, &OpError{"listen", net, nil, errMissingAddress}
}
l, err := listenPlan9(net, laddr)
if err != nil {
return
}
_, err = l.ctl.WriteString("headers")
if err != nil {
return
}
return &UDPConn{*l.plan9Conn()}, nil
}
// ListenMulticastUDP listens for incoming multicast UDP packets
// addressed to the group address gaddr on ifi, which specifies
// the interface to join. ListenMulticastUDP uses default
// multicast interface if ifi is nil.
func ListenMulticastUDP(net string, ifi *Interface, gaddr *UDPAddr) (*UDPConn, error) {
return nil, syscall.EPLAN9
}
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