200 lines
5.8 KiB
Go
200 lines
5.8 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package net
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import (
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"errors"
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"os"
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"syscall"
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"time"
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)
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// UDPConn is the implementation of the Conn and PacketConn interfaces
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// for UDP network connections.
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type UDPConn struct {
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conn
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}
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func newUDPConn(fd *netFD) *UDPConn { return &UDPConn{conn{fd}} }
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// ReadFromUDP reads a UDP packet from c, copying the payload into b.
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// It returns the number of bytes copied into b and the return address
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// that was on the packet.
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//
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// ReadFromUDP can be made to time out and return an error with
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// Timeout() == true after a fixed time limit; see SetDeadline and
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// SetReadDeadline.
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func (c *UDPConn) ReadFromUDP(b []byte) (n int, addr *UDPAddr, err error) {
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if !c.ok() || c.fd.data == nil {
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return 0, nil, syscall.EINVAL
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}
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buf := make([]byte, udpHeaderSize+len(b))
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m, err := c.fd.data.Read(buf)
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if err != nil {
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return
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}
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if m < udpHeaderSize {
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return 0, nil, errors.New("short read reading UDP header")
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}
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buf = buf[:m]
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h, buf := unmarshalUDPHeader(buf)
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n = copy(b, buf)
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return n, &UDPAddr{IP: h.raddr, Port: int(h.rport)}, nil
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}
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// ReadFrom implements the PacketConn ReadFrom method.
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func (c *UDPConn) ReadFrom(b []byte) (int, Addr, error) {
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if !c.ok() {
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return 0, nil, syscall.EINVAL
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}
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return c.ReadFromUDP(b)
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}
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// ReadMsgUDP reads a packet from c, copying the payload into b and
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// the associated out-of-band data into oob. It returns the number
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// of bytes copied into b, the number of bytes copied into oob, the
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// flags that were set on the packet and the source address of the
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// packet.
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func (c *UDPConn) ReadMsgUDP(b, oob []byte) (n, oobn, flags int, addr *UDPAddr, err error) {
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return 0, 0, 0, nil, syscall.EPLAN9
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}
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// WriteToUDP writes a UDP packet to addr via c, copying the payload
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// from b.
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//
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// WriteToUDP can be made to time out and return an error with
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// Timeout() == true after a fixed time limit; see SetDeadline and
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// SetWriteDeadline. On packet-oriented connections, write timeouts
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// are rare.
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func (c *UDPConn) WriteToUDP(b []byte, addr *UDPAddr) (int, error) {
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if !c.ok() || c.fd.data == nil {
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return 0, syscall.EINVAL
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}
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h := new(udpHeader)
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h.raddr = addr.IP.To16()
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h.laddr = c.fd.laddr.(*UDPAddr).IP.To16()
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h.ifcaddr = IPv6zero // ignored (receive only)
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h.rport = uint16(addr.Port)
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h.lport = uint16(c.fd.laddr.(*UDPAddr).Port)
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buf := make([]byte, udpHeaderSize+len(b))
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i := copy(buf, h.Bytes())
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copy(buf[i:], b)
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return c.fd.data.Write(buf)
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}
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// WriteTo implements the PacketConn WriteTo method.
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func (c *UDPConn) WriteTo(b []byte, addr Addr) (int, error) {
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if !c.ok() {
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return 0, syscall.EINVAL
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}
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a, ok := addr.(*UDPAddr)
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if !ok {
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return 0, &OpError{"write", c.fd.dir, addr, syscall.EINVAL}
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}
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return c.WriteToUDP(b, a)
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}
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// WriteMsgUDP writes a packet to addr via c, copying the payload from
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// b and the associated out-of-band data from oob. It returns the
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// number of payload and out-of-band bytes written.
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func (c *UDPConn) WriteMsgUDP(b, oob []byte, addr *UDPAddr) (n, oobn int, err error) {
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return 0, 0, syscall.EPLAN9
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}
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// DialUDP connects to the remote address raddr on the network net,
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// which must be "udp", "udp4", or "udp6". If laddr is not nil, it is
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// used as the local address for the connection.
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func DialUDP(net string, laddr, raddr *UDPAddr) (*UDPConn, error) {
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return dialUDP(net, laddr, raddr, noDeadline)
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}
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func dialUDP(net string, laddr, raddr *UDPAddr, deadline time.Time) (*UDPConn, error) {
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if !deadline.IsZero() {
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panic("net.dialUDP: deadline not implemented on Plan 9")
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}
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switch net {
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case "udp", "udp4", "udp6":
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default:
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return nil, UnknownNetworkError(net)
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}
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if raddr == nil {
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return nil, &OpError{"dial", net, nil, errMissingAddress}
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}
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fd, err := dialPlan9(net, laddr, raddr)
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if err != nil {
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return nil, err
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}
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return newUDPConn(fd), nil
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}
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const udpHeaderSize = 16*3 + 2*2
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type udpHeader struct {
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raddr, laddr, ifcaddr IP
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rport, lport uint16
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}
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func (h *udpHeader) Bytes() []byte {
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b := make([]byte, udpHeaderSize)
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i := 0
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i += copy(b[i:i+16], h.raddr)
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i += copy(b[i:i+16], h.laddr)
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i += copy(b[i:i+16], h.ifcaddr)
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b[i], b[i+1], i = byte(h.rport>>8), byte(h.rport), i+2
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b[i], b[i+1], i = byte(h.lport>>8), byte(h.lport), i+2
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return b
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}
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func unmarshalUDPHeader(b []byte) (*udpHeader, []byte) {
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h := new(udpHeader)
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h.raddr, b = IP(b[:16]), b[16:]
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h.laddr, b = IP(b[:16]), b[16:]
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h.ifcaddr, b = IP(b[:16]), b[16:]
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h.rport, b = uint16(b[0])<<8|uint16(b[1]), b[2:]
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h.lport, b = uint16(b[0])<<8|uint16(b[1]), b[2:]
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return h, b
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}
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// ListenUDP listens for incoming UDP packets addressed to the local
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// address laddr. Net must be "udp", "udp4", or "udp6". If laddr has
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// a port of 0, ListenUDP will choose an available port.
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// The LocalAddr method of the returned UDPConn can be used to
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// discover the port. The returned connection's ReadFrom and WriteTo
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// methods can be used to receive and send UDP packets with per-packet
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// addressing.
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func ListenUDP(net string, laddr *UDPAddr) (*UDPConn, error) {
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switch net {
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case "udp", "udp4", "udp6":
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default:
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return nil, UnknownNetworkError(net)
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}
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if laddr == nil {
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laddr = &UDPAddr{}
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}
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l, err := listenPlan9(net, laddr)
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if err != nil {
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return nil, err
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}
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_, err = l.ctl.WriteString("headers")
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if err != nil {
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return nil, err
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}
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l.data, err = os.OpenFile(l.dir+"/data", os.O_RDWR, 0)
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if err != nil {
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return nil, err
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}
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return newUDPConn(l.netFD()), nil
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}
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// ListenMulticastUDP listens for incoming multicast UDP packets
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// addressed to the group address gaddr on ifi, which specifies the
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// interface to join. ListenMulticastUDP uses default multicast
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// interface if ifi is nil.
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func ListenMulticastUDP(net string, ifi *Interface, gaddr *UDPAddr) (*UDPConn, error) {
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return nil, syscall.EPLAN9
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}
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