src/pkg/net/udpsock_posix.go - go - Git at Google

 // 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.

 // +build darwin freebsd linux openbsd windows

 // UDP sockets

 package net

 import (
 	"bytes"
 	"os"
 	"syscall"
 )

 func sockaddrToUDP(sa syscall.Sockaddr) Addr {
 	switch sa := sa.(type) {
 	case *syscall.SockaddrInet4:
 		return &UDPAddr{sa.Addr[0:], sa.Port}
 	case *syscall.SockaddrInet6:
 		return &UDPAddr{sa.Addr[0:], sa.Port}
 	}
 	return nil
 }

 func (a *UDPAddr) family() int {
 	if a == nil || len(a.IP) <= IPv4len {
 		return syscall.AF_INET
 	}
 	if a.IP.To4() != nil {
 		return syscall.AF_INET
 	}
 	return syscall.AF_INET6
 }

 func (a *UDPAddr) sockaddr(family int) (syscall.Sockaddr, os.Error) {
 	return ipToSockaddr(family, a.IP, a.Port)
 }

 func (a *UDPAddr) toAddr() sockaddr {
 	if a == nil { // nil *UDPAddr
 		return nil // nil interface
 	}
 	return a
 }

 // UDPConn is the implementation of the Conn and PacketConn
 // interfaces for UDP network connections.
 type UDPConn struct {
 	fd *netFD
 }

 func newUDPConn(fd *netFD) *UDPConn { return &UDPConn{fd} }

 func (c *UDPConn) ok() bool { return c != nil && c.fd != nil }

 // Implementation of the Conn interface - see Conn for documentation.

 // Read implements the net.Conn Read method.
 func (c *UDPConn) Read(b []byte) (n int, err os.Error) {
 	if !c.ok() {
 		return 0, os.EINVAL
 	}
 	return c.fd.Read(b)
 }

 // Write implements the net.Conn Write method.
 func (c *UDPConn) Write(b []byte) (n int, err os.Error) {
 	if !c.ok() {
 		return 0, os.EINVAL
 	}
 	return c.fd.Write(b)
 }

 // Close closes the UDP connection.
 func (c *UDPConn) Close() os.Error {
 	if !c.ok() {
 		return os.EINVAL
 	}
 	err := c.fd.Close()
 	c.fd = nil
 	return err
 }

 // LocalAddr returns the local network address.
 func (c *UDPConn) LocalAddr() Addr {
 	if !c.ok() {
 		return nil
 	}
 	return c.fd.laddr
 }

 // RemoteAddr returns the remote network address, a *UDPAddr.
 func (c *UDPConn) RemoteAddr() Addr {
 	if !c.ok() {
 		return nil
 	}
 	return c.fd.raddr
 }

 // SetTimeout implements the net.Conn SetTimeout method.
 func (c *UDPConn) SetTimeout(nsec int64) os.Error {
 	if !c.ok() {
 		return os.EINVAL
 	}
 	return setTimeout(c.fd, nsec)
 }

 // SetReadTimeout implements the net.Conn SetReadTimeout method.
 func (c *UDPConn) SetReadTimeout(nsec int64) os.Error {
 	if !c.ok() {
 		return os.EINVAL
 	}
 	return setReadTimeout(c.fd, nsec)
 }

 // SetWriteTimeout implements the net.Conn SetWriteTimeout method.
 func (c *UDPConn) SetWriteTimeout(nsec int64) os.Error {
 	if !c.ok() {
 		return os.EINVAL
 	}
 	return setWriteTimeout(c.fd, nsec)
 }

 // SetReadBuffer sets the size of the operating system's
 // receive buffer associated with the connection.
 func (c *UDPConn) SetReadBuffer(bytes int) os.Error {
 	if !c.ok() {
 		return os.EINVAL
 	}
 	return setReadBuffer(c.fd, bytes)
 }

 // SetWriteBuffer sets the size of the operating system's
 // transmit buffer associated with the connection.
 func (c *UDPConn) SetWriteBuffer(bytes int) os.Error {
 	if !c.ok() {
 		return os.EINVAL
 	}
 	return setWriteBuffer(c.fd, bytes)
 }

 // 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 SetTimeout and SetReadTimeout.
 func (c *UDPConn) ReadFromUDP(b []byte) (n int, addr *UDPAddr, err os.Error) {
 	if !c.ok() {
 		return 0, nil, os.EINVAL
 	}
 	n, sa, err := c.fd.ReadFrom(b)
 	switch sa := sa.(type) {
 	case *syscall.SockaddrInet4:
 		addr = &UDPAddr{sa.Addr[0:], sa.Port}
 	case *syscall.SockaddrInet6:
 		addr = &UDPAddr{sa.Addr[0:], sa.Port}
 	}
 	return
 }

 // ReadFrom implements the net.PacketConn ReadFrom method.
 func (c *UDPConn) ReadFrom(b []byte) (n int, addr Addr, err os.Error) {
 	if !c.ok() {
 		return 0, nil, os.EINVAL
 	}
 	n, uaddr, err := c.ReadFromUDP(b)
 	return n, uaddr.toAddr(), err
 }

 // 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 SetTimeout and SetWriteTimeout.
 // On packet-oriented connections, write timeouts are rare.
 func (c *UDPConn) WriteToUDP(b []byte, addr *UDPAddr) (n int, err os.Error) {
 	if !c.ok() {
 		return 0, os.EINVAL
 	}
 	sa, err1 := addr.sockaddr(c.fd.family)
 	if err1 != nil {
 		return 0, &OpError{Op: "write", Net: "udp", Addr: addr, Error: err1}
 	}
 	return c.fd.WriteTo(b, sa)
 }

 // WriteTo implements the net.PacketConn WriteTo method.
 func (c *UDPConn) WriteTo(b []byte, addr Addr) (n int, err os.Error) {
 	if !c.ok() {
 		return 0, os.EINVAL
 	}
 	a, ok := addr.(*UDPAddr)
 	if !ok {
 		return 0, &OpError{"writeto", "udp", addr, os.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 os.Error) {
 	switch net {
 	case "udp", "udp4", "udp6":
 	default:
 		return nil, UnknownNetworkError(net)
 	}
 	if raddr == nil {
 		return nil, &OpError{"dial", "udp", nil, errMissingAddress}
 	}
 	fd, e := internetSocket(net, laddr.toAddr(), raddr.toAddr(), syscall.SOCK_DGRAM, 0, "dial", sockaddrToUDP)
 	if e != nil {
 		return nil, e
 	}
 	return newUDPConn(fd), nil
 }

 // 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 os.Error) {
 	switch net {
 	case "udp", "udp4", "udp6":
 	default:
 		return nil, UnknownNetworkError(net)
 	}
 	if laddr == nil {
 		return nil, &OpError{"listen", "udp", nil, errMissingAddress}
 	}
 	fd, e := internetSocket(net, laddr.toAddr(), nil, syscall.SOCK_DGRAM, 0, "dial", sockaddrToUDP)
 	if e != nil {
 		return nil, e
 	}
 	return newUDPConn(fd), nil
 }

 // BindToDevice binds a UDPConn to a network interface.
 func (c *UDPConn) BindToDevice(device string) os.Error {
 	if !c.ok() {
 		return os.EINVAL
 	}
 	c.fd.incref()
 	defer c.fd.decref()
 	return os.NewSyscallError("setsockopt", syscall.BindToDevice(c.fd.sysfd, device))
 }

 // File returns a copy of the underlying os.File, set to blocking mode.
 // It is the caller's responsibility to close f when finished.
 // Closing c does not affect f, and closing f does not affect c.
 func (c *UDPConn) File() (f *os.File, err os.Error) { return c.fd.dup() }

 // JoinGroup joins the IP multicast group named by addr on ifi,
 // which specifies the interface to join.  JoinGroup uses the
 // default multicast interface if ifi is nil.
 func (c *UDPConn) JoinGroup(ifi *Interface, addr IP) os.Error {
 	if !c.ok() {
 		return os.EINVAL
 	}
 	ip := addr.To4()
 	if ip != nil {
 		return joinIPv4GroupUDP(c, ifi, ip)
 	}
 	return joinIPv6GroupUDP(c, ifi, addr)
 }

 // LeaveGroup exits the IP multicast group named by addr on ifi.
 func (c *UDPConn) LeaveGroup(ifi *Interface, addr IP) os.Error {
 	if !c.ok() {
 		return os.EINVAL
 	}
 	ip := addr.To4()
 	if ip != nil {
 		return leaveIPv4GroupUDP(c, ifi, ip)
 	}
 	return leaveIPv6GroupUDP(c, ifi, addr)
 }

 func joinIPv4GroupUDP(c *UDPConn, ifi *Interface, ip IP) os.Error {
 	mreq := &syscall.IPMreq{Multiaddr: [4]byte{ip[0], ip[1], ip[2], ip[3]}}
 	if err := setIPv4InterfaceToJoin(mreq, ifi); err != nil {
 		return &OpError{"joinipv4group", "udp", &IPAddr{ip}, err}
 	}
 	if err := os.NewSyscallError("setsockopt", syscall.SetsockoptIPMreq(c.fd.sysfd, syscall.IPPROTO_IP, syscall.IP_ADD_MEMBERSHIP, mreq)); err != nil {
 		return &OpError{"joinipv4group", "udp", &IPAddr{ip}, err}
 	}
 	return nil
 }

 func leaveIPv4GroupUDP(c *UDPConn, ifi *Interface, ip IP) os.Error {
 	mreq := &syscall.IPMreq{Multiaddr: [4]byte{ip[0], ip[1], ip[2], ip[3]}}
 	if err := setIPv4InterfaceToJoin(mreq, ifi); err != nil {
 		return &OpError{"leaveipv4group", "udp", &IPAddr{ip}, err}
 	}
 	if err := os.NewSyscallError("setsockopt", syscall.SetsockoptIPMreq(c.fd.sysfd, syscall.IPPROTO_IP, syscall.IP_DROP_MEMBERSHIP, mreq)); err != nil {
 		return &OpError{"leaveipv4group", "udp", &IPAddr{ip}, err}
 	}
 	return nil
 }

 func setIPv4InterfaceToJoin(mreq *syscall.IPMreq, ifi *Interface) os.Error {
 	if ifi == nil {
 		return nil
 	}
 	ifat, err := ifi.Addrs()
 	if err != nil {
 		return err
 	}
 	for _, ifa := range ifat {
 		if x := ifa.(*IPAddr).IP.To4(); x != nil {
 			copy(mreq.Interface[:], x)
 			break
 		}
 	}
 	if bytes.Equal(mreq.Multiaddr[:], IPv4zero) {
 		return os.EINVAL
 	}
 	return nil
 }

 func joinIPv6GroupUDP(c *UDPConn, ifi *Interface, ip IP) os.Error {
 	mreq := &syscall.IPv6Mreq{}
 	copy(mreq.Multiaddr[:], ip)
 	if ifi != nil {
 		mreq.Interface = uint32(ifi.Index)
 	}
 	if err := os.NewSyscallError("setsockopt", syscall.SetsockoptIPv6Mreq(c.fd.sysfd, syscall.IPPROTO_IPV6, syscall.IPV6_JOIN_GROUP, mreq)); err != nil {
 		return &OpError{"joinipv6group", "udp", &IPAddr{ip}, err}
 	}
 	return nil
 }

 func leaveIPv6GroupUDP(c *UDPConn, ifi *Interface, ip IP) os.Error {
 	mreq := &syscall.IPv6Mreq{}
 	copy(mreq.Multiaddr[:], ip)
 	if ifi != nil {
 		mreq.Interface = uint32(ifi.Index)
 	}
 	if err := os.NewSyscallError("setsockopt", syscall.SetsockoptIPv6Mreq(c.fd.sysfd, syscall.IPPROTO_IPV6, syscall.IPV6_LEAVE_GROUP, mreq)); err != nil {
 		return &OpError{"leaveipv6group", "udp", &IPAddr{ip}, err}
 	}
 	return nil
 }
	// 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.

	// +build darwin freebsd linux openbsd windows

	// UDP sockets

	package net

	import (
	"bytes"
	"os"
	"syscall"
	)

	func sockaddrToUDP(sa syscall.Sockaddr) Addr {
	switch sa := sa.(type) {
	case *syscall.SockaddrInet4:
	return &UDPAddr{sa.Addr[0:], sa.Port}
	case *syscall.SockaddrInet6:
	return &UDPAddr{sa.Addr[0:], sa.Port}
	}
	return nil
	}

	func (a *UDPAddr) family() int {
	if a == nil \|\| len(a.IP) <= IPv4len {
	return syscall.AF_INET
	}
	if a.IP.To4() != nil {
	return syscall.AF_INET
	}
	return syscall.AF_INET6
	}

	func (a *UDPAddr) sockaddr(family int) (syscall.Sockaddr, os.Error) {
	return ipToSockaddr(family, a.IP, a.Port)
	}

	func (a *UDPAddr) toAddr() sockaddr {
	if a == nil { // nil *UDPAddr
	return nil // nil interface
	}
	return a
	}

	// UDPConn is the implementation of the Conn and PacketConn
	// interfaces for UDP network connections.
	type UDPConn struct {
	fd *netFD
	}

	func newUDPConn(fd netFD) UDPConn { return &UDPConn{fd} }

	func (c *UDPConn) ok() bool { return c != nil && c.fd != nil }

	// Implementation of the Conn interface - see Conn for documentation.

	// Read implements the net.Conn Read method.
	func (c *UDPConn) Read(b []byte) (n int, err os.Error) {
	if !c.ok() {
	return 0, os.EINVAL
	}
	return c.fd.Read(b)
	}

	// Write implements the net.Conn Write method.
	func (c *UDPConn) Write(b []byte) (n int, err os.Error) {
	if !c.ok() {
	return 0, os.EINVAL
	}
	return c.fd.Write(b)
	}

	// Close closes the UDP connection.
	func (c *UDPConn) Close() os.Error {
	if !c.ok() {
	return os.EINVAL
	}
	err := c.fd.Close()
	c.fd = nil
	return err
	}

	// LocalAddr returns the local network address.
	func (c *UDPConn) LocalAddr() Addr {
	if !c.ok() {
	return nil
	}
	return c.fd.laddr
	}

	// RemoteAddr returns the remote network address, a *UDPAddr.
	func (c *UDPConn) RemoteAddr() Addr {
	if !c.ok() {
	return nil
	}
	return c.fd.raddr
	}

	// SetTimeout implements the net.Conn SetTimeout method.
	func (c *UDPConn) SetTimeout(nsec int64) os.Error {
	if !c.ok() {
	return os.EINVAL
	}
	return setTimeout(c.fd, nsec)
	}

	// SetReadTimeout implements the net.Conn SetReadTimeout method.
	func (c *UDPConn) SetReadTimeout(nsec int64) os.Error {
	if !c.ok() {
	return os.EINVAL
	}
	return setReadTimeout(c.fd, nsec)
	}

	// SetWriteTimeout implements the net.Conn SetWriteTimeout method.
	func (c *UDPConn) SetWriteTimeout(nsec int64) os.Error {
	if !c.ok() {
	return os.EINVAL
	}
	return setWriteTimeout(c.fd, nsec)
	}

	// SetReadBuffer sets the size of the operating system's
	// receive buffer associated with the connection.
	func (c *UDPConn) SetReadBuffer(bytes int) os.Error {
	if !c.ok() {
	return os.EINVAL
	}
	return setReadBuffer(c.fd, bytes)
	}

	// SetWriteBuffer sets the size of the operating system's
	// transmit buffer associated with the connection.
	func (c *UDPConn) SetWriteBuffer(bytes int) os.Error {
	if !c.ok() {
	return os.EINVAL
	}
	return setWriteBuffer(c.fd, bytes)
	}

	// 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 SetTimeout and SetReadTimeout.
	func (c UDPConn) ReadFromUDP(b []byte) (n int, addr UDPAddr, err os.Error) {
	if !c.ok() {
	return 0, nil, os.EINVAL
	}
	n, sa, err := c.fd.ReadFrom(b)
	switch sa := sa.(type) {
	case *syscall.SockaddrInet4:
	addr = &UDPAddr{sa.Addr[0:], sa.Port}
	case *syscall.SockaddrInet6:
	addr = &UDPAddr{sa.Addr[0:], sa.Port}
	}
	return
	}

	// ReadFrom implements the net.PacketConn ReadFrom method.
	func (c *UDPConn) ReadFrom(b []byte) (n int, addr Addr, err os.Error) {
	if !c.ok() {
	return 0, nil, os.EINVAL
	}
	n, uaddr, err := c.ReadFromUDP(b)
	return n, uaddr.toAddr(), err
	}

	// 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 SetTimeout and SetWriteTimeout.
	// On packet-oriented connections, write timeouts are rare.
	func (c UDPConn) WriteToUDP(b []byte, addr UDPAddr) (n int, err os.Error) {
	if !c.ok() {
	return 0, os.EINVAL
	}
	sa, err1 := addr.sockaddr(c.fd.family)
	if err1 != nil {
	return 0, &OpError{Op: "write", Net: "udp", Addr: addr, Error: err1}
	}
	return c.fd.WriteTo(b, sa)
	}

	// WriteTo implements the net.PacketConn WriteTo method.
	func (c *UDPConn) WriteTo(b []byte, addr Addr) (n int, err os.Error) {
	if !c.ok() {
	return 0, os.EINVAL
	}
	a, ok := addr.(*UDPAddr)
	if !ok {
	return 0, &OpError{"writeto", "udp", addr, os.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 os.Error) {
	switch net {
	case "udp", "udp4", "udp6":
	default:
	return nil, UnknownNetworkError(net)
	}
	if raddr == nil {
	return nil, &OpError{"dial", "udp", nil, errMissingAddress}
	}
	fd, e := internetSocket(net, laddr.toAddr(), raddr.toAddr(), syscall.SOCK_DGRAM, 0, "dial", sockaddrToUDP)
	if e != nil {
	return nil, e
	}
	return newUDPConn(fd), nil
	}

	// 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 os.Error) {
	switch net {
	case "udp", "udp4", "udp6":
	default:
	return nil, UnknownNetworkError(net)
	}
	if laddr == nil {
	return nil, &OpError{"listen", "udp", nil, errMissingAddress}
	}
	fd, e := internetSocket(net, laddr.toAddr(), nil, syscall.SOCK_DGRAM, 0, "dial", sockaddrToUDP)
	if e != nil {
	return nil, e
	}
	return newUDPConn(fd), nil
	}

	// BindToDevice binds a UDPConn to a network interface.
	func (c *UDPConn) BindToDevice(device string) os.Error {
	if !c.ok() {
	return os.EINVAL
	}
	c.fd.incref()
	defer c.fd.decref()
	return os.NewSyscallError("setsockopt", syscall.BindToDevice(c.fd.sysfd, device))
	}

	// File returns a copy of the underlying os.File, set to blocking mode.
	// It is the caller's responsibility to close f when finished.
	// Closing c does not affect f, and closing f does not affect c.
	func (c UDPConn) File() (f os.File, err os.Error) { return c.fd.dup() }

	// JoinGroup joins the IP multicast group named by addr on ifi,
	// which specifies the interface to join. JoinGroup uses the
	// default multicast interface if ifi is nil.
	func (c UDPConn) JoinGroup(ifi Interface, addr IP) os.Error {
	if !c.ok() {
	return os.EINVAL
	}
	ip := addr.To4()
	if ip != nil {
	return joinIPv4GroupUDP(c, ifi, ip)
	}
	return joinIPv6GroupUDP(c, ifi, addr)
	}

	// LeaveGroup exits the IP multicast group named by addr on ifi.
	func (c UDPConn) LeaveGroup(ifi Interface, addr IP) os.Error {
	if !c.ok() {
	return os.EINVAL
	}
	ip := addr.To4()
	if ip != nil {
	return leaveIPv4GroupUDP(c, ifi, ip)
	}
	return leaveIPv6GroupUDP(c, ifi, addr)
	}

	func joinIPv4GroupUDP(c UDPConn, ifi Interface, ip IP) os.Error {
	mreq := &syscall.IPMreq{Multiaddr: [4]byte{ip[0], ip[1], ip[2], ip[3]}}
	if err := setIPv4InterfaceToJoin(mreq, ifi); err != nil {
	return &OpError{"joinipv4group", "udp", &IPAddr{ip}, err}
	}
	if err := os.NewSyscallError("setsockopt", syscall.SetsockoptIPMreq(c.fd.sysfd, syscall.IPPROTO_IP, syscall.IP_ADD_MEMBERSHIP, mreq)); err != nil {
	return &OpError{"joinipv4group", "udp", &IPAddr{ip}, err}
	}
	return nil
	}

	func leaveIPv4GroupUDP(c UDPConn, ifi Interface, ip IP) os.Error {
	mreq := &syscall.IPMreq{Multiaddr: [4]byte{ip[0], ip[1], ip[2], ip[3]}}
	if err := setIPv4InterfaceToJoin(mreq, ifi); err != nil {
	return &OpError{"leaveipv4group", "udp", &IPAddr{ip}, err}
	}
	if err := os.NewSyscallError("setsockopt", syscall.SetsockoptIPMreq(c.fd.sysfd, syscall.IPPROTO_IP, syscall.IP_DROP_MEMBERSHIP, mreq)); err != nil {
	return &OpError{"leaveipv4group", "udp", &IPAddr{ip}, err}
	}
	return nil
	}

	func setIPv4InterfaceToJoin(mreq syscall.IPMreq, ifi Interface) os.Error {
	if ifi == nil {
	return nil
	}
	ifat, err := ifi.Addrs()
	if err != nil {
	return err
	}
	for _, ifa := range ifat {
	if x := ifa.(*IPAddr).IP.To4(); x != nil {
	copy(mreq.Interface[:], x)
	break
	}
	}
	if bytes.Equal(mreq.Multiaddr[:], IPv4zero) {
	return os.EINVAL
	}
	return nil
	}

	func joinIPv6GroupUDP(c UDPConn, ifi Interface, ip IP) os.Error {
	mreq := &syscall.IPv6Mreq{}
	copy(mreq.Multiaddr[:], ip)
	if ifi != nil {
	mreq.Interface = uint32(ifi.Index)
	}
	if err := os.NewSyscallError("setsockopt", syscall.SetsockoptIPv6Mreq(c.fd.sysfd, syscall.IPPROTO_IPV6, syscall.IPV6_JOIN_GROUP, mreq)); err != nil {
	return &OpError{"joinipv6group", "udp", &IPAddr{ip}, err}
	}
	return nil
	}

	func leaveIPv6GroupUDP(c UDPConn, ifi Interface, ip IP) os.Error {
	mreq := &syscall.IPv6Mreq{}
	copy(mreq.Multiaddr[:], ip)
	if ifi != nil {
	mreq.Interface = uint32(ifi.Index)
	}
	if err := os.NewSyscallError("setsockopt", syscall.SetsockoptIPv6Mreq(c.fd.sysfd, syscall.IPPROTO_IPV6, syscall.IPV6_LEAVE_GROUP, mreq)); err != nil {
	return &OpError{"leaveipv6group", "udp", &IPAddr{ip}, err}
	}
	return nil
	}