1// Copyright 2011 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
5package net
6
7import (
8	"os"
9	"syscall"
10)
11
12// interfaceMulticastAddrTable returns addresses for a specific
13// interface.
14func interfaceMulticastAddrTable(ifi *Interface) ([]Addr, error) {
15	tab, err := syscall.RouteRIB(syscall.NET_RT_IFLIST2, ifi.Index)
16	if err != nil {
17		return nil, os.NewSyscallError("route rib", err)
18	}
19	msgs, err := syscall.ParseRoutingMessage(tab)
20	if err != nil {
21		return nil, os.NewSyscallError("route message", err)
22	}
23	var ifmat []Addr
24	for _, m := range msgs {
25		switch m := m.(type) {
26		case *syscall.InterfaceMulticastAddrMessage:
27			if ifi.Index == int(m.Header.Index) {
28				ifma, err := newMulticastAddr(ifi, m)
29				if err != nil {
30					return nil, err
31				}
32				ifmat = append(ifmat, ifma...)
33			}
34		}
35	}
36	return ifmat, nil
37}
38
39func newMulticastAddr(ifi *Interface, m *syscall.InterfaceMulticastAddrMessage) ([]Addr, error) {
40	sas, err := syscall.ParseRoutingSockaddr(m)
41	if err != nil {
42		return nil, os.NewSyscallError("route sockaddr", err)
43	}
44	var ifmat []Addr
45	for _, sa := range sas {
46		switch sa := sa.(type) {
47		case *syscall.SockaddrInet4:
48			ifma := &IPAddr{IP: IPv4(sa.Addr[0], sa.Addr[1], sa.Addr[2], sa.Addr[3])}
49			ifmat = append(ifmat, ifma.toAddr())
50		case *syscall.SockaddrInet6:
51			ifma := &IPAddr{IP: make(IP, IPv6len)}
52			copy(ifma.IP, sa.Addr[:])
53			// NOTE: KAME based IPv6 protocol stack usually embeds
54			// the interface index in the interface-local or link-
55			// local address as the kernel-internal form.
56			if ifma.IP.IsInterfaceLocalMulticast() || ifma.IP.IsLinkLocalMulticast() {
57				ifma.IP[2], ifma.IP[3] = 0, 0
58			}
59			ifmat = append(ifmat, ifma.toAddr())
60		}
61	}
62	return ifmat, nil
63}
64