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("routerib", err)
18	}
19	msgs, err := syscall.ParseRoutingMessage(tab)
20	if err != nil {
21		return nil, os.NewSyscallError("parseroutingmessage", 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				if ifma != nil {
33					ifmat = append(ifmat, ifma)
34				}
35			}
36		}
37	}
38	return ifmat, nil
39}
40
41func newMulticastAddr(ifi *Interface, m *syscall.InterfaceMulticastAddrMessage) (*IPAddr, error) {
42	sas, err := syscall.ParseRoutingSockaddr(m)
43	if err != nil {
44		return nil, os.NewSyscallError("parseroutingsockaddr", err)
45	}
46	switch sa := sas[syscall.RTAX_IFA].(type) {
47	case *syscall.SockaddrInet4:
48		return &IPAddr{IP: IPv4(sa.Addr[0], sa.Addr[1], sa.Addr[2], sa.Addr[3])}, nil
49	case *syscall.SockaddrInet6:
50		ifma := IPAddr{IP: make(IP, IPv6len)}
51		copy(ifma.IP, sa.Addr[:])
52		// NOTE: KAME based IPv6 protcol stack usually embeds
53		// the interface index in the interface-local or
54		// link-local address as the kernel-internal form.
55		if ifma.IP.IsInterfaceLocalMulticast() || ifma.IP.IsLinkLocalMulticast() {
56			ifma.IP[2], ifma.IP[3] = 0, 0
57		}
58		return &ifma, nil
59	default:
60		return nil, nil
61	}
62}
63