IPv6 Multicasting (3) examples

Receiving multicast packets
struct ipv6_mreq mreq6;
struct in6_addr group;
struct sockaddr_storage ss;
struct sockaddr *from = (struct sockaddr *)&ss;
int fromlen;

s = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);  /* XXX use getaddrinfo instead */

/* join a multicast group */
mreq6.ipv6mr_interface = if_nametoindex(ifname);
mreq6.ipv6mr_multiaddr = group;
setsockopt(so, IPPROTO_IPV6, IPV6_JOIN_GROUP, &mreq6, sizeof(mreq6));

/* receive a multicast pakcet */
recvfrom(recvsock, (void *)recvbuf, sizeof(recvbuf), 0, from, &fromlen);

/* leave the group */
mreq6.ipv6mr_interface = if_nametoindex(ifname);
mreq6.ipv6mr_multiaddr = group;
setsockopt(so, IPPROTO_IPV6, IPV6_LEAVE_GROUP, &mreq6, sizeof(mreq6));