int mcast_join_source_group(int sockfd, const SA *src, socklen_t srclen,
    const SA *grp, socklen_t grplen,
    const char *ifname, u_int ifindex)
{
#ifdef MCAST_JOIN_SOURCE_GROUP
    struct group_source_req req;
    if (ifindex > 0) {
        req.gsr_interface = ifindex;
    } else if (ifname != NULL) {
        if ( (req.gsr_interface = if_nametoindex(ifname)) == 0) {
            errno = ENXIO;    /* i/f name not found */
            return(-1);
        }
    } else {
        req.gsr_interface = 0;
　  }
    if (grplen > sizeof(req.gsr_group) || srclen > sizeof(req.gsr_source)) {
        errno = EINVAL;
        return -1;
    }
    memcpy(&req.gsr_group, grp, grplen);
    memcpy(&req.gsr_source, src, srclen);
    return (setsockopt(sockfd, family_to_level(grp->sa_family),MCAST_JOIN_SOURCE_GROUP, &req, sizeof(req)));
#else
    switch (grp->sa_family) {
#ifdef IP_ADD_SOURCE_MEMBERSHIP
    case AF_INET: {
        struct ip_mreq_source    mreq;
        struct ifreq            ifreq;

        memcpy(&mreq.imr_multiaddr,
               &((struct sockaddr_in *) grp)->sin_addr,
               sizeof(struct in_addr));
        memcpy(&mreq.imr_sourceaddr,
               &((struct sockaddr_in *) src)->sin_addr,
               sizeof(struct in_addr));

        if (ifindex > 0) {
            if (if_indextoname(ifindex, ifreq.ifr_name) == NULL) {
                errno = ENXIO;    /* i/f index not found */
                return(-1);
            }
            goto doioctl;
        } else if (ifname != NULL) {
            strncpy(ifreq.ifr_name, ifname, IFNAMSIZ);
            doioctl:
            if (ioctl(sockfd, SIOCGIFADDR, &ifreq) < 0)
                return(-1);
            memcpy(&mreq.imr_interface,
                   &((struct sockaddr_in *) &ifreq.ifr_addr)->sin_addr,
                   sizeof(struct in_addr));
        } else
            mreq.imr_interface.s_addr = htonl(INADDR_ANY);

        return(setsockopt(sockfd, IPPROTO_IP, IP_ADD_SOURCE_MEMBERSHIP,
                          &mreq, sizeof(mreq)));
    }
#endif

#ifdef    IPV6
    case AF_INET6: /* IPv6 source-specific API is MCAST_JOIN_SOURCE_GROUP */
#endif
    default:
        errno = EAFNOSUPPORT;
        return(-1);
    }
#endif
}