mcast_block_source函数

#include    <errno.h>
#include    <sys/socket.h>

#define     SA    struct sockaddr

int mcast_block_source(int sockfd, const SA *src, 
    socklen_t srclen,const SA *grp, socklen_t grplen)
{
#ifdef MCAST_BLOCK_SOURCE
    struct group_source_req req;
    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_BLOCK_SOURCE, &req, sizeof(req)));
#else
    switch (grp->sa_family) {
#ifdef IP_BLOCK_SOURCE
        case AF_INET: {
            struct ip_mreq_source    mreq;

            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));
            mreq.imr_interface.s_addr = htonl(INADDR_ANY);

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

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