Exemplo n.º 1
0
/* This is sufficiently different from the TCP code (wrt SSL, etc) that it
 * resides in its own simpler function
 */
static int ncat_listen_dgram(int proto)
{
    struct {
        int fd;
        union sockaddr_u addr;
    } sockfd[NUM_LISTEN_ADDRS];
    int i, fdn = -1;
    int fdmax, nbytes, n, fds_ready;
    char buf[DEFAULT_UDP_BUF_LEN] = { 0 };
    char *tempbuf = NULL;
    fd_set read_fds;
    union sockaddr_u remotess;
    socklen_t sslen = sizeof(remotess.storage);
    struct timeval tv;
    struct timeval *tvp = NULL;
    unsigned int num_sockets;

    for (i = 0; i < NUM_LISTEN_ADDRS; i++) {
        sockfd[i].fd = -1;
        sockfd[i].addr.storage.ss_family = AF_UNSPEC;
    }

    FD_ZERO(&read_fds);

    /* Initialize remotess struct so recvfrom() doesn't hit the fan.. */
    zmem(&remotess.storage, sizeof(remotess.storage));
    remotess.storage.ss_family = o.af;

#ifdef WIN32
    set_pseudo_sigchld_handler(decrease_conn_count);
#else
    /* Reap on SIGCHLD */
    Signal(SIGCHLD, sigchld_handler);
    /* Ignore the SIGPIPE that occurs when a client disconnects suddenly and we
       send data to it before noticing. */
    Signal(SIGPIPE, SIG_IGN);
#endif

/* Not sure if this problem exists on Windows, but fcntl and /dev/null don't */
#ifndef WIN32
    /* Check whether stdin is closed. Because we treat this fd specially, we
     * can't risk it being reopened for an incoming connection, so we'll hold
     * it open instead. */
    if (fcntl(STDIN_FILENO, F_GETFD) == -1 && errno == EBADF) {
      logdebug("stdin is closed, attempting to reserve STDIN_FILENO\n");
      i = open("/dev/null", O_RDONLY);
      if (i >= 0 && i != STDIN_FILENO) {
        /* Oh well, we tried */
        logdebug("Couldn't reserve STDIN_FILENO\n");
        close(i);
      }
    }
#endif

    /* set for selecting udp listening sockets */
    fd_set listen_fds;
    fd_list_t listen_fdlist;
    FD_ZERO(&listen_fds);
    init_fdlist(&listen_fdlist, num_listenaddrs);

    num_sockets = 0;
    for (i = 0; i < num_listenaddrs; i++) {
        /* create the UDP listen sockets */
        sockfd[num_sockets].fd = do_listen(SOCK_DGRAM, proto, &listenaddrs[i]);
        if (sockfd[num_sockets].fd == -1) {
            if (o.debug > 0)
                logdebug("do_listen(\"%s\"): %s\n", inet_ntop_ez(&listenaddrs[i].storage, sizeof(listenaddrs[i].storage)), socket_strerror(socket_errno()));
            continue;
        }
        FD_SET(sockfd[num_sockets].fd, &listen_fds);
        add_fd(&listen_fdlist, sockfd[num_sockets].fd);
        sockfd[num_sockets].addr = listenaddrs[i];
        num_sockets++;
    }
    if (num_sockets == 0) {
        if (num_listenaddrs == 1)
            bye("Unable to open listening socket on %s: %s", inet_ntop_ez(&listenaddrs[0].storage, sizeof(listenaddrs[0].storage)), socket_strerror(socket_errno()));
        else
            bye("Unable to open any listening sockets.");
    }

    if (o.idletimeout > 0)
        tvp = &tv;

    while (1) {
        int i, j, conn_count, socket_n;

        if (fdn != -1) {
            /*remove socket descriptor which is burnt */
            FD_CLR(sockfd[fdn].fd, &listen_fds);
            rm_fd(&listen_fdlist, sockfd[fdn].fd);

            /* Rebuild the udp socket which got burnt */
            sockfd[fdn].fd = do_listen(SOCK_DGRAM, proto, &sockfd[fdn].addr);
            if (sockfd[fdn].fd == -1)
                bye("do_listen: %s", socket_strerror(socket_errno()));
            FD_SET(sockfd[fdn].fd, &listen_fds);
            add_fd(&listen_fdlist, sockfd[fdn].fd);

        }
        fdn = -1;
        socket_n = -1;
        fd_set fds;
        FD_ZERO(&fds);
        while (1) {
            /*
             * We just select to get a list of sockets which we can talk to
             */
            if (o.debug > 1)
                logdebug("selecting, fdmax %d\n", listen_fdlist.fdmax);
            fds = listen_fds;

            if (o.idletimeout > 0)
                ms_to_timeval(tvp, o.idletimeout);

            fds_ready = fselect(listen_fdlist.fdmax + 1, &fds, NULL, NULL, tvp);

            if (o.debug > 1)
                logdebug("select returned %d fds ready\n", fds_ready);

            if (fds_ready == 0)
                bye("Idle timeout expired (%d ms).", o.idletimeout);

            /*
             * Figure out which listening socket got a connection. This loop should
             * really call a function for each ready socket instead of breaking on
             * the first one.
             */
            for (i = 0; i <= listen_fdlist.fdmax && fds_ready > 0; i++) {
                /* Loop through descriptors until there is something ready */
                if (!FD_ISSET(i, &fds))
                    continue;

                /* Check each listening socket */
                for (j = 0; j < num_sockets; j++) {
                    if (i == sockfd[j].fd) {
                        if (o.debug > 1)
                            logdebug("Valid descriptor %d \n", i);
                        fdn = j;
                        socket_n = i;
                        break;
                    }
                }

                /* if we found a valid socket break */
                if (fdn != -1) {
                    fds_ready--;
                    break;
                }
            }

            /* Make sure someone connected */
            if (fdn == -1)
                continue;

            /*
             * We just peek so we can get the client connection details without
             * removing anything from the queue. Sigh.
             */
            nbytes = recvfrom(socket_n, buf, sizeof(buf), MSG_PEEK,
                              &remotess.sockaddr, &sslen);
            if (nbytes < 0) {
                loguser("%s.\n", socket_strerror(socket_errno()));
                close(socket_n);
                return 1;
            }

            /* Check conditions that might cause us to deny the connection. */
            conn_count = get_conn_count();
            if (conn_count >= o.conn_limit) {
                if (o.verbose)
                    loguser("New connection denied: connection limit reached (%d)\n", conn_count);
            } else if (!allow_access(&remotess)) {
                if (o.verbose)
                    loguser("New connection denied: not allowed\n");
            } else {
                /* Good to go. */
                break;
            }

            /* Dump the current datagram */
            nbytes = recv(socket_n, buf, sizeof(buf), 0);
            if (nbytes < 0) {
                loguser("%s.\n", socket_strerror(socket_errno()));
                close(socket_n);
                return 1;
            }
            ncat_log_recv(buf, nbytes);
        }

        if (o.debug > 1)
            logdebug("Valid Connection from %d\n", socket_n);

        conn_inc++;

        /*
         * We're using connected udp. This has the down side of only
         * being able to handle one udp client at a time
         */
        Connect(socket_n, &remotess.sockaddr, sslen);

        /* clean slate for buf */
        zmem(buf, sizeof(buf));

        /* are we executing a command? then do it */
        if (o.cmdexec) {
            struct fdinfo info = { 0 };

            info.fd = socket_n;
            if (o.keepopen)
                netrun(&info, o.cmdexec);
            else
                netexec(&info, o.cmdexec);
            continue;
        }

        FD_SET(socket_n, &read_fds);
        FD_SET(STDIN_FILENO, &read_fds);
        fdmax = socket_n;

        /* stdin -> socket and socket -> stdout */
        while (1) {
            fd_set fds;

            fds = read_fds;

            if (o.debug > 1)
                logdebug("udp select'ing\n");

            if (o.idletimeout > 0)
                ms_to_timeval(tvp, o.idletimeout);

            fds_ready = fselect(fdmax + 1, &fds, NULL, NULL, tvp);

            if (fds_ready == 0)
                bye("Idle timeout expired (%d ms).", o.idletimeout);

            if (FD_ISSET(STDIN_FILENO, &fds)) {
                nbytes = Read(STDIN_FILENO, buf, sizeof(buf));
                if (nbytes <= 0) {
                    if (nbytes < 0 && o.verbose) {
                        logdebug("Error reading from stdin: %s\n", strerror(errno));
                    } else if (nbytes == 0 && o.debug) {
                        logdebug("EOF on stdin\n");
                    }
                    FD_CLR(STDIN_FILENO, &read_fds);
                    if (nbytes < 0)
                        return 1;
                    continue;
                }
                if (o.crlf)
                    fix_line_endings((char *) buf, &nbytes, &tempbuf, &crlf_state);
                if (!o.recvonly) {
                    if (tempbuf != NULL)
                        n = send(socket_n, tempbuf, nbytes, 0);
                    else
                        n = send(socket_n, buf, nbytes, 0);
                    if (n < nbytes) {
                        loguser("%s.\n", socket_strerror(socket_errno()));
                        close(socket_n);
                        return 1;
                    }
                    ncat_log_send(buf, nbytes);
                }
                if (tempbuf != NULL) {
                    free(tempbuf);
                    tempbuf = NULL;
                }
            }
            if (FD_ISSET(socket_n, &fds)) {
                nbytes = recv(socket_n, buf, sizeof(buf), 0);
                if (nbytes < 0) {
                    loguser("%s.\n", socket_strerror(socket_errno()));
                    close(socket_n);
                    return 1;
                }
                ncat_log_recv(buf, nbytes);
                if (!o.sendonly)
                    Write(STDOUT_FILENO, buf, nbytes);
            }

            zmem(buf, sizeof(buf));
        }
    }

    return 0;
}
Exemplo n.º 2
0
/* This is sufficiently different from the TCP code (wrt SSL, etc) that it
 * resides in its own simpler function
 */
static int ncat_listen_dgram(int proto)
{
    int sockfd[NUM_LISTEN_ADDRS];
    int i, fdn = -1;
    int fdmax, nbytes, fds_ready;
    char buf[DEFAULT_UDP_BUF_LEN] = {0};
    char *tempbuf = NULL;
    fd_set read_fds;
    union sockaddr_u remotess;
    socklen_t sslen = sizeof(remotess.storage);

    for (i = 0; i < NUM_LISTEN_ADDRS; i++) {
        sockfd[i] = -1;
    }

    FD_ZERO(&read_fds);

    /* Initialize remotess struct so recvfrom() doesn't hit the fan.. */
    zmem(&remotess.storage, sizeof(remotess.storage));
    remotess.storage.ss_family = o.af;

#ifdef WIN32
    set_pseudo_sigchld_handler(decrease_conn_count);
#else
    /* Reap on SIGCHLD */
    Signal(SIGCHLD, sigchld_handler);
    /* Ignore the SIGPIPE that occurs when a client disconnects suddenly and we
       send data to it before noticing. */
    Signal(SIGPIPE, SIG_IGN);
#endif

    /* set for selecting udp listening sockets */
    fd_set listen_fds;
    fd_list_t listen_fdlist;
    FD_ZERO(&listen_fds);
    init_fdlist(&listen_fdlist, num_listenaddrs);

    for (i = 0; i < num_listenaddrs; i++) {
        /* create the UDP listen sockets */
        sockfd[i] = do_listen(SOCK_DGRAM, proto, &listenaddrs[i]);
        FD_SET(sockfd[i],&listen_fds);
        add_fd(&listen_fdlist, sockfd[i]);
    }

    while (1) {
        int i, j, conn_count, socket_n;

        if (fdn != -1) {
            /*remove socket descriptor which is burnt */
            FD_CLR(sockfd[fdn], &listen_fds);
            rm_fd(&listen_fdlist, sockfd[fdn]);

            /* Rebuild the udp socket which got burnt */
            sockfd[fdn] = do_listen(SOCK_DGRAM, proto, &listenaddrs[fdn]);
            FD_SET(sockfd[fdn],&listen_fds);
            add_fd(&listen_fdlist, sockfd[fdn]);

        }
        fdn = -1;
        socket_n = -1;
            fd_set fds;
            FD_ZERO(&fds);
        while (1) {
            /*
             * We just select to get a list of sockets which we can talk to
             */
            if (o.debug > 1)
                logdebug("selecting, fdmax %d\n", listen_fdlist.fdmax);
            fds = listen_fds;
            fds_ready = fselect(listen_fdlist.fdmax + 1, &fds, NULL, NULL, NULL);

            if (o.debug > 1)
                logdebug("select returned %d fds ready\n", fds_ready);


            /*
             * Figure out which listening socket got a connection. This loop should
             * really call a function for each ready socket instead of breaking on
             * the first one.
             */
            for (i = 0; i <= listen_fdlist.fdmax && fds_ready >0; i++) {
                /* Loop through descriptors until there is something ready */
                if (!FD_ISSET(i, &fds))
                    continue;

                /* Check each listening socket */
                for (j = 0; j < num_listenaddrs; j++) {
                    if (i == sockfd[j]) {
                        if (o.debug >1)
                            logdebug("Valid descriptor %d \n", i);
                        fdn = j;
                        socket_n = i;
                        break;
                    }
                }

                /* if we found a valid socket break */
                if (fdn != -1) {
                    fds_ready--;
                    break;
                }
            }

            /* Make sure someone connected */
            if (fdn == -1)
                continue;

            /*
             * We just peek so we can get the client connection details without
             * removing anything from the queue. Sigh.
             */
            nbytes = Recvfrom(socket_n, buf, sizeof(buf), MSG_PEEK,
                              &remotess.sockaddr, &sslen);

            /* Check conditions that might cause us to deny the connection. */
            conn_count = get_conn_count();
            if (conn_count >= o.conn_limit) {
                if (o.verbose)
                    loguser("New connection denied: connection limit reached (%d)\n", conn_count);
            } else if (!allow_access(&remotess)) {
                if (o.verbose)
                    loguser("New connection denied: not allowed\n");
            } else {
                /* Good to go. */
                break;
            }

            /* Dump the current datagram */
            Recv(socket_n, buf, sizeof(buf), 0);
        }

        if (o.debug > 1)
            logdebug("Valid Connection from %d\n", socket_n);

        conn_inc++;

        /*
         * We're using connected udp. This has the down side of only
         * being able to handle one udp client at a time
         */
        Connect(socket_n, &remotess.sockaddr, sslen);

        /* clean slate for buf */
        zmem(buf, sizeof(buf));

        /* are we executing a command? then do it */
        if (o.cmdexec) {
            struct fdinfo info = { 0 };

            info.fd = socket_n;
            if (o.keepopen)
                netrun(&info, o.cmdexec);
            else
                netexec(&info, o.cmdexec);
            continue;
        }

        FD_SET(socket_n, &read_fds);
        FD_SET(STDIN_FILENO, &read_fds);
        fdmax = socket_n;

        /* stdin -> socket and socket -> stdout */
        while (1) {
            fd_set fds;

            fds = read_fds;

            if (o.debug > 1)
                logdebug("udp select'ing\n");

            fds_ready = fselect(fdmax + 1, &fds, NULL, NULL, NULL);

            if (FD_ISSET(STDIN_FILENO, &fds)) {
                nbytes = Read(STDIN_FILENO, buf, sizeof(buf));
                if (nbytes < 0) {
                    loguser("%s.\n", strerror(errno));
                    return 1;
                } else if (nbytes == 0) {
                    return 0;
                }
                if (o.crlf)
                    fix_line_endings((char *) buf, &nbytes, &tempbuf, &crlf_state);
                if (!o.recvonly) {
                    if (tempbuf != NULL)
                        send(socket_n, tempbuf, nbytes, 0);
                    else
                        send(socket_n, buf, nbytes, 0);
                }
                if (tempbuf != NULL) {
                    free(tempbuf);
                    tempbuf = NULL;
                }
            }
            if (FD_ISSET(socket_n, &fds)) {
                nbytes = recv(socket_n, buf, sizeof(buf), 0);
                if (nbytes < 0) {
                    loguser("%s.\n", socket_strerror(socket_errno()));
                    close(socket_n);
                    return 1;
                }
                if (!o.sendonly)
                    Write(STDOUT_FILENO, buf, nbytes);
            }

            zmem(buf, sizeof(buf));
        }
    }

    return 0;
}
Exemplo n.º 3
0
static int ncat_listen_stream(int proto)
{
    int rc, i, fds_ready;
    fd_set listen_fds;
    struct timeval tv;
    struct timeval *tvp = NULL;
    unsigned int num_sockets;

    /* clear out structs */
    FD_ZERO(&master_readfds);
    FD_ZERO(&master_writefds);
    FD_ZERO(&master_broadcastfds);
    FD_ZERO(&listen_fds);
#ifdef HAVE_OPENSSL
    FD_ZERO(&sslpending_fds);
#endif
    zmem(&client_fdlist, sizeof(client_fdlist));
    zmem(&broadcast_fdlist, sizeof(broadcast_fdlist));

#ifdef WIN32
    set_pseudo_sigchld_handler(decrease_conn_count);
#else
    /* Reap on SIGCHLD */
    Signal(SIGCHLD, sigchld_handler);
    /* Ignore the SIGPIPE that occurs when a client disconnects suddenly and we
       send data to it before noticing. */
    Signal(SIGPIPE, SIG_IGN);
#endif

#ifdef HAVE_OPENSSL
    if (o.ssl)
        setup_ssl_listen();
#endif

/* Not sure if this problem exists on Windows, but fcntl and /dev/null don't */
#ifndef WIN32
    /* Check whether stdin is closed. Because we treat this fd specially, we
     * can't risk it being reopened for an incoming connection, so we'll hold
     * it open instead. */
    if (fcntl(STDIN_FILENO, F_GETFD) == -1 && errno == EBADF) {
      logdebug("stdin is closed, attempting to reserve STDIN_FILENO\n");
      rc = open("/dev/null", O_RDONLY);
      if (rc >= 0 && rc != STDIN_FILENO) {
        /* Oh well, we tried */
        logdebug("Couldn't reserve STDIN_FILENO\n");
        close(rc);
      }
    }
#endif

    /* We need a list of fds to keep current fdmax. The second parameter is a
       number added to the supplied connection limit, that will compensate
       maxfds for the added by default listen and stdin sockets. */
    init_fdlist(&client_fdlist, sadd(o.conn_limit, num_listenaddrs + 1));

    for (i = 0; i < NUM_LISTEN_ADDRS; i++)
        listen_socket[i] = -1;

    num_sockets = 0;
    for (i = 0; i < num_listenaddrs; i++) {
        /* setup the main listening socket */
        listen_socket[num_sockets] = do_listen(SOCK_STREAM, proto, &listenaddrs[i]);
        if (listen_socket[num_sockets] == -1) {
            if (o.debug > 0)
                logdebug("do_listen(\"%s\"): %s\n", inet_ntop_ez(&listenaddrs[i].storage, sizeof(listenaddrs[i].storage)), socket_strerror(socket_errno()));
            continue;
        }

        /* Make our listening socket non-blocking because there are timing issues
         * which could cause us to block on accept() even though select() says it's
         * readable.  See UNPv1 2nd ed, p422 for more.
         */
        unblock_socket(listen_socket[num_sockets]);

        /* setup select sets and max fd */
        FD_SET(listen_socket[num_sockets], &master_readfds);
        add_fd(&client_fdlist, listen_socket[num_sockets]);

        FD_SET(listen_socket[num_sockets], &listen_fds);

        num_sockets++;
    }
    if (num_sockets == 0) {
        if (num_listenaddrs == 1)
            bye("Unable to open listening socket on %s: %s", inet_ntop_ez(&listenaddrs[0].storage, sizeof(listenaddrs[0].storage)), socket_strerror(socket_errno()));
        else
            bye("Unable to open any listening sockets.");
    }

    add_fd(&client_fdlist, STDIN_FILENO);

    init_fdlist(&broadcast_fdlist, o.conn_limit);

    if (o.idletimeout > 0)
        tvp = &tv;

    while (1) {
        /* We pass these temporary descriptor sets to fselect, since fselect
           modifies the sets it receives. */
        fd_set readfds = master_readfds, writefds = master_writefds;
        struct fdinfo *fdi = NULL;

        if (o.debug > 1)
            logdebug("selecting, fdmax %d\n", client_fdlist.fdmax);

        if (o.debug > 1 && o.broker)
            logdebug("Broker connection count is %d\n", get_conn_count());

        if (o.idletimeout > 0)
            ms_to_timeval(tvp, o.idletimeout);

        fds_ready = fselect(client_fdlist.fdmax + 1, &readfds, &writefds, NULL, tvp);

        if (o.debug > 1)
            logdebug("select returned %d fds ready\n", fds_ready);

        if (fds_ready == 0)
            bye("Idle timeout expired (%d ms).", o.idletimeout);

        /*
         * FIXME: optimize this loop to look only at the fds in the fd list,
         * doing it this way means that if you have one descriptor that is very
         * large, say 500, and none close to it, that you'll loop many times for
         * nothing.
         */
        for (i = 0; i <= client_fdlist.fdmax && fds_ready > 0; i++) {
            /* Loop through descriptors until there's something to read */
            if (!FD_ISSET(i, &readfds) && !FD_ISSET(i, &writefds))
                continue;

            if (o.debug > 1)
                logdebug("fd %d is ready\n", i);

#ifdef HAVE_OPENSSL
            /* Is this an ssl socket pending a handshake? If so handle it. */
            if (o.ssl && FD_ISSET(i, &sslpending_fds)) {
                FD_CLR(i, &master_readfds);
                FD_CLR(i, &master_writefds);
                fdi = get_fdinfo(&client_fdlist, i);
                ncat_assert(fdi != NULL);
                switch (ssl_handshake(fdi)) {
                case NCAT_SSL_HANDSHAKE_COMPLETED:
                    /* Clear from sslpending_fds once ssl is established */
                    FD_CLR(i, &sslpending_fds);
                    post_handle_connection(*fdi);
                    break;
                case NCAT_SSL_HANDSHAKE_PENDING_WRITE:
                    FD_SET(i, &master_writefds);
                    break;
                case NCAT_SSL_HANDSHAKE_PENDING_READ:
                    FD_SET(i, &master_readfds);
                    break;
                case NCAT_SSL_HANDSHAKE_FAILED:
                default:
                    SSL_free(fdi->ssl);
                    Close(fdi->fd);
                    FD_CLR(i, &sslpending_fds);
                    FD_CLR(i, &master_readfds);
                    rm_fd(&client_fdlist, i);
                    /* Are we in single listening mode(without -k)? If so
                       then we should quit also. */
                    if (!o.keepopen && !o.broker)
                        return 1;
                    --conn_inc;
                    break;
                }
            } else
#endif
            if (FD_ISSET(i, &listen_fds)) {
                /* we have a new connection request */
                handle_connection(i);
            } else if (i == STDIN_FILENO) {
                if (o.broker) {
                    read_and_broadcast(i);
                } else {
                    /* Read from stdin and write to all clients. */
                    rc = read_stdin();
                    if (rc == 0) {
                        if (o.proto != IPPROTO_TCP || (o.proto == IPPROTO_TCP && o.sendonly)) {
                            /* There will be nothing more to send. If we're not
                               receiving anything, we can quit here. */
                            return 0;
                        }
                        if (!o.noshutdown) shutdown_sockets(SHUT_WR);
                    }
                    if (rc < 0)
                        return 1;
                }
            } else if (!o.sendonly) {
                if (o.broker) {
                    read_and_broadcast(i);
                } else {
                    /* Read from a client and write to stdout. */
                    rc = read_socket(i);
                    if (rc <= 0 && !o.keepopen)
                        return rc == 0 ? 0 : 1;
                }
            }

            fds_ready--;
        }
    }

    return 0;
}
Exemplo n.º 4
0
static int ncat_listen_stream(int proto)
{
    int rc, i, fds_ready;
    fd_set listen_fds;

    /* clear out structs */
    FD_ZERO(&master_readfds);
    FD_ZERO(&master_writefds);
    FD_ZERO(&master_broadcastfds);
    FD_ZERO(&listen_fds);
#ifdef HAVE_OPENSSL
    FD_ZERO(&sslpending_fds);
#endif
    zmem(&client_fdlist, sizeof(client_fdlist));
    zmem(&broadcast_fdlist, sizeof(broadcast_fdlist));

#ifdef WIN32
    set_pseudo_sigchld_handler(decrease_conn_count);
#else
    /* Reap on SIGCHLD */
    Signal(SIGCHLD, sigchld_handler);
    /* Ignore the SIGPIPE that occurs when a client disconnects suddenly and we
       send data to it before noticing. */
    Signal(SIGPIPE, SIG_IGN);
#endif

#ifdef HAVE_OPENSSL
    if (o.ssl)
        setup_ssl_listen();
#endif

    /* We need a list of fds to keep current fdmax. The second parameter is a
       number added to the supplied connection limit, that will compensate
       maxfds for the added by default listen and stdin sockets. */
    init_fdlist(&client_fdlist, sadd(o.conn_limit, num_listenaddrs + 1));

    for (i = 0; i < NUM_LISTEN_ADDRS; i++)
        listen_socket[i] = -1;

    for (i = 0; i < num_listenaddrs; i++) {
        /* setup the main listening socket */
        listen_socket[i] = do_listen(SOCK_STREAM, proto, &listenaddrs[i]);

        /* Make our listening socket non-blocking because there are timing issues
         * which could cause us to block on accept() even though select() says it's
         * readable.  See UNPv1 2nd ed, p422 for more.
         */
        unblock_socket(listen_socket[i]);

        /* setup select sets and max fd */
        FD_SET(listen_socket[i], &master_readfds);
        add_fd(&client_fdlist, listen_socket[i]);

        FD_SET(listen_socket[i], &listen_fds);
    }
    add_fd(&client_fdlist, STDIN_FILENO);

    init_fdlist(&broadcast_fdlist, o.conn_limit);

    while (1) {
        /* We pass these temporary descriptor sets to fselect, since fselect
           modifies the sets it receives. */
        fd_set readfds = master_readfds, writefds = master_writefds;
        struct fdinfo *fdi = NULL;

        if (o.debug > 1)
            logdebug("selecting, fdmax %d\n", client_fdlist.fdmax);

        if (o.debug > 1 && o.broker)
            logdebug("Broker connection count is %d\n", get_conn_count());

        fds_ready = fselect(client_fdlist.fdmax + 1, &readfds, &writefds, NULL, NULL);

        if (o.debug > 1)
            logdebug("select returned %d fds ready\n", fds_ready);

        /*
         * FIXME: optimize this loop to look only at the fds in the fd list,
         * doing it this way means that if you have one descriptor that is very
         * large, say 500, and none close to it, that you'll loop many times for
         * nothing.
         */
        for (i = 0; i <= client_fdlist.fdmax && fds_ready > 0; i++) {
            /* Loop through descriptors until there's something to read */
            if (!FD_ISSET(i, &readfds) && !FD_ISSET(i, &writefds))
                continue;

            if (o.debug > 1)
                logdebug("fd %d is ready\n", i);

#ifdef HAVE_OPENSSL
            /* Is this an ssl socket pending a handshake? If so handle it. */
            if (o.ssl && FD_ISSET(i, &sslpending_fds)) {
                FD_CLR(i, &master_readfds);
                FD_CLR(i, &master_writefds);
                fdi = get_fdinfo(&client_fdlist, i);
                switch(ssl_handshake(fdi)){
                case NCAT_SSL_HANDSHAKE_COMPLETED:
                    /* Clear from sslpending_fds once ssl is established */
                    FD_CLR(i, &sslpending_fds);
                    rm_fd(&client_fdlist, i);
                    post_handle_connection(*fdi);
                    break;
                case NCAT_SSL_HANDSHAKE_PENDING_WRITE:
                    FD_SET(i, &master_writefds);
                    break;
                case NCAT_SSL_HANDSHAKE_PENDING_READ:
                    FD_SET(i, &master_readfds);
                    break;
                case NCAT_SSL_HANDSHAKE_FAILED:
                default:
                    SSL_free(fdi->ssl);
                    Close(fdi->fd);
                    FD_CLR(i, &sslpending_fds);
                    FD_CLR(i, &master_readfds);
                    rm_fd(&client_fdlist, i);
                    /* Are we in single listening mode(without -k)? If so
                       then we should quit also. */
                    if (!o.keepopen && !o.broker)
                        return 1;
                    --conn_inc;
                    break;
                }
            } else
#endif
            if (FD_ISSET(i, &listen_fds)) {
                /* we have a new connection request */
                handle_connection(i);
            } else if (i == STDIN_FILENO) {
                if(o.broker) {
                    read_and_broadcast(i);
                }else {
                    /* Read from stdin and write to all clients. */
                    rc = read_stdin();
                    if (rc == 0 && o.sendonly)
                        /* There will be nothing more to send. If we're not
                           receiving anything, we can quit here. */
                        return 0;
                    if (rc < 0)
                        return 1;
                }
            } else if (!o.sendonly) {
                if(o.broker) {
                    read_and_broadcast(i);
                }else {
                    /* Read from a client and write to stdout. */
                    rc = read_socket(i);
                    if (rc <= 0 && !o.keepopen)
                        return rc == 0 ? 0 : 1;
                }
            }

            fds_ready--;
        }
    }

    return 0;
}