connection.c

/* Icecast
 *
 * This program is distributed under the GNU General Public License, version 2.
 * A copy of this license is included with this source.
 *
 * Copyright 2000-2004, Jack Moffitt <jack@xiph.org,
 *                      Michael Smith <msmith@xiph.org>,
 *                      oddsock <oddsock@xiph.org>,
 *                      Karl Heyes <karl@xiph.org>
 *                      and others (see AUTHORS for details).
 * Copyright 2011,      Dave 'justdave' Miller <justdave@mozilla.com>,
 * Copyright 2011-2014, Philipp "ph3-der-loewe" Schafft <lion@lion.leolix.org>,
 */

/* -*- c-basic-offset: 4; indent-tabs-mode: nil; -*- */
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#ifdef HAVE_POLL
#include <sys/poll.h>
#endif
#include <sys/types.h>

#ifndef _WIN32
#include <sys/socket.h>
#include <netinet/in.h>
#else
#include <winsock2.h>
#endif

#include "compat.h"

#include "common/thread/thread.h"
#include "common/avl/avl.h"
#include "common/net/sock.h"
#include "common/httpp/httpp.h"

#include "cfgfile.h"
#include "global.h"
#include "util.h"
#include "connection.h"
#include "refbuf.h"
#include "client.h"
#include "stats.h"
#include "logging.h"
#include "xslt.h"
#include "fserve.h"
#include "sighandler.h"

#include "yp.h"
#include "source.h"
#include "format.h"
#include "format_mp3.h"
#include "admin.h"
#include "auth.h"
#include "matchfile.h"

#define CATMODULE "connection"

/* Two different major types of source authentication.
   Shoutcast style is used only by the Shoutcast DSP
   and is a crazy version of HTTP.  It looks like :
     Source Client -> Connects to port + 1
     Source Client -> sends encoder password (plaintext)\r\n
     Icecast -> reads encoder password, if ok, sends OK2\r\n, else disconnects
     Source Client -> reads OK2\r\n, then sends http-type request headers
                      that contain the stream details (icy-name, etc..)
     Icecast -> reads headers, stores them
     Source Client -> starts sending MP3 data
     Source Client -> periodically updates metadata via admin.cgi call

   Icecast auth style uses HTTP and Basic Authorization.
*/

typedef struct client_queue_tag {
    client_t *client;
    int offset;
    int stream_offset;
    int shoutcast;
    char *shoutcast_mount;
    struct client_queue_tag *next;
} client_queue_t;

typedef struct _thread_queue_tag {
    thread_type *thread_id;
    struct _thread_queue_tag *next;
} thread_queue_t;

static spin_t _connection_lock; // protects _current_id, _con_queue, _con_queue_tail
static volatile unsigned long _current_id = 0;
static int _initialized = 0;

static volatile client_queue_t *_req_queue = NULL, **_req_queue_tail = &_req_queue;
static volatile client_queue_t *_con_queue = NULL, **_con_queue_tail = &_con_queue;
static int ssl_ok;
#ifdef HAVE_OPENSSL
static SSL_CTX *ssl_ctx;
#endif

/* filtering client connection based on IP */
static matchfile_t *banned_ip, *allowed_ip;

rwlock_t _source_shutdown_rwlock;

static void _handle_connection(void);

void connection_initialize(void)
{
    if (_initialized)
        return;

    thread_spin_create (&_connection_lock);
    thread_mutex_create(&move_clients_mutex);
    thread_rwlock_create(&_source_shutdown_rwlock);
    thread_cond_create(&global.shutdown_cond);
    _req_queue = NULL;
    _req_queue_tail = &_req_queue;
    _con_queue = NULL;
    _con_queue_tail = &_con_queue;

    _initialized = 1;
}

void connection_shutdown(void)
{
    if (!_initialized)
        return;

#ifdef HAVE_OPENSSL
    SSL_CTX_free (ssl_ctx);
#endif
    matchfile_release(banned_ip);
    matchfile_release(allowed_ip);
 
    thread_cond_destroy(&global.shutdown_cond);
    thread_rwlock_destroy(&_source_shutdown_rwlock);
    thread_spin_destroy (&_connection_lock);
    thread_mutex_destroy(&move_clients_mutex);

    _initialized = 0;
}

static unsigned long _next_connection_id(void)
{
    unsigned long id;

    thread_spin_lock(&_connection_lock);
    id = _current_id++;
    thread_spin_unlock(&_connection_lock);

    return id;
}


#ifdef HAVE_OPENSSL
static void get_ssl_certificate(ice_config_t *config)
{
    SSL_METHOD *method;
    long ssl_opts;
    config->tls_ok = ssl_ok = 0;

    SSL_load_error_strings(); /* readable error messages */
    SSL_library_init(); /* initialize library */

    method = SSLv23_server_method();
    ssl_ctx = SSL_CTX_new(method);
    ssl_opts = SSL_CTX_get_options(ssl_ctx);
#ifdef SSL_OP_NO_COMPRESSION
    SSL_CTX_set_options(ssl_ctx, ssl_opts|SSL_OP_NO_SSLv2|SSL_OP_NO_SSLv3|SSL_OP_NO_COMPRESSION);
#else
    SSL_CTX_set_options(ssl_ctx, ssl_opts|SSL_OP_NO_SSLv2|SSL_OP_NO_SSLv3);
#endif

    do {
        if (config->cert_file == NULL)
            break;
        if (SSL_CTX_use_certificate_chain_file (ssl_ctx, config->cert_file) <= 0) {
            ICECAST_LOG_WARN("Invalid cert file %s", config->cert_file);
            break;
        }
        if (SSL_CTX_use_PrivateKey_file (ssl_ctx, config->cert_file, SSL_FILETYPE_PEM) <= 0) {
            ICECAST_LOG_WARN("Invalid private key file %s", config->cert_file);
            break;
        }
        if (!SSL_CTX_check_private_key (ssl_ctx)) {
            ICECAST_LOG_ERROR("Invalid %s - Private key does not match cert public key", config->cert_file);
            break;
        }
        if (SSL_CTX_set_cipher_list(ssl_ctx, config->cipher_list) <= 0) {
            ICECAST_LOG_WARN("Invalid cipher list: %s", config->cipher_list);
        }
        config->tls_ok = ssl_ok = 1;
        ICECAST_LOG_INFO("Certificate found at %s", config->cert_file);
        ICECAST_LOG_INFO("Using ciphers %s", config->cipher_list);
        return;
    } while (0);
    ICECAST_LOG_INFO("No TLS capability on any configured ports");
}


/* handlers for reading and writing a connection_t when there is ssl
 * configured on the listening port
 */
static int connection_read_ssl(connection_t *con, void *buf, size_t len)
{
    int bytes = SSL_read(con->ssl, buf, len);

    if (bytes < 0) {
        switch (SSL_get_error(con->ssl, bytes)) {
            case SSL_ERROR_WANT_READ:
            case SSL_ERROR_WANT_WRITE:
            return -1;
        }
        con->error = 1;
    }
    return bytes;
}

static int connection_send_ssl(connection_t *con, const void *buf, size_t len)
{
    int bytes = SSL_write (con->ssl, buf, len);

    if (bytes < 0) {
        switch (SSL_get_error(con->ssl, bytes)){
            case SSL_ERROR_WANT_READ:
            case SSL_ERROR_WANT_WRITE:
                return -1;
        }
        con->error = 1;
    } else {
        con->sent_bytes += bytes;
    }
    return bytes;
}
#else

/* SSL not compiled in, so at least log it */
static void get_ssl_certificate(ice_config_t *config)
{
    ssl_ok = 0;
    ICECAST_LOG_INFO("No TLS capability. "
                     "Rebuild Icecast with openSSL support to enable this.");
}
#endif /* HAVE_OPENSSL */


/* handlers (default) for reading and writing a connection_t, no encrpytion
 * used just straight access to the socket
 */
static int connection_read(connection_t *con, void *buf, size_t len)
{
    int bytes = sock_read_bytes(con->sock, buf, len);
    if (bytes == 0)
        con->error = 1;
    if (bytes == -1 && !sock_recoverable(sock_error()))
        con->error = 1;
    return bytes;
}

static int connection_send(connection_t *con, const void *buf, size_t len)
{
    int bytes = sock_write_bytes(con->sock, buf, len);
    if (bytes < 0) {
        if (!sock_recoverable(sock_error()))
            con->error = 1;
    } else {
        con->sent_bytes += bytes;
    }
    return bytes;
}


/* return 0 if the passed ip address is not to be handled by icecast, non-zero otherwise */
static int accept_ip_address(char *ip) {
    if (matchfile_match(banned_ip, ip) > 0) {
        ICECAST_LOG_DEBUG("%s is banned", ip);
        return 0;
    }

    if (matchfile_match(allowed_ip, ip) > 0) {
        ICECAST_LOG_DEBUG("%s is allowed", ip);
        return 1;
    } else if (allowed_ip) {
        /* we are not on allow list but there is one, so reject */
        ICECAST_LOG_DEBUG("%s is not allowed", ip);
        return 0;
    }

    /* default: allow */
    return 1;
}


connection_t *connection_create (sock_t sock, sock_t serversock, char *ip)
{
    connection_t *con;
    con = (connection_t *)calloc(1, sizeof(connection_t));
    if (con) {
        con->sock       = sock;
        con->serversock = serversock;
        con->con_time   = time(NULL);
        con->id         = _next_connection_id();
        con->ip         = ip;
        con->read       = connection_read;
        con->send       = connection_send;
    }

    return con;
}

/* prepare connection for interacting over a SSL connection
 */
void connection_uses_ssl(connection_t *con)
{
#ifdef HAVE_OPENSSL
    if (con->ssl)
        return;

    con->read = connection_read_ssl;
    con->send = connection_send_ssl;
    con->ssl = SSL_new(ssl_ctx);
    SSL_set_accept_state(con->ssl);
    SSL_set_fd(con->ssl, con->sock);
#endif
}

ssize_t connection_read_bytes(connection_t *con, void *buf, size_t len)
{
    return con->read(con, buf, len);
}

static sock_t wait_for_serversock(int timeout)
{
#ifdef HAVE_POLL
    struct pollfd ufds [global.server_sockets];
    int i, ret;

    for(i=0; i < global.server_sockets; i++) {
        ufds[i].fd = global.serversock[i];
        ufds[i].events = POLLIN;
        ufds[i].revents = 0;
    }

    ret = poll(ufds, global.server_sockets, timeout);
    if(ret < 0) {
        return SOCK_ERROR;
    } else if(ret == 0) {
        return SOCK_ERROR;
    } else {
        int dst;
        for(i=0; i < global.server_sockets; i++) {
            if(ufds[i].revents & POLLIN)
                return ufds[i].fd;
            if(ufds[i].revents & (POLLHUP|POLLERR|POLLNVAL)) {
                if (ufds[i].revents & (POLLHUP|POLLERR)) {
                    sock_close (global.serversock[i]);
                    ICECAST_LOG_WARN("Had to close a listening socket");
                }
                global.serversock[i] = SOCK_ERROR;
            }
        }
        /* remove any closed sockets */
        for(i=0, dst=0; i < global.server_sockets; i++) {
            if (global.serversock[i] == SOCK_ERROR)
            continue;
            if (i!=dst)
            global.serversock[dst] = global.serversock[i];
            dst++;
        }
        global.server_sockets = dst;
        return SOCK_ERROR;
    }
#else
    fd_set rfds;
    struct timeval tv, *p=NULL;
    int i, ret;
    sock_t max = SOCK_ERROR;

    FD_ZERO(&rfds);

    for(i=0; i < global.server_sockets; i++) {
        FD_SET(global.serversock[i], &rfds);
        if (max == SOCK_ERROR || global.serversock[i] > max)
            max = global.serversock[i];
    }

    if(timeout >= 0) {
        tv.tv_sec = timeout/1000;
        tv.tv_usec = (timeout % 1000) * 1000;
        p = &tv;
    }

    ret = select(max+1, &rfds, NULL, NULL, p);
    if(ret < 0) {
        return SOCK_ERROR;
    } else if(ret == 0) {
        return SOCK_ERROR;
    } else {
        for(i=0; i < global.server_sockets; i++) {
            if(FD_ISSET(global.serversock[i], &rfds))
                return global.serversock[i];
        }
        return SOCK_ERROR; /* Should be impossible, stop compiler warnings */
    }
#endif
}

static connection_t *_accept_connection(int duration)
{
    sock_t sock, serversock;
    char *ip;

    serversock = wait_for_serversock (duration);
    if (serversock == SOCK_ERROR)
        return NULL;

    /* malloc enough room for a full IP address (including ipv6) */
    ip = (char *)malloc(MAX_ADDR_LEN);

    sock = sock_accept(serversock, ip, MAX_ADDR_LEN);
    if (sock != SOCK_ERROR) {
        connection_t *con = NULL;
        /* Make any IPv4 mapped IPv6 address look like a normal IPv4 address */
        if (strncmp(ip, "::ffff:", 7) == 0)
            memmove(ip, ip+7, strlen (ip+7)+1);

        if (accept_ip_address(ip))
            con = connection_create(sock, serversock, ip);
        if (con)
            return con;
        sock_close(sock);
    } else {
        if (!sock_recoverable(sock_error())) {
            ICECAST_LOG_WARN("accept() failed with error %d: %s", sock_error(), strerror(sock_error()));
            thread_sleep(500000);
        }
    }
    free(ip);
    return NULL;
}


/* add client to connection queue. At this point some header information
 * has been collected, so we now pass it onto the connection thread for
 * further processing
 */
static void _add_connection(client_queue_t *node)
{
    thread_spin_lock(&_connection_lock);
    *_con_queue_tail = node;
    _con_queue_tail = (volatile client_queue_t **) &node->next;
    thread_spin_unlock(&_connection_lock);
}


/* this returns queued clients for the connection thread. headers are
 * already provided, but need to be parsed.
 */
static client_queue_t *_get_connection(void)
{
    client_queue_t *node = NULL;

    thread_spin_lock(&_connection_lock);

    if (_con_queue){
        node = (client_queue_t *)_con_queue;
        _con_queue = node->next;
        if (_con_queue == NULL)
            _con_queue_tail = &_con_queue;
        node->next = NULL;
    }

    thread_spin_unlock(&_connection_lock);
    return node;
}


/* run along queue checking for any data that has come in or a timeout */
static void process_request_queue (void)
{
    client_queue_t **node_ref = (client_queue_t **)&_req_queue;
    ice_config_t *config = config_get_config();
    int timeout = config->header_timeout;
    config_release_config();

    while (*node_ref) {
        client_queue_t *node = *node_ref;
        client_t *client = node->client;
        int len = PER_CLIENT_REFBUF_SIZE - 1 - node->offset;
        char *buf = client->refbuf->data + node->offset;

        if (len > 0) {
            if (client->con->con_time + timeout <= time(NULL)) {
                len = 0;
            } else {
                len = client_read_bytes(client, buf, len);
            }
        }

        if (len > 0) {
            int pass_it = 1;
            char *ptr;

            /* handle \n, \r\n and nsvcap which for some strange reason has
             * EOL as \r\r\n */
            node->offset += len;
            client->refbuf->data[node->offset] = '\000';
            do {
                if (node->shoutcast == 1) {
                    /* password line */
                    if (strstr (client->refbuf->data, "\r\r\n") != NULL)
                        break;
                    if (strstr (client->refbuf->data, "\r\n") != NULL)
                        break;
                    if (strstr (client->refbuf->data, "\n") != NULL)
                        break;
                }
                /* stream_offset refers to the start of any data sent after the
                 * http style headers, we don't want to lose those */
                ptr = strstr(client->refbuf->data, "\r\r\n\r\r\n");
                if (ptr) {
                    node->stream_offset = (ptr+6) - client->refbuf->data;
                    break;
                }
                ptr = strstr(client->refbuf->data, "\r\n\r\n");
                if (ptr) {
                    node->stream_offset = (ptr+4) - client->refbuf->data;
                    break;
                }
                ptr = strstr(client->refbuf->data, "\n\n");
                if (ptr) {
                    node->stream_offset = (ptr+2) - client->refbuf->data;
                    break;
                }
                pass_it = 0;
            } while (0);

            if (pass_it) {
                if ((client_queue_t **)_req_queue_tail == &(node->next))
                    _req_queue_tail = (volatile client_queue_t **)node_ref;
                *node_ref = node->next;
                node->next = NULL;
                _add_connection(node);
                continue;
            }
        } else {
            if (len == 0 || client->con->error) {
                if ((client_queue_t **)_req_queue_tail == &node->next)
                    _req_queue_tail = (volatile client_queue_t **)node_ref;
                *node_ref = node->next;
                client_destroy(client);
                free(node);
                continue;
            }
        }
        node_ref = &node->next;
    }
    _handle_connection();
}


/* add node to the queue of requests. This is where the clients are when
 * initial http details are read.
 */
static void _add_request_queue(client_queue_t *node)
{
    *_req_queue_tail = node;
    _req_queue_tail = (volatile client_queue_t **)&node->next;
}

static client_queue_t *create_client_node(client_t *client)
{
    client_queue_t *node = calloc (1, sizeof (client_queue_t));
    ice_config_t *config;
    listener_t *listener;

    if (!node)
        return NULL;

    node->client = client;

    config = config_get_config();
    listener = config_get_listen_sock(config, client->con);

    if (listener) {
        if (listener->shoutcast_compat)
            node->shoutcast = 1;
        if (listener->ssl && ssl_ok)
            connection_uses_ssl(client->con);
        if (listener->shoutcast_mount)
            node->shoutcast_mount = strdup(listener->shoutcast_mount);
    }

    config_release_config();

    return node;
}

void connection_queue(connection_t *con)
{
    client_queue_t *node;
    client_t *client = NULL;

    global_lock();
    if (client_create(&client, con, NULL) < 0) {
        global_unlock();
        client_send_error(client, 403, 1, "Icecast connection limit reached");
        /* don't be too eager as this is an imposed hard limit */
        thread_sleep(400000);
        return;
    }

    /* setup client for reading incoming http */
    client->refbuf->data[PER_CLIENT_REFBUF_SIZE-1] = '\000';

    if (sock_set_blocking(client->con->sock, 0) || sock_set_nodelay(client->con->sock)) {
        global_unlock();
        ICECAST_LOG_WARN("Failed to set tcp options on client connection, dropping");
        client_destroy(client);
        return;
    }
    node = create_client_node(client);
    global_unlock();

    if (node == NULL) {
        client_destroy(client);
        return;
    }

    _add_request_queue(node);
    stats_event_inc(NULL, "connections");
}

void connection_accept_loop(void)
{
    connection_t *con;
    ice_config_t *config;
    int duration = 300;

    config = config_get_config();
    get_ssl_certificate(config);
    config_release_config();

    while (global.running == ICECAST_RUNNING) {
        con = _accept_connection (duration);

        if (con) {
            connection_queue(con);
            duration = 5;
        } else {
            if (_req_queue == NULL)
                duration = 300; /* use longer timeouts when nothing waiting */
        }
        process_request_queue();
    }

    /* Give all the other threads notification to shut down */
    thread_cond_broadcast(&global.shutdown_cond);

    /* wait for all the sources to shutdown */
    thread_rwlock_wlock(&_source_shutdown_rwlock);
    thread_rwlock_unlock(&_source_shutdown_rwlock);
}


/* Called when activating a source. Verifies that the source count is not
 * exceeded and applies any initial parameters.
 */
int connection_complete_source(source_t *source, int response)
{
    ice_config_t *config;

    global_lock();
    ICECAST_LOG_DEBUG("sources count is %d", global.sources);

    config = config_get_config();
    if (global.sources < config->source_limit) {
        const char *contenttype;
        mount_proxy *mountinfo;
        format_type_t format_type;

        /* setup format handler */
        contenttype = httpp_getvar (source->parser, "content-type");
        if (contenttype != NULL) {
            format_type = format_get_type(contenttype);

            if (format_type == FORMAT_ERROR) {
                config_release_config();
                global_unlock();
                if (response) {
                    client_send_error(source->client, 403, 1, "Content-type not supported");
                    source->client = NULL;
                }
                ICECAST_LOG_WARN("Content-type \"%s\" not supported, dropping source", contenttype);
                return -1;
            }
        } else if (source->parser->req_type == httpp_req_put) {
            config_release_config();
            global_unlock();
            if (response) {
                client_send_error(source->client, 403, 1, "No Content-type given");
                source->client = NULL;
            }
            ICECAST_LOG_ERROR("Content-type not given in PUT request, dropping source");
            return -1;
        } else {
            ICECAST_LOG_ERROR("No content-type header, falling back to backwards compatibility mode "
                    "for icecast 1.x relays. Assuming content is mp3. This behaviour is deprecated "
                    "and the source client will NOT work with future Icecast versions!");
            format_type = FORMAT_TYPE_GENERIC;
        }

        if (format_get_plugin (format_type, source) < 0) {
            global_unlock();
            config_release_config();
            if (response) {
                client_send_error(source->client, 403, 1, "internal format allocation problem");
                source->client = NULL;
            }
            ICECAST_LOG_WARN("plugin format failed for \"%s\"", source->mount);
            return -1;
        }

        global.sources++;
        stats_event_args(NULL, "sources", "%d", global.sources);
        global_unlock();

        source->running = 1;
        mountinfo = config_find_mount(config, source->mount, MOUNT_TYPE_NORMAL);
        source_update_settings(config, source, mountinfo);
        config_release_config();
        slave_rebuild_mounts();

        source->shutdown_rwlock = &_source_shutdown_rwlock;
        ICECAST_LOG_DEBUG("source is ready to start");

        return 0;
    }
    ICECAST_LOG_WARN("Request to add source when maximum source limit "
        "reached %d", global.sources);

    global_unlock();
    config_release_config();

    if (response) {
        client_send_error(source->client, 403, 1, "too many sources connected");
        source->client = NULL;
    }

    return -1;
}

static inline void source_startup(client_t *client, const char *uri)
{
    source_t *source;
    source = source_reserve(uri);

    if (source) {
        source->client = client;
        source->parser = client->parser;
        source->con = client->con;
        if (connection_complete_source(source, 1) < 0) {
            source_clear_source(source);
            source_free_source(source);
            return;
        }
        client->respcode = 200;
        if (client->protocol == ICECAST_PROTOCOL_SHOUTCAST) {
            client->respcode = 200;
            /* send this non-blocking but if there is only a partial write
             * then leave to header timeout */
            sock_write (client->con->sock, "OK2\r\nicy-caps:11\r\n\r\n");
            source->shoutcast_compat = 1;
            source_client_callback(client, source);
        } else {
            refbuf_t *ok = refbuf_new(PER_CLIENT_REFBUF_SIZE);
            const char *expectcontinue;
            const char *transfer_encoding;
            int status_to_send = 200;

            transfer_encoding = httpp_getvar(source->parser, "transfer-encoding");
            if (transfer_encoding && strcasecmp(transfer_encoding, HTTPP_ENCODING_IDENTITY) != 0) {
                client->encoding = httpp_encoding_new(transfer_encoding);
                if (!client->encoding) {
                    client_send_error(client, 501, 1, "Unimplemented");
                    return;
                }
            }

            /* For PUT support we check for 100-continue and send back a 100 to stay in spec */
            expectcontinue = httpp_getvar (source->parser, "expect");

            if (expectcontinue != NULL) {
#ifdef HAVE_STRCASESTR
                if (strcasestr (expectcontinue, "100-continue") != NULL)
#else
                ICECAST_LOG_WARN("OS doesn't support case insensitive substring checks...");
                if (strstr (expectcontinue, "100-continue") != NULL)
#endif
                {
                    status_to_send = 100;
                }
            }

            client->respcode = 200;
            util_http_build_header(ok->data, PER_CLIENT_REFBUF_SIZE, 0, 0, status_to_send, NULL, NULL, NULL, "", NULL, client);
            ok->len = strlen(ok->data);
            /* we may have unprocessed data read in, so don't overwrite it */
            ok->associated = client->refbuf;
            client->refbuf = ok;
            fserve_add_client_callback(client, source_client_callback, source);
        }
    } else {
        client_send_error(client, 403, 1, "Mountpoint in use");
        ICECAST_LOG_WARN("Mountpoint %s in use", uri);
    }
}

/* only called for native icecast source clients */
static void _handle_source_request(client_t *client, const char *uri)
{
    ICECAST_LOG_INFO("Source logging in at mountpoint \"%s\" from %s as role %s",
        uri, client->con->ip, client->role);

    if (uri[0] != '/') {
        ICECAST_LOG_WARN("source mountpoint not starting with /");
        client_send_error(client, 400, 1, "source mountpoint not starting with /");
        return;
    }

    source_startup(client, uri);
}


static void _handle_stats_request(client_t *client, char *uri)
{
    stats_event_inc(NULL, "stats_connections");

    client->respcode = 200;
    snprintf (client->refbuf->data, PER_CLIENT_REFBUF_SIZE,
        "HTTP/1.0 200 OK\r\n\r\n");
    client->refbuf->len = strlen(client->refbuf->data);
    fserve_add_client_callback(client, stats_callback, NULL);
}

/* if 0 is returned then the client should not be touched, however if -1
 * is returned then the caller is responsible for handling the client
 */
static int __add_listener_to_source(source_t *source, client_t *client)
{
    size_t loop = 10;

    do {
        ICECAST_LOG_DEBUG("max on %s is %ld (cur %lu)", source->mount,
            source->max_listeners, source->listeners);
        if (source->max_listeners == -1)
            break;
        if (source->listeners < (unsigned long)source->max_listeners)
            break;

        if (loop && source->fallback_when_full && source->fallback_mount) {
            source_t *next = source_find_mount (source->fallback_mount);
            if (!next) {
                ICECAST_LOG_ERROR("Fallback '%s' for full source '%s' not found",
                    source->mount, source->fallback_mount);
                return -1;
            }
            ICECAST_LOG_INFO("stream full, trying %s", next->mount);
            source = next;
            loop--;
            continue;
        }
        /* now we fail the client */
        return -1;
    } while (1);

    client->write_to_client = format_generic_write_to_client;
    client->check_buffer = format_check_http_buffer;
    client->refbuf->len = PER_CLIENT_REFBUF_SIZE;
    memset(client->refbuf->data, 0, PER_CLIENT_REFBUF_SIZE);

    /* lets add the client to the active list */
    avl_tree_wlock(source->pending_tree);
    avl_insert(source->pending_tree, client);
    avl_tree_unlock(source->pending_tree);

    if (source->running == 0 && source->on_demand) {
        /* enable on-demand relay to start, wake up the slave thread */
        ICECAST_LOG_DEBUG("kicking off on-demand relay");
        source->on_demand_req = 1;
    }
    ICECAST_LOG_DEBUG("Added client to %s", source->mount);
    return 0;
}