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).
 */

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

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

#ifndef _WIN32
#include <sys/time.h>
#include <sys/socket.h>
#include <netinet/in.h>
#else
#include <winsock2.h>
#define snprintf _snprintf
#define strcasecmp stricmp
#define strncasecmp strnicmp
#endif

#include "os.h"

#include "thread/thread.h"
#include "avl/avl.h"
#include "net/sock.h"
#include "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 "event.h"
#include "admin.h"
#include "auth.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.
*/
#define SHOUTCAST_SOURCE_AUTH 1
#define ICECAST_SOURCE_AUTH 0

typedef struct con_queue_tag {
    connection_t *con;
    struct con_queue_tag *next;
} con_queue_t;

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

static mutex_t _connection_mutex;
static volatile unsigned long _current_id = 0;
static int _initialized = 0;

volatile static con_queue_t *_queue = NULL;
static mutex_t _queue_mutex;

static thread_queue_t *_conhands = NULL;

rwlock_t _source_shutdown_rwlock;

static void *_handle_connection(void *arg);

void connection_initialize(void)
{
    if (_initialized) return;
    
    thread_mutex_create(&_connection_mutex);
    thread_mutex_create(&_queue_mutex);
    thread_mutex_create(&move_clients_mutex);
    thread_rwlock_create(&_source_shutdown_rwlock);
    thread_cond_create(&global.shutdown_cond);

    _initialized = 1;
}

void connection_shutdown(void)
{
    if (!_initialized) return;
    
    thread_cond_destroy(&global.shutdown_cond);
    thread_rwlock_destroy(&_source_shutdown_rwlock);
    thread_mutex_destroy(&_queue_mutex);
    thread_mutex_destroy(&_connection_mutex);
    thread_mutex_destroy(&move_clients_mutex);

    _initialized = 0;
}

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

    thread_mutex_lock(&_connection_mutex);
    id = _current_id++;
    thread_mutex_unlock(&_connection_mutex);

    return id;
}

connection_t *create_connection(sock_t sock, sock_t serversock, char *ip) {
    connection_t *con;
    con = (connection_t *)malloc(sizeof(connection_t));
    memset(con, 0, sizeof(connection_t));
    con->sock = sock;
    con->serversock = serversock;
    con->con_time = time(NULL);
    con->id = _next_connection_id();
    con->ip = ip;

    con->event_number = EVENT_NO_EVENT;
    con->event = NULL;

    return con;
}

static int wait_for_serversock(int timeout)
{
#ifdef HAVE_POLL
    struct pollfd ufds[MAX_LISTEN_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 -2;
    }
    else if(ret == 0) {
        return -1;
    }
    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))
                {
                    close (global.serversock[i]);
                    WARN0("Had to close a listening socket");
                }
                global.serversock[i] = -1;
            }
        }
        /* remove any closed sockets */
        for(i=0, dst=0; i < global.server_sockets; i++)
        {
            if (global.serversock[i] == -1)
                continue;
            if (i!=dst)
                global.serversock[dst] = global.serversock[i];
            dst++;
        }
        global.server_sockets = dst;
        return -1;
    }
#else
    fd_set rfds;
    struct timeval tv, *p=NULL;
    int i, ret;
    int max = -1;

    FD_ZERO(&rfds);

    for(i=0; i < global.server_sockets; i++) {
        FD_SET(global.serversock[i], &rfds);
        if(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 -2;
    }
    else if(ret == 0) {
        return -1;
    }
    else {
        for(i=0; i < global.server_sockets; i++) {
            if(FD_ISSET(global.serversock[i], &rfds))
                return global.serversock[i];
        }
        return -1; /* Should be impossible, stop compiler warnings */
    }
#endif
}

static connection_t *_accept_connection(void)
{
    int sock;
    connection_t *con;
    char *ip;
    int serversock; 

    serversock = wait_for_serversock(100);
    if(serversock < 0)
        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 >= 0) {
        con = create_connection(sock, serversock, ip);

        return con;
    }

    if (!sock_recoverable(sock_error()))
        WARN2("accept() failed with error %d: %s", sock_error(), strerror(sock_error()));
    
    free(ip);

    return NULL;
}

static void _add_connection(connection_t *con)
{
    con_queue_t *node;

    node = (con_queue_t *)malloc(sizeof(con_queue_t));
    
    thread_mutex_lock(&_queue_mutex);
    node->con = con;
    node->next = (con_queue_t *)_queue;
    _queue = node;
    thread_mutex_unlock(&_queue_mutex);
}

static void _push_thread(thread_queue_t **queue, thread_type *thread_id)
{
    /* create item */
    thread_queue_t *item = (thread_queue_t *)malloc(sizeof(thread_queue_t));
    item->thread_id = thread_id;
    item->next = NULL;


    thread_mutex_lock(&_queue_mutex);
    if (*queue == NULL) {
        *queue = item;
    } else {
        item->next = *queue;
        *queue = item;
    }
    thread_mutex_unlock(&_queue_mutex);
}

static thread_type *_pop_thread(thread_queue_t **queue)
{
    thread_type *id;
    thread_queue_t *item;

    thread_mutex_lock(&_queue_mutex);

    item = *queue;
    if (item == NULL) {
        thread_mutex_unlock(&_queue_mutex);
        return NULL;
    }

    *queue = item->next;
    item->next = NULL;
    id = item->thread_id;
    free(item);

    thread_mutex_unlock(&_queue_mutex);

    return id;
}

static void _build_pool(void)
{
    ice_config_t *config;
    int i;
    thread_type *tid;
    char buff[64];
    int threadpool_size;

    config = config_get_config();
    threadpool_size = config->threadpool_size;
    config_release_config();

    for (i = 0; i < threadpool_size; i++) {
        snprintf(buff, 64, "Connection Thread #%d", i);
        tid = thread_create(buff, _handle_connection, NULL, THREAD_ATTACHED);
        _push_thread(&_conhands, tid);
    }
}

static void _destroy_pool(void)
{
    thread_type *id;
    int i;

    i = 0;

    id = _pop_thread(&_conhands);
    while (id != NULL) {
        thread_join(id);
        id = _pop_thread(&_conhands);
    }
    INFO0("All connection threads down");
}

void connection_accept_loop(void)
{
    connection_t *con;

    _build_pool();

    while (global.running == ICE_RUNNING)
    {
        if (global . schedule_config_reread)
        {
            /* reread config file */
            INFO0("Scheduling config reread ...");

            connection_inject_event(EVENT_CONFIG_READ, NULL);
            global . schedule_config_reread = 0;
        }

        con = _accept_connection();

        if (con) {
            _add_connection(con);
        }
    }

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

    _destroy_pool();

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

static connection_t *_get_connection(void)
{
    con_queue_t *node = NULL;
    con_queue_t *oldnode = NULL;
    connection_t *con = NULL;

    /* common case, no new connections so don't bother taking locks */
    if (_queue == NULL)
        return NULL;

    thread_mutex_lock(&_queue_mutex);
    if (_queue) {
        node = (con_queue_t *)_queue;
        while (node->next) {
            oldnode = node;
            node = node->next;
        }
        
        /* node is now the last node
        ** and oldnode is the previous one, or NULL
        */
        if (oldnode) oldnode->next = NULL;
        else (_queue) = NULL;
    }
    thread_mutex_unlock(&_queue_mutex);

    if (node) {
        con = node->con;
        free(node);
    }

    return con;
}

void connection_inject_event(int eventnum, void *event_data) {
    connection_t *con = calloc(1, sizeof(connection_t));

    con->event_number = eventnum;
    con->event = event_data;

    _add_connection(con);
}


/* 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)
{
    ice_config_t *config = config_get_config();

    global_lock ();
    DEBUG1 ("sources count is %d", global.sources);

    if (global.sources < config->source_limit)
    {
        char *contenttype;
        mount_proxy *mountproxy = config->mounts;
        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)
            {
                global_unlock();
                config_release_config();
                if (source->client)
                    client_send_404 (source->client, "Content-type not supported");
                WARN1("Content-type \"%s\" not supported, dropping source", contenttype);
                return -1;
            }
        }
        else
        {
            WARN0("No content-type header, falling back to backwards compatibility mode "
                    "for icecast 1.x relays. Assuming content is mp3.");
            format_type = FORMAT_TYPE_GENERIC;
        }

        if (format_get_plugin (format_type, source) < 0)
        {
            global_unlock();
            config_release_config();
            if (source->client)
                client_send_404 (source->client, "internal format allocation problem");
            WARN1 ("plugin format failed for \"%s\"", source->mount);
            source->client = NULL;
            return -1;
        }

        global.sources++;
        global_unlock();

        /* set global settings first */
        source->queue_size_limit = config->queue_size_limit;
        source->timeout = config->source_timeout;
        source->burst_size = config->burst_size;

        /* for relays, we don't yet have a client, however we do require one
         * to retrieve the stream from.  This is created here, quite late,
         * because we can't use this client to return an error code/message,
         * so we only do this once we know we're going to accept the source.
         */
        if (source->client == NULL)
            source->client = client_create (source->con, source->parser);

        while (mountproxy)
        {
            if (strcmp (mountproxy->mountname, source->mount) == 0)
            {
                source_apply_mount (source, mountproxy);
                break;
            }
            mountproxy = mountproxy->next;
        }
        config_release_config();

        source->shutdown_rwlock = &_source_shutdown_rwlock;
        DEBUG0 ("source is ready to start");

        return 0;
    }
    WARN1("Request to add source when maximum source limit "
            "reached %d", global.sources);

    global_unlock();
    config_release_config();

    if (source->client)
        client_send_404 (source->client, "too many sources connected");

    return -1;
}


static int _check_pass_http(http_parser_t *parser, 
        char *correctuser, char *correctpass)
{
    /* This will look something like "Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==" */
    char *header = httpp_getvar(parser, "authorization");
    char *userpass, *tmp;
    char *username, *password;

    if(header == NULL)
        return 0;

    if(strncmp(header, "Basic ", 6))
        return 0;

    userpass = util_base64_decode(header+6);
    if(userpass == NULL) {
        WARN1("Base64 decode of Authorization header \"%s\" failed",
                header+6);
        return 0;
    }

    tmp = strchr(userpass, ':');
    if(!tmp) {
        free(userpass);
        return 0;
    }
    *tmp = 0;
    username = userpass;
    password = tmp+1;

    if(strcmp(username, correctuser) || strcmp(password, correctpass)) {
        free(userpass);
        return 0;
    }
    free(userpass);

    return 1;
}

static int _check_pass_icy(http_parser_t *parser, char *correctpass)
{
    char *password;

    password = httpp_getvar(parser, HTTPP_VAR_ICYPASSWORD);
    if(!password)
        return 0;

    if (strcmp(password, correctpass))
        return 0;
    else
        return 1;
}

static int _check_pass_ice(http_parser_t *parser, char *correctpass)
{
    char *password;

    password = httpp_getvar(parser, "ice-password");
    if(!password)
        password = "";

    if (strcmp(password, correctpass))
        return 0;
    else
        return 1;
}

int connection_check_admin_pass(http_parser_t *parser)
{
    int ret;
    ice_config_t *config = config_get_config();
    char *pass = config->admin_password;
    char *user = config->admin_username;
    char *protocol;

    if(!pass || !user) {
        config_release_config();
        return 0;
    }

    protocol = httpp_getvar (parser, HTTPP_VAR_PROTOCOL);
    if (protocol && strcmp (protocol, "ICY") == 0)
        ret = _check_pass_icy (parser, pass);
    else 
        ret = _check_pass_http (parser, user, pass);
    config_release_config();
    return ret;
}

int connection_check_relay_pass(http_parser_t *parser)
{
    int ret;
    ice_config_t *config = config_get_config();
    char *pass = config->relay_password;
    char *user = "relay";

    if(!pass || !user) {
        config_release_config();
        return 0;
    }

    ret = _check_pass_http(parser, user, pass);
    config_release_config();
    return ret;
}

int connection_check_source_pass(http_parser_t *parser, char *mount)
{
    ice_config_t *config = config_get_config();
    char *pass = config->source_password;
    char *user = "source";
    int ret;
    int ice_login = config->ice_login;
    char *protocol;

    mount_proxy *mountinfo = config->mounts;
    thread_mutex_lock(&(config_locks()->mounts_lock));

    while(mountinfo) {
        if(!strcmp(mountinfo->mountname, mount)) {
            if(mountinfo->password)
                pass = mountinfo->password;
            if(mountinfo->username)
                user = mountinfo->username;
            break;
        }
        mountinfo = mountinfo->next;
    }

    thread_mutex_unlock(&(config_locks()->mounts_lock));

    if(!pass) {
        WARN0("No source password set, rejecting source");
        config_release_config();
        return 0;
    }

    protocol = httpp_getvar(parser, HTTPP_VAR_PROTOCOL);
    if(protocol != NULL && !strcmp(protocol, "ICY")) {
        ret = _check_pass_icy(parser, pass);
    }
    else {
        ret = _check_pass_http(parser, user, pass);
        if(!ret && ice_login)
        {
            ret = _check_pass_ice(parser, pass);
            if(ret)
                WARN0("Source is using deprecated icecast login");
        }
    }
    config_release_config();
    return ret;
}


static void _handle_source_request(connection_t *con, 
        http_parser_t *parser, char *uri, int auth_style)
{
    client_t *client;
    source_t *source;

    client = client_create(con, parser);

    INFO1("Source logging in at mountpoint \"%s\"", uri);

    if (uri[0] != '/')
    {
        WARN0 ("source mountpoint not starting with /");
        client_send_401 (client);
        return;
    }

    if (auth_style == ICECAST_SOURCE_AUTH) {
        if (!connection_check_source_pass(parser, uri)) {
            /* We commonly get this if the source client is using the wrong
             * protocol: attempt to diagnose this and return an error
             */
            /* TODO: Do what the above comment says */
            INFO1("Source (%s) attempted to login with invalid or missing password", uri);
            client_send_401(client);
            return;
        }
    }
    source = source_reserve (uri);
    if (source)
    {
        if (auth_style == SHOUTCAST_SOURCE_AUTH) {
            source->shoutcast_compat = 1;
        }
        source->client = client;
        source->parser = parser;
        source->con = con;
        if (connection_complete_source (source) < 0)
        {
            source->client = NULL;
            source_free_source (source);
        }
        else
            thread_create ("Source Thread", source_client_thread,
                    source, THREAD_DETACHED);
    }
    else
    {
        client_send_404 (client, "Mountpoint in use");
        WARN1 ("Mountpoint %s in use", uri);
    }
}


static void _handle_stats_request(connection_t *con, 
        http_parser_t *parser, char *uri)
{
    stats_connection_t *stats;

    stats_event_inc(NULL, "stats_connections");
                
    if (!connection_check_admin_pass(parser)) {
        ERROR0("Bad password for stats connection");
        connection_close(con);
        httpp_destroy(parser);
        return;
    }
                    
    stats_event_inc(NULL, "stats");
                    
    /* create stats connection and create stats handler thread */
    stats = (stats_connection_t *)malloc(sizeof(stats_connection_t));
    stats->parser = parser;
    stats->con = con;
                    
    thread_create("Stats Connection", stats_connection, (void *)stats, THREAD_DETACHED);
}

static void _handle_get_request(connection_t *con,
        http_parser_t *parser, char *passed_uri)
{
    char *fullpath;
    client_t *client;
    int bytes;
    struct stat statbuf;
    source_t *source;
    int fileserve;
    char *host = NULL;
    int port;
    int i;
    char *serverhost = NULL;
    int serverport = 0;
    aliases *alias;
    ice_config_t *config;
    int client_limit;
    int ret;
    char *uri = passed_uri;

    config = config_get_config();
    fileserve = config->fileserve;
    if (config->hostname)
        host = strdup (config->hostname);
    port = config->port;
    for(i = 0; i < global.server_sockets; i++) {
        if(global.serversock[i] == con->serversock) {
            serverhost = config->listeners[i].bind_address;
            serverport = config->listeners[i].port;
            break;
        }
    }
    alias = config->aliases;
    client_limit = config->client_limit;

    /* there are several types of HTTP GET clients
    ** media clients, which are looking for a source (eg, URI = /stream.ogg)
    ** stats clients, which are looking for /admin/stats.xml
    ** and directory server authorizers, which are looking for /GUID-xxxxxxxx 
    ** (where xxxxxx is the GUID in question) - this isn't implemented yet.
    ** we need to handle the latter two before the former, as the latter two
    ** aren't subject to the limits.
    */
    /* TODO: add GUID-xxxxxx */

    /* Handle aliases */
    while(alias) {
        if(strcmp(uri, alias->source) == 0 && (alias->port == -1 || alias->port == serverport) && (alias->bind_address == NULL || (serverhost != NULL && strcmp(alias->bind_address, serverhost) == 0))) {
            uri = strdup (alias->destination);
            DEBUG2 ("alias has made %s into %s", passed_uri, uri);
            break;
        }
        alias = alias->next;
    }
    config_release_config();

    /* make a client */
    client = client_create(con, parser);
    stats_event_inc(NULL, "client_connections");

    /* Dispatch all admin requests */
    if ((strcmp(uri, "/admin.cgi") == 0) ||
        (strncmp(uri, "/admin/", 7) == 0)) {
        admin_handle_request(client, uri);
        if (uri != passed_uri) free (uri);
        free (host);
        return;
    }

    /* Here we are parsing the URI request to see
    ** if the extension is .xsl, if so, then process
    ** this request as an XSLT request
    */
    fullpath = util_get_path_from_normalised_uri(uri);
    if (util_check_valid_extension(fullpath) == XSLT_CONTENT) {
        /* If the file exists, then transform it, otherwise, write a 404 */
        if (stat(fullpath, &statbuf) == 0) {
            DEBUG0("Stats request, sending XSL transformed stats");
            client->respcode = 200;
            bytes = sock_write(client->con->sock, 
                    "HTTP/1.0 200 OK\r\nContent-Type: text/html\r\n\r\n");
            if(bytes > 0) client->con->sent_bytes = bytes;
            stats_transform_xslt(client, fullpath);
            client_destroy(client);
        }
        else {
            client_send_404(client, "The file you requested could not be found");
        }
        free(fullpath);
        if (uri != passed_uri) free (uri);
        free (host);
        return;
    }
    else if(fileserve && stat(fullpath, &statbuf) == 0 && 
#ifdef _WIN32
            ((statbuf.st_mode) & _S_IFREG))
#else
            S_ISREG(statbuf.st_mode)) 
#endif
    {
        fserve_client_create(client, fullpath);
        free(fullpath);
        if (uri != passed_uri) free (uri);
        free (host);
        return;
    }
    free(fullpath);

    if(strcmp(util_get_extension(uri), "m3u") == 0) {
        char *sourceuri = strdup(uri);
        char *dot = strrchr(sourceuri, '.');
        *dot = 0;
        client->respcode = 200;
        bytes = sock_write(client->con->sock,
                    "HTTP/1.0 200 OK\r\n"
                    "Content-Type: audio/x-mpegurl\r\n\r\n"
                    "http://%s:%d%s\r\n", 
                    host, 
                    port,
                    sourceuri
                    );
        if(bytes > 0) client->con->sent_bytes = bytes;
        client_destroy(client);
        free(sourceuri);
        if (uri != passed_uri) free (uri);
        free (host);
        return;
    }
    free (host);

    global_lock();
    if (global.clients >= client_limit) {
        global_unlock();
        client_send_404(client,
                "The server is already full. Try again later.");
        if (uri != passed_uri) free (uri);
        return;
    }
    global_unlock();
                    
    avl_tree_rlock(global.source_tree);
    source = source_find_mount(uri);
    if (source) {
        DEBUG0("Source found for client");

        /* The source may not be the requested source - it might have gone
         * via one or more fallbacks. We only reject it for no-mount if it's
         * the originally requested source
         */
        if(strcmp(uri, source->mount) == 0 && source->no_mount) {
            avl_tree_unlock(global.source_tree);
            client_send_404(client, "This mount is unavailable.");
            if (uri != passed_uri) free (uri);
            return;
        }
        if (source->running == 0)
        {
            avl_tree_unlock(global.source_tree);
            DEBUG0("inactive source, client dropped");
            client_send_404(client, "This mount is unavailable.");
            if (uri != passed_uri) free (uri);
            return;
        }

        /* Check for any required authentication first */
        if(source->authenticator != NULL) {
            ret = auth_check_client(source, client);
            if(ret != AUTH_OK) {
                avl_tree_unlock(global.source_tree);
                if (ret == AUTH_FORBIDDEN) {
                    INFO1("Client attempted to log multiple times to source "
                        "(\"%s\")", uri);
                    client_send_403(client);
                }
                else {
                /* If not FORBIDDEN, default to 401 */
                    INFO1("Client attempted to log in to source (\"%s\")with "
                        "incorrect or missing password", uri);
                    client_send_401(client);
                }
                if (uri != passed_uri) free (uri);
                return;
            }
        }

        /* And then check that there's actually room in the server... */
        global_lock();
        if (global.clients >= client_limit) {
            global_unlock();
            avl_tree_unlock(global.source_tree);
            client_send_404(client, 
                    "The server is already full. Try again later.");
            if (uri != passed_uri) free (uri);
            return;
        }
        /* Early-out for per-source max listeners. This gets checked again
         * by the source itself, later. This route gives a useful message to
         * the client, also.
         */
        else if(source->max_listeners != -1 && 
                source->listeners >= source->max_listeners) 
        {
            global_unlock();