/* Licensed to the Apache Software Foundation (ASF) under one or more

 * contributor license agreements.  See the NOTICE file distributed with

 * this work for additional information regarding copyright ownership.

 * The ASF licenses this file to You under the Apache License, Version 2.0

 * (the "License"); you may not use this file except in compliance with

 * the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

/*

 * This module is used to load Apache modules at runtime. This means that the

 * server functionality can be extended without recompiling and even without

 * taking the server down at all. Only a HUP or AP_SIG_GRACEFUL signal

 * needs to be sent to the server to reload the dynamically loaded modules.

 *

 * To use, you'll first need to build your module as a shared library, then

 * update your configuration (httpd.conf) to get the Apache core to load the

 * module at start-up.

 *

 * The easiest way to build a module as a shared library is to use the

 * `SharedModule' command in the Configuration file, instead of `AddModule'.

 * You should also change the file extension from `.o' to `.so'. So, for

 * example, to build the status module as a shared library edit Configuration

 * and change

 *   AddModule    modules/standard/mod_status.o

 * to

 *   SharedModule modules/standard/mod_status.so

 *

 * Run Configure and make. Now Apache's httpd binary will _not_ include

 * mod_status. Instead a shared object called mod_status.so will be build, in

 * the modules/standard directory. You can build most of the modules as shared

 * libraries like this.

 *

 * To use the shared module, move the .so file(s) into an appropriate

 * directory. You might like to create a directory called "modules" under you

 * server root for this (e.g. /usr/local/httpd/modules).

 *

 * Then edit your conf/httpd.conf file, and add LoadModule lines. For

 * example

 *   LoadModule  status_module   modules/mod_status.so

 *

 * The first argument is the module's structure name (look at the end of the

 * module source to find this). The second option is the path to the module

 * file, relative to the server root.  Put these directives right at the top

 * of your httpd.conf file.

 *

 * Now you can start Apache. A message will be logged at "debug" level to your

 * error_log to confirm that the module(s) are loaded (use "LogLevel debug"

 * directive to get these log messages).

 *

 * If you edit the LoadModule directives while the server is live you can get

 * Apache to re-load the modules by sending it a HUP or AP_SIG_GRACEFUL

 * signal as normal.  You can use this to dynamically change the capability

 * of your server without bringing it down.

 *

 * Because currently there is only limited builtin support in the Configure

 * script for creating the shared library files (`.so'), please consult your

 * vendors cc(1), ld(1) and dlopen(3) manpages to find out the appropriate

 * compiler and linker flags and insert them manually into the Configuration

 * file under CFLAGS_SHLIB, LDFLAGS_SHLIB and LDFLAGS_SHLIB_EXPORT.

 *

 * If you still have problems figuring out the flags both try the paper

 *     http://developer.netscape.com/library/documentation/enterprise

 *                                          /unix/svrplug.htm#1013807

 * or install a Perl 5 interpreter on your platform and then run the command

 *

 *     $ perl -V:usedl -V:ccdlflags -V:cccdlflags -V:lddlflags

 *

 * This gives you what type of dynamic loading Perl 5 uses on your platform

 * and which compiler and linker flags Perl 5 uses to create the shared object

 * files.

 *

 * Another location where you can find useful hints is the `ltconfig' script

 * of the GNU libtool 1.2 package. Search for your platform name inside the

 * various "case" constructs.

 *

 */

#include "apr.h"

#include "apr_dso.h"

#include "apr_strings.h"

#include "apr_errno.h"

#include "ap_config.h"

#include "httpd.h"

#include "http_config.h"

#include "http_log.h"

#include "http_core.h"

#include "mod_so.h"

module AP_MODULE_DECLARE_DATA so_module;

/*

 * Server configuration to keep track of actually

 * loaded modules and the corresponding module name.

 */

typedef struct so_server_conf {

    apr_array_header_t *loaded_modules;

} so_server_conf;

static void *so_sconf_create(apr_pool_t *p, server_rec *s)

{

    so_server_conf *soc;

    soc = (so_server_conf *)apr_pcalloc(p, sizeof(so_server_conf));

    soc->loaded_modules = apr_array_make(p, DYNAMIC_MODULE_LIMIT,

                                     sizeof(ap_module_symbol_t));

    return (void *)soc;

}

#ifndef NO_DLOPEN

/*

 * This is the cleanup for a loaded shared object. It unloads the module.

 * This is called as a cleanup function from the core.

 */

static apr_status_t unload_module(void *data)

{

    ap_module_symbol_t *modi = (ap_module_symbol_t*)data;

    /* only unload if module information is still existing */

    if (modi->modp == NULL)

        return APR_SUCCESS;

    /* remove the module pointer from the core structure */

    ap_remove_loaded_module(modi->modp);

    /* destroy the module information */

    modi->modp = NULL;

    modi->name = NULL;

    return APR_SUCCESS;

}

static const char *dso_load(cmd_parms *cmd, apr_dso_handle_t **modhandlep,

                            const char *filename, const char **used_filename)

{

    int retry = 0;

    const char *fullname = ap_server_root_relative(cmd->temp_pool, filename);

    char my_error[256];

    if (filename != NULL && ap_strchr_c(filename, '/') == NULL) {

        /* retry on error without path to use dlopen()'s search path */

        retry = 1;

    }

    if (fullname == NULL && !retry) {

        return apr_psprintf(cmd->temp_pool, "Invalid %s path %s",

                            cmd->cmd->name, filename);

    }

    *used_filename = fullname;

    if (apr_dso_load(modhandlep, fullname, cmd->pool) == APR_SUCCESS) {

        return NULL;

    }

    if (retry) {

        *used_filename = filename;

        if (apr_dso_load(modhandlep, filename, cmd->pool) == APR_SUCCESS)

            return NULL;

    }

    return apr_pstrcat(cmd->temp_pool, "Cannot load ", filename,

                        " into server: ",

                        apr_dso_error(*modhandlep, my_error, sizeof(my_error)),

                        NULL);

}

/*

 * This is called for the directive LoadModule and actually loads

 * a shared object file into the address space of the server process.

 */

static const char *load_module(cmd_parms *cmd, void *dummy,

                               const char *modname, const char *filename)

{

    apr_dso_handle_t *modhandle;

    apr_dso_handle_sym_t modsym;

    module *modp;

    const char *module_file;

    so_server_conf *sconf;

    ap_module_symbol_t *modi;

    ap_module_symbol_t *modie;

    int i;

    const char *error;

    /* we need to setup this value for dummy to make sure that we don't try

     * to add a non-existent tree into the build when we return to

     * execute_now.

     */

    *(ap_directive_t **)dummy = NULL;

    /*

     * check for already existing module

     * If it already exists, we have nothing to do

     * Check both dynamically-loaded modules and statically-linked modules.

     */

    sconf = (so_server_conf *)ap_get_module_config(cmd->server->module_config,

                                                &so_module);

    modie = (ap_module_symbol_t *)sconf->loaded_modules->elts;

    for (i = 0; i < sconf->loaded_modules->nelts; i++) {

        modi = &modie[i];

        if (modi->name != NULL && strcmp(modi->name, modname) == 0) {

            ap_log_perror(APLOG_MARK, APLOG_WARNING, 0, cmd->pool, APLOGNO(01574)

                          "module %s is already loaded, skipping",

                          modname);

            return NULL;

        }

    }

    for (i = 0; ap_preloaded_modules[i]; i++) {

        const char *preload_name;

        apr_size_t preload_len;

        apr_size_t thismod_len;

        modp = ap_preloaded_modules[i];

        /* make sure we're comparing apples with apples

         * make sure name of preloaded module is mod_FOO.c

         * make sure name of structure being loaded is FOO_module

         */

        if (memcmp(modp->name, "mod_", 4)) {

            continue;

        }

        preload_name = modp->name + strlen("mod_");

        preload_len = strlen(preload_name) - 2;

        if (strlen(modname) <= strlen("_module")) {

            continue;

        }

        thismod_len = strlen(modname) - strlen("_module");

        if (strcmp(modname + thismod_len, "_module")) {

            continue;

        }

        if (thismod_len != preload_len) {

            continue;

        }

        if (!memcmp(modname, preload_name, preload_len)) {

            return apr_pstrcat(cmd->pool, "module ", modname,

                               " is built-in and can't be loaded",

                               NULL);

        }

    }

    modi = apr_array_push(sconf->loaded_modules);

    modi->name = modname;

    /*

     * Load the file into the Apache address space

     */

    error = dso_load(cmd, &modhandle, filename, &module_file);

    if (error)

        return error;

    ap_log_perror(APLOG_MARK, APLOG_DEBUG, 0, cmd->pool, APLOGNO(01575)

                 "loaded module %s from %s", modname, module_file);

    /*

     * Retrieve the pointer to the module structure through the module name:

     * First with the hidden variant (prefix `AP_') and then with the plain

     * symbol name.

     */

    if (apr_dso_sym(&modsym, modhandle, modname) != APR_SUCCESS) {

        char my_error[256];

        return apr_pstrcat(cmd->pool, "Can't locate API module structure `",

                          modname, "' in file ", module_file, ": ",

                          apr_dso_error(modhandle, my_error, sizeof(my_error)),

                          NULL);

    }

    modp = (module*) modsym;

    modp->dynamic_load_handle = (apr_dso_handle_t *)modhandle;

    modi->modp = modp;

    /*

     * Make sure the found module structure is really a module structure

     *

     */

    if (modp->magic != MODULE_MAGIC_COOKIE) {

        return apr_psprintf(cmd->pool, "API module structure '%s' in file %s "

                            "is garbled - expected signature %08lx but saw "

                            "%08lx - perhaps this is not an Apache module DSO, "

                            "or was compiled for a different Apache version?",

                            modname, module_file,

                            MODULE_MAGIC_COOKIE, modp->magic);

    }

    /*

     * Add this module to the Apache core structures

     */

    error = ap_add_loaded_module(modp, cmd->pool, modname);

    if (error) {

        return error;

    }

    /*

     * Register a cleanup in the config apr_pool_t (normally pconf). When

     * we do a restart (or shutdown) this cleanup will cause the

     * shared object to be unloaded.

     */

    apr_pool_cleanup_register(cmd->pool, modi, unload_module, apr_pool_cleanup_null);

    /*

     * Finally we need to run the configuration process for the module

     */

    ap_single_module_configure(cmd->pool, cmd->server, modp);

    return NULL;

}

/*

 * This implements the LoadFile directive and loads an arbitrary

 * shared object file into the address space of the server process.

 */

static const char *load_file(cmd_parms *cmd, void *dummy, const char *filename)

{

    apr_dso_handle_t *handle;

    const char *used_file, *error;

    error = dso_load(cmd, &handle, filename, &used_file);

    if (error)

        return error;

    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, NULL, APLOGNO(01576)

                 "loaded file %s", used_file);

    return NULL;

}

static module *ap_find_loaded_module_symbol(server_rec *s, const char *modname)

{

    so_server_conf *sconf;

    ap_module_symbol_t *modi;

    ap_module_symbol_t *modie;

    int i;

    sconf = (so_server_conf *)ap_get_module_config(s->module_config,

                                                   &so_module);

    modie = (ap_module_symbol_t *)sconf->loaded_modules->elts;

    for (i = 0; i < sconf->loaded_modules->nelts; i++) {

        modi = &modie[i];

        if (modi->name != NULL && strcmp(modi->name, modname) == 0) {

            return modi->modp;

        }

    }

    return NULL;

}

static void dump_loaded_modules(apr_pool_t *p, server_rec *s)

{

    ap_module_symbol_t *modie;

    ap_module_symbol_t *modi;

    so_server_conf *sconf;

    int i;

    apr_file_t *out = NULL;

    if (!ap_exists_config_define("DUMP_MODULES")) {

        return;

    }

    apr_file_open_stdout(&out, p);

    apr_file_printf(out, "Loaded Modules:\n");

    sconf = (so_server_conf *)ap_get_module_config(s->module_config,

                                                   &so_module);

    for (i = 0; ; i++) {

        modi = &ap_prelinked_module_symbols[i];

        if (modi->name != NULL) {

            apr_file_printf(out, " %s (static)\n", modi->name);

        }

        else {

            break;

        }

    }

    modie = (ap_module_symbol_t *)sconf->loaded_modules->elts;

    for (i = 0; i < sconf->loaded_modules->nelts; i++) {

        modi = &modie[i];

        if (modi->name != NULL) {

            apr_file_printf(out, " %s (shared)\n", modi->name);

        }

    }

}

#else /* not NO_DLOPEN */

static const char *load_file(cmd_parms *cmd, void *dummy, const char *filename)

{

    ap_log_perror(APLOG_MARK, APLOG_STARTUP, 0, cmd->pool, APLOGNO(01577)

                 "WARNING: LoadFile not supported on this platform");

    return NULL;

}

static const char *load_module(cmd_parms *cmd, void *dummy,

                               const char *modname, const char *filename)

{

    ap_log_perror(APLOG_MARK, APLOG_STARTUP, 0, cmd->pool, APLOGNO(01578)

                 "WARNING: LoadModule not supported on this platform");

    return NULL;

}

#endif /* NO_DLOPEN */

static void register_hooks(apr_pool_t *p)

{

#ifndef NO_DLOPEN

    APR_REGISTER_OPTIONAL_FN(ap_find_loaded_module_symbol);

    ap_hook_test_config(dump_loaded_modules, NULL, NULL, APR_HOOK_MIDDLE);

#endif

}

static const command_rec so_cmds[] = {

    AP_INIT_TAKE2("LoadModule", load_module, NULL, RSRC_CONF | EXEC_ON_READ,

      "a module name and the name of a shared object file to load it from"),

    AP_INIT_ITERATE("LoadFile", load_file, NULL, RSRC_CONF  | EXEC_ON_READ,

      "shared object file or library to load into the server at runtime"),

    { NULL }

};

AP_DECLARE_MODULE(so) = {

   STANDARD20_MODULE_STUFF,

   NULL,                 /* create per-dir config */

   NULL,                 /* merge per-dir config */

   so_sconf_create,      /* server config */

   NULL,                 /* merge server config */

   so_cmds,              /* command apr_table_t */

   register_hooks        /* register hooks */

};