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258 lines
7.5 KiB
C
258 lines
7.5 KiB
C
/*
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Copyright (c) 2020-2021 Roger Light <roger@atchoo.org>
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All rights reserved. This program and the accompanying materials
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are made available under the terms of the Eclipse Public License 2.0
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and Eclipse Distribution License v1.0 which accompany this distribution.
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The Eclipse Public License is available at
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https://www.eclipse.org/legal/epl-2.0/
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and the Eclipse Distribution License is available at
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http://www.eclipse.org/org/documents/edl-v10.php.
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SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
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Contributors:
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Abilio Marques - initial implementation and documentation.
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*/
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/*
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* This is an *example* plugin which demonstrates how to jail a client.
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* It mounts such client topics in a subtree starting with the client id.
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* It modifies it's subscriptions and the topics of the messages destined to
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* that client. It also modifies the topics of the messages published
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* by the client.
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*
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* client | event | destination | original topic | modified topic
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* -------|-------|-------------|----------------------|--------------------
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* jailed | sub | --- | topic | ${jailed_id}/topic
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* normal | pub | jailed | ${jailed_id}/topic | topic
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* jailed | pub | normal | topic | ${jailed_id}/topic
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*
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* For simplicity of this example, all clients with id starting with "jailed"
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* will be jailed. All other clients will work as normal.
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*
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* Two jailed clients cannot interact with each other. Normal clients can interact
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* with any jailed client by publishing or subscribing to the mounted topic.
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*
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* You should be very sure of what you are doing before making use of this feature.
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*
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* Compile with:
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* gcc -I<path to mosquitto-repo/include> -fPIC -shared mosquitto_topic_jail.c -o mosquitto_topic_jail.so
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*
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* Use in config with:
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*
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* plugin /path/to/mosquitto_topic_jail.so
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*
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* Note that this only works on Mosquitto 2.0 or later.
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*/
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#include <stdio.h>
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#include <string.h>
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#include "mosquitto_broker.h"
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#include "mosquitto_plugin.h"
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#include "mosquitto.h"
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#include "mqtt_protocol.h"
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#define PLUGIN_NAME "topic-jail"
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#define PLUGIN_VERSION "1.0"
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#define UNUSED(A) (void)(A)
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MOSQUITTO_PLUGIN_DECLARE_VERSION(5);
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static mosquitto_plugin_id_t *mosq_pid = NULL;
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static bool is_jailed(const char *str)
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{
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return strncmp("jailed", str, 6) == 0;
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}
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static int callback_message_in(int event, void *event_data, void *userdata)
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{
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struct mosquitto_evt_message *ed = event_data;
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char *new_topic;
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size_t new_topic_len;
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UNUSED(event);
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UNUSED(userdata);
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const char *clientid = mosquitto_client_id(ed->client);
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if(!is_jailed(clientid)){
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/* will only modify the topic of jailed clients */
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return MOSQ_ERR_SUCCESS;
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}
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/* put the clientid on front of the topic */
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/* calculate the length of the new payload */
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new_topic_len = strlen(clientid) + sizeof('/') + strlen(ed->topic) + 1;
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/* Allocate some memory - use
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* mosquitto_calloc/mosquitto_malloc/mosquitto_strdup when allocating, to
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* allow the broker to track memory usage */
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new_topic = mosquitto_calloc(1, new_topic_len);
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if(new_topic == NULL){
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return MOSQ_ERR_NOMEM;
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}
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/* prepend the clientid to the topic */
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snprintf(new_topic, new_topic_len, "%s/%s", clientid, ed->topic);
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/* Assign the new topic to the event data structure. You
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* must *not* free the original topic, it will be handled by the
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* broker. */
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ed->topic = new_topic;
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return MOSQ_ERR_SUCCESS;
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}
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static int callback_message_out(int event, void *event_data, void *userdata)
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{
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struct mosquitto_evt_message *ed = event_data;
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size_t clientid_len;
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UNUSED(event);
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UNUSED(userdata);
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const char *clientid = mosquitto_client_id(ed->client);
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if(!is_jailed(clientid)){
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/* will only modify the topic of jailed clients */
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return MOSQ_ERR_SUCCESS;
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}
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/* remove the clientid from the front of the topic */
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clientid_len = strlen(clientid);
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if(strlen(ed->topic) <= clientid_len + 1){
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/* the topic is not long enough to contain the
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* clientid + '/' */
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return MOSQ_ERR_SUCCESS;
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}
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if(!strncmp(clientid, ed->topic, clientid_len) && ed->topic[clientid_len] == '/'){
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/* Allocate some memory - use
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* mosquitto_calloc/mosquitto_malloc/mosquitto_strdup when allocating, to
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* allow the broker to track memory usage */
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/* skip the clientid + '/' */
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char *new_topic = mosquitto_strdup(ed->topic + clientid_len + 1);
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if(new_topic == NULL){
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return MOSQ_ERR_NOMEM;
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}
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/* Assign the new topic to the event data structure. You
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* must *not* free the original topic, it will be handled by the
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* broker. */
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ed->topic = new_topic;
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}
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return MOSQ_ERR_SUCCESS;
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}
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static int callback_subscribe(int event, void *event_data, void *userdata)
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{
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struct mosquitto_evt_subscribe *ed = event_data;
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char *new_sub;
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size_t new_sub_len;
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UNUSED(event);
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UNUSED(userdata);
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const char *clientid = mosquitto_client_id(ed->client);
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if(!is_jailed(clientid)){
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/* will only modify the topic of jailed clients */
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return MOSQ_ERR_SUCCESS;
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}
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/* put the clientid on front of the topic */
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/* calculate the length of the new payload */
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new_sub_len = strlen(clientid) + sizeof('/') + strlen(ed->data.topic_filter) + 1;
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/* Allocate some memory - use
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* mosquitto_calloc/mosquitto_malloc/mosquitto_strdup when allocating, to
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* allow the broker to track memory usage */
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new_sub = mosquitto_calloc(1, new_sub_len);
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if(new_sub == NULL){
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return MOSQ_ERR_NOMEM;
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}
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/* prepend the clientid to the subscription */
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snprintf(new_sub, new_sub_len, "%s/%s", clientid, ed->data.topic_filter);
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/* Assign the new topic to the event data structure. You
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* must *not* free the original topic, it will be handled by the
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* broker. */
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ed->data.topic_filter = new_sub;
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return MOSQ_ERR_SUCCESS;
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}
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static int callback_unsubscribe(int event, void *event_data, void *userdata)
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{
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struct mosquitto_evt_unsubscribe *ed = event_data;
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char *new_sub;
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size_t new_sub_len;
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UNUSED(event);
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UNUSED(userdata);
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const char *clientid = mosquitto_client_id(ed->client);
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if(!is_jailed(clientid)){
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/* will only modify the topic of jailed clients */
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return MOSQ_ERR_SUCCESS;
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}
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/* put the clientid on front of the topic */
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/* calculate the length of the new payload */
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new_sub_len = strlen(clientid) + sizeof('/') + strlen(ed->data.topic_filter) + 1;
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/* Allocate some memory - use
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* mosquitto_calloc/mosquitto_malloc/mosquitto_strdup when allocating, to
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* allow the broker to track memory usage */
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new_sub = mosquitto_calloc(1, new_sub_len);
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if(new_sub == NULL){
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return MOSQ_ERR_NOMEM;
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}
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/* prepend the clientid to the subscription */
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snprintf(new_sub, new_sub_len, "%s/%s", clientid, ed->data.topic_filter);
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/* Assign the new topic to the event data structure. You
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* must *not* free the original topic, it will be handled by the
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* broker. */
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ed->data.topic_filter = new_sub;
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return MOSQ_ERR_SUCCESS;
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}
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int mosquitto_plugin_init(mosquitto_plugin_id_t *identifier, void **user_data, struct mosquitto_opt *opts, int opt_count)
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{
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UNUSED(user_data);
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UNUSED(opts);
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UNUSED(opt_count);
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mosq_pid = identifier;
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mosquitto_plugin_set_info(identifier, PLUGIN_NAME, PLUGIN_VERSION);
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int rc;
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rc = mosquitto_callback_register(mosq_pid, MOSQ_EVT_MESSAGE_IN, callback_message_in, NULL, NULL);
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if(rc) return rc;
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rc = mosquitto_callback_register(mosq_pid, MOSQ_EVT_MESSAGE_OUT, callback_message_out, NULL, NULL);
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if(rc) return rc;
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rc = mosquitto_callback_register(mosq_pid, MOSQ_EVT_SUBSCRIBE, callback_subscribe, NULL, NULL);
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if(rc) return rc;
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rc = mosquitto_callback_register(mosq_pid, MOSQ_EVT_UNSUBSCRIBE, callback_unsubscribe, NULL, NULL);
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return rc;
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}
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