mirror of
https://github.com/eclipse/mosquitto.git
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113 lines
3.2 KiB
C
113 lines
3.2 KiB
C
/*
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Copyright (c) 2020 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 EDL-1.0
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Contributors:
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Roger Light - 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 modify the payload of
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* a message after it is received by the broker and before it is sent on to
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* other clients.
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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_payload_modification.c -o mosquitto_payload_modification.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_payload_modification.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 UNUSED(A) (void)(A)
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static mosquitto_plugin_id_t *mosq_pid = NULL;
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static int callback_message(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_payload;
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uint32_t new_payloadlen;
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UNUSED(event);
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UNUSED(userdata);
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/* This simply adds "hello " to the front of every payload. You can of
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* course do much more complicated message processing if needed. */
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/* Calculate the length of our new payload */
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new_payloadlen = ed->payloadlen + (uint32_t)strlen("hello ")+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_payload = mosquitto_calloc(1, new_payloadlen);
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if(new_payload == NULL){
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return MOSQ_ERR_NOMEM;
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}
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/* Print "hello " to the payload */
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snprintf(new_payload, new_payloadlen, "hello ");
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memcpy(new_payload+(uint32_t)strlen("hello "), ed->payload, ed->payloadlen);
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/* Assign the new payload and payloadlen to the event data structure. You
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* must *not* free the original payload, it will be handled by the
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* broker. */
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ed->payload = new_payload;
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ed->payloadlen = new_payloadlen;
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return MOSQ_ERR_SUCCESS;
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}
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int mosquitto_plugin_version(int supported_version_count, const int *supported_versions)
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{
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int i;
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for(i=0; i<supported_version_count; i++){
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if(supported_versions[i] == 5){
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return 5;
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}
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}
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return -1;
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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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return mosquitto_callback_register(mosq_pid, MOSQ_EVT_MESSAGE, callback_message, NULL, NULL);
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}
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int mosquitto_plugin_cleanup(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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return mosquitto_callback_unregister(mosq_pid, MOSQ_EVT_MESSAGE, callback_message, NULL);
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}
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