feat(mosq): Add example with two brokers synced on P2P

Broker-less two chip example which virtual private IoT
networks on MQTT protocol.

.github/workflows/mosq__build.yml

@@ -17,7 +17,8 @@ jobs:
     runs-on: ubuntu-22.04
     container: espressif/idf:${{ matrix.idf_ver }}
     env:
-      TEST_DIR: components/mosquitto/examples/broker
+      TEST_DIR: components/mosquitto/examples
+      TARGET_TEST: broker
       TARGET_TEST_DIR: build_esp32_default
     steps:
       - name: Checkout esp-protocols
@@ -29,14 +30,15 @@ jobs:
         run: |
           . ${IDF_PATH}/export.sh
           pip install idf-component-manager idf-build-apps --upgrade
-          python ci/build_apps.py ${TEST_DIR}
-          cd ${TEST_DIR}
+          python ci/build_apps.py -c ${TEST_DIR} -m components/mosquitto/.build-test-rules.yml
+          # upload only the target test artifacts
+          cd ${TEST_DIR}/${TARGET_TEST}
           ${GITHUB_WORKSPACE}/ci/clean_build_artifacts.sh `pwd`/${TARGET_TEST_DIR}
           zip -qur artifacts.zip ${TARGET_TEST_DIR}
       - uses: actions/upload-artifact@v4
         with:
           name: mosq_target_esp32_${{ matrix.idf_ver }}
-          path: ${{ env.TEST_DIR }}/artifacts.zip
+          path: ${{ env.TEST_DIR }}/${{ env.TARGET_TEST }}/artifacts.zip
           if-no-files-found: error
 
   test_mosq:

ci/check_copyright_ignore.txt

@@ -0,0 +1 @@
+components/mosquitto/examples/serverless_mqtt/components/libjuice/port/juice_random.c

components/mosquitto/.build-test-rules.yml

@@ -0,0 +1,3 @@
+components/mosquitto/examples/serverless_mqtt:
+  disable:
+    - if: IDF_TARGET not in ["esp32", "esp32s3", "esp32c3"]

components/mosquitto/examples/serverless_mqtt/CMakeLists.txt

@@ -0,0 +1,6 @@
+# The following five lines of boilerplate have to be in your project's
+# CMakeLists in this exact order for cmake to work correctly
+cmake_minimum_required(VERSION 3.16)
+
+include($ENV{IDF_PATH}/tools/cmake/project.cmake)
+project(serverless_mqtt)

components/mosquitto/examples/serverless_mqtt/README.md

@@ -0,0 +1,53 @@
+# Brokerless MQTT Example
+
+MQTT served by (two) mosquitto's running on two ESP chips.
+
+* Leverages MQTT connectivity between two private networks without cloud premisses.
+* Creates two local MQTT servers (on ESP32x's) which are being synchronized over peer to peer connection (established via ICE protocol, by [libjuice](https://github.com/paullouisageneau/libjuice)).
+
+## How it works
+
+This example needs two ESP32 chipsets, that will create two separate Wi-Fi networks (IoT networks) used for IoT devices.
+Each IoT network is served by an MQTT server (using mosquitto component).
+This example will also synchronize these two MQTT brokers, as if there was only one IoT network with one broker.
+This example creates a peer to peer connection between two chipsets to keep them synchronize. This connection utilizes libjuice (which implements a simplified ICE-UDP) to traverse NATs, which enabling direct connection between two private networks behind NATs.
+
+* Diagram
+
+![demo](serverless.png)
+
+Here's a step-by-step procedure of establishing this remote connection:
+1) Initialize and start Wi-Fi AP (for IoT networks) and Wi-Fi station (for internet connection)
+2) Start mosquitto broker on IoT network
+3) Start libjuice to gather connection candidates
+4) Synchronize using a public MQTT broker and exchange ICE descriptors
+5) Establish ICE UDP connection between the two ESP32 chipsets
+6) Start forwarding mqtt messages
+   - Each remote datagram (received from ICE-UDP channel) is re-published to the local MQTT server
+   - Each local MQTT message (received from mosquitto on_message callback) is sent in ICE-UDP datagram
+
+## How to use this example
+
+You need two ESP32 devices that support Wi-Fi station and Wi-Fi software access point.
+
+* Configure Wi-Fi credentials for both devices on both interfaces
+  * These devices would be deployed in distinct Wi-Fi environments, so the Wi-Fi station credentials would likely be different.
+  * They also create their own IoT network (on the soft-AP interface) Wi-Fi, so the AP credentials would likely be the same, suggesting the IoT networks will be keep synchronized (even though these are two distict Wi-Fi networks).
+* Choose `CONFIG_EXAMPLE_SERVERLESS_ROLE_PEER1` for one device and `CONFIG_EXAMPLE_SERVERLESS_ROLE_PEER2` for another. It's not important which device is PEER1, since the code is symmetric, but these two devices need to have different role.
+* Optionally: You can use `idf.py` `-D` and `-B` flag to keep separate build directories and sdkconfigs for these two roles
+```
+idf.py -B build1 -DSDKCONFIG=build1/sdkconfig menuconfig build flash monitor
+```
+* Flash and run the two devices and wait for them to connect and synchronize.
+* Now you can test MQTT connectivity, for example:
+  * Join PEER1 device's AP and connect to the MQTT broker with one or more clients, subscribing to one or more topics.
+  * Join PEER2 device's AP and connect to the MQTT broker with one or more clients, subscribing to one or more topics.
+  * Whenever you publish to a topic, all subscribed clients should receive the message, no matter which Wi-Fi network they're connected to.
+
+## Warning
+
+This example uses libjuice as a dependency:
+
+* libjuice (UDP Interactive Connectivity Establishment): https://github.com/paullouisageneau/libjuice
+
+which is distributed under Mozilla Public License v2.0.

components/mosquitto/examples/serverless_mqtt/components/libjuice/CMakeLists.txt

@@ -0,0 +1,44 @@
+set(LIBJUICE_VERSION "73785387eafe15c02b6a210edb10f722474e8e14")
+set(LIBJUICE_URL "https://github.com/paullouisageneau/libjuice/archive/${LIBJUICE_VERSION}.zip")
+
+set(libjuice_dir ${CMAKE_BINARY_DIR}/libjuice/libjuice-${LIBJUICE_VERSION})
+
+# Fetch the library
+if(NOT EXISTS ${libjuice_dir})
+        message(STATUS "Downloading libjuice ${LIBJUICE_VERSION}...")
+        file(DOWNLOAD ${LIBJUICE_URL} ${CMAKE_BINARY_DIR}/libjuice.zip SHOW_PROGRESS)
+        execute_process(COMMAND unzip -o ${CMAKE_BINARY_DIR}/libjuice.zip -d ${CMAKE_BINARY_DIR}/libjuice
+                WORKING_DIRECTORY ${CMAKE_BINARY_DIR})
+endif()
+
+set(JUICE_SOURCES   ${libjuice_dir}/src/addr.c
+                    ${libjuice_dir}/src/agent.c
+                    ${libjuice_dir}/src/base64.c
+                    ${libjuice_dir}/src/conn.c
+                    ${libjuice_dir}/src/conn_mux.c
+                    ${libjuice_dir}/src/conn_poll.c
+                    ${libjuice_dir}/src/conn_thread.c
+                    ${libjuice_dir}/src/const_time.c
+                    ${libjuice_dir}/src/crc32.c
+                    ${libjuice_dir}/src/hash.c
+                    ${libjuice_dir}/src/ice.c
+                    ${libjuice_dir}/src/juice.c
+                    ${libjuice_dir}/src/log.c
+                    ${libjuice_dir}/src/server.c
+                    ${libjuice_dir}/src/stun.c
+                    ${libjuice_dir}/src/timestamp.c
+                    ${libjuice_dir}/src/turn.c
+                    ${libjuice_dir}/src/udp.c
+# Use hmac from mbedtls and random numbers from esp_random:
+#                    ${libjuice_dir}/src/hmac.c
+#                    ${libjuice_dir}/src/random.c
+        )
+
+idf_component_register(SRCS     port/juice_random.c
+                                ${JUICE_SOURCES}
+                       INCLUDE_DIRS "include"  "${libjuice_dir}/include" "${libjuice_dir}/include/juice"
+                       REQUIRES esp_netif
+                       PRIV_REQUIRES sock_utils)
+
+target_compile_options(${COMPONENT_LIB} PRIVATE "-Wno-format")
+set_source_files_properties(${libjuice_dir}/src/udp.c PROPERTIES COMPILE_FLAGS -Wno-unused-variable)

components/mosquitto/examples/serverless_mqtt/components/libjuice/include/ifaddrs.h

@@ -0,0 +1,13 @@
+/*
+ * SPDX-FileCopyrightText: 2024 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Unlicense OR CC0-1.0
+ */
+#pragma once
+
+// Purpose of this header is to replace udp_sendto() to avoid name conflict with lwip
+// added here since ifaddrs.h is included from juice_udp sources
+#define udp_sendto juice_udp_sendto
+
+// other than that, let's just include the ifaddrs (from sock_utils)
+#include_next "ifaddrs.h"

components/mosquitto/examples/serverless_mqtt/components/libjuice/port/juice_random.c

@@ -0,0 +1,40 @@
+/**
+ * Copyright (c) 2020 Paul-Louis Ageneau
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+#include "esp_random.h"
+
+void juice_random(void *buf, size_t size)
+{
+    esp_fill_random(buf, size);
+}
+
+void juice_random_str64(char *buf, size_t size)
+{
+    static const char chars64[] =
+        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+    size_t i = 0;
+    for (i = 0; i + 1 < size; ++i) {
+        uint8_t byte = 0;
+        juice_random(&byte, 1);
+        buf[i] = chars64[byte & 0x3F];
+    }
+    buf[i] = '\0';
+}
+
+uint32_t juice_rand32(void)
+{
+    uint32_t r = 0;
+    juice_random(&r, sizeof(r));
+    return r;
+}
+
+uint64_t juice_rand64(void)
+{
+    uint64_t r = 0;
+    juice_random(&r, sizeof(r));
+    return r;
+}

components/mosquitto/examples/serverless_mqtt/main/CMakeLists.txt

@@ -0,0 +1,4 @@
+idf_component_register(SRCS "serverless_mqtt.c"
+                            "wifi_connect.c"
+                    INCLUDE_DIRS "."
+                    REQUIRES libjuice nvs_flash mqtt json esp_wifi)

components/mosquitto/examples/serverless_mqtt/main/Kconfig.projbuild

@@ -0,0 +1,85 @@
+menu "Example Configuration"
+
+    menu "AP Configuration"
+        comment "AP Configuration"
+
+        config EXAMPLE_AP_SSID
+            string "Wi-Fi SSID"
+            default "myssid"
+            help
+                Set the SSID of Wi-Fi ap interface.
+
+        config EXAMPLE_AP_PASSWORD
+            string "Wi-Fi Password"
+            default "12345678"
+            help
+                Set the password of Wi-Fi ap interface.
+
+    endmenu
+
+    menu "STA Configuration"
+        comment "STA Configuration"
+
+        config EXAMPLE_STA_SSID
+            string "WiFi Station SSID"
+            default "mystationssid"
+            help
+                SSID for the example's sta to connect to.
+
+        config EXAMPLE_STA_PASSWORD
+            string "WiFi Station Password"
+            default "mystationpassword"
+            help
+                WiFi station password for the example to use.
+    endmenu
+
+    config EXAMPLE_MQTT_BROKER_URI
+        string "MQTT Broker URL"
+        default "mqtt://mqtt.eclipseprojects.io"
+        help
+            URL of the mqtt broker use for synchronisation and exchanging
+            ICE connect info (description and candidates).
+
+    config EXAMPLE_MQTT_SYNC_TOPIC
+        string "MQTT topic for synchronisation"
+        default "/topic/serverless_mqtt"
+        help
+            MQTT topic used fo synchronisation.
+
+    config EXAMPLE_STUN_SERVER
+        string "Hostname of STUN server"
+        default "stun.l.google.com"
+        help
+            STUN server hostname.
+
+    config EXAMPLE_MQTT_CLIENT_STACK_SIZE
+        int "Stack size for mqtt client"
+        default 16384
+        help
+            Set stack size for the mqtt client.
+            Need more stack, since calling juice API from the handler.
+
+    config EXAMPLE_MQTT_BROKER_PORT
+        int "port for the mosquitto to listen to"
+        default 1883
+        help
+            This is a port which the local mosquitto uses.
+
+    choice EXAMPLE_SERVERLESS_ROLE
+        prompt "Choose your role"
+        default EXAMPLE_SERVERLESS_ROLE_PEER1
+        help
+            Choose either peer1 or peer2.
+            It's not very important which device is peer1
+            (peer-1 sends sync messages, peer2 listens for them)
+            It is important that we have two peers,
+            one with peer1 config, another one with peer2 config
+
+        config EXAMPLE_SERVERLESS_ROLE_PEER1
+            bool "peer1"
+
+        config EXAMPLE_SERVERLESS_ROLE_PEER2
+            bool "peer2"
+    endchoice
+
+endmenu

components/mosquitto/examples/serverless_mqtt/main/idf_component.yml

@@ -0,0 +1,5 @@
+## IDF Component Manager Manifest File
+dependencies:
+  espressif/mosquitto:
+    override_path: ../../..
+  espressif/sock_utils: "*"