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net: latmon: Add latency monitor service
Latmon service to interface with Xenomai's Latmus. Link: https://evlproject.org/core/benchmarks/#latmus-gpio-response-time Signed-off-by: Jorge Ramirez-Ortiz <[email protected]>
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‎doc/connectivity/networking/api/latmon.rst‎

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.. _latmon:
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Latmon Network Service
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######################
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.. contents::
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:local:
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:depth: 2
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Overview
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********
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Provides the functionality required for network-based latency monitoring, including socket
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management, client-server communication, and data exchange with the Latmus service running
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on the System Under Test (SUT).
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The Latmon network service is responsible for establishing and managing network
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communication between the Latmon application (running on a Zephyr-based board) and
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the Latmus service (running on the SUT).
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It uses TCP sockets for reliable communication and UDP sockets for broadcasting
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the IP address of the Latmon device.
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API Reference
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*************
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.. doxygengroup:: latmon
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Features
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********
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- **Socket Management**: Creates and manages TCP and UDP sockets for communication.
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- **Client-Server Communication**: Handles incoming connections from the Latmus service.
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- **Data Exchange**: Sends latency metrics and histogram data to the Latmus service.
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- **IP Address Broadcasting**: Broadcasts the IP address of the Latmon device to facilitate
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discovery by the Latmus service.
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- **Thread-Safe Design**: Uses Zephyr's kernel primitives (e.g., message queues and semaphores) for
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synchronization.
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Key Components
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**************
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Socket Management
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=================
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The service provides functions to create, bind, and listen on sockets.
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It also supports sending and receiving data over TCP and UDP.
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Message Queue
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=============
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A message queue (``latmon_msgq``) is used to pass messages between threads,
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ensuring thread-safe communication.
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Synchronization
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===============
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Semaphores (``latmon_done`` and ``monitor_done``) are used to synchronize the monitoring
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process and ensure proper cleanup.
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Thread Management
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=================
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The service uses Zephyr threads to handle incoming connections and manage the
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monitoring process.
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Workflow
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********
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Socket Creation
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===============
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The ``net_latmon_get_socket()`` function is called to create and configure a TCP socket to
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communicate with the Latmus service. A connection address can be specified as a paramenter to
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bind the socket to a specific interface and port.
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Connection Handling
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===================
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The ``net_latmon_connect()`` function waits for a connection from the Latmus service.
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If no connection is received within the timeout period, the service broadcasts its IP address
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using UDP and returns ``-EAGAIN``.
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If the broadcast request cannot be sent, the function returns ``-1``, and the client should quit.
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Monitoring Start
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================
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Once a connection is established, the ``net_latmon_start()`` function is called to
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start the monitoring process. This function uses a callback to calculate latency deltas
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and sends the data to the Latmus service.
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Monitoring Status
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=================
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The ``net_latmon_running()`` function can be used to check if the monitoring process is active.
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Thread Management
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=================
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The service uses Zephyr threads to handle incoming connections and manage the monitoring
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process.
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Enabling the Latmon Service
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***************************
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The following configuration option must be enabled in the :file:`prj.conf` file.
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- :kconfig:option:`CONFIG_NET_LATMON`
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The following options may be configured to customize the Latmon service:
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- :kconfig:option:`CONFIG_NET_LATMON_PORT` - Port number for the Latmon service.
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- :kconfig:option:`CONFIG_NET_LATMON_XFER_THREAD_STACK_SIZE`
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- :kconfig:option:`CONFIG_NET_LATMON_XFER_THREAD_PRIORITY`
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- :kconfig:option:`CONFIG_NET_LATMON_THREAD_STACK_SIZE`
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- :kconfig:option:`CONFIG_NET_LATMON_THREAD_PRIORITY`
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- :kconfig:option:`CONFIG_NET_LATMON_MONITOR_THREAD_STACK_SIZE`
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- :kconfig:option:`CONFIG_NET_LATMON_MONITOR_THREAD_PRIORITY`
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Example Usage
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*************
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.. code-block:: c
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#include <zephyr/net/latmon.h>
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#include <zephyr/net/socket.h>
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void main(void)
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{
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struct in_addr ip;
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int server_socket, client_socket;
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/* Create and configure the server socket */
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server_socket = net_latmon_get_socket();
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while (1) {
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/* Wait for a connection from the Latmus service */
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client_socket = net_latmon_connect(server_socket, &ip);
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if (client_socket < 0) {
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if (client_socket == -EAGAIN) {
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continue;
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}
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goto out;
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}
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/* Start the latency monitoring process */
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net_latmon_start(client_socket, measure_latency_cycles);
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}
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out:
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close(socket);
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}

‎doc/connectivity/networking/api/protocols.rst‎

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mqtt_sn
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ptp
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tftp
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latmon

‎include/zephyr/net/latmon.h‎

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/** @file
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* @brief Latency Monitor API
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*/
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/*
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* Copyright (c) 2025 Jorge A. Ramirez Ortiz <[email protected]>
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#ifndef ZEPHYR_INCLUDE_NET_LATMON_H_
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#define ZEPHYR_INCLUDE_NET_LATMON_H_
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#include <zephyr/kernel.h>
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#include <zephyr/net/net_ip.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* @brief Latency Monitor
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* @defgroup latmon Latency Monitor
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* @ingroup networking
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* @{
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*/
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/**
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* @typedef net_latmon_measure_t
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* @brief Callback function type for retrieving latency deltas.
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*
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* @param delta Pointer to store the calculated latency delta in cycles.
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* @return 0 on success, negative errno code on failure.
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*/
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typedef int (*net_latmon_measure_t)(uint32_t *delta);
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/**
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* @brief Start the latency monitor.
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*
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* @details This function starts the latency monitor, which measures
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* latency using the provided callback function to calculate deltas. Samples
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* are sent to the connected Latmus client.
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*
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* @param latmus A valid socket descriptor connected to latmus
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* @param measure_func A callback function to execute the delta calculation.
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*/
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void net_latmon_start(int latmus, net_latmon_measure_t measure_func);
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/**
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* @brief Wait for a connection from a Latmus client.
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*
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* @details This function blocks until a Latmus client connects to the
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* specified socket. Once connected, the client's IP address is stored
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* in the provided `ip` structure.
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*
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* @param socket A valid socket descriptor for listening.
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* @param ip The client's IP address.
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* @return A valid client socket descriptor connected to latmus on success,
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* negative errno code on failure.
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*
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*/
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int net_latmon_connect(int socket, struct in_addr *ip);
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/**
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* @brief Get a socket for the Latmus service.
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*
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* @details This function creates and returns a socket to wait for Latmus
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* connections
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*
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* @param ip The IP address to bind the socket to. If NULL, the socket
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* will be bound to the first available address using the build time configured
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* latmus port.
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*
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* @return A valid socket descriptor on success, negative errno code on failure.
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*/
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int net_latmon_get_socket(struct sockaddr *ip);
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/**
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* @brief Check if the latency monitor is running.
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*
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* @details This function checks whether the latency monitor is currently
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* active and running.
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*
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* @return True if the latency monitor is running, false if it is waiting for a
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* Latmus connection
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*/
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bool net_latmon_running(void);
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/**
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* @}
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*/
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#ifdef __cplusplus
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}
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#endif
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#endif /* ZEPHYR_INCLUDE_NET_LATMON_H_ */

‎subsys/net/lib/CMakeLists.txt‎

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add_subdirectory_ifdef(CONFIG_MQTT_LIB mqtt)
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add_subdirectory_ifdef(CONFIG_MQTT_SN_LIB mqtt_sn)
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add_subdirectory_ifdef(CONFIG_PTP ptp)
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add_subdirectory_ifdef(CONFIG_NET_LATMON latmon)
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add_subdirectory_ifdef(CONFIG_TFTP_LIB tftp)
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add_subdirectory_ifdef(CONFIG_NET_CONFIG_SETTINGS config)
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add_subdirectory_ifdef(CONFIG_NET_SOCKETS sockets)

‎subsys/net/lib/Kconfig‎

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source "subsys/net/lib/dns/Kconfig"
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source "subsys/net/lib/latmon/Kconfig"
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source "subsys/net/lib/mqtt/Kconfig"
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source "subsys/net/lib/mqtt_sn/Kconfig"

‎subsys/net/lib/latmon/CMakeLists.txt‎

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zephyr_library()
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zephyr_library_sources(
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latmon.c
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)

‎subsys/net/lib/latmon/Kconfig‎

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# Copyright (c) 2025 Jorge A. Ramirez-Ortiz <[email protected]>
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# SPDX-License-Identifier: Apache-2.0
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config NET_LATMON
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bool "Latency monitoring support"
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select NET_SOCKETS
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depends on NET_TCP
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help
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This option enables the latency monitoring support for Zephyr
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config NET_LATMON_PORT
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int "Latmon - Latmus communication port"
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default 2306
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help
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Specify the port number used for Latmon - Latmus communication.
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config NET_LATMON_XFER_THREAD_STACK_SIZE
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int "Stack size for the network transfer thread"
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default 8192
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help
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Specify the stack size for the network transfer thread used in latency monitoring.
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config NET_LATMON_XFER_THREAD_PRIORITY
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int "Priority for the network transfer thread"
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default 14
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help
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Specify the priority for the network transfer thread used in latency monitoring.
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config NET_LATMON_THREAD_STACK_SIZE
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int "Stack size for the Latmon thread"
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default 8192
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help
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Specify the stack size for the Latmon thread used in latency monitoring.
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config NET_LATMON_THREAD_PRIORITY
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int "Priority for the Latmon thread"
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default 14
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help
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Specify the priority for the Latmon thread used in latency monitoring.
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config NET_LATMON_MONITOR_THREAD_STACK_SIZE
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int "Stack size for the monitor thread"
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default 8192
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help
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Specify the stack size for the monitor thread used in latency monitoring.
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config NET_LATMON_MONITOR_THREAD_PRIORITY
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int "Priority for the monitor thread"
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default -16
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help
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Specify the priority for the monitor thread used in latency monitoring.
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module = LATMON
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module-dep = NET_LOG
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module-str = Latency monitoring Service
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module-help = This option enables the latency monitoring support for Zephyr
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source "subsys/net/Kconfig.template.log_config.net"

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