net: sntp: implement SNTP server library

include/zephyr/net/sntp_server.h

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2025 Lothar Felten <lothar.felten@gmail.com>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @file
+ * @brief SNTP (Simple Network Time Protocol, RFC5905) Server
+ */
+
+#ifndef ZEPHYR_INCLUDE_NET_SNTP_SERVER_H_
+#define ZEPHYR_INCLUDE_NET_SNTP_SERVER_H_
+
+#include <zephyr/posix/time.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief Simple Network Time Protocol Server API
+ * @defgroup sntp SNTP
+ * @since 4.3
+ * @version 0.1.0
+ * @ingroup networking
+ * @{
+ */
+
+/**
+ * @brief Set SNTP time source id and stratum
+ * @param refid the reference ID (RFC5905, Fig.12)
+ * @param stratum indicating the stratum of the clock source
+ * @param precision an exponent of two, where the resulting value is the precision
+ * of the system clock in seconds.
+ *
+ * @return 0 if ok, <0 if error.
+ */
+int sntp_server_clock_source(unsigned char *refid, unsigned char stratum, char precision);
+
+#ifdef __cplusplus
+}
+#endif
+
+/**
+ * @}
+ */
+
+#endif /* ZEPHYR_INCLUDE_NET_SNTP_SERVER_H_ */

samples/net/cloud/aws_iot_mqtt/prj.conf

@@ -39,6 +39,7 @@ CONFIG_NET_DHCPV4=y
 
 # SNTP
 CONFIG_SNTP=y
+CONFIG_SNTP_CLIENT=y
 CONFIG_NET_CONFIG_CLOCK_SNTP_INIT=y
 CONFIG_NET_CONFIG_SNTP_INIT_SERVER="0.pool.ntp.org"
 

samples/net/sockets/sntp_server/CMakeLists.txt

@@ -0,0 +1,10 @@
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(sntp_server)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})
+
+include(${ZEPHYR_BASE}/samples/net/common/common.cmake)

samples/net/sockets/sntp_server/Kconfig

@@ -0,0 +1,3 @@
+# Copyright (c) 2025 Lothar Felten <lothar.felten@gmail.com>
+
+source "Kconfig.zephyr"

samples/net/sockets/sntp_server/README.rst

@@ -0,0 +1,33 @@
+.. zephyr:code-sample:: sntp-server
+ :name: SNTP server
+ :relevant-api: bsd_sockets sntp
+
+ SNTP to get the current time from the host.
+
+Overview
+********
+
+This sample is a simple SNTP server implementation.
+The demo will query a SNTP server and set the system time and date.
+When the local clock is set, the system will respond to SNTP queries
+on port 123, the default SNTP port.
+You can query the server using a SNTP client, such as ntpdig or sntp.
+
+This demo assumes that the platform of choice has networking support,
+some adjustments to the configuration may be needed.
+
+Building and Running
+********************
+
+See the `net-tools`_ project for more details.
+
+This sample can be built and executed on QEMU or native_sim board as
+described in :ref:`networking_with_qemu`.
+
+.. _`net-tools`: https://github.com/zephyrproject-rtos/net-tools
+
+Wi-Fi
+=====
+
+The IPv4 Wi-Fi support can be enabled in the sample with
+:ref:`Wi-Fi snippet <snippet-wifi-ipv4>`.

samples/net/sockets/sntp_server/overlay-nsos.conf

@@ -0,0 +1,11 @@
+# Copyright (c) 2025 Embeint Inc
+
+CONFIG_ETH_NATIVE_TAP=n
+CONFIG_NET_DRIVERS=y
+CONFIG_NET_SOCKETS=y
+CONFIG_NET_SOCKETS_OFFLOAD=y
+CONFIG_NET_NATIVE_OFFLOADED_SOCKETS=y
+CONFIG_HEAP_MEM_POOL_SIZE=4096
+
+# IPv6 DAD requires lower level network interface access, below exposed socket-level access
+CONFIG_NET_IPV6_DAD=n

samples/net/sockets/sntp_server/prj.conf

@@ -0,0 +1,35 @@
+# General config
+CONFIG_REQUIRES_FULL_LIBC=y
+CONFIG_POSIX_API=y
+
+# Networking config
+CONFIG_NETWORKING=y
+CONFIG_NET_IPV4=y
+CONFIG_NET_IPV6=y
+CONFIG_NET_UDP=y
+CONFIG_NET_SHELL=y
+
+# Sockets
+CONFIG_NET_SOCKETS=y
+CONFIG_NET_SOCKETS_SERVICE=y
+
+# Network driver config
+CONFIG_TEST_RANDOM_GENERATOR=y
+
+# Network address config
+CONFIG_NET_CONFIG_SETTINGS=y
+CONFIG_NET_CONFIG_NEED_IPV4=y
+CONFIG_NET_DHCPV4=y
+CONFIG_NET_CONFIG_NEED_IPV6=y
+
+# SNTP
+CONFIG_SNTP=y
+CONFIG_DNS_RESOLVER=y
+CONFIG_SNTP_CLIENT=y
+CONFIG_SNTP_SERVER=y
+
+CONFIG_MAIN_STACK_SIZE=2048
+# Network debug config
+CONFIG_LOG=y
+CONFIG_NET_LOG=y
+CONFIG_SNTP_LOG_LEVEL_DBG=y

samples/net/sockets/sntp_server/sample.yaml

@@ -0,0 +1,20 @@
+sample:
+ description: SNTP server sample
+ name: sntp_server
+common:
+ harness: net
+ tags: net
+tests:
+ sample.net.sockets.sntp_server:
+ platform_allow:
+ - qemu_x86
+ - native_sim
+ sample.net.sockets.sntp_server.native:
+ platform_allow:
+ - native_sim
+ integration_platforms:
+ - native_sim
+ extra_configs:
+ - CONFIG_NATIVE_SIM_SLOWDOWN_TO_REAL_TIME=y
+ extra_args:
+ - EXTRA_CONF_FILE="overlay-nsos.conf"

samples/net/sockets/sntp_server/src/main.c

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2025 Lothar Felten <lothar.felten@gmail.com>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/logging/log.h>
+LOG_MODULE_REGISTER(sntp_demo, LOG_LEVEL_DBG);
+
+#include <zephyr/net/sntp_server.h>
+#include <zephyr/net/sntp.h>
+#include "net_sample_common.h"
+
+int main(void)
+{
+struct sntp_time t;
+struct timespec tp;
+int ret;
+
+LOG_INF("waiting for network");
+wait_for_network();
+ret = sntp_simple("ptbtime1.ptb.de", SYS_FOREVER_MS, &t);
+if (ret < 0) {
+LOG_ERR("SNTP client error (%d)", ret);
+return 0;
+}
+tp.tv_sec = t.seconds;
+tp.tv_nsec = t.fraction / 1000;
+ret = sys_clock_settime(SYS_CLOCK_REALTIME, &tp);
+if (ret < 0) {
+LOG_ERR("SNTP unable to set system time (%d)", ret);
+return 0;
+}
+
+sntp_server_clock_source("XDEV", 2, -6);
+return 0;
+}

subsys/net/lib/sntp/CMakeLists.txt

@@ -1,6 +1,13 @@
 # SPDX-License-Identifier: Apache-2.0
 
-zephyr_sources(
+zephyr_sources_ifdef(CONFIG_SNTP
  sntp.c
+)
+
+zephyr_sources_ifdef(CONFIG_SNTP_CLIENT
  sntp_simple.c
 )
+
+zephyr_sources_ifdef(CONFIG_SNTP_SERVER
+ sntp_server.c
+)

subsys/net/lib/sntp/Kconfig

@@ -5,10 +5,17 @@ menuconfig SNTP
 bool "SNTP (Simple Network Time Protocol)"
 depends on NET_SOCKETS
 help
- Enable SNTP client library
+ Enable SNTP support library
 
 if SNTP
 
+config SNTP_CLIENT
+bool "SNTP client support"
+help
+ This option enables SNTP client support
+
+if SNTP_CLIENT
+
 config SNTP_UNCERTAINTY
 bool "Calculate SNTP uncertainty and set uptime timestamp"
 help
@@ -19,10 +26,31 @@ config SNTP_UNCERTAINTY
  Enabling this option uses more resources (memory) and is not normally
  needed.
 
+endif # SNTP client
+
+config SNTP_SERVER
+bool "SNTP client support"
+help
+ This option enables SNTP server support
+
+if SNTP_SERVER
+
+config SNTP_SERVER_STACK_SIZE
+int "Stack size of the SNTP server thread"
+default 1024
+
+config SNTP_SERVER_THREAD_PRIORITY
+int "SNTP server thread priority"
+default NUM_PREEMPT_PRIORITIES
+help
+ Priority of SNTP server thread.
+
+endif # SNTP server
+
 module = SNTP
 module-dep = NET_LOG
 module-str = Log level for SNTP
-module-help = Enable debug message of SNTP client library.
+module-help = Enable debug message of SNTP library.
 source "subsys/net/Kconfig.template.log_config.net"
 
 endif # SNTP

subsys/net/lib/sntp/sntp.c

@@ -13,14 +13,7 @@ LOG_MODULE_REGISTER(net_sntp, CONFIG_SNTP_LOG_LEVEL);
 #include "sntp_pkt.h"
 #include <limits.h>
 
-#define SNTP_LI_MAX 3
-#define SNTP_VERSION_NUMBER 3
-#define SNTP_MODE_CLIENT 3
-#define SNTP_MODE_SERVER 4
-#define SNTP_STRATUM_KOD 0 /* kiss-o'-death */
-#define OFFSET_1970_JAN_1 2208988800
-
-static void sntp_pkt_dump(struct sntp_pkt *pkt)
+void sntp_pkt_dump(struct sntp_pkt *pkt)
 {
 if (!pkt) {
 return;

subsys/net/lib/sntp/sntp_pkt.h

@@ -9,6 +9,15 @@
 
 #include <zephyr/types.h>
 
+#define SNTP_LI_MAX 3
+#define SNTP_VERSION_NUMBER 3
+#define SNTP_MODE_CLIENT 3
+#define SNTP_MODE_SERVER 4
+#define SNTP_LEAP_INDICATOR_NONE 0
+#define SNTP_LEAP_INDICATOR_CLOCK_INVALID 3
+#define SNTP_STRATUM_KOD 0 /* kiss-o'-death */
+#define OFFSET_1970_JAN_1 2208988800
+
 struct sntp_pkt {
 #if defined(CONFIG_LITTLE_ENDIAN)
 uint8_t mode: 3;
@@ -27,12 +36,14 @@ struct sntp_pkt {
 uint32_t ref_id;
 uint32_t ref_tm_s;
 uint32_t ref_tm_f;
-uint32_t orig_tm_s;/* Originate timestamp seconds */
-uint32_t orig_tm_f;/* Originate timestamp seconds fraction */
-uint32_t rx_tm_s;/* Receive timestamp seconds */
-uint32_t rx_tm_f;/* Receive timestamp seconds fraction */
-uint32_t tx_tm_s;/* Transmit timestamp seconds */
-uint32_t tx_tm_f;/* Transmit timestamp seconds fraction */
+uint32_t orig_tm_s; /* Originate timestamp seconds */
+uint32_t orig_tm_f; /* Originate timestamp seconds fraction */
+uint32_t rx_tm_s; /* Receive timestamp seconds */
+uint32_t rx_tm_f; /* Receive timestamp seconds fraction */
+uint32_t tx_tm_s; /* Transmit timestamp seconds */
+uint32_t tx_tm_f; /* Transmit timestamp seconds fraction */
 } __packed;
 
+void sntp_pkt_dump(struct sntp_pkt *pkt);
+
 #endif