/** * @file * SNTP client module * * This is simple "SNTP" client for the lwIP raw API. * It is a minimal implementation of SNTPv4 as specified in RFC 4330. * * For a list of some public NTP servers, see this link : * http://support.ntp.org/bin/view/Servers/NTPPoolServers * * @todo: * - set/change servers at runtime * - complete SNTP_CHECK_RESPONSE checks 3 and 4 * - support broadcast/multicast mode? */ /* * Redistribution and use in source and binary forms, with or without modification, * are permitted provided that the following conditions are met: * * 1. Redistributions of source code must retain the above copyright notice, * this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright notice, * this list of conditions and the following disclaimer in the documentation * and/or other materials provided with the distribution. * 3. The name of the author may not be used to endorse or promote products * derived from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY * OF SUCH DAMAGE. * * This file is part of the lwIP TCP/IP stack. * * Author: Simon Goldschmidt (lwIP raw API part) */ #include "lwip/opt.h" #include "sntp.h" #include "lwip/lwip_timers.h" #include "lwip/udp.h" #include "lwip/dns.h" #include "lwip/ip_addr.h" #include "lwip/pbuf.h" #include #include #if LWIP_UDP /** * SNTP_DEBUG: Enable debugging for SNTP. */ #ifndef SNTP_DEBUG #define SNTP_DEBUG LWIP_DBG_OFF #endif /** SNTP server port */ #ifndef SNTP_PORT #define SNTP_PORT 123 #endif /** Set this to 1 to allow SNTP_SERVER_ADDRESS to be a DNS name */ #ifndef SNTP_SERVER_DNS #define SNTP_SERVER_DNS 1 #endif /** Set this to 1 to support more than one server */ #ifndef SNTP_SUPPORT_MULTIPLE_SERVERS #define SNTP_SUPPORT_MULTIPLE_SERVERS 0 #endif /** \def SNTP_SERVER_ADDRESS * \brief SNTP server address: * - as IPv4 address in "u32_t" format * - as a DNS name if SNTP_SERVER_DNS is set to 1 * May contain multiple server names (e.g. "pool.ntp.org","second.time.server") */ #ifndef SNTP_SERVER_ADDRESS #if SNTP_SERVER_DNS #define SNTP_SERVER_ADDRESS "pool.ntp.org" #else #define SNTP_SERVER_ADDRESS "213.161.194.93" /* pool.ntp.org */ #endif #endif /** Sanity check: * Define this to * - 0 to turn off sanity checks (default; smaller code) * - >= 1 to check address and port of the response packet to ensure the * response comes from the server we sent the request to. * - >= 2 to check returned Originate Timestamp against Transmit Timestamp * sent to the server (to ensure response to older request). * - >= 3 @todo: discard reply if any of the LI, Stratum, or Transmit Timestamp * fields is 0 or the Mode field is not 4 (unicast) or 5 (broadcast). * - >= 4 @todo: to check that the Root Delay and Root Dispersion fields are each * greater than or equal to 0 and less than infinity, where infinity is * currently a cozy number like one second. This check avoids using a * server whose synchronization source has expired for a very long time. */ #ifndef SNTP_CHECK_RESPONSE #define SNTP_CHECK_RESPONSE 0 #endif /** According to the RFC, this shall be a random delay * between 1 and 5 minutes (in milliseconds) to prevent load peaks. * This can be defined to a random generation function, * which must return the delay in milliseconds as u32_t. * Turned off by default. */ #ifndef SNTP_STARTUP_DELAY #define SNTP_STARTUP_DELAY 0 #endif /** SNTP receive timeout - in milliseconds * Also used as retry timeout - this shouldn't be too low. * Default is 3 seconds. */ #ifndef SNTP_RECV_TIMEOUT #define SNTP_RECV_TIMEOUT 3000 #endif /** SNTP update delay - in milliseconds * Default is 1 hour. */ #ifndef SNTP_UPDATE_DELAY #define SNTP_UPDATE_DELAY 3600000 #endif #if (SNTP_UPDATE_DELAY < 15000) && !SNTP_SUPPRESS_DELAY_CHECK #error "SNTPv4 RFC 4330 enforces a minimum update time of 15 seconds!" #endif /* Realtek added for sntp update */ static unsigned int sntp_update_tick = 0; static time_t sntp_update_sec = 0; static time_t sntp_update_usec = 0; #define SNTP_SET_SYSTEM_TIME_US(sec, usec) do { \ sntp_update_tick = xTaskGetTickCount(); \ sntp_update_sec = sec; \ sntp_update_usec = usec; \ } while(0) void sntp_get_lasttime(long *sec, long *usec, unsigned int *tick) { *sec = sntp_update_sec; *usec = sntp_update_usec; *tick = sntp_update_tick; } time_t sntp_gen_system_time(int timezone) { // struct tm current_tm; unsigned int update_tick; long update_sec, update_usec, current_sec = 0; sntp_get_lasttime(&update_sec, &update_usec, &update_tick); unsigned int current_tick = xTaskGetTickCount(); if(update_tick) { long tick_diff_sec, tick_diff_ms; tick_diff_sec = (current_tick - update_tick) / configTICK_RATE_HZ; tick_diff_ms = (current_tick - update_tick) % configTICK_RATE_HZ / portTICK_RATE_MS; update_sec += tick_diff_sec; update_usec += (tick_diff_ms * 1000); current_sec = update_sec + update_usec / 1000000 + timezone * 3600; } else { // current_sec = current_tick / configTICK_RATE_HZ; current_sec = update_usec; } return current_sec; /* current_tm = *(localtime(¤t_sec)); current_tm.tm_year += 1900; current_tm.tm_mon += 1; return current_tm; */ } /* End of Realtek added */ /** SNTP macro to change system time and/or the update the RTC clock */ #ifndef SNTP_SET_SYSTEM_TIME #define SNTP_SET_SYSTEM_TIME(sec) ((void)sec) #endif /** SNTP macro to change system time including microseconds */ #ifdef SNTP_SET_SYSTEM_TIME_US #define SNTP_CALC_TIME_US 1 #define SNTP_RECEIVE_TIME_SIZE 2 #else #define SNTP_SET_SYSTEM_TIME_US(sec, us) #define SNTP_CALC_TIME_US 0 #define SNTP_RECEIVE_TIME_SIZE 1 #endif /** SNTP macro to get system time, used with SNTP_CHECK_RESPONSE >= 2 * to send in request and compare in response. */ #ifndef SNTP_GET_SYSTEM_TIME #define SNTP_GET_SYSTEM_TIME(sec, us) do { (sec) = 0; (us) = 0; } while(0) #endif /** Default retry timeout (in milliseconds) if the response * received is invalid. * This is doubled with each retry until SNTP_RETRY_TIMEOUT_MAX is reached. */ #ifndef SNTP_RETRY_TIMEOUT #define SNTP_RETRY_TIMEOUT SNTP_RECV_TIMEOUT #endif /** Maximum retry timeout (in milliseconds). */ #ifndef SNTP_RETRY_TIMEOUT_MAX #define SNTP_RETRY_TIMEOUT_MAX (SNTP_RETRY_TIMEOUT * 10) #endif /** Increase retry timeout with every retry sent * Default is on to conform to RFC. */ #ifndef SNTP_RETRY_TIMEOUT_EXP #define SNTP_RETRY_TIMEOUT_EXP 1 #endif /* the various debug levels for this file */ #define SNTP_DEBUG_TRACE (SNTP_DEBUG | LWIP_DBG_TRACE) #define SNTP_DEBUG_STATE (SNTP_DEBUG | LWIP_DBG_STATE) #define SNTP_DEBUG_WARN (SNTP_DEBUG | LWIP_DBG_LEVEL_WARNING) #define SNTP_DEBUG_WARN_STATE (SNTP_DEBUG | LWIP_DBG_LEVEL_WARNING | LWIP_DBG_STATE) #define SNTP_DEBUG_SERIOUS (SNTP_DEBUG | LWIP_DBG_LEVEL_SERIOUS) #define SNTP_ERR_KOD 1 /* SNTP protocol defines */ #define SNTP_MSG_LEN 48 #define SNTP_OFFSET_LI_VN_MODE 0 #define SNTP_LI_MASK 0xC0 #define SNTP_LI_NO_WARNING 0x00 #define SNTP_LI_LAST_MINUTE_61_SEC 0x01 #define SNTP_LI_LAST_MINUTE_59_SEC 0x02 #define SNTP_LI_ALARM_CONDITION 0x03 /* (clock not synchronized) */ #define SNTP_VERSION_MASK 0x38 #define SNTP_VERSION (4/* NTP Version 4*/<<3) #define SNTP_MODE_MASK 0x07 #define SNTP_MODE_CLIENT 0x03 #define SNTP_MODE_SERVER 0x04 #define SNTP_MODE_BROADCAST 0x05 #define SNTP_OFFSET_STRATUM 1 #define SNTP_STRATUM_KOD 0x00 #define SNTP_OFFSET_ORIGINATE_TIME 24 #define SNTP_OFFSET_RECEIVE_TIME 32 #define SNTP_OFFSET_TRANSMIT_TIME 40 /* number of seconds between 1900 and 1970 */ #define DIFF_SEC_1900_1970 (2208988800UL) /** * SNTP packet format (without optional fields) * Timestamps are coded as 64 bits: * - 32 bits seconds since Jan 01, 1970, 00:00 * - 32 bits seconds fraction (0-padded) * For future use, if the MSB in the seconds part is set, seconds are based * on Feb 07, 2036, 06:28:16. */ #ifdef PACK_STRUCT_USE_INCLUDES # include "arch/bpstruct.h" #endif PACK_STRUCT_BEGIN struct sntp_msg { PACK_STRUCT_FIELD(u8_t li_vn_mode); PACK_STRUCT_FIELD(u8_t stratum); PACK_STRUCT_FIELD(u8_t poll); PACK_STRUCT_FIELD(u8_t precision); PACK_STRUCT_FIELD(u32_t root_delay); PACK_STRUCT_FIELD(u32_t root_dispersion); PACK_STRUCT_FIELD(u32_t reference_identifier); PACK_STRUCT_FIELD(u32_t reference_timestamp[2]); PACK_STRUCT_FIELD(u32_t originate_timestamp[2]); PACK_STRUCT_FIELD(u32_t receive_timestamp[2]); PACK_STRUCT_FIELD(u32_t transmit_timestamp[2]); } PACK_STRUCT_STRUCT; PACK_STRUCT_END #ifdef PACK_STRUCT_USE_INCLUDES # include "arch/epstruct.h" #endif /* function prototypes */ static void sntp_request(void *arg); /** The UDP pcb used by the SNTP client */ static struct udp_pcb* sntp_pcb; /** Addresses of servers */ static char* sntp_server_addresses[] = {SNTP_SERVER_ADDRESS}; #if SNTP_SUPPORT_MULTIPLE_SERVERS /** The currently used server (initialized to 0) */ static u8_t sntp_current_server; static u8_t sntp_num_servers = sizeof(sntp_server_addresses)/sizeof(char*); #else /* SNTP_SUPPORT_MULTIPLE_SERVERS */ #define sntp_current_server 0 #endif /* SNTP_SUPPORT_MULTIPLE_SERVERS */ #if SNTP_RETRY_TIMEOUT_EXP #define SNTP_RESET_RETRY_TIMEOUT() sntp_retry_timeout = SNTP_RETRY_TIMEOUT /** Retry time, initialized with SNTP_RETRY_TIMEOUT and doubled with each retry. */ static u32_t sntp_retry_timeout; #else /* SNTP_RETRY_TIMEOUT_EXP */ #define SNTP_RESET_RETRY_TIMEOUT() #define sntp_retry_timeout SNTP_RETRY_TIMEOUT #endif /* SNTP_RETRY_TIMEOUT_EXP */ #if SNTP_CHECK_RESPONSE >= 1 /** Saves the last server address to compare with response */ static ip_addr_t sntp_last_server_address; #endif /* SNTP_CHECK_RESPONSE >= 1 */ #if SNTP_CHECK_RESPONSE >= 2 /** Saves the last timestamp sent (which is sent back by the server) * to compare against in response */ static u32_t sntp_last_timestamp_sent[2]; #endif /* SNTP_CHECK_RESPONSE >= 2 */ /** * SNTP processing of received timestamp */ static void sntp_process(u32_t *receive_timestamp) { /* convert SNTP time (1900-based) to unix GMT time (1970-based) * @todo: if MSB is 1, SNTP time is 2036-based! */ time_t t = (ntohl(receive_timestamp[0]) - DIFF_SEC_1900_1970); #if SNTP_CALC_TIME_US u32_t us = ntohl(receive_timestamp[1]) / 4295; SNTP_SET_SYSTEM_TIME_US(t, us); /* display local time from GMT time */ LWIP_DEBUGF(SNTP_DEBUG_TRACE, ("sntp_process: %s, %"U32_F" us", ctime(&t), us)); #else /* SNTP_CALC_TIME_US */ /* change system time and/or the update the RTC clock */ SNTP_SET_SYSTEM_TIME(t); /* display local time from GMT time */ LWIP_DEBUGF(SNTP_DEBUG_TRACE, ("sntp_process: %s", ctime(&t))); #endif /* SNTP_CALC_TIME_US */ } /** * Initialize request struct to be sent to server. */ static void sntp_initialize_request(struct sntp_msg *req) { memset(req, 0, SNTP_MSG_LEN); req->li_vn_mode = SNTP_LI_NO_WARNING | SNTP_VERSION | SNTP_MODE_CLIENT; #if SNTP_CHECK_RESPONSE >= 2 { u32_t sntp_time_sec, sntp_time_us; /* fill in transmit timestamp and save it in 'sntp_last_timestamp_sent' */ SNTP_GET_SYSTEM_TIME(sntp_time_sec, sntp_time_us); sntp_last_timestamp_sent[0] = htonl(sntp_time_sec + DIFF_SEC_1900_1970); req->transmit_timestamp[0] = sntp_last_timestamp_sent[0]; /* we send/save us instead of fraction to be faster... */ sntp_last_timestamp_sent[1] = htonl(sntp_time_us); req->transmit_timestamp[1] = sntp_last_timestamp_sent[1]; } #endif /* SNTP_CHECK_RESPONSE >= 2 */ } /** * Retry: send a new request (and increase retry timeout). * * @param arg is unused (only necessary to conform to sys_timeout) */ static void sntp_retry(void* arg) { LWIP_UNUSED_ARG(arg); LWIP_DEBUGF(SNTP_DEBUG_STATE, ("sntp_retry: Next request will be sent in %"U32_F" ms\n", sntp_retry_timeout)); /* set up a timer to send a retry and increase the retry delay */ sys_timeout(sntp_retry_timeout, sntp_request, NULL); #if SNTP_RETRY_TIMEOUT_EXP { u32_t new_retry_timeout; /* increase the timeout for next retry */ new_retry_timeout = sntp_retry_timeout << 1; /* limit to maximum timeout and prevent overflow */ if ((new_retry_timeout <= SNTP_RETRY_TIMEOUT_MAX) && (new_retry_timeout > sntp_retry_timeout)) { sntp_retry_timeout = new_retry_timeout; } } #endif /* SNTP_RETRY_TIMEOUT_EXP */ } #if SNTP_SUPPORT_MULTIPLE_SERVERS /** * If Kiss-of-Death is received (or another packet parsing error), * try the next server or retry the current server and increase the retry * timeout if only one server is available. * * @param arg is unused (only necessary to conform to sys_timeout) */ static void sntp_try_next_server(void* arg) { LWIP_UNUSED_ARG(arg); if (sntp_num_servers > 1) { /* new server: reset retry timeout */ SNTP_RESET_RETRY_TIMEOUT(); sntp_current_server++; if (sntp_current_server >= sntp_num_servers) { sntp_current_server = 0; } LWIP_DEBUGF(SNTP_DEBUG_STATE, ("sntp_try_next_server: Sending request to server %"U16_F"\n", (u16_t)sntp_current_server)); /* instantly send a request to the next server */ sntp_request(NULL); } else { sntp_retry(NULL); } } #else /* SNTP_SUPPORT_MULTIPLE_SERVERS */ /* Always retry on error if only one server is supported */ #define sntp_try_next_server sntp_retry #endif /* SNTP_SUPPORT_MULTIPLE_SERVERS */ /** UDP recv callback for the sntp pcb */ static void sntp_recv(void *arg, struct udp_pcb* pcb, struct pbuf *p, ip_addr_t *addr, u16_t port) { u8_t mode; u8_t stratum; u32_t receive_timestamp[SNTP_RECEIVE_TIME_SIZE]; err_t err; LWIP_UNUSED_ARG(arg); LWIP_UNUSED_ARG(pcb); /* packet received: stop retry timeout */ sys_untimeout(sntp_try_next_server, NULL); sys_untimeout(sntp_request, NULL); err = ERR_ARG; #if SNTP_CHECK_RESPONSE >= 1 /* check server address and port */ if (ip_addr_cmp(addr, &sntp_last_server_address) && (port == SNTP_PORT)) #else /* SNTP_CHECK_RESPONSE >= 1 */ LWIP_UNUSED_ARG(addr); LWIP_UNUSED_ARG(port); #endif /* SNTP_CHECK_RESPONSE >= 1 */ { /* process the response */ if (p->tot_len == SNTP_MSG_LEN) { pbuf_copy_partial(p, &mode, 1, SNTP_OFFSET_LI_VN_MODE); mode &= SNTP_MODE_MASK; /* if this is a SNTP response... */ if ((mode == SNTP_MODE_SERVER) || (mode == SNTP_MODE_BROADCAST)) { pbuf_copy_partial(p, &stratum, 1, SNTP_OFFSET_STRATUM); if (stratum == SNTP_STRATUM_KOD) { /* Kiss-of-death packet. Use another server or increase UPDATE_DELAY. */ err = SNTP_ERR_KOD; LWIP_DEBUGF(SNTP_DEBUG_STATE, ("sntp_recv: Received Kiss-of-Death\n")); } else { #if SNTP_CHECK_RESPONSE >= 2 /* check originate_timetamp against sntp_last_timestamp_sent */ u32_t originate_timestamp[2]; pbuf_copy_partial(p, &originate_timestamp, 8, SNTP_OFFSET_ORIGINATE_TIME); if ((originate_timestamp[0] != sntp_last_timestamp_sent[0]) || (originate_timestamp[1] != sntp_last_timestamp_sent[1])) { LWIP_DEBUGF(SNTP_DEBUG_WARN, ("sntp_recv: Invalid originate timestamp in response\n")); } else #endif /* SNTP_CHECK_RESPONSE >= 2 */ /* @todo: add code for SNTP_CHECK_RESPONSE >= 3 and >= 4 here */ { /* correct answer */ err = ERR_OK; pbuf_copy_partial(p, &receive_timestamp, SNTP_RECEIVE_TIME_SIZE * 4, SNTP_OFFSET_RECEIVE_TIME); } } } else { LWIP_DEBUGF(SNTP_DEBUG_WARN, ("sntp_recv: Invalid mode in response: %"U16_F"\n", (u16_t)mode)); } } else { LWIP_DEBUGF(SNTP_DEBUG_WARN, ("sntp_recv: Invalid packet length: %"U16_F"\n", p->tot_len)); } } pbuf_free(p); if (err == ERR_OK) { /* Correct response, reset retry timeout */ SNTP_RESET_RETRY_TIMEOUT(); sntp_process(receive_timestamp); /* Set up timeout for next request */ sys_timeout((u32_t)SNTP_UPDATE_DELAY, sntp_request, NULL); LWIP_DEBUGF(SNTP_DEBUG_STATE, ("sntp_recv: Scheduled next time request: %"U32_F" ms\n", (u32_t)SNTP_UPDATE_DELAY)); } else if (err == SNTP_ERR_KOD) { /* Kiss-of-death packet. Use another server or increase UPDATE_DELAY. */ sntp_try_next_server(NULL); } else { /* another error, try the same server again */ sntp_retry(NULL); } } /** Actually send an sntp request to a server. * * @param server_addr resolved IP address of the SNTP server */ static void sntp_send_request(ip_addr_t *server_addr) { struct pbuf* p; p = pbuf_alloc(PBUF_TRANSPORT, SNTP_MSG_LEN, PBUF_RAM); if (p != NULL) { struct sntp_msg *sntpmsg = (struct sntp_msg *)p->payload; LWIP_DEBUGF(SNTP_DEBUG_STATE, ("sntp_send_request: Sending request to server\n")); /* initialize request message */ sntp_initialize_request(sntpmsg); /* send request */ udp_sendto(sntp_pcb, p, server_addr, SNTP_PORT); /* free the pbuf after sending it */ pbuf_free(p); /* set up receive timeout: try next server or retry on timeout */ sys_timeout((u32_t)SNTP_RECV_TIMEOUT, sntp_try_next_server, NULL); #if SNTP_CHECK_RESPONSE >= 1 /* save server address to verify it in sntp_recv */ ip_addr_set(&sntp_last_server_address, server_addr); #endif /* SNTP_CHECK_RESPONSE >= 1 */ } else { LWIP_DEBUGF(SNTP_DEBUG_SERIOUS, ("sntp_send_request: Out of memory, trying again in %"U32_F" ms\n", (u32_t)SNTP_RETRY_TIMEOUT)); /* out of memory: set up a timer to send a retry */ sys_timeout((u32_t)SNTP_RETRY_TIMEOUT, sntp_request, NULL); } } #if SNTP_SERVER_DNS /** * DNS found callback when using DNS names as server address. */ static void sntp_dns_found(const char* hostname, ip_addr_t *ipaddr, void *arg) { LWIP_UNUSED_ARG(hostname); LWIP_UNUSED_ARG(arg); if (ipaddr != NULL) { /* Address resolved, send request */ LWIP_DEBUGF(SNTP_DEBUG_STATE, ("sntp_dns_found: Server address resolved, sending request\n")); sntp_send_request(ipaddr); } else { /* DNS resolving failed -> try another server */ LWIP_DEBUGF(SNTP_DEBUG_WARN_STATE, ("sntp_dns_found: Failed to resolve server address resolved, trying next server\n")); sntp_try_next_server(NULL); } } #endif /* SNTP_SERVER_DNS */ /** * Send out an sntp request. * * @param arg is unused (only necessary to conform to sys_timeout) */ static void sntp_request(void *arg) { ip_addr_t sntp_server_address; err_t err; LWIP_UNUSED_ARG(arg); /* initialize SNTP server address */ #if SNTP_SERVER_DNS err = dns_gethostbyname(sntp_server_addresses[sntp_current_server], &sntp_server_address, sntp_dns_found, NULL); if (err == ERR_INPROGRESS) { /* DNS request sent, wait for sntp_dns_found being called */ LWIP_DEBUGF(SNTP_DEBUG_STATE, ("sntp_request: Waiting for server address to be resolved.\n")); return; } #else /* SNTP_SERVER_DNS */ err = ipaddr_aton(sntp_server_addresses[sntp_current_server], &sntp_server_address) ? ERR_OK : ERR_ARG; #endif /* SNTP_SERVER_DNS */ if (err == ERR_OK) { sntp_send_request(&sntp_server_address); } else { /* address conversion failed, try another server */ LWIP_DEBUGF(SNTP_DEBUG_WARN_STATE, ("sntp_request: Invalid server address, trying next server.\n")); sys_timeout((u32_t)SNTP_RETRY_TIMEOUT, sntp_try_next_server, NULL); } } /** * Initialize this module. * Send out request instantly or after SNTP_STARTUP_DELAY. */ void sntp_init(void) { if (sntp_pcb == NULL) { SNTP_RESET_RETRY_TIMEOUT(); sntp_pcb = udp_new(); LWIP_ASSERT("Failed to allocate udp pcb for sntp client", sntp_pcb != NULL); if (sntp_pcb != NULL) { udp_recv(sntp_pcb, sntp_recv, NULL); #if SNTP_STARTUP_DELAY sys_timeout((u32_t)SNTP_STARTUP_DELAY, sntp_request, NULL); #else sntp_request(NULL); #endif rtl_printf("SNTP start.\n"); } } } /** * Stop this module. */ void sntp_stop(void) { if (sntp_pcb != NULL) { sys_untimeout(sntp_request, NULL); udp_remove(sntp_pcb); sntp_pcb = NULL; rtl_printf("SNTP stop.\n"); } } #endif /* LWIP_UDP */