Commit 72534b83 authored by Marcus Penate's avatar Marcus Penate Committed by Mahesh Mahadevan
Browse files

net: lib: sntp_simple: Handle responses from previous iterations 



SNTP simple runs request iterations with exponential backoff.
If the net interface is a slower connection (ie. CAT M1 modems)
then the request will be sent but the response may take time to
be received, thus causing a timeout and another request to be sent.
Because of the nature of UDP and the fact that the same socket
(source IP/port combo) is being used for both requests, a delayed
response to the first request can be received as the response to the
second request, causing -EINVAL to be returned when the timestamps
mismatch (see subsys/net/lib/sntp/sntp.c). The solution provided
retries receiving the response when the timestamp is mismatched
(without sending an additional request).

Signed-off-by: default avatarMarcus Penate <marcus.penate@ellenbytech.com>
parent 4d8acdf9

include/zephyr/net/sntp.h

+14 −3
Original line number Diff line number Diff line
@@ -73,13 +73,24 @@ int sntp_init(struct sntp_ctx *ctx, struct sockaddr *addr, 
 *

 * @param ctx Address of sntp context.

 * @param timeout Timeout of waiting for sntp response (in milliseconds).

 * @param time Timestamp including integer and fractional seconds since

 * @param ts Timestamp including integer and fractional seconds since

 * 1 Jan 1970 (output).

 *

 * @return 0 if ok, <0 if error (-ETIMEDOUT if timeout).

 */

int sntp_query(struct sntp_ctx *ctx, uint32_t timeout, struct sntp_time *ts);



/**

 * @brief Attempt to receive an SNTP response after issuing a query

 *

 * @param ctx Address of sntp context.

 * @param timeout Timeout of waiting for sntp response (in milliseconds).

 * @param ts Timestamp including integer and fractional seconds since

 * 1 Jan 1970 (output).

 *

 * @return 0 if ok, <0 if error (-ETIMEDOUT if timeout).

 */

int sntp_query(struct sntp_ctx *ctx, uint32_t timeout,

	       struct sntp_time *time);

int sntp_recv_response(struct sntp_ctx *ctx, uint32_t timeout, struct sntp_time *ts);



/**

 * @brief Release SNTP context

subsys/net/lib/sntp/sntp.c

+36 −36
Original line number Diff line number Diff line
@@ -70,7 +70,7 @@ static int32_t parse_response(uint8_t *data, uint16_t len, struct sntp_time *exp 
		NET_DBG("Mismatch originate timestamp: %d.%09d, expect: %llu.%09u",

			ntohl(pkt->orig_tm_s), ntohl(pkt->orig_tm_f), expected_orig_ts->seconds,

			expected_orig_ts->fraction);

		return -EINVAL;

		return -ERANGE;

	}



	if (pkt->mode != SNTP_MODE_SERVER) {
@@ -151,38 +151,6 @@ static int32_t parse_response(uint8_t *data, uint16_t len, struct sntp_time *exp 
	return 0;

}



static int sntp_recv_response(struct sntp_ctx *sntp, uint32_t timeout,

			      struct sntp_time *time)

{

	struct sntp_pkt buf = { 0 };

	int status;

	int rcvd;



	status = zsock_poll(sntp->sock.fds, sntp->sock.nfds, timeout);

	if (status < 0) {

		NET_ERR("Error in poll:%d", errno);

		return -errno;

	}



	if (status == 0) {

		return -ETIMEDOUT;

	}



	rcvd = zsock_recv(sntp->sock.fd, (uint8_t *)&buf, sizeof(buf), 0);

	if (rcvd < 0) {

		return -errno;

	}



	if (rcvd != sizeof(struct sntp_pkt)) {

		return -EMSGSIZE;

	}



	status = parse_response((uint8_t *)&buf, sizeof(buf),

				&sntp->expected_orig_ts,

				time);

	return status;

}



int sntp_init(struct sntp_ctx *ctx, struct sockaddr *addr, socklen_t addr_len)

{

	int ret;
@@ -213,13 +181,13 @@ int sntp_init(struct sntp_ctx *ctx, struct sockaddr *addr, socklen_t addr_len) 
	return 0;

}



int sntp_query(struct sntp_ctx *ctx, uint32_t timeout, struct sntp_time *time)

int sntp_query(struct sntp_ctx *ctx, uint32_t timeout, struct sntp_time *ts)

{

	struct sntp_pkt tx_pkt = { 0 };

	int ret = 0;

	int64_t ts_us = 0;



	if (!ctx || !time) {

	if (!ctx || !ts) {

		return -EFAULT;

	}
@@ -239,7 +207,39 @@ int sntp_query(struct sntp_ctx *ctx, uint32_t timeout, struct sntp_time *time) 
		return ret;

	}



	return sntp_recv_response(ctx, timeout, time);

	return sntp_recv_response(ctx, timeout, ts);

}



int sntp_recv_response(struct sntp_ctx *ctx, uint32_t timeout,

			      struct sntp_time *ts)

{

	struct sntp_pkt buf = { 0 };

	int status;

	int rcvd;



	status = zsock_poll(ctx->sock.fds, ctx->sock.nfds, timeout);

	if (status < 0) {

		NET_ERR("Error in poll:%d", errno);

		return -errno;

	}



	if (status == 0) {

		return -ETIMEDOUT;

	}



	rcvd = zsock_recv(ctx->sock.fd, (uint8_t *)&buf, sizeof(buf), 0);

	if (rcvd < 0) {

		return -errno;

	}



	if (rcvd != sizeof(struct sntp_pkt)) {

		return -EMSGSIZE;

	}



	status = parse_response((uint8_t *)&buf, sizeof(buf),

				&ctx->expected_orig_ts,

				ts);

	return status;

}



void sntp_close(struct sntp_ctx *ctx)

subsys/net/lib/sntp/sntp_simple.c

+24 −1
Original line number Diff line number Diff line
@@ -4,6 +4,7 @@ 
 * SPDX-License-Identifier: Apache-2.0

 */

#include <errno.h>

#include <stdbool.h>



#include <zephyr/net/sntp.h>

#include <zephyr/net/socketutils.h>
@@ -15,6 +16,7 @@ static int sntp_simple_helper(struct sockaddr *addr, socklen_t addr_len, uint32_ 
	struct sntp_ctx sntp_ctx;

	uint64_t deadline;

	uint32_t iter_timeout;

	bool first_iter;



	res = sntp_init(&sntp_ctx, addr, addr_len);

	if (res < 0) {
@@ -29,18 +31,39 @@ static int sntp_simple_helper(struct sockaddr *addr, socklen_t addr_len, uint32_ 


	/* Timeout for current iteration */

	iter_timeout = 100;

	first_iter = true;



	while (k_uptime_get() < deadline) {

		res = sntp_query(&sntp_ctx, iter_timeout, ts);



		if (res != -ETIMEDOUT) {

			if (false == first_iter && -ERANGE == res) {

				while (-ERANGE == res) {

					/* Possible out of order packet received.

					 * Retry recv with current iteration timeout

					 * until an error or timeout (flushing the socket

					 * of old iteration responses until we timeout or

					 * receive our iteration's response)

					 */

					res = sntp_recv_response(&sntp_ctx, iter_timeout, ts);

				}



				if (res != ETIMEDOUT) {

					break;

				}

			} else {

				break;

			}

		}



		/* Exponential backoff with limit */

		if (iter_timeout < 1000) {

			iter_timeout *= 2;

		}



		if (first_iter) {

			first_iter = false;

		}

	}



	sntp_close(&sntp_ctx);

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