72534b83e4
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: Marcus Penate <marcus.penate@ellenbytech.com>
111 lines
2.3 KiB
C
111 lines
2.3 KiB
C
/*
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* Copyright (c) 2019 Linaro Limited
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <errno.h>
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#include <stdbool.h>
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#include <zephyr/net/sntp.h>
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#include <zephyr/net/socketutils.h>
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static int sntp_simple_helper(struct sockaddr *addr, socklen_t addr_len, uint32_t timeout,
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struct sntp_time *ts)
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{
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int res;
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struct sntp_ctx sntp_ctx;
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uint64_t deadline;
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uint32_t iter_timeout;
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bool first_iter;
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res = sntp_init(&sntp_ctx, addr, addr_len);
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if (res < 0) {
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return res;
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}
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if (timeout == SYS_FOREVER_MS) {
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deadline = (uint64_t)timeout;
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} else {
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deadline = k_uptime_get() + (uint64_t)timeout;
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}
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/* Timeout for current iteration */
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iter_timeout = 100;
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first_iter = true;
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while (k_uptime_get() < deadline) {
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res = sntp_query(&sntp_ctx, iter_timeout, ts);
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if (res != -ETIMEDOUT) {
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if (false == first_iter && -ERANGE == res) {
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while (-ERANGE == res) {
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/* Possible out of order packet received.
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* Retry recv with current iteration timeout
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* until an error or timeout (flushing the socket
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* of old iteration responses until we timeout or
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* receive our iteration's response)
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*/
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res = sntp_recv_response(&sntp_ctx, iter_timeout, ts);
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}
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if (res != ETIMEDOUT) {
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break;
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}
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} else {
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break;
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}
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}
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/* Exponential backoff with limit */
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if (iter_timeout < 1000) {
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iter_timeout *= 2;
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}
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if (first_iter) {
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first_iter = false;
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}
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}
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sntp_close(&sntp_ctx);
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return res;
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}
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int sntp_simple_addr(struct sockaddr *addr, socklen_t addr_len, uint32_t timeout,
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struct sntp_time *ts)
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{
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/* 123 is the standard SNTP port per RFC4330 */
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int res = net_port_set_default(addr, 123);
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if (res < 0) {
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return res;
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}
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return sntp_simple_helper(addr, addr_len, timeout, ts);
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}
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int sntp_simple(const char *server, uint32_t timeout, struct sntp_time *ts)
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{
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int res;
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static struct zsock_addrinfo hints;
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struct zsock_addrinfo *addr;
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hints.ai_family = AF_UNSPEC;
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hints.ai_socktype = SOCK_DGRAM;
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hints.ai_protocol = 0;
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/* 123 is the standard SNTP port per RFC4330 */
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res = net_getaddrinfo_addr_str(server, "123", &hints, &addr);
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if (res < 0) {
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/* Just in case, as namespace for getaddrinfo errors is
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* different from errno errors.
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*/
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errno = EDOM;
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return res;
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}
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res = sntp_simple_helper(addr->ai_addr, addr->ai_addrlen, timeout, ts);
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zsock_freeaddrinfo(addr);
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return res;
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}
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