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SNTP: Unify timestamp extraction from response packet

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Avoid piecemeal invocation of pbuf_copy_partial() for each SNTP header
field. The new code may sometimes copy more than necessary, but the
complexity is reduced.
This commit is contained in:
Daniel Elstner 2017-03-27 00:04:23 +02:00 committed by goldsimon
parent 2fa9cd8530
commit cc77b308a4
1 changed files with 41 additions and 19 deletions
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60
src/apps/sntp/sntp.c
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@ -154,6 +154,29 @@
} while (0)
#endif /* !SNTP_GET_SYSTEM_TIME_NTP */
/* Start offset of the timestamps to extract from the SNTP packet */
#define SNTP_OFFSET_TIMESTAMPS \
(SNTP_OFFSET_TRANSMIT_TIME + 8 - sizeof(struct sntp_timestamps))
/**
* 64-bit NTP timestamp, in network byte order.
*/
struct sntp_time {
u32_t sec;
u32_t frac;
};
/**
* Timestamps to be extracted from the NTP header.
*/
struct sntp_timestamps {
#if SNTP_CHECK_RESPONSE >= 2
struct sntp_time orig;
struct sntp_time recv;
#endif
struct sntp_time xmit;
};
/**
* SNTP packet format (without optional fields)
* Timestamps are coded as 64 bits:
@ -225,8 +248,8 @@ static ip_addr_t sntp_last_server_address;
#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];
* to compare against in response. Stored in network byte order. */
static struct sntp_time sntp_last_timestamp_sent;
#endif /* SNTP_CHECK_RESPONSE >= 2 */
#ifndef sntp_format_time
@ -244,13 +267,13 @@ sntp_format_time(s32_t sec)
* SNTP processing of received timestamp
*/
static void
sntp_process(u32_t *receive_timestamp)
sntp_process(const struct sntp_timestamps *timestamps)
{
s32_t sec;
u32_t frac;
sec = lwip_ntohl(receive_timestamp[0]);
frac = lwip_ntohl(receive_timestamp[1]);
sec = lwip_ntohl(timestamps->xmit.sec);
frac = lwip_ntohl(timestamps->xmit.frac);
SNTP_SET_SYSTEM_TIME_NTP(sec, frac);
LWIP_DEBUGF(SNTP_DEBUG_TRACE, ("sntp_process: %s, %" U32_F " us\n",
@ -274,8 +297,8 @@ sntp_initialize_request(struct sntp_msg *req)
sec = lwip_htonl(sec);
frac = lwip_htonl(frac);
sntp_last_timestamp_sent[0] = sec;
sntp_last_timestamp_sent[1] = frac;
sntp_last_timestamp_sent.sec = sec;
sntp_last_timestamp_sent.frac = frac;
req->transmit_timestamp[0] = sec;
req->transmit_timestamp[1] = frac;
}
@ -360,9 +383,9 @@ sntp_try_next_server(void* arg)
static void
sntp_recv(void *arg, struct udp_pcb* pcb, struct pbuf *p, const ip_addr_t *addr, u16_t port)
{
struct sntp_timestamps timestamps;
u8_t mode;
u8_t stratum;
u32_t receive_timestamp[2];
err_t err;
LWIP_UNUSED_ARG(arg);
@ -384,32 +407,31 @@ sntp_recv(void *arg, struct udp_pcb* pcb, struct pbuf *p, const ip_addr_t *addr,
{
/* 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;
mode = pbuf_get_at(p, SNTP_OFFSET_LI_VN_MODE) & SNTP_MODE_MASK;
/* if this is a SNTP response... */
if (((sntp_opmode == SNTP_OPMODE_POLL) && (mode == SNTP_MODE_SERVER)) ||
((sntp_opmode == SNTP_OPMODE_LISTENONLY) && (mode == SNTP_MODE_BROADCAST))) {
pbuf_copy_partial(p, &stratum, 1, SNTP_OFFSET_STRATUM);
stratum = pbuf_get_at(p, 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 {
pbuf_copy_partial(p, &timestamps, sizeof(timestamps),
SNTP_OFFSET_TIMESTAMPS);
#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"));
if (timestamps.orig.sec != sntp_last_timestamp_sent.sec ||
timestamps.orig.frac != sntp_last_timestamp_sent.frac) {
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, 8, SNTP_OFFSET_TRANSMIT_TIME);
}
}
} else {
@ -429,7 +451,7 @@ sntp_recv(void *arg, struct udp_pcb* pcb, struct pbuf *p, const ip_addr_t *addr,
#endif /* SNTP_CHECK_RESPONSE >= 1 */
pbuf_free(p);
if (err == ERR_OK) {
sntp_process(receive_timestamp);
sntp_process(&timestamps);
/* Set up timeout for next request (only if poll response was received)*/
if (sntp_opmode == SNTP_OPMODE_POLL) {