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SNTP: Streamline timestamp handling

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Generalize the NTP timestamp conversion arithmetic, and provide hooks
for using native NTP timestamps when setting or getting the system
clock time. Convert microseconds to a fraction as needed when getting
the system time.
This commit is contained in:
Daniel Elstner 2017-03-27 00:01:04 +02:00 committed by goldsimon
parent 9323ad3211
commit 2fa9cd8530
2 changed files with 81 additions and 51 deletions
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124
src/apps/sntp/sntp.c
View File

@ -76,17 +76,6 @@
#error "SNTPv4 RFC 4330 enforces a minimum update time of 15 seconds (define SNTP_SUPPRESS_DELAY_CHECK to disable this error)!"
#endif
/* Configure behaviour depending on microsecond or second precision */
#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
/* 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)
@ -121,18 +110,55 @@
#define SNTP_OFFSET_RECEIVE_TIME 32
#define SNTP_OFFSET_TRANSMIT_TIME 40
/* number of seconds between 1900 and 1970 (MSB=1)*/
#define DIFF_SEC_1900_1970 (2208988800UL)
/* number of seconds between 1970 and Feb 7, 2036 (6:28:16 UTC) (MSB=0) */
#define DIFF_SEC_1970_2036 (2085978496UL)
/* Number of seconds between 1970 and Feb 7, 2036 06:28:16 UTC (epoch 1) */
#define DIFF_SEC_1970_2036 ((u32_t)2085978496L)
/** Convert NTP timestamp fraction to microseconds.
*/
#ifndef SNTP_FRAC_TO_US
# if LWIP_HAVE_INT64
# define SNTP_FRAC_TO_US(f) ((u32_t)(((u64_t)(f) * 1000000UL) >> 32))
# else
# define SNTP_FRAC_TO_US(f) ((u32_t)(f) / 4295)
# endif
#endif /* !SNTP_FRAC_TO_US */
/* Configure behaviour depending on native, microsecond or second precision.
* Treat NTP timestamps as signed two's-complement integers. This way,
* timestamps that have the MSB set simply become negative offsets from
* the epoch (Feb 7, 2036 06:28:16 UTC). Representable dates range from
* 1968 to 2104.
*/
#ifndef SNTP_SET_SYSTEM_TIME_NTP
# ifdef SNTP_SET_SYSTEM_TIME_US
# define SNTP_SET_SYSTEM_TIME_NTP(s, f) \
SNTP_SET_SYSTEM_TIME_US((u32_t)((s) + DIFF_SEC_1970_2036), SNTP_FRAC_TO_US(f))
# else
# define SNTP_SET_SYSTEM_TIME_NTP(s, f) \
SNTP_SET_SYSTEM_TIME((u32_t)((s) + DIFF_SEC_1970_2036))
# endif
#endif /* !SNTP_SET_SYSTEM_TIME_NTP */
/* Get the system time either natively as NTP timestamp or convert from
* Unix time in seconds and microseconds. Take care to avoid overflow if the
* microsecond value is at the maximum of 999999. Also add 0.5 us fudge to
* avoid special values like 0, and to mask round-off errors that would
* otherwise break round-trip conversion identity.
*/
#ifndef SNTP_GET_SYSTEM_TIME_NTP
# define SNTP_GET_SYSTEM_TIME_NTP(s, f) do { \
u32_t sec_, usec_; \
SNTP_GET_SYSTEM_TIME(sec_, usec_); \
(s) = (s32_t)(sec_ - DIFF_SEC_1970_2036); \
(f) = usec_ * 4295 - ((usec_ * 2143) >> 16) + 2147; \
} while (0)
#endif /* !SNTP_GET_SYSTEM_TIME_NTP */
/**
* 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.
* - signed 32 bits seconds since Feb 07, 2036, 06:28:16 UTC (epoch 1)
* - unsigned 32 bits seconds fraction (2^32 = 1 second)
*/
#ifdef PACK_STRUCT_USE_INCLUDES
# include "arch/bpstruct.h"
@ -203,34 +229,32 @@ static ip_addr_t sntp_last_server_address;
static u32_t sntp_last_timestamp_sent[2];
#endif /* SNTP_CHECK_RESPONSE >= 2 */
#ifndef sntp_format_time
/* Debug print helper. */
static const char *
sntp_format_time(s32_t sec)
{
time_t ut;
ut = (u32_t)((u32_t)sec + DIFF_SEC_1970_2036);
return ctime(&ut);
}
#endif /* !sntp_format_time */
/**
* SNTP processing of received timestamp
*/
static void
sntp_process(u32_t *receive_timestamp)
{
/* convert SNTP time (1900-based) to unix GMT time (1970-based)
* if MSB is 0, SNTP time is 2036-based!
*/
u32_t rx_secs = lwip_ntohl(receive_timestamp[0]);
int is_1900_based = ((rx_secs & 0x80000000) != 0);
u32_t t = is_1900_based ? (rx_secs - DIFF_SEC_1900_1970) : (rx_secs + DIFF_SEC_1970_2036);
time_t tim = t;
s32_t sec;
u32_t frac;
#if SNTP_CALC_TIME_US
u32_t us = lwip_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(&tim), us));
sec = lwip_ntohl(receive_timestamp[0]);
frac = lwip_ntohl(receive_timestamp[1]);
#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(&tim)));
#endif /* SNTP_CALC_TIME_US */
LWIP_UNUSED_ARG(tim);
SNTP_SET_SYSTEM_TIME_NTP(sec, frac);
LWIP_DEBUGF(SNTP_DEBUG_TRACE, ("sntp_process: %s, %" U32_F " us\n",
sntp_format_time(sec), SNTP_FRAC_TO_US(frac)));
}
/**
@ -244,14 +268,16 @@ sntp_initialize_request(struct sntp_msg *req)
#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] = lwip_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] = lwip_htonl(sntp_time_us);
req->transmit_timestamp[1] = sntp_last_timestamp_sent[1];
u32_t sec, frac;
/* Get the transmit timestamp */
SNTP_GET_SYSTEM_TIME_NTP(sec, frac);
sec = lwip_htonl(sec);
frac = lwip_htonl(frac);
sntp_last_timestamp_sent[0] = sec;
sntp_last_timestamp_sent[1] = frac;
req->transmit_timestamp[0] = sec;
req->transmit_timestamp[1] = frac;
}
#endif /* SNTP_CHECK_RESPONSE >= 2 */
}
@ -336,7 +362,7 @@ sntp_recv(void *arg, struct udp_pcb* pcb, struct pbuf *p, const ip_addr_t *addr,
{
u8_t mode;
u8_t stratum;
u32_t receive_timestamp[SNTP_RECEIVE_TIME_SIZE];
u32_t receive_timestamp[2];
err_t err;
LWIP_UNUSED_ARG(arg);
@ -383,7 +409,7 @@ sntp_recv(void *arg, struct udp_pcb* pcb, struct pbuf *p, const ip_addr_t *addr,
{
/* correct answer */
err = ERR_OK;
pbuf_copy_partial(p, &receive_timestamp, SNTP_RECEIVE_TIME_SIZE * 4, SNTP_OFFSET_TRANSMIT_TIME);
pbuf_copy_partial(p, &receive_timestamp, 8, SNTP_OFFSET_TRANSMIT_TIME);
}
}
} else {

8
src/include/lwip/apps/sntp_opts.h
View File

@ -46,8 +46,10 @@
*/
/** SNTP macro to change system time in seconds
* Define SNTP_SET_SYSTEM_TIME_US(sec, us) to set the time in microseconds instead of this one
* if you need the additional precision.
* Define SNTP_SET_SYSTEM_TIME_US(sec, us) to set the time in microseconds
* instead of this one if you need the additional precision. Alternatively,
* define SNTP_SET_SYSTEM_TIME_NTP(sec, frac) in order to work with native
* NTP timestamps instead.
*/
#if !defined SNTP_SET_SYSTEM_TIME || defined __DOXYGEN__
#define SNTP_SET_SYSTEM_TIME(sec) LWIP_UNUSED_ARG(sec)
@ -141,6 +143,8 @@
/** SNTP macro to get system time, used with SNTP_CHECK_RESPONSE >= 2
* to send in request and compare in response.
* Alternatively, define SNTP_GET_SYSTEM_TIME_NTP(sec, frac) in order to
* work with native NTP timestamps instead.
*/
#if !defined SNTP_GET_SYSTEM_TIME || defined __DOXYGEN__
#define SNTP_GET_SYSTEM_TIME(sec, us) do { (sec) = 0; (us) = 0; } while(0)