From 85acf71d2579ebe4eec05c6f31901adffa700adc Mon Sep 17 00:00:00 2001 From: Miroslav Lichvar Date: Fri, 16 Sep 2022 15:06:36 +0200 Subject: ntpd: make NTP client and server Y2036/2038-ready The 32-bit integer part of the NTP timestamp overflows in year 2036, which starts the second NTP era. Modify the timestamp conversion to shift values between 1900-1970 (in the first era) to the second era to enable the client to measure its offset correctly until year 2106 (assuming 64-bit time_t). Also update the conversion from double used when stepping the clock to work with 64-bit time_t after reaching the maximum 32-bit value in 2038 and the server conversion to work correctly in the next NTP era. function old new delta lfp_to_d 51 64 +13 step_time 326 332 +6 .rodata 105260 105264 +4 d_to_lfp 100 86 -14 ------------------------------------------------------------------------------ (add/remove: 0/0 grow/shrink: 3/1 up/down: 23/-14) Total: 9 bytes Signed-off-by: Miroslav Lichvar Signed-off-by: Denys Vlasenko --- networking/ntpd.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) (limited to 'networking') diff --git a/networking/ntpd.c b/networking/ntpd.c index 204e1d7c2..4365166ff 100644 --- a/networking/ntpd.c +++ b/networking/ntpd.c @@ -554,7 +554,7 @@ gettime1900d(void) static void d_to_tv(struct timeval *tv, double d) { - tv->tv_sec = (long)d; + tv->tv_sec = (time_t)d; tv->tv_usec = (d - tv->tv_sec) * 1000000; } @@ -565,6 +565,14 @@ lfp_to_d(l_fixedpt_t lfp) lfp.int_partl = ntohl(lfp.int_partl); lfp.fractionl = ntohl(lfp.fractionl); ret = (double)lfp.int_partl + ((double)lfp.fractionl / UINT_MAX); + /* + * Shift timestamps before 1970 to the second NTP era (2036-2106): + * int_partl value of OFFSET_1900_1970 (2208988800) is interpreted as + * the start of year 1970 and it is the minimal representable time, + * all values form the sequence 2208988800..0xffffffff,0..2208988799. + */ + if (lfp.int_partl < OFFSET_1900_1970) + ret += (double)(1ULL << 32); /* because int_partl is 32-bit wide */ return ret; } static NOINLINE double @@ -582,8 +590,8 @@ d_to_lfp(l_fixedpt_t *lfp, double d) { uint32_t intl; uint32_t frac; - intl = (uint32_t)d; - frac = (uint32_t)((d - intl) * UINT_MAX); + intl = (uint32_t)(time_t)d; + frac = (uint32_t)((d - (time_t)d) * UINT_MAX); lfp->int_partl = htonl(intl); lfp->fractionl = htonl(frac); } -- cgit v1.2.1