d54cfbdce4
When the series of commits is complete, things like https://cert.litnet.lt/en/docs/ntp-distributed-reflection-dos-attacks should be fixed. PR: bin/148836 (except that we import a newer version) Asked by: Too many MFC after: 2 weeks
57 lines
1.6 KiB
C
57 lines
1.6 KiB
C
/*
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* calyearstart - determine the NTP time at midnight of January 1 in
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* the year of the given date.
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*/
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#include <sys/types.h>
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#include "ntp_types.h"
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#include "ntp_calendar.h"
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#include "ntp_stdlib.h"
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#include "ntp_assert.h"
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/*
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* Juergen Perlinger, 2008-11-12
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* Use the result of 'caljulian' to get the delta from the time stamp to the
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* beginning of the year. Do not make a second trip through 'caltontp' after
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* fixing the date, apart for invariant tests.
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*/
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u_long
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calyearstart(u_long ntp_time)
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{
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struct calendar jt;
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ntp_u_int32_t delta;
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caljulian(ntp_time,&jt);
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/*
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* Now we have days since yearstart (unity-based) and the time in that
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* day. Simply merge these together to seconds and subtract that from
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* input time. That's faster than going through the calendar stuff
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* again...
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*/
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delta = (ntp_u_int32_t)jt.yearday * SECSPERDAY
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+ (ntp_u_int32_t)jt.hour * MINSPERHR * SECSPERMIN
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+ (ntp_u_int32_t)jt.minute * SECSPERMIN
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+ (ntp_u_int32_t)jt.second
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- SECSPERDAY; /* yearday is unity-based... */
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# if ISC_CHECK_INVARIANT
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/*
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* check that this computes properly: do a roundtrip! That's the only
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* sensible test here, but it's a rather expensive invariant...
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*/
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jt.yearday = 0;
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jt.month = 1;
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jt.monthday = 1;
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jt.hour = 0;
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jt.minute = 0;
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jt.second = 0;
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NTP_INVARIANT((ntp_u_int32_t)(caltontp(&jt) + delta) == (ntp_u_int32_t)ntp_time);
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# endif
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/* The NTP time stamps (l_fp) count seconds unsigned mod 2**32, so we
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* have to calculate this in the proper way!
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*/
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return (ntp_u_int32_t)(ntp_time - delta);
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}
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