1 /* 2 * ntp_leapsec.h - leap second processing for NTPD 3 * 4 * Written by Juergen Perlinger (perlinger@ntp.org) for the NTP project. 5 * The contents of 'html/copyright.html' apply. 6 * ---------------------------------------------------------------------- 7 * This is an attempt to get the leap second handling into a dedicated 8 * module to make the somewhat convoluted logic testable. 9 */ 10 11 #ifndef NTP_LEAPSEC_H 12 #define NTP_LEAPSEC_H 13 14 struct stat; 15 16 17 /* function pointer types. Note that 'fprintf' and 'getc' can be casted 18 * to the dumper resp. reader type, provided the auxiliary argument is a 19 * valid FILE pointer in hat case. 20 */ 21 typedef void (*leapsec_dumper)(void*, const char *fmt, ...); 22 typedef int (*leapsec_reader)(void*); 23 24 struct leap_table; 25 typedef struct leap_table leap_table_t; 26 27 /* Validate a stream containing a leap second file in the NIST / NTPD 28 * format that can also be loaded via 'leapsec_load()'. This uses 29 * the SHA1 hash and preprocessing as described in the NIST leapsecond 30 * file. 31 */ 32 #define LSVALID_GOODHASH 1 /* valid signature */ 33 #define LSVALID_NOHASH 0 /* no signature in file */ 34 #define LSVALID_BADHASH -1 /* signature mismatch */ 35 #define LSVALID_BADFORMAT -2 /* signature not parseable */ 36 37 extern int leapsec_validate(leapsec_reader, void*); 38 39 40 /* Set/get electric mode 41 * Electric mode is defined as the operation mode where the system clock 42 * automagically manages the leap second, so we don't have to care about 43 * stepping the clock. (This should be the case with most systems, 44 * including the current implementation of the Win32 timekeeping.) 45 * 46 * The consequence of electric mode is that we do not 'see' the leap 47 * second, and no client actions are needed when crossing the leap era 48 * boundary. In manual (aka non-electric) mode the clock will simply 49 * step forward untill *we* (that is, this module) tells the client app 50 * to step at the right time. This needs a slightly different type of 51 * processing, so switching between those two modes should not be done 52 * too close to a leap second. The transition might be lost in that 53 * case. (The limit is actual 2 sec before transition.) 54 * 55 * OTOH, this is a system characteristic, so it's expected to be set 56 * properly somewhere after system start and retain the value. 57 * 58 * Simply querying the state or setting it to the same value as before 59 * does not have any unwanted side effects. You can query by giving a 60 * negative value for the switch. 61 */ 62 extern int/*BOOL*/ leapsec_electric(int/*BOOL*/ on); 63 64 /* Query result for a leap era. This is the minimal stateless 65 * information available for a time stamp in UTC. 66 */ 67 struct leap_era { 68 vint64 ebase; /* era base (UTC of start) */ 69 vint64 ttime; /* era end (UTC of next leap second) */ 70 int16_t taiof; /* offset to TAI in this era */ 71 }; 72 typedef struct leap_era leap_era_t; 73 74 /* Query result for a leap second schedule 75 * 'ebase' is the nominal UTC time when the current leap era 76 * started. (Era base time) 77 * 'ttime' is the next transition point in full time scale. (Nominal UTC 78 * time when the next leap era starts.) 79 * 'ddist' is the distance to the transition, in clock seconds. 80 * This is the distance to the due time, which is different 81 * from the transition time if the mode is non-electric. 82 * Only valid if 'tai_diff' is not zero. 83 * 'tai_offs' is the CURRENT distance from clock (UTC) to TAI. Always 84 * valid. 85 * 'tai_diff' is the change in TAI offset after the next leap 86 * transition. Zero if nothing is pending or too far ahead. 87 * 'warped' is set only once, when the the leap second occurred between 88 * two queries. Always zero in electric mode. If non-zero, 89 * immediately step the clock. 90 * 'proximity' is a proximity warning. See definitions below. This is 91 * more useful than an absolute difference to the leap second. 92 * 'dynamic' != 0 if entry was requested by clock/peer 93 */ 94 struct leap_result { 95 vint64 ebase; 96 vint64 ttime; 97 uint32_t ddist; 98 int16_t tai_offs; 99 int16_t tai_diff; 100 int16_t warped; 101 uint8_t proximity; 102 uint8_t dynamic; 103 }; 104 typedef struct leap_result leap_result_t; 105 106 /* The leap signature is used in two distinct circumstances, and it has 107 * slightly different content in these cases: 108 * - it is used to indictae the time range covered by the leap second 109 * table, and then it contains the last transition, TAI offset after 110 * the final transition, and the expiration time. 111 * - it is used to query data for AUTOKEY updates, and then it contains 112 * the *current* TAI offset, the *next* transition time and the 113 * expiration time of the table. 114 */ 115 struct leap_signature { 116 uint32_t etime; /* expiration time */ 117 uint32_t ttime; /* transition time */ 118 int16_t taiof; /* total offset to TAI */ 119 }; 120 typedef struct leap_signature leap_signature_t; 121 122 123 #ifdef LEAP_SMEAR 124 125 struct leap_smear_info { 126 int enabled; /* not 0 if smearing is generally enabled */ 127 int in_progress; /* not 0 if smearing is in progress, i.e. the offset has been computed */ 128 int leap_occurred; /* not 0 if the leap second has already occurred, i.e., during the leap second */ 129 double doffset; /* the current smear offset as double */ 130 l_fp offset; /* the current smear offset */ 131 uint32_t t_offset; /* the current time for which a smear offset has been computed */ 132 long interval; /* smear interval, in [s], should be at least some hours */ 133 double intv_start; /* start time of the smear interval */ 134 double intv_end; /* end time of the smear interval */ 135 }; 136 typedef struct leap_smear_info leap_smear_info_t; 137 138 #endif /* LEAP_SMEAR */ 139 140 141 #define LSPROX_NOWARN 0 /* clear radar screen */ 142 #define LSPROX_SCHEDULE 1 /* less than 1 month to target*/ 143 #define LSPROX_ANNOUNCE 2 /* less than 1 day to target */ 144 #define LSPROX_ALERT 3 /* less than 10 sec to target */ 145 146 /* Get the current or alternate table pointer. Getting the alternate 147 * pointer will automatically copy the primary table, so it can be 148 * subsequently modified. 149 */ 150 extern leap_table_t *leapsec_get_table(int alternate); 151 152 /* Set the current leap table. Accepts only return values from 153 * 'leapsec_get_table()', so it's hard to do something wrong. Returns 154 * TRUE if the current table is the requested one. 155 */ 156 extern int/*BOOL*/ leapsec_set_table(leap_table_t *); 157 158 /* Clear all leap second data. Use it for init & cleanup */ 159 extern void leapsec_clear(leap_table_t*); 160 161 /* Load a leap second file. If 'blimit' is set, do not store (but 162 * register with their TAI offset) leap entries before the build date. 163 * Update the leap signature data on the fly. 164 */ 165 extern int/*BOOL*/ leapsec_load(leap_table_t*, leapsec_reader, 166 void*, int blimit); 167 168 /* Dump the current leap table in readable format, using the provided 169 * dump formatter function. 170 */ 171 extern void leapsec_dump(const leap_table_t*, leapsec_dumper func, void *farg); 172 173 /* Read a leap second file from stream. This is a convenience wrapper 174 * around the generic load function, 'leapsec_load()'. 175 */ 176 extern int/*BOOL*/ leapsec_load_stream(FILE * fp, const char * fname, 177 int/*BOOL*/logall); 178 179 /* Read a leap second file from file. It checks that the file exists and 180 * (if 'force' is not applied) the ctime/mtime has changed since the 181 * last load. If the file has to be loaded, either due to 'force' or 182 * changed time stamps, the 'stat()' results of the file are stored in 183 * '*sb' for the next cycle. Returns TRUE on successful load, FALSE 184 * otherwise. Uses 'leapsec_load_stream()' internally. 185 */ 186 extern int/*BOOL*/ leapsec_load_file(const char * fname, struct stat * sb, 187 int/*BOOL*/force, int/*BOOL*/logall); 188 189 /* Get the current leap data signature. This consists of the last 190 * ransition, the table expiration, and the total TAI difference at the 191 * last transition. This is valid even if the leap transition itself was 192 * culled due to the build date limit. 193 */ 194 extern void leapsec_getsig(leap_signature_t * psig); 195 196 /* Check if the leap table is expired at the given time. 197 */ 198 extern int/*BOOL*/ leapsec_expired(uint32_t when, const time_t * pivot); 199 200 /* Get the distance to expiration in days. 201 * Returns negative values if expired, zero if there are less than 24hrs 202 * left, and positive numbers otherwise. 203 */ 204 extern int32_t leapsec_daystolive(uint32_t when, const time_t * pivot); 205 206 /* Reset the current leap frame, so the next query will do proper table 207 * lookup from fresh. Suppresses a possible leap era transition detection 208 * for the next query. 209 */ 210 extern void leapsec_reset_frame(void); 211 212 #if 0 /* currently unused -- possibly revived later */ 213 /* Given a transition time, the TAI offset valid after that and an 214 * expiration time, try to establish a system leap transition. Only 215 * works if the existing table is extended. On success, updates the 216 * signature data. 217 */ 218 extern int/*BOOL*/ leapsec_add_fix(int offset, uint32_t ttime, uint32_t etime, 219 const time_t * pivot); 220 #endif 221 222 /* Take a time stamp and create a leap second frame for it. This will 223 * schedule a leap second for the beginning of the next month, midnight 224 * UTC. The 'insert' argument tells if a leap second is added (!=0) or 225 * removed (==0). We do not handle multiple inserts (yet?) 226 * 227 * Returns 1 if the insert worked, 0 otherwise. (It's not possible to 228 * insert a leap second into the current history -- only appending 229 * towards the future is allowed!) 230 * 231 * 'ntp_now' is subject to era unfolding. The entry is marked 232 * dynamic. The leap signature is NOT updated. 233 */ 234 extern int/*BOOL*/ leapsec_add_dyn(int/*BOOL*/ insert, uint32_t ntp_now, 235 const time_t * pivot); 236 237 /* Take a time stamp and get the associated leap information. The time 238 * stamp is subject to era unfolding around the pivot or the current 239 * system time if pivot is NULL. Sets the information in '*qr' and 240 * returns TRUE if a leap second era boundary was crossed between the 241 * last and the current query. In that case, qr->warped contains the 242 * required clock stepping, which is always zero in electric mode. 243 */ 244 extern int/*BOOL*/ leapsec_query(leap_result_t * qr, uint32_t ntpts, 245 const time_t * pivot); 246 247 /* For a given time stamp, fetch the data for the bracketing leap 248 * era. The time stamp is subject to NTP era unfolding. 249 */ 250 extern int/*BOOL*/ leapsec_query_era(leap_era_t * qr, uint32_t ntpts, 251 const time_t * pivot); 252 253 /* Get the current leap frame info. Returns TRUE if the result contains 254 * useable data, FALSE if there is currently no leap second frame. 255 * This merely replicates some results from a previous query, but since 256 * it does not check the current time, only the following entries are 257 * meaningful: 258 * qr->ttime; 259 * qr->tai_offs; 260 * qr->tai_diff; 261 * qr->dynamic; 262 */ 263 extern int/*BOOL*/ leapsec_frame(leap_result_t *qr); 264 265 266 /* Process a AUTOKEY TAI offset information. This *might* augment the 267 * current leap data table with the given TAI offset. 268 * Returns TRUE if action was taken, FALSE otherwise. 269 */ 270 extern int/*BOOL*/ leapsec_autokey_tai(int tai_offset, uint32_t ntpnow, 271 const time_t * pivot); 272 273 /* reset global state for unit tests */ 274 extern void leapsec_ut_pristine(void); 275 276 #endif /* !defined(NTP_LEAPSEC_H) */ 277