The Tcpdump Group git mirrors - tcpdump/blob - print-ntp.c

   1 /*
   2  * Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that: (1) source code distributions
   7  * retain the above copyright notice and this paragraph in its entirety, (2)
   8  * distributions including binary code include the above copyright notice and
   9  * this paragraph in its entirety in the documentation or other materials
  10  * provided with the distribution, and (3) all advertising materials mentioning
  11  * features or use of this software display the following acknowledgement:
  12  * ``This product includes software developed by the University of California,
  13  * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
  14  * the University nor the names of its contributors may be used to endorse
  15  * or promote products derived from this software without specific prior
  16  * written permission.
  17  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
  18  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
  19  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  20  *
  21  *      By Jeffrey Mogul/DECWRL
  22  *      loosely based on print-bootp.c
  23  */
  24
  25 /* \summary: Network Time Protocol (NTP) printer */
  26
  27 /*
  28  * specification:
  29  *
  30  * RFC 1119 - NTPv2
  31  * RFC 1305 - NTPv3
  32  * RFC 5905 - NTPv4
  33  */
  34
  35 #ifdef HAVE_CONFIG_H
  36 #include <config.h>
  37 #endif
  38
  39 #include "netdissect-stdinc.h"
  40
  41 #ifdef HAVE_STRFTIME
  42 #include <time.h>
  43 #endif
  44
  45 #include "netdissect.h"
  46 #include "addrtoname.h"
  47 #include "extract.h"
  48
  49
  50 /*
  51  * Based on ntp.h from the U of MD implementation
  52  *      This file is based on Version 2 of the NTP spec (RFC1119).
  53  */
  54
  55 /*
  56  *  Definitions for the masses
  57  */
  58 #define JAN_1970        INT64_T_CONSTANT(2208988800)    /* 1970 - 1900 in seconds */
  59
  60 /*
  61  * Structure definitions for NTP fixed point values
  62  *
  63  *    0                   1                   2                   3
  64  *    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  65  *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  66  *   |                         Integer Part                          |
  67  *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  68  *   |                         Fraction Part                         |
  69  *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  70  *
  71  *    0                   1                   2                   3
  72  *    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  73  *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  74  *   |            Integer Part       |     Fraction Part             |
  75  *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  76 */
  77 struct l_fixedpt {
  78         nd_uint32_t int_part;
  79         nd_uint32_t fraction;
  80 };
  81
  82 struct s_fixedpt {
  83         nd_uint16_t int_part;
  84         nd_uint16_t fraction;
  85 };
  86
  87 /* rfc2030
  88  *                      1                   2                   3
  89  *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  90  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  91  * |LI | VN  |Mode |    Stratum    |     Poll      |   Precision   |
  92  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  93  * |                          Root Delay                           |
  94  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  95  * |                       Root Dispersion                         |
  96  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  97  * |                     Reference Identifier                      |
  98  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  99  * |                                                               |
 100  * |                   Reference Timestamp (64)                    |
 101  * |                                                               |
 102  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 103  * |                                                               |
 104  * |                   Originate Timestamp (64)                    |
 105  * |                                                               |
 106  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 107  * |                                                               |
 108  * |                    Receive Timestamp (64)                     |
 109  * |                                                               |
 110  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 111  * |                                                               |
 112  * |                    Transmit Timestamp (64)                    |
 113  * |                                                               |
 114  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 115  * |                 Key Identifier (optional) (32)                |
 116  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 117  * |                                                               |
 118  * |                                                               |
 119  * |                 Message Digest (optional) (128)               |
 120  * |                                                               |
 121  * |                                                               |
 122  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 123  */
 124
 125 /* Length of the NTP data message with the mandatory fields ("the header")
 126  * and without any optional fields (extension, Key Identifier,
 127  * Message Digest).
 128  */
 129 #define NTP_TIMEMSG_MINLEN 48U
 130
 131 struct ntp_time_data {
 132         nd_uint8_t status;              /* status of local clock and leap info */
 133         nd_uint8_t stratum;             /* Stratum level */
 134         nd_int8_t ppoll;                /* poll value */
 135         nd_int8_t precision;
 136         struct s_fixedpt root_delay;
 137         struct s_fixedpt root_dispersion;
 138         nd_uint32_t refid;
 139         struct l_fixedpt ref_timestamp;
 140         struct l_fixedpt org_timestamp;
 141         struct l_fixedpt rec_timestamp;
 142         struct l_fixedpt xmt_timestamp;
 143         nd_uint32_t key_id;
 144         nd_uint8_t  message_digest[20];
 145 };
 146 /*
 147  *      Leap Second Codes (high order two bits)
 148  */
 149 #define NO_WARNING      0x00    /* no warning */
 150 #define PLUS_SEC        0x40    /* add a second (61 seconds) */
 151 #define MINUS_SEC       0x80    /* minus a second (59 seconds) */
 152 #define ALARM           0xc0    /* alarm condition (clock unsynchronized) */
 153
 154 /*
 155  *      Clock Status Bits that Encode Version
 156  */
 157 #define NTPVERSION_1    0x08
 158 #define VERSIONMASK     0x38
 159 #define VERSIONSHIFT    3
 160 #define LEAPMASK        0xc0
 161 #define LEAPSHIFT       6
 162 #ifdef MODEMASK
 163 #undef MODEMASK                                 /* Solaris sucks */
 164 #endif
 165 #define MODEMASK        0x07
 166 #define MODESHIFT       0
 167
 168 /*
 169  *      Code values
 170  */
 171 #define MODE_UNSPEC     0       /* unspecified */
 172 #define MODE_SYM_ACT    1       /* symmetric active */
 173 #define MODE_SYM_PAS    2       /* symmetric passive */
 174 #define MODE_CLIENT     3       /* client */
 175 #define MODE_SERVER     4       /* server */
 176 #define MODE_BROADCAST  5       /* broadcast */
 177 #define MODE_CONTROL    6       /* control message */
 178 #define MODE_RES2       7       /* reserved */
 179
 180 /*
 181  *      Stratum Definitions
 182  */
 183 #define UNSPECIFIED     0
 184 #define PRIM_REF        1       /* radio clock */
 185 #define INFO_QUERY      62      /* **** THIS implementation dependent **** */
 186 #define INFO_REPLY      63      /* **** THIS implementation dependent **** */
 187
 188 static void p_sfix(netdissect_options *ndo, const struct s_fixedpt *);
 189 static void p_ntp_time(netdissect_options *, const struct l_fixedpt *);
 190 static void p_ntp_delta(netdissect_options *, const struct l_fixedpt *, const struct l_fixedpt *);
 191 static void p_poll(netdissect_options *, const int);
 192
 193 static const struct tok ntp_mode_values[] = {
 194     { MODE_UNSPEC,    "unspecified" },
 195     { MODE_SYM_ACT,   "symmetric active" },
 196     { MODE_SYM_PAS,   "symmetric passive" },
 197     { MODE_CLIENT,    "Client" },
 198     { MODE_SERVER,    "Server" },
 199     { MODE_BROADCAST, "Broadcast" },
 200     { MODE_CONTROL,   "Control Message" },
 201     { MODE_RES2,      "Reserved" },
 202     { 0, NULL }
 203 };
 204
 205 static const struct tok ntp_leapind_values[] = {
 206     { NO_WARNING,     "" },
 207     { PLUS_SEC,       "+1s" },
 208     { MINUS_SEC,      "-1s" },
 209     { ALARM,          "clock unsynchronized" },
 210     { 0, NULL }
 211 };
 212
 213 static const struct tok ntp_stratum_values[] = {
 214         { UNSPECIFIED,  "unspecified" },
 215         { PRIM_REF,     "primary reference" },
 216         { 0, NULL }
 217 };
 218
 219 /* draft-ietf-ntp-mode-6-cmds-02
 220  *  0                   1                   2                   3
 221  *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 222  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 223  * |LI |  VN |Mode |R|E|M| OpCode  |       Sequence Number         |
 224  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 225  * |            Status             |       Association ID          |
 226  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 227  * |            Offset             |            Count              |
 228  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 229  * |                                                               |
 230  * /                    Data (up to 468 bytes)                     /
 231  * |                                                               |
 232  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 233  * |                    Padding (optional)                         |
 234  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 235  * |                                                               |
 236  * /              Authenticator (optional, 96 bytes)               /
 237  * |                                                               |
 238  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 239  *
 240  *               Figure 1: NTP Control Message Header
 241  */
 242
 243 /* Length of the NTP control message with the mandatory fields ("the header")
 244  * and without any optional fields (Data, Padding, Authenticator).
 245  */
 246 #define NTP_CTRLMSG_MINLEN 12U
 247
 248 struct ntp_control_data {
 249         nd_uint8_t      magic;          /* LI, VN, Mode */
 250         nd_uint8_t      control;        /* R, E, M, OpCode */
 251         nd_uint16_t     sequence;       /* Sequence Number */
 252         nd_uint16_t     status;         /* Status */
 253         nd_uint16_t     assoc;          /* Association ID */
 254         nd_uint16_t     offset;         /* Offset */
 255         nd_uint16_t     count;          /* Count */
 256         nd_uint8_t      data[564];      /* Data, [Padding, [Authenticator]] */
 257 };
 258
 259 /*
 260  * Print NTP time requests and responses
 261  */
 262 static void
 263 ntp_time_print(netdissect_options *ndo,
 264                const struct ntp_time_data *bp, u_int length)
 265 {
 266         uint8_t stratum;
 267
 268         if (length < NTP_TIMEMSG_MINLEN)
 269                 goto invalid;
 270
 271         ND_TCHECK_1(bp->stratum);
 272         stratum = GET_U_1(bp->stratum);
 273         ND_PRINT(", Stratum %u (%s)",
 274                 stratum,
 275                 tok2str(ntp_stratum_values, (stratum >=2 && stratum<=15) ? "secondary reference" : "reserved", stratum));
 276
 277         ND_TCHECK_1(bp->ppoll);
 278         ND_PRINT(", poll %d", GET_S_1(bp->ppoll));
 279         p_poll(ndo, GET_S_1(bp->ppoll));
 280
 281         ND_TCHECK_1(bp->precision);
 282         ND_PRINT(", precision %d", GET_S_1(bp->precision));
 283
 284         ND_TCHECK_SIZE(&bp->root_delay);
 285         ND_PRINT("\n\tRoot Delay: ");
 286         p_sfix(ndo, &bp->root_delay);
 287
 288         ND_TCHECK_SIZE(&bp->root_dispersion);
 289         ND_PRINT(", Root dispersion: ");
 290         p_sfix(ndo, &bp->root_dispersion);
 291
 292         ND_TCHECK_4(bp->refid);
 293         ND_PRINT(", Reference-ID: ");
 294         /* Interpretation depends on stratum */
 295         switch (stratum) {
 296
 297         case UNSPECIFIED:
 298                 ND_PRINT("(unspec)");
 299                 break;
 300
 301         case PRIM_REF:
 302                 if (nd_printn(ndo, (const u_char *)&(bp->refid), 4, ndo->ndo_snapend))
 303                         goto trunc;
 304                 break;
 305
 306         case INFO_QUERY:
 307                 ND_PRINT("%s INFO_QUERY", GET_IPADDR_STRING(bp->refid));
 308                 /* this doesn't have more content */
 309                 return;
 310
 311         case INFO_REPLY:
 312                 ND_PRINT("%s INFO_REPLY", GET_IPADDR_STRING(bp->refid));
 313                 /* this is too complex to be worth printing */
 314                 return;
 315
 316         default:
 317                 /* In NTPv4 (RFC 5905) refid is an IPv4 address or first 32 bits of
 318                    MD5 sum of IPv6 address */
 319                 ND_PRINT("0x%08x", GET_BE_U_4(bp->refid));
 320                 break;
 321         }
 322
 323         ND_TCHECK_SIZE(&bp->ref_timestamp);
 324         ND_PRINT("\n\t  Reference Timestamp:  ");
 325         p_ntp_time(ndo, &(bp->ref_timestamp));
 326
 327         ND_TCHECK_SIZE(&bp->org_timestamp);
 328         ND_PRINT("\n\t  Originator Timestamp: ");
 329         p_ntp_time(ndo, &(bp->org_timestamp));
 330
 331         ND_TCHECK_SIZE(&bp->rec_timestamp);
 332         ND_PRINT("\n\t  Receive Timestamp:    ");
 333         p_ntp_time(ndo, &(bp->rec_timestamp));
 334
 335         ND_TCHECK_SIZE(&bp->xmt_timestamp);
 336         ND_PRINT("\n\t  Transmit Timestamp:   ");
 337         p_ntp_time(ndo, &(bp->xmt_timestamp));
 338
 339         ND_PRINT("\n\t    Originator - Receive Timestamp:  ");
 340         p_ntp_delta(ndo, &(bp->org_timestamp), &(bp->rec_timestamp));
 341
 342         ND_PRINT("\n\t    Originator - Transmit Timestamp: ");
 343         p_ntp_delta(ndo, &(bp->org_timestamp), &(bp->xmt_timestamp));
 344
 345         /* FIXME: this code is not aware of any extension fields */
 346         if (length == NTP_TIMEMSG_MINLEN + 4) {         /* Optional: key-id (crypto-NAK) */
 347                 ND_TCHECK_4(bp->key_id);
 348                 ND_PRINT("\n\tKey id: %u", GET_BE_U_4(bp->key_id));
 349         } else if (length == NTP_TIMEMSG_MINLEN + 4 + 16) {     /* Optional: key-id + 128-bit digest */
 350                 ND_TCHECK_4(bp->key_id);
 351                 ND_PRINT("\n\tKey id: %u", GET_BE_U_4(bp->key_id));
 352                 ND_TCHECK_LEN(bp->message_digest, 16);
 353                 ND_PRINT("\n\tAuthentication: %08x%08x%08x%08x",
 354                          GET_BE_U_4(bp->message_digest),
 355                          GET_BE_U_4(bp->message_digest + 4),
 356                          GET_BE_U_4(bp->message_digest + 8),
 357                          GET_BE_U_4(bp->message_digest + 12));
 358         } else if (length == NTP_TIMEMSG_MINLEN + 4 + 20) {     /* Optional: key-id + 160-bit digest */
 359                 ND_TCHECK_4(bp->key_id);
 360                 ND_PRINT("\n\tKey id: %u", GET_BE_U_4(bp->key_id));
 361                 ND_TCHECK_LEN(bp->message_digest, 20);
 362                 ND_PRINT("\n\tAuthentication: %08x%08x%08x%08x%08x",
 363                          GET_BE_U_4(bp->message_digest),
 364                          GET_BE_U_4(bp->message_digest + 4),
 365                          GET_BE_U_4(bp->message_digest + 8),
 366                          GET_BE_U_4(bp->message_digest + 12),
 367                          GET_BE_U_4(bp->message_digest + 16));
 368         } else if (length > NTP_TIMEMSG_MINLEN) {
 369                 ND_PRINT("\n\t(%u more bytes after the header)", length - NTP_TIMEMSG_MINLEN);
 370         }
 371         return;
 372
 373 invalid:
 374         nd_print_invalid(ndo);
 375         ND_TCHECK_LEN(bp, length);
 376         return;
 377
 378 trunc:
 379         nd_print_trunc(ndo);
 380 }
 381
 382 /*
 383  * Print NTP control message requests and responses
 384  */
 385 static void
 386 ntp_control_print(netdissect_options *ndo,
 387                   const struct ntp_control_data *cd, u_int length)
 388 {
 389         uint8_t control, R, E, M, opcode;
 390         uint16_t sequence, status, assoc, offset, count;
 391
 392         if (length < NTP_CTRLMSG_MINLEN)
 393                 goto invalid;
 394
 395         ND_TCHECK_1(cd->control);
 396         control = GET_U_1(cd->control);
 397         R = (control & 0x80) != 0;
 398         E = (control & 0x40) != 0;
 399         M = (control & 0x20) != 0;
 400         opcode = control & 0x1f;
 401         ND_PRINT(", %s, %s, %s, OpCode=%u\n",
 402                   R ? "Response" : "Request", E ? "Error" : "OK",
 403                   M ? "More" : "Last", opcode);
 404
 405         ND_TCHECK_2(cd->sequence);
 406         sequence = GET_BE_U_2(cd->sequence);
 407         ND_PRINT("\tSequence=%hu", sequence);
 408
 409         ND_TCHECK_2(cd->status);
 410         status = GET_BE_U_2(cd->status);
 411         ND_PRINT(", Status=%#hx", status);
 412
 413         ND_TCHECK_2(cd->assoc);
 414         assoc = GET_BE_U_2(cd->assoc);
 415         ND_PRINT(", Assoc.=%hu", assoc);
 416
 417         ND_TCHECK_2(cd->offset);
 418         offset = GET_BE_U_2(cd->offset);
 419         ND_PRINT(", Offset=%hu", offset);
 420
 421         ND_TCHECK_2(cd->count);
 422         count = GET_BE_U_2(cd->count);
 423         ND_PRINT(", Count=%hu", count);
 424
 425         if (NTP_CTRLMSG_MINLEN + count > length)
 426                 goto invalid;
 427         if (count != 0) {
 428                 ND_TCHECK_LEN(cd->data, count);
 429                 ND_PRINT("\n\tTO-BE-DONE: data not interpreted");
 430         }
 431         return;
 432
 433 invalid:
 434         nd_print_invalid(ndo);
 435         ND_TCHECK_LEN(cd, length);
 436         return;
 437
 438 trunc:
 439         nd_print_trunc(ndo);
 440 }
 441
 442 union ntpdata {
 443         struct ntp_time_data    td;
 444         struct ntp_control_data cd;
 445 };
 446
 447 /*
 448  * Print NTP requests, handling the common VN, LI, and Mode
 449  */
 450 void
 451 ntp_print(netdissect_options *ndo,
 452           const u_char *cp, u_int length)
 453 {
 454         const union ntpdata *bp = (const union ntpdata *)cp;
 455         u_int mode, version, leapind;
 456         uint8_t status;
 457
 458         ndo->ndo_protocol = "ntp";
 459         ND_TCHECK_1(bp->td.status);
 460         status = GET_U_1(bp->td.status);
 461
 462         version = (status & VERSIONMASK) >> VERSIONSHIFT;
 463         ND_PRINT("NTPv%u", version);
 464
 465         mode = (status & MODEMASK) >> MODESHIFT;
 466         if (!ndo->ndo_vflag) {
 467                 ND_PRINT(", %s, length %u",
 468                          tok2str(ntp_mode_values, "Unknown mode", mode),
 469                          length);
 470                 return;
 471         }
 472
 473         ND_PRINT(", %s, length %u\n",
 474                   tok2str(ntp_mode_values, "Unknown mode", mode), length);
 475
 476         /* leapind = (status & LEAPMASK) >> LEAPSHIFT; */
 477         leapind = (status & LEAPMASK);
 478         ND_PRINT("\tLeap indicator: %s (%u)",
 479                  tok2str(ntp_leapind_values, "Unknown", leapind),
 480                  leapind);
 481
 482         switch (mode) {
 483
 484         case MODE_UNSPEC:
 485         case MODE_SYM_ACT:
 486         case MODE_SYM_PAS:
 487         case MODE_CLIENT:
 488         case MODE_SERVER:
 489         case MODE_BROADCAST:
 490                 ntp_time_print(ndo, &bp->td, length);
 491                 break;
 492
 493         case MODE_CONTROL:
 494                 ntp_control_print(ndo, &bp->cd, length);
 495                 break;
 496
 497         default:
 498                 break;                  /* XXX: not implemented! */
 499         }
 500         return;
 501
 502 trunc:
 503         nd_print_trunc(ndo);
 504 }
 505
 506 static void
 507 p_sfix(netdissect_options *ndo,
 508        const struct s_fixedpt *sfp)
 509 {
 510         int i;
 511         int f;
 512         double ff;
 513
 514         i = GET_BE_U_2(sfp->int_part);
 515         f = GET_BE_U_2(sfp->fraction);
 516         ff = f / 65536.0;               /* shift radix point by 16 bits */
 517         f = (int)(ff * 1000000.0);      /* Treat fraction as parts per million */
 518         ND_PRINT("%d.%06d", i, f);
 519 }
 520
 521 #define FMAXINT (4294967296.0)  /* floating point rep. of MAXINT */
 522
 523 static void
 524 p_ntp_time(netdissect_options *ndo,
 525            const struct l_fixedpt *lfp)
 526 {
 527         uint32_t i;
 528         uint32_t uf;
 529         uint32_t f;
 530         double ff;
 531
 532         i = GET_BE_U_4(lfp->int_part);
 533         uf = GET_BE_U_4(lfp->fraction);
 534         ff = uf;
 535         if (ff < 0.0)           /* some compilers are buggy */
 536                 ff += FMAXINT;
 537         ff = ff / FMAXINT;                      /* shift radix point by 32 bits */
 538         f = (uint32_t)(ff * 1000000000.0);      /* treat fraction as parts per billion */
 539         ND_PRINT("%u.%09u", i, f);
 540
 541 #ifdef HAVE_STRFTIME
 542         /*
 543          * print the UTC time in human-readable format.
 544          */
 545         if (i) {
 546             int64_t seconds_64bit = (int64_t)i - JAN_1970;
 547             time_t seconds;
 548             struct tm *tm;
 549             char time_buf[128];
 550
 551             seconds = (time_t)seconds_64bit;
 552             if (seconds != seconds_64bit) {
 553                 /*
 554                  * It doesn't fit into a time_t, so we can't hand it
 555                  * to gmtime.
 556                  */
 557                 ND_PRINT(" (unrepresentable)");
 558             } else {
 559                 tm = gmtime(&seconds);
 560                 if (tm == NULL) {
 561                     /*
 562                      * gmtime() can't handle it.
 563                      * (Yes, that might happen with some version of
 564                      * Microsoft's C library.)
 565                      */
 566                     ND_PRINT(" (unrepresentable)");
 567                 } else {
 568                     /* use ISO 8601 (RFC3339) format */
 569                     strftime(time_buf, sizeof (time_buf), "%Y-%m-%dT%H:%M:%SZ", tm);
 570                     ND_PRINT(" (%s)", time_buf);
 571                 }
 572             }
 573         }
 574 #endif
 575 }
 576
 577 /* Prints time difference between *lfp and *olfp */
 578 static void
 579 p_ntp_delta(netdissect_options *ndo,
 580             const struct l_fixedpt *olfp,
 581             const struct l_fixedpt *lfp)
 582 {
 583         uint32_t u, uf;
 584         uint32_t ou, ouf;
 585         uint32_t i;
 586         uint32_t f;
 587         double ff;
 588         int signbit;
 589
 590         u = GET_BE_U_4(lfp->int_part);
 591         ou = GET_BE_U_4(olfp->int_part);
 592         uf = GET_BE_U_4(lfp->fraction);
 593         ouf = GET_BE_U_4(olfp->fraction);
 594         if (ou == 0 && ouf == 0) {
 595                 p_ntp_time(ndo, lfp);
 596                 return;
 597         }
 598
 599         if (u > ou) {           /* new is definitely greater than old */
 600                 signbit = 0;
 601                 i = u - ou;
 602                 f = uf - ouf;
 603                 if (ouf > uf)   /* must borrow from high-order bits */
 604                         i -= 1;
 605         } else if (u < ou) {    /* new is definitely less than old */
 606                 signbit = 1;
 607                 i = ou - u;
 608                 f = ouf - uf;
 609                 if (uf > ouf)   /* must borrow from the high-order bits */
 610                         i -= 1;
 611         } else {                /* int_part is zero */
 612                 i = 0;
 613                 if (uf > ouf) {
 614                         signbit = 0;
 615                         f = uf - ouf;
 616                 } else {
 617                         signbit = 1;
 618                         f = ouf - uf;
 619                 }
 620         }
 621
 622         ff = f;
 623         if (ff < 0.0)           /* some compilers are buggy */
 624                 ff += FMAXINT;
 625         ff = ff / FMAXINT;                      /* shift radix point by 32 bits */
 626         f = (uint32_t)(ff * 1000000000.0);      /* treat fraction as parts per billion */
 627         ND_PRINT("%s%u.%09u", signbit ? "-" : "+", i, f);
 628 }
 629
 630 /* Prints polling interval in log2 as seconds or fraction of second */
 631 static void
 632 p_poll(netdissect_options *ndo,
 633        const int poll_interval)
 634 {
 635         if (poll_interval <= -32 || poll_interval >= 32)
 636                 return;
 637
 638         if (poll_interval >= 0)
 639                 ND_PRINT(" (%us)", 1U << poll_interval);
 640         else
 641                 ND_PRINT(" (1/%us)", 1U << -poll_interval);
 642 }
 643