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 #ifdef HAVE_CONFIG_H
  28 #include "config.h"
  29 #endif
  30
  31 #include <netdissect-stdinc.h>
  32
  33 #ifdef HAVE_STRFTIME
  34 #include <time.h>
  35 #endif
  36
  37 #include "netdissect.h"
  38 #include "addrtoname.h"
  39 #include "extract.h"
  40
  41 static const char tstr[] = " [|ntp]";
  42
  43 /*
  44  * Based on ntp.h from the U of MD implementation
  45  *      This file is based on Version 2 of the NTP spec (RFC1119).
  46  */
  47
  48 /*
  49  *  Definitions for the masses
  50  */
  51 #define JAN_1970        2208988800U     /* 1970 - 1900 in seconds */
  52
  53 /*
  54  * Structure definitions for NTP fixed point values
  55  *
  56  *    0                   1                   2                   3
  57  *    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
  58  *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  59  *   |                         Integer Part                          |
  60  *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  61  *   |                         Fraction Part                         |
  62  *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  63  *
  64  *    0                   1                   2                   3
  65  *    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
  66  *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  67  *   |            Integer Part       |     Fraction Part             |
  68  *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  69 */
  70 struct l_fixedpt {
  71         nd_uint32_t int_part;
  72         nd_uint32_t fraction;
  73 } UNALIGNED;
  74
  75 struct s_fixedpt {
  76         nd_uint16_t int_part;
  77         nd_uint16_t fraction;
  78 } UNALIGNED;
  79
  80 /* rfc2030
  81  *                      1                   2                   3
  82  *  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
  83  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  84  * |LI | VN  |Mode |    Stratum    |     Poll      |   Precision   |
  85  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  86  * |                          Root Delay                           |
  87  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  88  * |                       Root Dispersion                         |
  89  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  90  * |                     Reference Identifier                      |
  91  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  92  * |                                                               |
  93  * |                   Reference Timestamp (64)                    |
  94  * |                                                               |
  95  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  96  * |                                                               |
  97  * |                   Originate Timestamp (64)                    |
  98  * |                                                               |
  99  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 100  * |                                                               |
 101  * |                    Receive Timestamp (64)                     |
 102  * |                                                               |
 103  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 104  * |                                                               |
 105  * |                    Transmit Timestamp (64)                    |
 106  * |                                                               |
 107  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 108  * |                 Key Identifier (optional) (32)                |
 109  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 110  * |                                                               |
 111  * |                                                               |
 112  * |                 Message Digest (optional) (128)               |
 113  * |                                                               |
 114  * |                                                               |
 115  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 116  */
 117
 118 /* Length of the NTP data message with the mandatory fields ("the header")
 119  * and without any optional fields (extension, Key Identifier,
 120  * Message Digest).
 121  */
 122 #define NTP_TIMEMSG_MINLEN 48U
 123
 124 struct ntp_time_data {
 125         nd_uint8_t status;              /* status of local clock and leap info */
 126         nd_uint8_t stratum;             /* Stratum level */
 127         nd_int8_t ppoll;                /* poll value */
 128         nd_int8_t precision;
 129         struct s_fixedpt root_delay;
 130         struct s_fixedpt root_dispersion;
 131         nd_uint32_t refid;
 132         struct l_fixedpt ref_timestamp;
 133         struct l_fixedpt org_timestamp;
 134         struct l_fixedpt rec_timestamp;
 135         struct l_fixedpt xmt_timestamp;
 136         nd_uint32_t key_id;
 137         nd_uint8_t  message_digest[20];
 138 } UNALIGNED;
 139 /*
 140  *      Leap Second Codes (high order two bits)
 141  */
 142 #define NO_WARNING      0x00    /* no warning */
 143 #define PLUS_SEC        0x40    /* add a second (61 seconds) */
 144 #define MINUS_SEC       0x80    /* minus a second (59 seconds) */
 145 #define ALARM           0xc0    /* alarm condition (clock unsynchronized) */
 146
 147 /*
 148  *      Clock Status Bits that Encode Version
 149  */
 150 #define NTPVERSION_1    0x08
 151 #define VERSIONMASK     0x38
 152 #define VERSIONSHIFT    3
 153 #define LEAPMASK        0xc0
 154 #define LEAPSHIFT       6
 155 #ifdef MODEMASK
 156 #undef MODEMASK                                 /* Solaris sucks */
 157 #endif
 158 #define MODEMASK        0x07
 159 #define MODESHIFT       0
 160
 161 /*
 162  *      Code values
 163  */
 164 #define MODE_UNSPEC     0       /* unspecified */
 165 #define MODE_SYM_ACT    1       /* symmetric active */
 166 #define MODE_SYM_PAS    2       /* symmetric passive */
 167 #define MODE_CLIENT     3       /* client */
 168 #define MODE_SERVER     4       /* server */
 169 #define MODE_BROADCAST  5       /* broadcast */
 170 #define MODE_CONTROL    6       /* control message */
 171 #define MODE_RES2       7       /* reserved */
 172
 173 /*
 174  *      Stratum Definitions
 175  */
 176 #define UNSPECIFIED     0
 177 #define PRIM_REF        1       /* radio clock */
 178 #define INFO_QUERY      62      /* **** THIS implementation dependent **** */
 179 #define INFO_REPLY      63      /* **** THIS implementation dependent **** */
 180
 181 static void p_sfix(netdissect_options *ndo, const struct s_fixedpt *);
 182 static void p_ntp_time(netdissect_options *, const struct l_fixedpt *);
 183 static void p_ntp_delta(netdissect_options *, const struct l_fixedpt *, const struct l_fixedpt *);
 184 static void p_poll(netdissect_options *, register const int);
 185
 186 static const struct tok ntp_mode_values[] = {
 187     { MODE_UNSPEC,    "unspecified" },
 188     { MODE_SYM_ACT,   "symmetric active" },
 189     { MODE_SYM_PAS,   "symmetric passive" },
 190     { MODE_CLIENT,    "Client" },
 191     { MODE_SERVER,    "Server" },
 192     { MODE_BROADCAST, "Broadcast" },
 193     { MODE_CONTROL,   "Control Message" },
 194     { MODE_RES2,      "Reserved" },
 195     { 0, NULL }
 196 };
 197
 198 static const struct tok ntp_leapind_values[] = {
 199     { NO_WARNING,     "" },
 200     { PLUS_SEC,       "+1s" },
 201     { MINUS_SEC,      "-1s" },
 202     { ALARM,          "clock unsynchronized" },
 203     { 0, NULL }
 204 };
 205
 206 static const struct tok ntp_stratum_values[] = {
 207         { UNSPECIFIED,  "unspecified" },
 208         { PRIM_REF,     "primary reference" },
 209         { 0, NULL }
 210 };
 211
 212 /* draft-ietf-ntp-mode-6-cmds-02
 213  *  0                   1                   2                   3
 214  *  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
 215  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 216  * |LI |  VN |Mode |R|E|M| OpCode  |       Sequence Number         |
 217  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 218  * |            Status             |       Association ID          |
 219  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 220  * |            Offset             |            Count              |
 221  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 222  * |                                                               |
 223  * /                    Data (up to 468 bytes)                     /
 224  * |                                                               |
 225  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 226  * |                    Padding (optional)                         |
 227  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 228  * |                                                               |
 229  * /              Authenticator (optional, 96 bytes)               /
 230  * |                                                               |
 231  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 232  *
 233  *               Figure 1: NTP Control Message Header
 234  */
 235
 236 /* Length of the NTP control message with the mandatory fields ("the header")
 237  * and without any optional fields (Data, Padding, Authenticator).
 238  */
 239 #define NTP_CTRLMSG_MINLEN 12U
 240
 241 struct ntp_control_data {
 242         nd_uint8_t      magic;          /* LI, VN, Mode */
 243         nd_uint8_t      control;        /* R, E, M, OpCode */
 244         nd_uint16_t     sequence;       /* Sequence Number */
 245         nd_uint16_t     status;         /* Status */
 246         nd_uint16_t     assoc;          /* Association ID */
 247         nd_uint16_t     offset;         /* Offset */
 248         nd_uint16_t     count;          /* Count */
 249         nd_uint8_t      data[564];      /* Data, [Padding, [Authenticator]] */
 250 } UNALIGNED;
 251
 252 /*
 253  * Print NTP time requests and responses
 254  */
 255 static void
 256 ntp_time_print(netdissect_options *ndo,
 257                register const struct ntp_time_data *bp, u_int length)
 258 {
 259         int mode, version, leapind;
 260
 261         if (length < NTP_TIMEMSG_MINLEN)
 262                 goto invalid;
 263
 264         ND_TCHECK(bp->status);
 265
 266         version = (int)(bp->status & VERSIONMASK) >> VERSIONSHIFT;
 267         ND_PRINT((ndo, "NTPv%d", version));
 268
 269         mode = bp->status & MODEMASK;
 270         if (!ndo->ndo_vflag) {
 271                 ND_PRINT((ndo, ", %s, length %u",
 272                           tok2str(ntp_mode_values, "Unknown mode", mode),
 273                           length));
 274                 return;
 275         }
 276
 277         ND_PRINT((ndo, ", length %u\n\t%s",
 278                   length,
 279                   tok2str(ntp_mode_values, "Unknown mode", mode)));
 280
 281         leapind = bp->status & LEAPMASK;
 282         ND_PRINT((ndo, ", Leap indicator: %s (%u)",
 283                   tok2str(ntp_leapind_values, "Unknown", leapind),
 284                   leapind));
 285
 286         ND_TCHECK(bp->stratum);
 287         ND_PRINT((ndo, ", Stratum %u (%s)",
 288                 bp->stratum,
 289                 tok2str(ntp_stratum_values, (bp->stratum >=2 && bp->stratum<=15) ? "secondary reference" : "reserved", bp->stratum)));
 290
 291         ND_TCHECK(bp->ppoll);
 292         ND_PRINT((ndo, ", poll %d", bp->ppoll));
 293         p_poll(ndo, bp->ppoll);
 294
 295         ND_TCHECK(bp->precision);
 296         ND_PRINT((ndo, ", precision %d", bp->precision));
 297
 298         ND_TCHECK(bp->root_delay);
 299         ND_PRINT((ndo, "\n\tRoot Delay: "));
 300         p_sfix(ndo, &bp->root_delay);
 301
 302         ND_TCHECK(bp->root_dispersion);
 303         ND_PRINT((ndo, ", Root dispersion: "));
 304         p_sfix(ndo, &bp->root_dispersion);
 305
 306         ND_TCHECK(bp->refid);
 307         ND_PRINT((ndo, ", Reference-ID: "));
 308         /* Interpretation depends on stratum */
 309         switch (bp->stratum) {
 310
 311         case UNSPECIFIED:
 312                 ND_PRINT((ndo, "(unspec)"));
 313                 break;
 314
 315         case PRIM_REF:
 316                 if (fn_printn(ndo, (const u_char *)&(bp->refid), 4, ndo->ndo_snapend))
 317                         goto trunc;
 318                 break;
 319
 320         case INFO_QUERY:
 321                 ND_PRINT((ndo, "%s INFO_QUERY", ipaddr_string(ndo, &(bp->refid))));
 322                 /* this doesn't have more content */
 323                 return;
 324
 325         case INFO_REPLY:
 326                 ND_PRINT((ndo, "%s INFO_REPLY", ipaddr_string(ndo, &(bp->refid))));
 327                 /* this is too complex to be worth printing */
 328                 return;
 329
 330         default:
 331                 /* In NTPv4 (RFC 5905) refid is an IPv4 address or first 32 bits of
 332                    MD5 sum of IPv6 address */
 333                 ND_PRINT((ndo, "0x%08x", EXTRACT_32BITS(&bp->refid)));
 334                 break;
 335         }
 336
 337         ND_TCHECK(bp->ref_timestamp);
 338         ND_PRINT((ndo, "\n\t  Reference Timestamp:  "));
 339         p_ntp_time(ndo, &(bp->ref_timestamp));
 340
 341         ND_TCHECK(bp->org_timestamp);
 342         ND_PRINT((ndo, "\n\t  Originator Timestamp: "));
 343         p_ntp_time(ndo, &(bp->org_timestamp));
 344
 345         ND_TCHECK(bp->rec_timestamp);
 346         ND_PRINT((ndo, "\n\t  Receive Timestamp:    "));
 347         p_ntp_time(ndo, &(bp->rec_timestamp));
 348
 349         ND_TCHECK(bp->xmt_timestamp);
 350         ND_PRINT((ndo, "\n\t  Transmit Timestamp:   "));
 351         p_ntp_time(ndo, &(bp->xmt_timestamp));
 352
 353         ND_PRINT((ndo, "\n\t    Originator - Receive Timestamp:  "));
 354         p_ntp_delta(ndo, &(bp->org_timestamp), &(bp->rec_timestamp));
 355
 356         ND_PRINT((ndo, "\n\t    Originator - Transmit Timestamp: "));
 357         p_ntp_delta(ndo, &(bp->org_timestamp), &(bp->xmt_timestamp));
 358
 359         /* FIXME: this code is not aware of any extension fields */
 360         if (length == NTP_TIMEMSG_MINLEN + 4) {         /* Optional: key-id (crypto-NAK) */
 361                 ND_TCHECK(bp->key_id);
 362                 ND_PRINT((ndo, "\n\tKey id: %u", EXTRACT_32BITS(&bp->key_id)));
 363         } else if (length == NTP_TIMEMSG_MINLEN + 4 + 16) {     /* Optional: key-id + 128-bit digest */
 364                 ND_TCHECK(bp->key_id);
 365                 ND_PRINT((ndo, "\n\tKey id: %u", EXTRACT_32BITS(&bp->key_id)));
 366                 ND_TCHECK2(bp->message_digest, 16);
 367                 ND_PRINT((ndo, "\n\tAuthentication: %08x%08x%08x%08x",
 368                                EXTRACT_32BITS(bp->message_digest),
 369                                EXTRACT_32BITS(bp->message_digest + 4),
 370                                EXTRACT_32BITS(bp->message_digest + 8),
 371                                EXTRACT_32BITS(bp->message_digest + 12)));
 372         } else if (length == NTP_TIMEMSG_MINLEN + 4 + 20) {     /* Optional: key-id + 160-bit digest */
 373                 ND_TCHECK(bp->key_id);
 374                 ND_PRINT((ndo, "\n\tKey id: %u", EXTRACT_32BITS(&bp->key_id)));
 375                 ND_TCHECK2(bp->message_digest, 20);
 376                 ND_PRINT((ndo, "\n\tAuthentication: %08x%08x%08x%08x%08x",
 377                                EXTRACT_32BITS(bp->message_digest),
 378                                EXTRACT_32BITS(bp->message_digest + 4),
 379                                EXTRACT_32BITS(bp->message_digest + 8),
 380                                EXTRACT_32BITS(bp->message_digest + 12),
 381                                EXTRACT_32BITS(bp->message_digest + 16)));
 382         } else if (length > NTP_TIMEMSG_MINLEN) {
 383                 ND_PRINT((ndo, "\n\t(%u more bytes after the header)", length - NTP_TIMEMSG_MINLEN));
 384         }
 385         return;
 386
 387 invalid:
 388         ND_PRINT((ndo, " %s", istr));
 389         ND_TCHECK2(*bp, length);
 390         return;
 391
 392 trunc:
 393         ND_PRINT((ndo, " %s", tstr));
 394 }
 395
 396 /*
 397  * Print NTP control message requests and responses
 398  */
 399 static void
 400 ntp_control_print(netdissect_options *ndo,
 401                   register const struct ntp_control_data *cd, u_int length)
 402 {
 403         u_char R, E, M, opcode;
 404         uint16_t sequence, status, assoc, offset, count;
 405
 406         if (length < NTP_CTRLMSG_MINLEN)
 407                 goto invalid;
 408
 409         ND_TCHECK(cd->control);
 410         R = (cd->control & 0x80) != 0;
 411         E = (cd->control & 0x40) != 0;
 412         M = (cd->control & 0x20) != 0;
 413         opcode = cd->control & 0x1f;
 414         ND_PRINT((ndo, ", %s, %s, %s, OpCode=%u\n",
 415                   R ? "Response" : "Request", E ? "Error" : "OK",
 416                   M ? "More" : "Last", (unsigned)opcode));
 417
 418         ND_TCHECK(cd->sequence);
 419         sequence = EXTRACT_16BITS(&cd->sequence);
 420         ND_PRINT((ndo, "\tSequence=%hu", sequence));
 421
 422         ND_TCHECK(cd->status);
 423         status = EXTRACT_16BITS(&cd->status);
 424         ND_PRINT((ndo, ", Status=%#hx", status));
 425
 426         ND_TCHECK(cd->assoc);
 427         assoc = EXTRACT_16BITS(&cd->assoc);
 428         ND_PRINT((ndo, ", Assoc.=%hu", assoc));
 429
 430         ND_TCHECK(cd->offset);
 431         offset = EXTRACT_16BITS(&cd->offset);
 432         ND_PRINT((ndo, ", Offset=%hu", offset));
 433
 434         ND_TCHECK(cd->count);
 435         count = EXTRACT_16BITS(&cd->count);
 436         ND_PRINT((ndo, ", Count=%hu", count));
 437
 438         if (NTP_CTRLMSG_MINLEN + count > length)
 439                 goto invalid;
 440         if (count != 0) {
 441                 ND_TCHECK2(cd->data, count);
 442                 ND_PRINT((ndo, "\n\tTO-BE-DONE: data not interpreted"));
 443         }
 444         return;
 445
 446 invalid:
 447         ND_PRINT((ndo, " %s", istr));
 448         ND_TCHECK2(*cd, length);
 449         return;
 450
 451 trunc:
 452         ND_PRINT((ndo, " %s", tstr));
 453 }
 454
 455 union ntpdata {
 456         struct ntp_time_data    td;
 457         struct ntp_control_data cd;
 458 };
 459
 460 /*
 461  * Print NTP requests, handling the common VN, LI, and Mode
 462  */
 463 void
 464 ntp_print(netdissect_options *ndo,
 465           register const u_char *cp, u_int length)
 466 {
 467         register const union ntpdata *bp = (const union ntpdata *)cp;
 468         int mode, version, leapind;
 469
 470         ND_TCHECK(bp->td.status);
 471
 472         version = (bp->td.status & VERSIONMASK) >> VERSIONSHIFT;
 473         ND_PRINT((ndo, "NTPv%d", version));
 474
 475         mode = (bp->td.status & MODEMASK) >> MODESHIFT;
 476         if (!ndo->ndo_vflag) {
 477                 ND_PRINT((ndo, ", %s, length %u",
 478                           tok2str(ntp_mode_values, "Unknown mode", mode),
 479                           length));
 480                 return;
 481         }
 482
 483         ND_PRINT((ndo, ", %s, length %u\n",
 484                   tok2str(ntp_mode_values, "Unknown mode", mode), length));
 485
 486         /* leapind = (bp->td.status & LEAPMASK) >> LEAPSHIFT; */
 487         leapind = (bp->td.status & LEAPMASK);
 488         ND_PRINT((ndo, "\tLeap indicator: %s (%u)",
 489                   tok2str(ntp_leapind_values, "Unknown", leapind),
 490                   leapind));
 491
 492         if (mode >= MODE_UNSPEC && mode <= MODE_BROADCAST)
 493                 ntp_time_print(ndo, &bp->td, length);
 494         else if (mode == MODE_CONTROL)
 495                 ntp_control_print(ndo, &bp->cd, length);
 496         else
 497                 {;}                     /* XXX: not implemented! */
 498         return;
 499
 500 trunc:
 501         ND_PRINT((ndo, " %s", tstr));
 502 }
 503
 504 static void
 505 p_sfix(netdissect_options *ndo,
 506        register const struct s_fixedpt *sfp)
 507 {
 508         register int i;
 509         register int f;
 510         register double ff;
 511
 512         i = EXTRACT_16BITS(&sfp->int_part);
 513         f = EXTRACT_16BITS(&sfp->fraction);
 514         ff = f / 65536.0;               /* shift radix point by 16 bits */
 515         f = (int)(ff * 1000000.0);      /* Treat fraction as parts per million */
 516         ND_PRINT((ndo, "%d.%06d", i, f));
 517 }
 518
 519 #define FMAXINT (4294967296.0)  /* floating point rep. of MAXINT */
 520
 521 static void
 522 p_ntp_time(netdissect_options *ndo,
 523            register const struct l_fixedpt *lfp)
 524 {
 525         register int32_t i;
 526         register uint32_t uf;
 527         register uint32_t f;
 528         register double ff;
 529
 530         i = EXTRACT_32BITS(&lfp->int_part);
 531         uf = EXTRACT_32BITS(&lfp->fraction);
 532         ff = uf;
 533         if (ff < 0.0)           /* some compilers are buggy */
 534                 ff += FMAXINT;
 535         ff = ff / FMAXINT;                      /* shift radix point by 32 bits */
 536         f = (uint32_t)(ff * 1000000000.0);      /* treat fraction as parts per billion */
 537         ND_PRINT((ndo, "%u.%09d", i, f));
 538
 539 #ifdef HAVE_STRFTIME
 540         /*
 541          * print the UTC time in human-readable format.
 542          */
 543         if (i) {
 544             time_t seconds = i - JAN_1970;
 545             struct tm *tm;
 546             char time_buf[128];
 547
 548             tm = gmtime(&seconds);
 549             /* use ISO 8601 (RFC3339) format */
 550             strftime(time_buf, sizeof (time_buf), "%Y-%m-%dT%H:%M:%S", tm);
 551             ND_PRINT((ndo, " (%s)", time_buf));
 552         }
 553 #endif
 554 }
 555
 556 /* Prints time difference between *lfp and *olfp */
 557 static void
 558 p_ntp_delta(netdissect_options *ndo,
 559             register const struct l_fixedpt *olfp,
 560             register const struct l_fixedpt *lfp)
 561 {
 562         register int32_t i;
 563         register uint32_t u, uf;
 564         register uint32_t ou, ouf;
 565         register uint32_t f;
 566         register double ff;
 567         int signbit;
 568
 569         u = EXTRACT_32BITS(&lfp->int_part);
 570         ou = EXTRACT_32BITS(&olfp->int_part);
 571         uf = EXTRACT_32BITS(&lfp->fraction);
 572         ouf = EXTRACT_32BITS(&olfp->fraction);
 573         if (ou == 0 && ouf == 0) {
 574                 p_ntp_time(ndo, lfp);
 575                 return;
 576         }
 577
 578         i = u - ou;
 579
 580         if (i > 0) {            /* new is definitely greater than old */
 581                 signbit = 0;
 582                 f = uf - ouf;
 583                 if (ouf > uf)   /* must borrow from high-order bits */
 584                         i -= 1;
 585         } else if (i < 0) {     /* new is definitely less than old */
 586                 signbit = 1;
 587                 f = ouf - uf;
 588                 if (uf > ouf)   /* must carry into the high-order bits */
 589                         i += 1;
 590                 i = -i;
 591         } else {                /* int_part is zero */
 592                 if (uf > ouf) {
 593                         signbit = 0;
 594                         f = uf - ouf;
 595                 } else {
 596                         signbit = 1;
 597                         f = ouf - uf;
 598                 }
 599         }
 600
 601         ff = f;
 602         if (ff < 0.0)           /* some compilers are buggy */
 603                 ff += FMAXINT;
 604         ff = ff / FMAXINT;                      /* shift radix point by 32 bits */
 605         f = (uint32_t)(ff * 1000000000.0);      /* treat fraction as parts per billion */
 606         ND_PRINT((ndo, "%s%d.%09d", signbit ? "-" : "+", i, f));
 607 }
 608
 609 /* Prints polling interval in log2 as seconds or fraction of second */
 610 static void
 611 p_poll(netdissect_options *ndo,
 612        register const int poll_interval)
 613 {
 614         if (poll_interval <= -32 || poll_interval >= 32)
 615                 return;
 616
 617         if (poll_interval >= 0)
 618                 ND_PRINT((ndo, " (%us)", 1U << poll_interval));
 619         else
 620                 ND_PRINT((ndo, " (1/%us)", 1U << -poll_interval));
 621 }
 622