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 #include "ntp.h"
  50
  51 /*
  52  * Based on ntp.h from the U of MD implementation
  53  *      This file is based on Version 2 of the NTP spec (RFC1119).
  54  */
  55
  56 /* rfc2030
  57  *                      1                   2                   3
  58  *  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
  59  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  60  * |LI | VN  |Mode |    Stratum    |     Poll      |   Precision   |
  61  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  62  * |                          Root Delay                           |
  63  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  64  * |                       Root Dispersion                         |
  65  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  66  * |                     Reference Identifier                      |
  67  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  68  * |                                                               |
  69  * |                   Reference Timestamp (64)                    |
  70  * |                                                               |
  71  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  72  * |                                                               |
  73  * |                   Originate Timestamp (64)                    |
  74  * |                                                               |
  75  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  76  * |                                                               |
  77  * |                    Receive Timestamp (64)                     |
  78  * |                                                               |
  79  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  80  * |                                                               |
  81  * |                    Transmit Timestamp (64)                    |
  82  * |                                                               |
  83  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  84  * |                 Key Identifier (optional) (32)                |
  85  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  86  * |                                                               |
  87  * |                                                               |
  88  * |                 Message Digest (optional) (128)               |
  89  * |                                                               |
  90  * |                                                               |
  91  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  92  */
  93
  94 /* Length of the NTP data message with the mandatory fields ("the header")
  95  * and without any optional fields (extension, Key Identifier,
  96  * Message Digest).
  97  */
  98 #define NTP_TIMEMSG_MINLEN 48U
  99
 100 struct ntp_time_data {
 101         nd_uint8_t status;              /* status of local clock and leap info */
 102         nd_uint8_t stratum;             /* Stratum level */
 103         nd_int8_t ppoll;                /* poll value */
 104         nd_int8_t precision;
 105         struct s_fixedpt root_delay;
 106         struct s_fixedpt root_dispersion;
 107         nd_uint32_t refid;
 108         struct l_fixedpt ref_timestamp;
 109         struct l_fixedpt org_timestamp;
 110         struct l_fixedpt rec_timestamp;
 111         struct l_fixedpt xmt_timestamp;
 112         nd_uint32_t key_id;
 113         nd_uint8_t  message_digest[20];
 114 };
 115 /*
 116  *      Leap Second Codes (high order two bits)
 117  */
 118 #define NO_WARNING      0x00    /* no warning */
 119 #define PLUS_SEC        0x40    /* add a second (61 seconds) */
 120 #define MINUS_SEC       0x80    /* minus a second (59 seconds) */
 121 #define ALARM           0xc0    /* alarm condition (clock unsynchronized) */
 122
 123 /*
 124  *      Clock Status Bits that Encode Version
 125  */
 126 #define NTPVERSION_1    0x08
 127 #define VERSIONMASK     0x38
 128 #define VERSIONSHIFT    3
 129 #define LEAPMASK        0xc0
 130 #define LEAPSHIFT       6
 131 #ifdef MODEMASK
 132 #undef MODEMASK                                 /* Solaris sucks */
 133 #endif
 134 #define MODEMASK        0x07
 135 #define MODESHIFT       0
 136
 137 /*
 138  *      Code values
 139  */
 140 #define MODE_UNSPEC     0       /* unspecified */
 141 #define MODE_SYM_ACT    1       /* symmetric active */
 142 #define MODE_SYM_PAS    2       /* symmetric passive */
 143 #define MODE_CLIENT     3       /* client */
 144 #define MODE_SERVER     4       /* server */
 145 #define MODE_BROADCAST  5       /* broadcast */
 146 #define MODE_CONTROL    6       /* control message */
 147 #define MODE_RES2       7       /* reserved */
 148
 149 /*
 150  *      Stratum Definitions
 151  */
 152 #define UNSPECIFIED     0
 153 #define PRIM_REF        1       /* radio clock */
 154 #define INFO_QUERY      62      /* **** THIS implementation dependent **** */
 155 #define INFO_REPLY      63      /* **** THIS implementation dependent **** */
 156
 157 static void p_sfix(netdissect_options *ndo, const struct s_fixedpt *);
 158 static void p_ntp_delta(netdissect_options *, const struct l_fixedpt *, const struct l_fixedpt *);
 159 static void p_poll(netdissect_options *, const int);
 160
 161 static const struct tok ntp_mode_values[] = {
 162     { MODE_UNSPEC,    "unspecified" },
 163     { MODE_SYM_ACT,   "symmetric active" },
 164     { MODE_SYM_PAS,   "symmetric passive" },
 165     { MODE_CLIENT,    "Client" },
 166     { MODE_SERVER,    "Server" },
 167     { MODE_BROADCAST, "Broadcast" },
 168     { MODE_CONTROL,   "Control Message" },
 169     { MODE_RES2,      "Reserved" },
 170     { 0, NULL }
 171 };
 172
 173 static const struct tok ntp_leapind_values[] = {
 174     { NO_WARNING,     "" },
 175     { PLUS_SEC,       "+1s" },
 176     { MINUS_SEC,      "-1s" },
 177     { ALARM,          "clock unsynchronized" },
 178     { 0, NULL }
 179 };
 180
 181 static const struct tok ntp_stratum_values[] = {
 182         { UNSPECIFIED,  "unspecified" },
 183         { PRIM_REF,     "primary reference" },
 184         { 0, NULL }
 185 };
 186
 187 /* draft-ietf-ntp-mode-6-cmds-02
 188  *  0                   1                   2                   3
 189  *  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
 190  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 191  * |LI |  VN |Mode |R|E|M| OpCode  |       Sequence Number         |
 192  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 193  * |            Status             |       Association ID          |
 194  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 195  * |            Offset             |            Count              |
 196  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 197  * |                                                               |
 198  * /                    Data (up to 468 bytes)                     /
 199  * |                                                               |
 200  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 201  * |                    Padding (optional)                         |
 202  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 203  * |                                                               |
 204  * /              Authenticator (optional, 96 bytes)               /
 205  * |                                                               |
 206  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 207  *
 208  *               Figure 1: NTP Control Message Header
 209  */
 210
 211 /* Length of the NTP control message with the mandatory fields ("the header")
 212  * and without any optional fields (Data, Padding, Authenticator).
 213  */
 214 #define NTP_CTRLMSG_MINLEN 12U
 215
 216 struct ntp_control_data {
 217         nd_uint8_t      magic;          /* LI, VN, Mode */
 218         nd_uint8_t      control;        /* R, E, M, OpCode */
 219         nd_uint16_t     sequence;       /* Sequence Number */
 220         nd_uint16_t     status;         /* Status */
 221         nd_uint16_t     assoc;          /* Association ID */
 222         nd_uint16_t     offset;         /* Offset */
 223         nd_uint16_t     count;          /* Count */
 224         nd_uint8_t      data[564];      /* Data, [Padding, [Authenticator]] */
 225 };
 226
 227 /*
 228  * Print NTP time requests and responses
 229  */
 230 static void
 231 ntp_time_print(netdissect_options *ndo,
 232                const struct ntp_time_data *bp, u_int length)
 233 {
 234         uint8_t stratum;
 235
 236         if (length < NTP_TIMEMSG_MINLEN)
 237                 goto invalid;
 238
 239         ND_TCHECK_1(bp->stratum);
 240         stratum = GET_U_1(bp->stratum);
 241         ND_PRINT(", Stratum %u (%s)",
 242                 stratum,
 243                 tok2str(ntp_stratum_values, (stratum >=2 && stratum<=15) ? "secondary reference" : "reserved", stratum));
 244
 245         ND_TCHECK_1(bp->ppoll);
 246         ND_PRINT(", poll %d", GET_S_1(bp->ppoll));
 247         p_poll(ndo, GET_S_1(bp->ppoll));
 248
 249         ND_TCHECK_1(bp->precision);
 250         ND_PRINT(", precision %d", GET_S_1(bp->precision));
 251
 252         ND_TCHECK_SIZE(&bp->root_delay);
 253         ND_PRINT("\n\tRoot Delay: ");
 254         p_sfix(ndo, &bp->root_delay);
 255
 256         ND_TCHECK_SIZE(&bp->root_dispersion);
 257         ND_PRINT(", Root dispersion: ");
 258         p_sfix(ndo, &bp->root_dispersion);
 259
 260         ND_TCHECK_4(bp->refid);
 261         ND_PRINT(", Reference-ID: ");
 262         /* Interpretation depends on stratum */
 263         switch (stratum) {
 264
 265         case UNSPECIFIED:
 266                 ND_PRINT("(unspec)");
 267                 break;
 268
 269         case PRIM_REF:
 270                 if (nd_printn(ndo, (const u_char *)&(bp->refid), 4, ndo->ndo_snapend))
 271                         goto trunc;
 272                 break;
 273
 274         case INFO_QUERY:
 275                 ND_PRINT("%s INFO_QUERY", GET_IPADDR_STRING(bp->refid));
 276                 /* this doesn't have more content */
 277                 return;
 278
 279         case INFO_REPLY:
 280                 ND_PRINT("%s INFO_REPLY", GET_IPADDR_STRING(bp->refid));
 281                 /* this is too complex to be worth printing */
 282                 return;
 283
 284         default:
 285                 /* In NTPv4 (RFC 5905) refid is an IPv4 address or first 32 bits of
 286                    MD5 sum of IPv6 address */
 287                 ND_PRINT("0x%08x", GET_BE_U_4(bp->refid));
 288                 break;
 289         }
 290
 291         ND_TCHECK_SIZE(&bp->ref_timestamp);
 292         ND_PRINT("\n\t  Reference Timestamp:  ");
 293         p_ntp_time(ndo, &(bp->ref_timestamp));
 294
 295         ND_TCHECK_SIZE(&bp->org_timestamp);
 296         ND_PRINT("\n\t  Originator Timestamp: ");
 297         p_ntp_time(ndo, &(bp->org_timestamp));
 298
 299         ND_TCHECK_SIZE(&bp->rec_timestamp);
 300         ND_PRINT("\n\t  Receive Timestamp:    ");
 301         p_ntp_time(ndo, &(bp->rec_timestamp));
 302
 303         ND_TCHECK_SIZE(&bp->xmt_timestamp);
 304         ND_PRINT("\n\t  Transmit Timestamp:   ");
 305         p_ntp_time(ndo, &(bp->xmt_timestamp));
 306
 307         ND_PRINT("\n\t    Originator - Receive Timestamp:  ");
 308         p_ntp_delta(ndo, &(bp->org_timestamp), &(bp->rec_timestamp));
 309
 310         ND_PRINT("\n\t    Originator - Transmit Timestamp: ");
 311         p_ntp_delta(ndo, &(bp->org_timestamp), &(bp->xmt_timestamp));
 312
 313         /* FIXME: this code is not aware of any extension fields */
 314         if (length == NTP_TIMEMSG_MINLEN + 4) {         /* Optional: key-id (crypto-NAK) */
 315                 ND_TCHECK_4(bp->key_id);
 316                 ND_PRINT("\n\tKey id: %u", GET_BE_U_4(bp->key_id));
 317         } else if (length == NTP_TIMEMSG_MINLEN + 4 + 16) {     /* Optional: key-id + 128-bit digest */
 318                 ND_TCHECK_4(bp->key_id);
 319                 ND_PRINT("\n\tKey id: %u", GET_BE_U_4(bp->key_id));
 320                 ND_TCHECK_LEN(bp->message_digest, 16);
 321                 ND_PRINT("\n\tAuthentication: %08x%08x%08x%08x",
 322                          GET_BE_U_4(bp->message_digest),
 323                          GET_BE_U_4(bp->message_digest + 4),
 324                          GET_BE_U_4(bp->message_digest + 8),
 325                          GET_BE_U_4(bp->message_digest + 12));
 326         } else if (length == NTP_TIMEMSG_MINLEN + 4 + 20) {     /* Optional: key-id + 160-bit digest */
 327                 ND_TCHECK_4(bp->key_id);
 328                 ND_PRINT("\n\tKey id: %u", GET_BE_U_4(bp->key_id));
 329                 ND_TCHECK_LEN(bp->message_digest, 20);
 330                 ND_PRINT("\n\tAuthentication: %08x%08x%08x%08x%08x",
 331                          GET_BE_U_4(bp->message_digest),
 332                          GET_BE_U_4(bp->message_digest + 4),
 333                          GET_BE_U_4(bp->message_digest + 8),
 334                          GET_BE_U_4(bp->message_digest + 12),
 335                          GET_BE_U_4(bp->message_digest + 16));
 336         } else if (length > NTP_TIMEMSG_MINLEN) {
 337                 ND_PRINT("\n\t(%u more bytes after the header)", length - NTP_TIMEMSG_MINLEN);
 338         }
 339         return;
 340
 341 invalid:
 342         nd_print_invalid(ndo);
 343         ND_TCHECK_LEN(bp, length);
 344         return;
 345
 346 trunc:
 347         nd_print_trunc(ndo);
 348 }
 349
 350 /*
 351  * Print NTP control message requests and responses
 352  */
 353 static void
 354 ntp_control_print(netdissect_options *ndo,
 355                   const struct ntp_control_data *cd, u_int length)
 356 {
 357         uint8_t control, R, E, M, opcode;
 358         uint16_t sequence, status, assoc, offset, count;
 359
 360         if (length < NTP_CTRLMSG_MINLEN)
 361                 goto invalid;
 362
 363         ND_TCHECK_1(cd->control);
 364         control = GET_U_1(cd->control);
 365         R = (control & 0x80) != 0;
 366         E = (control & 0x40) != 0;
 367         M = (control & 0x20) != 0;
 368         opcode = control & 0x1f;
 369         ND_PRINT(", %s, %s, %s, OpCode=%u\n",
 370                   R ? "Response" : "Request", E ? "Error" : "OK",
 371                   M ? "More" : "Last", opcode);
 372
 373         ND_TCHECK_2(cd->sequence);
 374         sequence = GET_BE_U_2(cd->sequence);
 375         ND_PRINT("\tSequence=%hu", sequence);
 376
 377         ND_TCHECK_2(cd->status);
 378         status = GET_BE_U_2(cd->status);
 379         ND_PRINT(", Status=%#hx", status);
 380
 381         ND_TCHECK_2(cd->assoc);
 382         assoc = GET_BE_U_2(cd->assoc);
 383         ND_PRINT(", Assoc.=%hu", assoc);
 384
 385         ND_TCHECK_2(cd->offset);
 386         offset = GET_BE_U_2(cd->offset);
 387         ND_PRINT(", Offset=%hu", offset);
 388
 389         ND_TCHECK_2(cd->count);
 390         count = GET_BE_U_2(cd->count);
 391         ND_PRINT(", Count=%hu", count);
 392
 393         if (NTP_CTRLMSG_MINLEN + count > length)
 394                 goto invalid;
 395         if (count != 0) {
 396                 ND_TCHECK_LEN(cd->data, count);
 397                 ND_PRINT("\n\tTO-BE-DONE: data not interpreted");
 398         }
 399         return;
 400
 401 invalid:
 402         nd_print_invalid(ndo);
 403         ND_TCHECK_LEN(cd, length);
 404         return;
 405
 406 trunc:
 407         nd_print_trunc(ndo);
 408 }
 409
 410 union ntpdata {
 411         struct ntp_time_data    td;
 412         struct ntp_control_data cd;
 413 };
 414
 415 /*
 416  * Print NTP requests, handling the common VN, LI, and Mode
 417  */
 418 void
 419 ntp_print(netdissect_options *ndo,
 420           const u_char *cp, u_int length)
 421 {
 422         const union ntpdata *bp = (const union ntpdata *)cp;
 423         u_int mode, version, leapind;
 424         uint8_t status;
 425
 426         ndo->ndo_protocol = "ntp";
 427         ND_TCHECK_1(bp->td.status);
 428         status = GET_U_1(bp->td.status);
 429
 430         version = (status & VERSIONMASK) >> VERSIONSHIFT;
 431         ND_PRINT("NTPv%u", version);
 432
 433         mode = (status & MODEMASK) >> MODESHIFT;
 434         if (!ndo->ndo_vflag) {
 435                 ND_PRINT(", %s, length %u",
 436                          tok2str(ntp_mode_values, "Unknown mode", mode),
 437                          length);
 438                 return;
 439         }
 440
 441         ND_PRINT(", %s, length %u\n",
 442                   tok2str(ntp_mode_values, "Unknown mode", mode), length);
 443
 444         /* leapind = (status & LEAPMASK) >> LEAPSHIFT; */
 445         leapind = (status & LEAPMASK);
 446         ND_PRINT("\tLeap indicator: %s (%u)",
 447                  tok2str(ntp_leapind_values, "Unknown", leapind),
 448                  leapind);
 449
 450         switch (mode) {
 451
 452         case MODE_UNSPEC:
 453         case MODE_SYM_ACT:
 454         case MODE_SYM_PAS:
 455         case MODE_CLIENT:
 456         case MODE_SERVER:
 457         case MODE_BROADCAST:
 458                 ntp_time_print(ndo, &bp->td, length);
 459                 break;
 460
 461         case MODE_CONTROL:
 462                 ntp_control_print(ndo, &bp->cd, length);
 463                 break;
 464
 465         default:
 466                 break;                  /* XXX: not implemented! */
 467         }
 468         return;
 469
 470 trunc:
 471         nd_print_trunc(ndo);
 472 }
 473
 474 static void
 475 p_sfix(netdissect_options *ndo,
 476        const struct s_fixedpt *sfp)
 477 {
 478         int i;
 479         int f;
 480         double ff;
 481
 482         i = GET_BE_U_2(sfp->int_part);
 483         f = GET_BE_U_2(sfp->fraction);
 484         ff = f / 65536.0;               /* shift radix point by 16 bits */
 485         f = (int)(ff * 1000000.0);      /* Treat fraction as parts per million */
 486         ND_PRINT("%d.%06d", i, f);
 487 }
 488
 489 /* Prints time difference between *lfp and *olfp */
 490 static void
 491 p_ntp_delta(netdissect_options *ndo,
 492             const struct l_fixedpt *olfp,
 493             const struct l_fixedpt *lfp)
 494 {
 495         uint32_t u, uf;
 496         uint32_t ou, ouf;
 497         uint32_t i;
 498         uint32_t f;
 499         double ff;
 500         int signbit;
 501
 502         u = GET_BE_U_4(lfp->int_part);
 503         ou = GET_BE_U_4(olfp->int_part);
 504         uf = GET_BE_U_4(lfp->fraction);
 505         ouf = GET_BE_U_4(olfp->fraction);
 506         if (ou == 0 && ouf == 0) {
 507                 p_ntp_time(ndo, lfp);
 508                 return;
 509         }
 510
 511         if (u > ou) {           /* new is definitely greater than old */
 512                 signbit = 0;
 513                 i = u - ou;
 514                 f = uf - ouf;
 515                 if (ouf > uf)   /* must borrow from high-order bits */
 516                         i -= 1;
 517         } else if (u < ou) {    /* new is definitely less than old */
 518                 signbit = 1;
 519                 i = ou - u;
 520                 f = ouf - uf;
 521                 if (uf > ouf)   /* must borrow from the high-order bits */
 522                         i -= 1;
 523         } else {                /* int_part is zero */
 524                 i = 0;
 525                 if (uf > ouf) {
 526                         signbit = 0;
 527                         f = uf - ouf;
 528                 } else {
 529                         signbit = 1;
 530                         f = ouf - uf;
 531                 }
 532         }
 533
 534         ff = f;
 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("%s%u.%09u", signbit ? "-" : "+", i, f);
 540 }
 541
 542 /* Prints polling interval in log2 as seconds or fraction of second */
 543 static void
 544 p_poll(netdissect_options *ndo,
 545        const int poll_interval)
 546 {
 547         if (poll_interval <= -32 || poll_interval >= 32)
 548                 return;
 549
 550         if (poll_interval >= 0)
 551                 ND_PRINT(" (%us)", 1U << poll_interval);
 552         else
 553                 ND_PRINT(" (1/%us)", 1U << -poll_interval);
 554 }
 555