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 #include <config.h>
  36
  37 #include "netdissect-stdinc.h"
  38 #include "netdissect-ctype.h"
  39
  40 #define ND_LONGJMP_FROM_TCHECK
  41 #include "netdissect.h"
  42 #include "addrtoname.h"
  43 #include "extract.h"
  44
  45 #include "ntp.h"
  46
  47 /*
  48  * Based on ntp.h from the U of MD implementation
  49  *      This file is based on Version 2 of the NTP spec (RFC1119).
  50  */
  51
  52 /* RFC 5905 updated by RFC 7822
  53  *                      1                   2                   3
  54  *  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
  55  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  56  * |LI | VN  |Mode |    Stratum    |     Poll      |   Precision   |
  57  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  58  * |                          Root Delay                           |
  59  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  60  * |                       Root Dispersion                         |
  61  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  62  * |                     Reference Identifier                      |
  63  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  64  * |                                                               |
  65  * |                   Reference Timestamp (64)                    |
  66  * |                                                               |
  67  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  68  * |                                                               |
  69  * |                   Originate Timestamp (64)                    |
  70  * |                                                               |
  71  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  72  * |                                                               |
  73  * |                    Receive Timestamp (64)                     |
  74  * |                                                               |
  75  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  76  * |                                                               |
  77  * |                    Transmit Timestamp (64)                    |
  78  * |                                                               |
  79  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  80  * |                                                               |
  81  * .                                                               .
  82  * .                 Optional Extensions (variable)                .
  83  * .                                                               .
  84  * |                                                               |
  85  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  86  */
  87
  88 /* Length of the NTP data message with the mandatory fields ("the header")
  89  * and without any optional fields (extension, Key Identifier,
  90  * Message Digest).
  91  */
  92 #define NTP_TIMEMSG_MINLEN 48U
  93
  94 struct ntp_time_data {
  95         nd_uint8_t status;              /* status of local clock and leap info */
  96         nd_uint8_t stratum;             /* Stratum level */
  97         nd_int8_t ppoll;                /* poll value */
  98         nd_int8_t precision;
  99         struct s_fixedpt root_delay;
 100         struct s_fixedpt root_dispersion;
 101         nd_uint32_t refid;
 102         struct l_fixedpt ref_timestamp;
 103         struct l_fixedpt org_timestamp;
 104         struct l_fixedpt rec_timestamp;
 105         struct l_fixedpt xmt_timestamp;
 106         /* extension fields and/or MAC follow */
 107 };
 108
 109 struct ntp_extension_field {
 110         nd_uint16_t     type;
 111         nd_uint16_t     length;
 112         /* body follows */
 113 };
 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 static u_int p_ext_fields(netdissect_options *, const u_char *, u_int length);
 161
 162 static const struct tok ntp_mode_values[] = {
 163     { MODE_UNSPEC,    "unspecified" },
 164     { MODE_SYM_ACT,   "symmetric active" },
 165     { MODE_SYM_PAS,   "symmetric passive" },
 166     { MODE_CLIENT,    "Client" },
 167     { MODE_SERVER,    "Server" },
 168     { MODE_BROADCAST, "Broadcast" },
 169     { MODE_CONTROL,   "Control Message" },
 170     { MODE_RES2,      "Reserved" },
 171     { 0, NULL }
 172 };
 173
 174 static const struct tok ntp_leapind_values[] = {
 175     { NO_WARNING,     "" },
 176     { PLUS_SEC,       "+1s" },
 177     { MINUS_SEC,      "-1s" },
 178     { ALARM,          "clock unsynchronized" },
 179     { 0, NULL }
 180 };
 181
 182 static const struct tok ntp_stratum_values[] = {
 183         { UNSPECIFIED,  "unspecified" },
 184         { PRIM_REF,     "primary reference" },
 185         { 0, NULL }
 186 };
 187
 188 static const struct tok ntp_ef_types[] = {
 189         { 0x0104,       "Unique Identifier" },
 190         { 0x0204,       "NTS Cookie" },
 191         { 0x0304,       "NTS Cookie Placeholder" },
 192         { 0x0404,       "NTS Authenticator and Encrypted Extension Fields" },
 193         { 0x2005,       "Checksum Complement" },
 194         { 0, NULL }
 195 };
 196
 197 /* draft-ietf-ntp-mode-6-cmds-02
 198  *  0                   1                   2                   3
 199  *  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
 200  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 201  * |LI |  VN |Mode |R|E|M| OpCode  |       Sequence Number         |
 202  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 203  * |            Status             |       Association ID          |
 204  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 205  * |            Offset             |            Count              |
 206  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 207  * |                                                               |
 208  * /                    Data (up to 468 bytes)                     /
 209  * |                                                               |
 210  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 211  * |                    Padding (optional)                         |
 212  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 213  * |                                                               |
 214  * /              Authenticator (optional, 96 bytes)               /
 215  * |                                                               |
 216  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 217  *
 218  *               Figure 1: NTP Control Message Header
 219  */
 220
 221 /* Length of the NTP control message with the mandatory fields ("the header")
 222  * and without any optional fields (Data, Padding, Authenticator).
 223  */
 224 #define NTP_CTRLMSG_MINLEN 12U
 225
 226 struct ntp_control_data {
 227         nd_uint8_t      magic;          /* LI, VN, Mode */
 228         nd_uint8_t      control;        /* R, E, M, OpCode */
 229         nd_uint16_t     sequence;       /* Sequence Number */
 230         nd_uint16_t     status;         /* Status */
 231         nd_uint16_t     assoc;          /* Association ID */
 232         nd_uint16_t     offset;         /* Offset */
 233         nd_uint16_t     count;          /* Count */
 234         nd_uint8_t      data[564];      /* Data, [Padding, [Authenticator]] */
 235 };
 236
 237 /*
 238  * Print NTP time requests and responses
 239  */
 240 static void
 241 ntp_time_print(netdissect_options *ndo,
 242                const struct ntp_time_data *bp, u_int length, u_int version)
 243 {
 244         const u_char *mac;
 245         uint8_t stratum;
 246         u_int efs_len;
 247
 248         if (length < NTP_TIMEMSG_MINLEN)
 249                 goto invalid;
 250
 251         stratum = GET_U_1(bp->stratum);
 252         ND_PRINT(", Stratum %u (%s)",
 253                 stratum,
 254                 tok2str(ntp_stratum_values, (stratum >=2 && stratum<=15) ? "secondary reference" : "reserved", stratum));
 255
 256         ND_PRINT(", poll %d", GET_S_1(bp->ppoll));
 257         p_poll(ndo, GET_S_1(bp->ppoll));
 258
 259         ND_PRINT(", precision %d", GET_S_1(bp->precision));
 260
 261         ND_PRINT("\n\tRoot Delay: ");
 262         p_sfix(ndo, &bp->root_delay);
 263
 264         ND_PRINT(", Root dispersion: ");
 265         p_sfix(ndo, &bp->root_dispersion);
 266
 267         ND_PRINT(", Reference-ID: ");
 268         /* Interpretation depends on stratum */
 269         switch (stratum) {
 270
 271         case UNSPECIFIED:
 272                 /* NTPv4 (RFC 5905, section 7.4) formalizes that refid _may_
 273                  * contain a printable, four-character, left justified, zero
 274                  * filled ASCII string ("kiss code") for status reporting
 275                  * and debugging. Some kiss codes are defined in the RFC as
 276                  * initial set for a new IANA registry, but the list may be
 277                  * modified or extended in the future, and unregistered kiss
 278                  * codes are possible (and are being seen in the field).
 279                  */
 280                 if (!ND_ASCII_ISPRINT((bp->refid)[0])) {
 281                         ND_PRINT("(unspec)");
 282                         ND_TCHECK_4(bp->refid);
 283                 } else {
 284                         nd_printjn(ndo, (const u_char *)&(bp->refid), 4);
 285                 }
 286                 break;
 287
 288         case PRIM_REF:
 289                 nd_printjn(ndo, (const u_char *)&(bp->refid), 4);
 290                 break;
 291
 292         case INFO_QUERY:
 293                 ND_PRINT("%s INFO_QUERY", GET_IPADDR_STRING(bp->refid));
 294                 /* this doesn't have more content */
 295                 return;
 296
 297         case INFO_REPLY:
 298                 ND_PRINT("%s INFO_REPLY", GET_IPADDR_STRING(bp->refid));
 299                 /* this is too complex to be worth printing */
 300                 return;
 301
 302         default:
 303                 /* In NTPv4 (RFC 5905) refid is an IPv4 address or first 32 bits of
 304                    MD5 sum of IPv6 address */
 305                 ND_PRINT("0x%08x", GET_BE_U_4(bp->refid));
 306                 break;
 307         }
 308
 309         ND_PRINT("\n\t  Reference Timestamp:  ");
 310         p_ntp_time(ndo, &(bp->ref_timestamp));
 311
 312         ND_PRINT("\n\t  Originator Timestamp: ");
 313         p_ntp_time(ndo, &(bp->org_timestamp));
 314
 315         ND_PRINT("\n\t  Receive Timestamp:    ");
 316         p_ntp_time(ndo, &(bp->rec_timestamp));
 317
 318         ND_PRINT("\n\t  Transmit Timestamp:   ");
 319         p_ntp_time(ndo, &(bp->xmt_timestamp));
 320
 321         ND_PRINT("\n\t    Originator - Receive Timestamp:  ");
 322         p_ntp_delta(ndo, &(bp->org_timestamp), &(bp->rec_timestamp));
 323
 324         ND_PRINT("\n\t    Originator - Transmit Timestamp: ");
 325         p_ntp_delta(ndo, &(bp->org_timestamp), &(bp->xmt_timestamp));
 326
 327         if (version == 4)
 328                 efs_len = p_ext_fields(ndo, (const u_char *)bp + NTP_TIMEMSG_MINLEN, length - NTP_TIMEMSG_MINLEN);
 329         else
 330                 efs_len = 0;
 331
 332         mac = (const u_char *)bp + NTP_TIMEMSG_MINLEN + efs_len;
 333
 334         if (length == NTP_TIMEMSG_MINLEN + efs_len + 4) {       /* Optional: key-id (crypto-NAK) */
 335                 ND_PRINT("\n\tKey id: %u", GET_BE_U_4(mac));
 336         } else if (length == NTP_TIMEMSG_MINLEN + efs_len + 4 + 16) {   /* Optional: key-id + 128-bit digest */
 337                 ND_PRINT("\n\tKey id: %u", GET_BE_U_4(mac));
 338                 ND_PRINT("\n\tAuthentication: %08x%08x%08x%08x",
 339                          GET_BE_U_4(mac + 4),
 340                          GET_BE_U_4(mac + 8),
 341                          GET_BE_U_4(mac + 12),
 342                          GET_BE_U_4(mac + 16));
 343         } else if (length == NTP_TIMEMSG_MINLEN + efs_len + 4 + 20) {   /* Optional: key-id + 160-bit digest */
 344                 ND_PRINT("\n\tKey id: %u", GET_BE_U_4(mac));
 345                 ND_PRINT("\n\tAuthentication: %08x%08x%08x%08x%08x",
 346                          GET_BE_U_4(mac + 4),
 347                          GET_BE_U_4(mac + 8),
 348                          GET_BE_U_4(mac + 12),
 349                          GET_BE_U_4(mac + 16),
 350                          GET_BE_U_4(mac + 20));
 351         } else if (length > NTP_TIMEMSG_MINLEN + efs_len) {
 352                 ND_PRINT("\n\t(%u more bytes after the header and extension fields)",
 353                                 length - NTP_TIMEMSG_MINLEN - efs_len);
 354         }
 355         return;
 356
 357 invalid:
 358         nd_print_invalid(ndo);
 359         ND_TCHECK_LEN(bp, length);
 360 }
 361
 362 /*
 363  * Print NTP control message requests and responses
 364  */
 365 static void
 366 ntp_control_print(netdissect_options *ndo,
 367                   const struct ntp_control_data *cd, u_int length)
 368 {
 369         uint8_t control, R, E, M, opcode;
 370         uint16_t sequence, status, assoc, offset, count;
 371
 372         if (length < NTP_CTRLMSG_MINLEN)
 373                 goto invalid;
 374
 375         control = GET_U_1(cd->control);
 376         R = (control & 0x80) != 0;
 377         E = (control & 0x40) != 0;
 378         M = (control & 0x20) != 0;
 379         opcode = control & 0x1f;
 380         ND_PRINT(", %s, %s, %s, OpCode=%u\n",
 381                   R ? "Response" : "Request", E ? "Error" : "OK",
 382                   M ? "More" : "Last", opcode);
 383
 384         sequence = GET_BE_U_2(cd->sequence);
 385         ND_PRINT("\tSequence=%hu", sequence);
 386
 387         status = GET_BE_U_2(cd->status);
 388         ND_PRINT(", Status=%#hx", status);
 389
 390         assoc = GET_BE_U_2(cd->assoc);
 391         ND_PRINT(", Assoc.=%hu", assoc);
 392
 393         offset = GET_BE_U_2(cd->offset);
 394         ND_PRINT(", Offset=%hu", offset);
 395
 396         count = GET_BE_U_2(cd->count);
 397         ND_PRINT(", Count=%hu", count);
 398
 399         if (NTP_CTRLMSG_MINLEN + count > length)
 400                 goto invalid;
 401         if (count != 0) {
 402                 ND_TCHECK_LEN(cd->data, count);
 403                 ND_PRINT("\n\tTO-BE-DONE: data not interpreted");
 404         }
 405         return;
 406
 407 invalid:
 408         nd_print_invalid(ndo);
 409         ND_TCHECK_LEN(cd, length);
 410 }
 411
 412 union ntpdata {
 413         struct ntp_time_data    td;
 414         struct ntp_control_data cd;
 415 };
 416
 417 /*
 418  * Print NTP requests, handling the common VN, LI, and Mode
 419  */
 420 void
 421 ntp_print(netdissect_options *ndo,
 422           const u_char *cp, u_int length)
 423 {
 424         const union ntpdata *bp = (const union ntpdata *)cp;
 425         u_int mode, version, leapind;
 426         uint8_t status;
 427
 428         ndo->ndo_protocol = "ntp";
 429         status = GET_U_1(bp->td.status);
 430
 431         version = (status & VERSIONMASK) >> VERSIONSHIFT;
 432         ND_PRINT("NTPv%u", version);
 433
 434         mode = (status & MODEMASK) >> MODESHIFT;
 435         if (!ndo->ndo_vflag) {
 436                 ND_PRINT(", %s, length %u",
 437                          tok2str(ntp_mode_values, "Unknown mode", mode),
 438                          length);
 439                 return;
 440         }
 441
 442         ND_PRINT(", %s, length %u\n",
 443                   tok2str(ntp_mode_values, "Unknown mode", mode), length);
 444
 445         /* leapind = (status & LEAPMASK) >> LEAPSHIFT; */
 446         leapind = (status & LEAPMASK);
 447         ND_PRINT("\tLeap indicator: %s (%u)",
 448                  tok2str(ntp_leapind_values, "Unknown", leapind),
 449                  leapind);
 450
 451         switch (mode) {
 452
 453         case MODE_UNSPEC:
 454         case MODE_SYM_ACT:
 455         case MODE_SYM_PAS:
 456         case MODE_CLIENT:
 457         case MODE_SERVER:
 458         case MODE_BROADCAST:
 459                 ntp_time_print(ndo, &bp->td, length, version);
 460                 break;
 461
 462         case MODE_CONTROL:
 463                 ntp_control_print(ndo, &bp->cd, length);
 464                 break;
 465
 466         default:
 467                 break;                  /* XXX: not implemented! */
 468         }
 469 }
 470
 471 static void
 472 p_sfix(netdissect_options *ndo,
 473        const struct s_fixedpt *sfp)
 474 {
 475         int i;
 476         int f;
 477         double ff;
 478
 479         i = GET_BE_U_2(sfp->int_part);
 480         f = GET_BE_U_2(sfp->fraction);
 481         ff = f / 65536.0;               /* shift radix point by 16 bits */
 482         f = (int)(ff * 1000000.0);      /* Treat fraction as parts per million */
 483         ND_PRINT("%d.%06d", i, f);
 484 }
 485
 486 /* Prints time difference between *lfp and *olfp */
 487 static void
 488 p_ntp_delta(netdissect_options *ndo,
 489             const struct l_fixedpt *olfp,
 490             const struct l_fixedpt *lfp)
 491 {
 492         uint32_t u, uf;
 493         uint32_t ou, ouf;
 494         uint32_t i;
 495         uint32_t f;
 496         double ff;
 497         int signbit;
 498
 499         u = GET_BE_U_4(lfp->int_part);
 500         ou = GET_BE_U_4(olfp->int_part);
 501         uf = GET_BE_U_4(lfp->fraction);
 502         ouf = GET_BE_U_4(olfp->fraction);
 503         if (ou == 0 && ouf == 0) {
 504                 p_ntp_time(ndo, lfp);
 505                 return;
 506         }
 507
 508         if (u > ou) {           /* new is definitely greater than old */
 509                 signbit = 0;
 510                 i = u - ou;
 511                 f = uf - ouf;
 512                 if (ouf > uf)   /* must borrow from high-order bits */
 513                         i -= 1;
 514         } else if (u < ou) {    /* new is definitely less than old */
 515                 signbit = 1;
 516                 i = ou - u;
 517                 f = ouf - uf;
 518                 if (uf > ouf)   /* must borrow from the high-order bits */
 519                         i -= 1;
 520         } else {                /* int_part is zero */
 521                 i = 0;
 522                 if (uf > ouf) {
 523                         signbit = 0;
 524                         f = uf - ouf;
 525                 } else {
 526                         signbit = 1;
 527                         f = ouf - uf;
 528                 }
 529         }
 530
 531         ff = f;
 532         if (ff < 0.0)           /* some compilers are buggy */
 533                 ff += FMAXINT;
 534         ff = ff / FMAXINT;                      /* shift radix point by 32 bits */
 535         f = (uint32_t)(ff * 1000000000.0);      /* treat fraction as parts per billion */
 536         ND_PRINT("%s%u.%09u", signbit ? "-" : "+", i, f);
 537 }
 538
 539 /* Prints polling interval in log2 as seconds or fraction of second */
 540 static void
 541 p_poll(netdissect_options *ndo,
 542        const int poll_interval)
 543 {
 544         if (poll_interval <= -32 || poll_interval >= 32)
 545                 return;
 546
 547         if (poll_interval >= 0)
 548                 ND_PRINT(" (%us)", 1U << poll_interval);
 549         else
 550                 ND_PRINT(" (1/%us)", 1U << -poll_interval);
 551 }
 552
 553 /* Prints an NTPv4 extension field */
 554 static void
 555 p_ntp_ef(netdissect_options *ndo, u_int type, u_int length, const u_char *ef_body)
 556 {
 557         ND_PRINT("\n\t  %s", tok2str(ntp_ef_types, "Unknown type", type));
 558         ND_PRINT(" (0x%04x), length %u", type, length);
 559
 560         if (ndo->ndo_vflag > 2)
 561                 hex_print(ndo, "\n\t    ", ef_body, length - 4);
 562         else {
 563                 /*
 564                  * If we're not going to print it, at least make sure
 565                  * it's present in the packet, so if ef_len is too long,
 566                  * we stop.
 567                  */
 568                 ND_TCHECK_LEN(ef_body, length - 4);
 569         }
 570 }
 571
 572 /* Prints list of extension fields per RFC 7822 */
 573 static u_int
 574 p_ext_fields(netdissect_options *ndo, const u_char *cp, u_int length)
 575 {
 576         const struct ntp_extension_field *ef;
 577         u_int ef_type, ef_len, efs_len;
 578         int first_ef;
 579
 580         first_ef = 1;
 581         efs_len = 0;
 582
 583         /* RFC 7822 requires the last EF in the packet to have at least
 584            28 octets to avoid ambiguity with MACs */
 585         while (length - efs_len >= 28) {
 586                 ef = (const struct ntp_extension_field *)(cp + efs_len);
 587                 ef_type = GET_BE_U_2(ef->type);
 588                 ef_len = GET_BE_U_2(ef->length);
 589
 590                 if (efs_len + ef_len > length || ef_len < 4 || ef_len % 4 != 0) {
 591                         nd_print_invalid(ndo);
 592                         break;
 593                 }
 594
 595                 if (first_ef) {
 596                         ND_PRINT("\n\tExtension fields:");
 597                         first_ef = 0;
 598                 }
 599
 600                 p_ntp_ef(ndo, ef_type, ef_len, (const u_char *)(ef + 1));
 601
 602                 /*
 603                  * The entire extension field is guaranteed to be in the
 604                  * captured data, as p_ntp_ef() will longjmp out if it
 605                  * isn't.
 606                  *
 607                  * As the total length of the captured data fits in a
 608                  * u_int, this means that the total length of all the
 609                  * extension fields will fit in a u_int, so this will
 610                  * never overflow.
 611                  */
 612                 efs_len += ef_len;
 613         }
 614
 615         return efs_len;
 616 }