net/ipv4/netfilter/ip_nat_snmp_basic.c

   1 /*
   2  * ip_nat_snmp_basic.c
   3  *
   4  * Basic SNMP Application Layer Gateway
   5  *
   6  * This IP NAT module is intended for use with SNMP network
   7  * discovery and monitoring applications where target networks use
   8  * conflicting private address realms.
   9  *
  10  * Static NAT is used to remap the networks from the view of the network
  11  * management system at the IP layer, and this module remaps some application
  12  * layer addresses to match.
  13  *
  14  * The simplest form of ALG is performed, where only tagged IP addresses
  15  * are modified.  The module does not need to be MIB aware and only scans
  16  * messages at the ASN.1/BER level.
  17  *
  18  * Currently, only SNMPv1 and SNMPv2 are supported.
  19  *
  20  * More information on ALG and associated issues can be found in
  21  * RFC 2962
  22  *
  23  * The ASB.1/BER parsing code is derived from the gxsnmp package by Gregory
  24  * McLean & Jochen Friedrich, stripped down for use in the kernel.
  25  *
  26  * Copyright (c) 2000 RP Internet (www.rpi.net.au).
  27  *
  28  * This program is free software; you can redistribute it and/or modify
  29  * it under the terms of the GNU General Public License as published by
  30  * the Free Software Foundation; either version 2 of the License, or
  31  * (at your option) any later version.
  32  * This program is distributed in the hope that it will be useful,
  33  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  34  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  35  * GNU General Public License for more details.
  36  * You should have received a copy of the GNU General Public License
  37  * along with this program; if not, write to the Free Software
  38  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  39  *
  40  * Author: James Morris <jmorris@intercode.com.au>
  41  *
  42  * Updates:
  43  * 2000-08-06: Convert to new helper API (Harald Welte).
  44  *
  45  */
  46 #include <linux/config.h>
  47 #include <linux/module.h>
  48 #include <linux/types.h>
  49 #include <linux/kernel.h>
  50 #include <linux/netfilter_ipv4.h>
  51 #include <linux/netfilter_ipv4/ip_nat.h>
  52 #include <linux/netfilter_ipv4/ip_nat_helper.h>
  53 #include <linux/ip.h>
  54 #include <net/checksum.h>
  55 #include <net/udp.h>
  56 #include <asm/uaccess.h>
  57
  58 MODULE_LICENSE("GPL");
  59 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
  60 MODULE_DESCRIPTION("Basic SNMP Application Layer Gateway");
  61
  62 #define SNMP_PORT 161
  63 #define SNMP_TRAP_PORT 162
  64 #define NOCT1(n) (u_int8_t )((n) & 0xff)
  65
  66 static int debug;
  67 static spinlock_t snmp_lock = SPIN_LOCK_UNLOCKED;
  68
  69 /*
  70  * Application layer address mapping mimics the NAT mapping, but
  71  * only for the first octet in this case (a more flexible system
  72  * can be implemented if needed).
  73  */
  74 struct oct1_map
  75 {
  76         u_int8_t from;
  77         u_int8_t to;
  78 };
  79
  80
  81 /*****************************************************************************
  82  *
  83  * Basic ASN.1 decoding routines (gxsnmp author Dirk Wisse)
  84  *
  85  *****************************************************************************/
  86
  87 /* Class */
  88 #define ASN1_UNI        0       /* Universal */
  89 #define ASN1_APL        1       /* Application */
  90 #define ASN1_CTX        2       /* Context */
  91 #define ASN1_PRV        3       /* Private */
  92
  93 /* Tag */
  94 #define ASN1_EOC        0       /* End Of Contents */
  95 #define ASN1_BOL        1       /* Boolean */
  96 #define ASN1_INT        2       /* Integer */
  97 #define ASN1_BTS        3       /* Bit String */
  98 #define ASN1_OTS        4       /* Octet String */
  99 #define ASN1_NUL        5       /* Null */
 100 #define ASN1_OJI        6       /* Object Identifier  */
 101 #define ASN1_OJD        7       /* Object Description */
 102 #define ASN1_EXT        8       /* External */
 103 #define ASN1_SEQ        16      /* Sequence */
 104 #define ASN1_SET        17      /* Set */
 105 #define ASN1_NUMSTR     18      /* Numerical String */
 106 #define ASN1_PRNSTR     19      /* Printable String */
 107 #define ASN1_TEXSTR     20      /* Teletext String */
 108 #define ASN1_VIDSTR     21      /* Video String */
 109 #define ASN1_IA5STR     22      /* IA5 String */
 110 #define ASN1_UNITIM     23      /* Universal Time */
 111 #define ASN1_GENTIM     24      /* General Time */
 112 #define ASN1_GRASTR     25      /* Graphical String */
 113 #define ASN1_VISSTR     26      /* Visible String */
 114 #define ASN1_GENSTR     27      /* General String */
 115
 116 /* Primitive / Constructed methods*/
 117 #define ASN1_PRI        0       /* Primitive */
 118 #define ASN1_CON        1       /* Constructed */
 119
 120 /*
 121  * Error codes.
 122  */
 123 #define ASN1_ERR_NOERROR                0
 124 #define ASN1_ERR_DEC_EMPTY              2
 125 #define ASN1_ERR_DEC_EOC_MISMATCH       3
 126 #define ASN1_ERR_DEC_LENGTH_MISMATCH    4
 127 #define ASN1_ERR_DEC_BADVALUE           5
 128
 129 /*
 130  * ASN.1 context.
 131  */
 132 struct asn1_ctx
 133 {
 134         int error;                      /* Error condition */
 135         unsigned char *pointer;         /* Octet just to be decoded */
 136         unsigned char *begin;           /* First octet */
 137         unsigned char *end;             /* Octet after last octet */
 138 };
 139
 140 /*
 141  * Octet string (not null terminated)
 142  */
 143 struct asn1_octstr
 144 {
 145         unsigned char *data;
 146         unsigned int len;
 147 };
 148
 149 static void asn1_open(struct asn1_ctx *ctx,
 150                       unsigned char *buf,
 151                       unsigned int len)
 152 {
 153         ctx->begin = buf;
 154         ctx->end = buf + len;
 155         ctx->pointer = buf;
 156         ctx->error = ASN1_ERR_NOERROR;
 157 }
 158
 159 static unsigned char asn1_octet_decode(struct asn1_ctx *ctx, unsigned char *ch)
 160 {
 161         if (ctx->pointer >= ctx->end) {
 162                 ctx->error = ASN1_ERR_DEC_EMPTY;
 163                 return 0;
 164         }
 165         *ch = *(ctx->pointer)++;
 166         return 1;
 167 }
 168
 169 static unsigned char asn1_tag_decode(struct asn1_ctx *ctx, unsigned int *tag)
 170 {
 171         unsigned char ch;
 172
 173         *tag = 0;
 174
 175         do
 176         {
 177                 if (!asn1_octet_decode(ctx, &ch))
 178                         return 0;
 179                 *tag <<= 7;
 180                 *tag |= ch & 0x7F;
 181         } while ((ch & 0x80) == 0x80);
 182         return 1;
 183 }
 184
 185 static unsigned char asn1_id_decode(struct asn1_ctx *ctx,
 186                                     unsigned int *cls,
 187                                     unsigned int *con,
 188                                     unsigned int *tag)
 189 {
 190         unsigned char ch;
 191
 192         if (!asn1_octet_decode(ctx, &ch))
 193                 return 0;
 194
 195         *cls = (ch & 0xC0) >> 6;
 196         *con = (ch & 0x20) >> 5;
 197         *tag = (ch & 0x1F);
 198
 199         if (*tag == 0x1F) {
 200                 if (!asn1_tag_decode(ctx, tag))
 201                         return 0;
 202         }
 203         return 1;
 204 }
 205
 206 static unsigned char asn1_length_decode(struct asn1_ctx *ctx,
 207                                         unsigned int *def,
 208                                         unsigned int *len)
 209 {
 210         unsigned char ch, cnt;
 211
 212         if (!asn1_octet_decode(ctx, &ch))
 213                 return 0;
 214
 215         if (ch == 0x80)
 216                 *def = 0;
 217         else {
 218                 *def = 1;
 219
 220                 if (ch < 0x80)
 221                         *len = ch;
 222                 else {
 223                         cnt = (unsigned char) (ch & 0x7F);
 224                         *len = 0;
 225
 226                         while (cnt > 0) {
 227                                 if (!asn1_octet_decode(ctx, &ch))
 228                                         return 0;
 229                                 *len <<= 8;
 230                                 *len |= ch;
 231                                 cnt--;
 232                         }
 233                 }
 234         }
 235         return 1;
 236 }
 237
 238 static unsigned char asn1_header_decode(struct asn1_ctx *ctx,
 239                                         unsigned char **eoc,
 240                                         unsigned int *cls,
 241                                         unsigned int *con,
 242                                         unsigned int *tag)
 243 {
 244         unsigned int def, len;
 245
 246         if (!asn1_id_decode(ctx, cls, con, tag))
 247                 return 0;
 248
 249         if (!asn1_length_decode(ctx, &def, &len))
 250                 return 0;
 251
 252         if (def)
 253                 *eoc = ctx->pointer + len;
 254         else
 255                 *eoc = 0;
 256         return 1;
 257 }
 258
 259 static unsigned char asn1_eoc_decode(struct asn1_ctx *ctx, unsigned char *eoc)
 260 {
 261         unsigned char ch;
 262
 263         if (eoc == 0) {
 264                 if (!asn1_octet_decode(ctx, &ch))
 265                         return 0;
 266
 267                 if (ch != 0x00) {
 268                         ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
 269                         return 0;
 270                 }
 271
 272                 if (!asn1_octet_decode(ctx, &ch))
 273                         return 0;
 274
 275                 if (ch != 0x00) {
 276                         ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
 277                         return 0;
 278                 }
 279                 return 1;
 280         } else {
 281                 if (ctx->pointer != eoc) {
 282                         ctx->error = ASN1_ERR_DEC_LENGTH_MISMATCH;
 283                         return 0;
 284                 }
 285                 return 1;
 286         }
 287 }
 288
 289 static unsigned char asn1_null_decode(struct asn1_ctx *ctx, unsigned char *eoc)
 290 {
 291         ctx->pointer = eoc;
 292         return 1;
 293 }
 294
 295 static unsigned char asn1_long_decode(struct asn1_ctx *ctx,
 296                                       unsigned char *eoc,
 297                                       long *integer)
 298 {
 299         unsigned char ch;
 300         unsigned int  len;
 301
 302         if (!asn1_octet_decode(ctx, &ch))
 303                 return 0;
 304
 305         *integer = (signed char) ch;
 306         len = 1;
 307
 308         while (ctx->pointer < eoc) {
 309                 if (++len > sizeof (long)) {
 310                         ctx->error = ASN1_ERR_DEC_BADVALUE;
 311                         return 0;
 312                 }
 313
 314                 if (!asn1_octet_decode(ctx, &ch))
 315                         return 0;
 316
 317                 *integer <<= 8;
 318                 *integer |= ch;
 319         }
 320         return 1;
 321 }
 322
 323 static unsigned char asn1_uint_decode(struct asn1_ctx *ctx,
 324                                       unsigned char *eoc,
 325                                       unsigned int *integer)
 326 {
 327         unsigned char ch;
 328         unsigned int  len;
 329
 330         if (!asn1_octet_decode(ctx, &ch))
 331                 return 0;
 332
 333         *integer = ch;
 334         if (ch == 0) len = 0;
 335         else len = 1;
 336
 337         while (ctx->pointer < eoc) {
 338                 if (++len > sizeof (unsigned int)) {
 339                         ctx->error = ASN1_ERR_DEC_BADVALUE;
 340                         return 0;
 341                 }
 342
 343                 if (!asn1_octet_decode(ctx, &ch))
 344                         return 0;
 345
 346                 *integer <<= 8;
 347                 *integer |= ch;
 348         }
 349         return 1;
 350 }
 351
 352 static unsigned char asn1_ulong_decode(struct asn1_ctx *ctx,
 353                                        unsigned char *eoc,
 354                                        unsigned long *integer)
 355 {
 356         unsigned char ch;
 357         unsigned int  len;
 358
 359         if (!asn1_octet_decode(ctx, &ch))
 360                 return 0;
 361
 362         *integer = ch;
 363         if (ch == 0) len = 0;
 364         else len = 1;
 365
 366         while (ctx->pointer < eoc) {
 367                 if (++len > sizeof (unsigned long)) {
 368                         ctx->error = ASN1_ERR_DEC_BADVALUE;
 369                         return 0;
 370                 }
 371
 372                 if (!asn1_octet_decode(ctx, &ch))
 373                         return 0;
 374
 375                 *integer <<= 8;
 376                 *integer |= ch;
 377         }
 378         return 1;
 379 }
 380
 381 static unsigned char asn1_octets_decode(struct asn1_ctx *ctx,
 382                                         unsigned char *eoc,
 383                                         unsigned char **octets,
 384                                         unsigned int *len)
 385 {
 386         unsigned char *ptr;
 387
 388         *len = 0;
 389
 390         *octets = kmalloc(eoc - ctx->pointer, GFP_ATOMIC);
 391         if (*octets == NULL) {
 392                 if (net_ratelimit())
 393                         printk("OOM in bsalg (%d)\n", __LINE__);
 394                 return 0;
 395         }
 396
 397         ptr = *octets;
 398         while (ctx->pointer < eoc) {
 399                 if (!asn1_octet_decode(ctx, (unsigned char *)ptr++)) {
 400                         kfree(*octets);
 401                         *octets = NULL;
 402                         return 0;
 403                 }
 404                 (*len)++;
 405         }
 406         return 1;
 407 }
 408
 409 static unsigned char asn1_subid_decode(struct asn1_ctx *ctx,
 410                                        unsigned long *subid)
 411 {
 412         unsigned char ch;
 413
 414         *subid = 0;
 415
 416         do {
 417                 if (!asn1_octet_decode(ctx, &ch))
 418                         return 0;
 419
 420                 *subid <<= 7;
 421                 *subid |= ch & 0x7F;
 422         } while ((ch & 0x80) == 0x80);
 423         return 1;
 424 }
 425
 426 static unsigned char asn1_oid_decode(struct asn1_ctx *ctx,
 427                                      unsigned char *eoc,
 428                                      unsigned long **oid,
 429                                      unsigned int *len)
 430 {
 431         unsigned long subid;
 432         unsigned int  size;
 433         unsigned long *optr;
 434
 435         size = eoc - ctx->pointer + 1;
 436         *oid = kmalloc(size * sizeof(unsigned long), GFP_ATOMIC);
 437         if (*oid == NULL) {
 438                 if (net_ratelimit())
 439                         printk("OOM in bsalg (%d)\n", __LINE__);
 440                 return 0;
 441         }
 442
 443         optr = *oid;
 444
 445         if (!asn1_subid_decode(ctx, &subid)) {
 446                 kfree(*oid);
 447                 *oid = NULL;
 448                 return 0;
 449         }
 450
 451         if (subid < 40) {
 452                 optr [0] = 0;
 453                 optr [1] = subid;
 454         } else if (subid < 80) {
 455                 optr [0] = 1;
 456                 optr [1] = subid - 40;
 457         } else {
 458                 optr [0] = 2;
 459                 optr [1] = subid - 80;
 460         }
 461
 462         *len = 2;
 463         optr += 2;
 464
 465         while (ctx->pointer < eoc) {
 466                 if (++(*len) > size) {
 467                         ctx->error = ASN1_ERR_DEC_BADVALUE;
 468                         kfree(*oid);
 469                         *oid = NULL;
 470                         return 0;
 471                 }
 472
 473                 if (!asn1_subid_decode(ctx, optr++)) {
 474                         kfree(*oid);
 475                         *oid = NULL;
 476                         return 0;
 477                 }
 478         }
 479         return 1;
 480 }
 481
 482 /*****************************************************************************
 483  *
 484  * SNMP decoding routines (gxsnmp author Dirk Wisse)
 485  *
 486  *****************************************************************************/
 487
 488 /* SNMP Versions */
 489 #define SNMP_V1                         0
 490 #define SNMP_V2C                        1
 491 #define SNMP_V2                         2
 492 #define SNMP_V3                         3
 493
 494 /* Default Sizes */
 495 #define SNMP_SIZE_COMM                  256
 496 #define SNMP_SIZE_OBJECTID              128
 497 #define SNMP_SIZE_BUFCHR                256
 498 #define SNMP_SIZE_BUFINT                128
 499 #define SNMP_SIZE_SMALLOBJECTID         16
 500
 501 /* Requests */
 502 #define SNMP_PDU_GET                    0
 503 #define SNMP_PDU_NEXT                   1
 504 #define SNMP_PDU_RESPONSE               2
 505 #define SNMP_PDU_SET                    3
 506 #define SNMP_PDU_TRAP1                  4
 507 #define SNMP_PDU_BULK                   5
 508 #define SNMP_PDU_INFORM                 6
 509 #define SNMP_PDU_TRAP2                  7
 510
 511 /* Errors */
 512 #define SNMP_NOERROR                    0
 513 #define SNMP_TOOBIG                     1
 514 #define SNMP_NOSUCHNAME                 2
 515 #define SNMP_BADVALUE                   3
 516 #define SNMP_READONLY                   4
 517 #define SNMP_GENERROR                   5
 518 #define SNMP_NOACCESS                   6
 519 #define SNMP_WRONGTYPE                  7
 520 #define SNMP_WRONGLENGTH                8
 521 #define SNMP_WRONGENCODING              9
 522 #define SNMP_WRONGVALUE                 10
 523 #define SNMP_NOCREATION                 11
 524 #define SNMP_INCONSISTENTVALUE          12
 525 #define SNMP_RESOURCEUNAVAILABLE        13
 526 #define SNMP_COMMITFAILED               14
 527 #define SNMP_UNDOFAILED                 15
 528 #define SNMP_AUTHORIZATIONERROR         16
 529 #define SNMP_NOTWRITABLE                17
 530 #define SNMP_INCONSISTENTNAME           18
 531
 532 /* General SNMP V1 Traps */
 533 #define SNMP_TRAP_COLDSTART             0
 534 #define SNMP_TRAP_WARMSTART             1
 535 #define SNMP_TRAP_LINKDOWN              2
 536 #define SNMP_TRAP_LINKUP                3
 537 #define SNMP_TRAP_AUTFAILURE            4
 538 #define SNMP_TRAP_EQPNEIGHBORLOSS       5
 539 #define SNMP_TRAP_ENTSPECIFIC           6
 540
 541 /* SNMPv1 Types */
 542 #define SNMP_NULL                0
 543 #define SNMP_INTEGER             1    /* l  */
 544 #define SNMP_OCTETSTR            2    /* c  */
 545 #define SNMP_DISPLAYSTR          2    /* c  */
 546 #define SNMP_OBJECTID            3    /* ul */
 547 #define SNMP_IPADDR              4    /* uc */
 548 #define SNMP_COUNTER             5    /* ul */
 549 #define SNMP_GAUGE               6    /* ul */
 550 #define SNMP_TIMETICKS           7    /* ul */
 551 #define SNMP_OPAQUE              8    /* c  */
 552
 553 /* Additional SNMPv2 Types */
 554 #define SNMP_UINTEGER            5    /* ul */
 555 #define SNMP_BITSTR              9    /* uc */
 556 #define SNMP_NSAP               10    /* uc */
 557 #define SNMP_COUNTER64          11    /* ul */
 558 #define SNMP_NOSUCHOBJECT       12
 559 #define SNMP_NOSUCHINSTANCE     13
 560 #define SNMP_ENDOFMIBVIEW       14
 561
 562 union snmp_syntax
 563 {
 564         unsigned char uc[0];    /* 8 bit unsigned */
 565         char c[0];              /* 8 bit signed */
 566         unsigned long ul[0];    /* 32 bit unsigned */
 567         long l[0];              /* 32 bit signed */
 568 };
 569
 570 struct snmp_object
 571 {
 572         unsigned long *id;
 573         unsigned int id_len;
 574         unsigned short type;
 575         unsigned int syntax_len;
 576         union snmp_syntax syntax;
 577 };
 578
 579 struct snmp_request
 580 {
 581         unsigned long id;
 582         unsigned int error_status;
 583         unsigned int error_index;
 584 };
 585
 586 struct snmp_v1_trap
 587 {
 588         unsigned long *id;
 589         unsigned int id_len;
 590         unsigned long ip_address;       /* pointer  */
 591         unsigned int general;
 592         unsigned int specific;
 593         unsigned long time;
 594 };
 595
 596 /* SNMP types */
 597 #define SNMP_IPA    0
 598 #define SNMP_CNT    1
 599 #define SNMP_GGE    2
 600 #define SNMP_TIT    3
 601 #define SNMP_OPQ    4
 602 #define SNMP_C64    6
 603
 604 /* SNMP errors */
 605 #define SERR_NSO    0
 606 #define SERR_NSI    1
 607 #define SERR_EOM    2
 608
 609 static inline void mangle_address(unsigned char *begin,
 610                                   unsigned char *addr,
 611                                   const struct oct1_map *map,
 612                                   u_int16_t *check);
 613 struct snmp_cnv
 614 {
 615         unsigned int class;
 616         unsigned int tag;
 617         int syntax;
 618 };
 619
 620 static struct snmp_cnv snmp_conv [] =
 621 {
 622         {ASN1_UNI, ASN1_NUL, SNMP_NULL},
 623         {ASN1_UNI, ASN1_INT, SNMP_INTEGER},
 624         {ASN1_UNI, ASN1_OTS, SNMP_OCTETSTR},
 625         {ASN1_UNI, ASN1_OTS, SNMP_DISPLAYSTR},
 626         {ASN1_UNI, ASN1_OJI, SNMP_OBJECTID},
 627         {ASN1_APL, SNMP_IPA, SNMP_IPADDR},
 628         {ASN1_APL, SNMP_CNT, SNMP_COUNTER},     /* Counter32 */
 629         {ASN1_APL, SNMP_GGE, SNMP_GAUGE},       /* Gauge32 == Unsigned32  */
 630         {ASN1_APL, SNMP_TIT, SNMP_TIMETICKS},
 631         {ASN1_APL, SNMP_OPQ, SNMP_OPAQUE},
 632
 633         /* SNMPv2 data types and errors */
 634         {ASN1_UNI, ASN1_BTS, SNMP_BITSTR},
 635         {ASN1_APL, SNMP_C64, SNMP_COUNTER64},
 636         {ASN1_CTX, SERR_NSO, SNMP_NOSUCHOBJECT},
 637         {ASN1_CTX, SERR_NSI, SNMP_NOSUCHINSTANCE},
 638         {ASN1_CTX, SERR_EOM, SNMP_ENDOFMIBVIEW},
 639         {0,       0,       -1}
 640 };
 641
 642 static unsigned char snmp_tag_cls2syntax(unsigned int tag,
 643                                          unsigned int cls,
 644                                          unsigned short *syntax)
 645 {
 646         struct snmp_cnv *cnv;
 647
 648         cnv = snmp_conv;
 649
 650         while (cnv->syntax != -1) {
 651                 if (cnv->tag == tag && cnv->class == cls) {
 652                         *syntax = cnv->syntax;
 653                         return 1;
 654                 }
 655                 cnv++;
 656         }
 657         return 0;
 658 }
 659
 660 static unsigned char snmp_object_decode(struct asn1_ctx *ctx,
 661                                         struct snmp_object **obj)
 662 {
 663         unsigned int cls, con, tag, len, idlen;
 664         unsigned short type;
 665         unsigned char *eoc, *end, *p;
 666         unsigned long *lp, *id;
 667         unsigned long ul;
 668         long  l;
 669
 670         *obj = NULL;
 671         id = NULL;
 672
 673         if (!asn1_header_decode(ctx, &eoc, &cls, &con, &tag))
 674                 return 0;
 675
 676         if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
 677                 return 0;
 678
 679         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 680                 return 0;
 681
 682         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
 683                 return 0;
 684
 685         if (!asn1_oid_decode(ctx, end, &id, &idlen))
 686                 return 0;
 687
 688         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag)) {
 689                 kfree(id);
 690                 return 0;
 691         }
 692
 693         if (con != ASN1_PRI) {
 694                 kfree(id);
 695                 return 0;
 696         }
 697
 698         if (!snmp_tag_cls2syntax(tag, cls, &type)) {
 699                 kfree(id);
 700                 return 0;
 701         }
 702
 703         switch (type) {
 704                 case SNMP_INTEGER:
 705                         len = sizeof(long);
 706                         if (!asn1_long_decode(ctx, end, &l)) {
 707                                 kfree(id);
 708                                 return 0;
 709                         }
 710                         *obj = kmalloc(sizeof(struct snmp_object) + len,
 711                                        GFP_ATOMIC);
 712                         if (*obj == NULL) {
 713                                 kfree(id);
 714                                 if (net_ratelimit())
 715                                         printk("OOM in bsalg (%d)\n", __LINE__);
 716                                 return 0;
 717                         }
 718                         (*obj)->syntax.l[0] = l;
 719                         break;
 720                 case SNMP_OCTETSTR:
 721                 case SNMP_OPAQUE:
 722                         if (!asn1_octets_decode(ctx, end, &p, &len)) {
 723                                 kfree(id);
 724                                 return 0;
 725                         }
 726                         *obj = kmalloc(sizeof(struct snmp_object) + len,
 727                                        GFP_ATOMIC);
 728                         if (*obj == NULL) {
 729                                 kfree(id);
 730                                 if (net_ratelimit())
 731                                         printk("OOM in bsalg (%d)\n", __LINE__);
 732                                 return 0;
 733                         }
 734                         memcpy((*obj)->syntax.c, p, len);
 735                         kfree(p);
 736                         break;
 737                 case SNMP_NULL:
 738                 case SNMP_NOSUCHOBJECT:
 739                 case SNMP_NOSUCHINSTANCE:
 740                 case SNMP_ENDOFMIBVIEW:
 741                         len = 0;
 742                         *obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
 743                         if (*obj == NULL) {
 744                                 kfree(id);
 745                                 if (net_ratelimit())
 746                                         printk("OOM in bsalg (%d)\n", __LINE__);
 747                                 return 0;
 748                         }
 749                         if (!asn1_null_decode(ctx, end)) {
 750                                 kfree(id);
 751                                 kfree(*obj);
 752                                 *obj = NULL;
 753                                 return 0;
 754                         }
 755                         break;
 756                 case SNMP_OBJECTID:
 757                         if (!asn1_oid_decode(ctx, end, (unsigned long **)&lp, &len)) {
 758                                 kfree(id);
 759                                 return 0;
 760                         }
 761                         len *= sizeof(unsigned long);
 762                         *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
 763                         if (*obj == NULL) {
 764                                 kfree(id);
 765                                 if (net_ratelimit())
 766                                         printk("OOM in bsalg (%d)\n", __LINE__);
 767                                 return 0;
 768                         }
 769                         memcpy((*obj)->syntax.ul, lp, len);
 770                         kfree(lp);
 771                         break;
 772                 case SNMP_IPADDR:
 773                         if (!asn1_octets_decode(ctx, end, &p, &len)) {
 774                                 kfree(id);
 775                                 return 0;
 776                         }
 777                         if (len != 4) {
 778                                 kfree(p);
 779                                 kfree(id);
 780                                 return 0;
 781                         }
 782                         *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
 783                         if (*obj == NULL) {
 784                                 kfree(p);
 785                                 kfree(id);
 786                                 if (net_ratelimit())
 787                                         printk("OOM in bsalg (%d)\n", __LINE__);
 788                                 return 0;
 789                         }
 790                         memcpy((*obj)->syntax.uc, p, len);
 791                         kfree(p);
 792                         break;
 793                 case SNMP_COUNTER:
 794                 case SNMP_GAUGE:
 795                 case SNMP_TIMETICKS:
 796                         len = sizeof(unsigned long);
 797                         if (!asn1_ulong_decode(ctx, end, &ul)) {
 798                                 kfree(id);
 799                                 return 0;
 800                         }
 801                         *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
 802                         if (*obj == NULL) {
 803                                 kfree(id);
 804                                 if (net_ratelimit())
 805                                         printk("OOM in bsalg (%d)\n", __LINE__);
 806                                 return 0;
 807                         }
 808                         (*obj)->syntax.ul[0] = ul;
 809                         break;
 810                 default:
 811                         kfree(id);
 812                         return 0;
 813         }
 814
 815         (*obj)->syntax_len = len;
 816         (*obj)->type = type;
 817         (*obj)->id = id;
 818         (*obj)->id_len = idlen;
 819
 820         if (!asn1_eoc_decode(ctx, eoc)) {
 821                 kfree(id);
 822                 kfree(*obj);
 823                 *obj = NULL;
 824                 return 0;
 825         }
 826         return 1;
 827 }
 828
 829 static unsigned char snmp_request_decode(struct asn1_ctx *ctx,
 830                                          struct snmp_request *request)
 831 {
 832         unsigned int cls, con, tag;
 833         unsigned char *end;
 834
 835         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 836                 return 0;
 837
 838         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
 839                 return 0;
 840
 841         if (!asn1_ulong_decode(ctx, end, &request->id))
 842                 return 0;
 843
 844         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 845                 return 0;
 846
 847         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
 848                 return 0;
 849
 850         if (!asn1_uint_decode(ctx, end, &request->error_status))
 851                 return 0;
 852
 853         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 854                 return 0;
 855
 856         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
 857                 return 0;
 858
 859         if (!asn1_uint_decode(ctx, end, &request->error_index))
 860                 return 0;
 861
 862         return 1;
 863 }
 864
 865 static unsigned char snmp_trap_decode(struct asn1_ctx *ctx,
 866                                       struct snmp_v1_trap *trap,
 867                                       const struct oct1_map *map,
 868                                       u_int16_t *check)
 869 {
 870         unsigned int cls, con, tag, len;
 871         unsigned char *end;
 872
 873         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 874                 return 0;
 875
 876         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
 877                 return 0;
 878
 879         if (!asn1_oid_decode(ctx, end, &trap->id, &trap->id_len))
 880                 return 0;
 881
 882         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 883                 goto err_id_free;
 884
 885         if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_IPA) ||
 886               (cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_OTS)))
 887                 goto err_id_free;
 888
 889         if (!asn1_octets_decode(ctx, end, (unsigned char **)&trap->ip_address, &len))
 890                 goto err_id_free;
 891
 892         /* IPv4 only */
 893         if (len != 4)
 894                 goto err_addr_free;
 895
 896         mangle_address(ctx->begin, ctx->pointer - 4, map, check);
 897
 898         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 899                 goto err_addr_free;
 900
 901         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
 902                 goto err_addr_free;
 903
 904         if (!asn1_uint_decode(ctx, end, &trap->general))
 905                 goto err_addr_free;
 906
 907         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 908                 goto err_addr_free;
 909
 910         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
 911                 goto err_addr_free;
 912
 913         if (!asn1_uint_decode(ctx, end, &trap->specific))
 914                 goto err_addr_free;
 915
 916         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 917                 goto err_addr_free;
 918
 919         if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_TIT) ||
 920               (cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_INT)))
 921                 goto err_addr_free;
 922
 923         if (!asn1_ulong_decode(ctx, end, &trap->time))
 924                 goto err_addr_free;
 925
 926         return 1;
 927
 928 err_id_free:
 929         kfree(trap->id);
 930
 931 err_addr_free:
 932         kfree((unsigned long *)trap->ip_address);
 933
 934         return 0;
 935 }
 936
 937 /*****************************************************************************
 938  *
 939  * Misc. routines
 940  *
 941  *****************************************************************************/
 942
 943 static void hex_dump(unsigned char *buf, size_t len)
 944 {
 945         size_t i;
 946
 947         for (i = 0; i < len; i++) {
 948                 if (i && !(i % 16))
 949                         printk("\n");
 950                 printk("%02x ", *(buf + i));
 951         }
 952         printk("\n");
 953 }
 954
 955 /*
 956  * Fast checksum update for possibly oddly-aligned UDP byte, from the
 957  * code example in the draft.
 958  */
 959 static void fast_csum(unsigned char *csum,
 960                       const unsigned char *optr,
 961                       const unsigned char *nptr,
 962                       int odd)
 963 {
 964         long x, old, new;
 965
 966         x = csum[0] * 256 + csum[1];
 967
 968         x =~ x & 0xFFFF;
 969
 970         if (odd) old = optr[0] * 256;
 971         else old = optr[0];
 972
 973         x -= old & 0xFFFF;
 974         if (x <= 0) {
 975                 x--;
 976                 x &= 0xFFFF;
 977         }
 978
 979         if (odd) new = nptr[0] * 256;
 980         else new = nptr[0];
 981
 982         x += new & 0xFFFF;
 983         if (x & 0x10000) {
 984                 x++;
 985                 x &= 0xFFFF;
 986         }
 987
 988         x =~ x & 0xFFFF;
 989         csum[0] = x / 256;
 990         csum[1] = x & 0xFF;
 991 }
 992
 993 /*
 994  * Mangle IP address.
 995  *      - begin points to the start of the snmp messgae
 996  *      - addr points to the start of the address
 997  */
 998 static inline void mangle_address(unsigned char *begin,
 999                                   unsigned char *addr,
1000                                   const struct oct1_map *map,
1001                                   u_int16_t *check)
1002 {
1003         if (map->from == NOCT1(*addr)) {
1004                 u_int32_t old;
1005
1006                 if (debug)
1007                         memcpy(&old, (unsigned char *)addr, sizeof(old));
1008
1009                 *addr = map->to;
1010
1011                 /* Update UDP checksum if being used */
1012                 if (*check) {
1013                         unsigned char odd = !((addr - begin) % 2);
1014
1015                         fast_csum((unsigned char *)check,
1016                                   &map->from, &map->to, odd);
1017
1018                 }
1019
1020                 if (debug)
1021                         printk(KERN_DEBUG "bsalg: mapped %u.%u.%u.%u to "
1022                                "%u.%u.%u.%u\n", NIPQUAD(old), NIPQUAD(*addr));
1023         }
1024 }
1025
1026 /*
1027  * Parse and mangle SNMP message according to mapping.
1028  * (And this is the fucking 'basic' method).
1029  */
1030 static int snmp_parse_mangle(unsigned char *msg,
1031                              u_int16_t len,
1032                              const struct oct1_map *map,
1033                              u_int16_t *check)
1034 {
1035         unsigned char *eoc, *end;
1036         unsigned int cls, con, tag, vers, pdutype;
1037         struct asn1_ctx ctx;
1038         struct asn1_octstr comm;
1039         struct snmp_object **obj;
1040
1041         if (debug > 1)
1042                 hex_dump(msg, len);
1043
1044         asn1_open(&ctx, msg, len);
1045
1046         /*
1047          * Start of SNMP message.
1048          */
1049         if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
1050                 return 0;
1051         if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
1052                 return 0;
1053
1054         /*
1055          * Version 1 or 2 handled.
1056          */
1057         if (!asn1_header_decode(&ctx, &end, &cls, &con, &tag))
1058                 return 0;
1059         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
1060                 return 0;
1061         if (!asn1_uint_decode (&ctx, end, &vers))
1062                 return 0;
1063         if (debug > 1)
1064                 printk(KERN_DEBUG "bsalg: snmp version: %u\n", vers + 1);
1065         if (vers > 1)
1066                 return 1;
1067
1068         /*
1069          * Community.
1070          */
1071         if (!asn1_header_decode (&ctx, &end, &cls, &con, &tag))
1072                 return 0;
1073         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OTS)
1074                 return 0;
1075         if (!asn1_octets_decode(&ctx, end, &comm.data, &comm.len))
1076                 return 0;
1077         if (debug > 1) {
1078                 unsigned int i;
1079
1080                 printk(KERN_DEBUG "bsalg: community: ");
1081                 for (i = 0; i < comm.len; i++)
1082                         printk("%c", comm.data[i]);
1083                 printk("\n");
1084         }
1085         kfree(comm.data);
1086
1087         /*
1088          * PDU type
1089          */
1090         if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &pdutype))
1091                 return 0;
1092         if (cls != ASN1_CTX || con != ASN1_CON)
1093                 return 0;
1094         if (debug > 1) {
1095                 unsigned char *pdus[] = {
1096                         [SNMP_PDU_GET] = "get",
1097                         [SNMP_PDU_NEXT] = "get-next",
1098                         [SNMP_PDU_RESPONSE] = "response",
1099                         [SNMP_PDU_SET] = "set",
1100                         [SNMP_PDU_TRAP1] = "trapv1",
1101                         [SNMP_PDU_BULK] = "bulk",
1102                         [SNMP_PDU_INFORM] = "inform",
1103                         [SNMP_PDU_TRAP2] = "trapv2"
1104                 };
1105
1106                 if (pdutype > SNMP_PDU_TRAP2)
1107                         printk(KERN_DEBUG "bsalg: bad pdu type %u\n", pdutype);
1108                 else
1109                         printk(KERN_DEBUG "bsalg: pdu: %s\n", pdus[pdutype]);
1110         }
1111         if (pdutype != SNMP_PDU_RESPONSE &&
1112             pdutype != SNMP_PDU_TRAP1 && pdutype != SNMP_PDU_TRAP2)
1113                 return 1;
1114
1115         /*
1116          * Request header or v1 trap
1117          */
1118         if (pdutype == SNMP_PDU_TRAP1) {
1119                 struct snmp_v1_trap trap;
1120                 unsigned char ret = snmp_trap_decode(&ctx, &trap, map, check);
1121
1122                 /* Discard trap allocations regardless */
1123                 kfree(trap.id);
1124                 kfree((unsigned long *)trap.ip_address);
1125
1126                 if (!ret)
1127                         return ret;
1128
1129         } else {
1130                 struct snmp_request req;
1131
1132                 if (!snmp_request_decode(&ctx, &req))
1133                         return 0;
1134
1135                 if (debug > 1)
1136                         printk(KERN_DEBUG "bsalg: request: id=0x%lx error_status=%u "
1137                         "error_index=%u\n", req.id, req.error_status,
1138                         req.error_index);
1139         }
1140
1141         /*
1142          * Loop through objects, look for IP addresses to mangle.
1143          */
1144         if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
1145                 return 0;
1146
1147         if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
1148                 return 0;
1149
1150         obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
1151         if (obj == NULL) {
1152                 if (net_ratelimit())
1153                         printk(KERN_WARNING "OOM in bsalg(%d)\n", __LINE__);
1154                 return 0;
1155         }
1156
1157         while (!asn1_eoc_decode(&ctx, eoc)) {
1158                 unsigned int i;
1159
1160                 if (!snmp_object_decode(&ctx, obj)) {
1161                         if (*obj) {
1162                                 if ((*obj)->id)
1163                                         kfree((*obj)->id);
1164                                 kfree(*obj);
1165                         }
1166                         kfree(obj);
1167                         return 0;
1168                 }
1169
1170                 if (debug > 1) {
1171                         printk(KERN_DEBUG "bsalg: object: ");
1172                         for (i = 0; i < (*obj)->id_len; i++) {
1173                                 if (i > 0)
1174                                         printk(".");
1175                                 printk("%lu", (*obj)->id[i]);
1176                         }
1177                         printk(": type=%u\n", (*obj)->type);
1178
1179                 }
1180
1181                 if ((*obj)->type == SNMP_IPADDR)
1182                         mangle_address(ctx.begin, ctx.pointer - 4 , map, check);
1183
1184                 kfree((*obj)->id);
1185                 kfree(*obj);
1186         }
1187         kfree(obj);
1188
1189         if (!asn1_eoc_decode(&ctx, eoc))
1190                 return 0;
1191
1192         return 1;
1193 }
1194
1195 /*****************************************************************************
1196  *
1197  * NAT routines.
1198  *
1199  *****************************************************************************/
1200
1201 /*
1202  * SNMP translation routine.
1203  */
1204 static int snmp_translate(struct ip_conntrack *ct,
1205                           struct ip_nat_info *info,
1206                           enum ip_conntrack_info ctinfo,
1207                           unsigned int hooknum,
1208                           struct sk_buff **pskb)
1209 {
1210         struct iphdr *iph = (*pskb)->nh.iph;
1211         struct udphdr *udph = (struct udphdr *)((u_int32_t *)iph + iph->ihl);
1212         u_int16_t udplen = ntohs(udph->len);
1213         u_int16_t paylen = udplen - sizeof(struct udphdr);
1214         int dir = CTINFO2DIR(ctinfo);
1215         struct oct1_map map;
1216
1217         /*
1218          * Determine mappping for application layer addresses based
1219          * on NAT manipulations for the packet.
1220          */
1221         if (dir == IP_CT_DIR_ORIGINAL) {
1222                 /* SNAT traps */
1223                 map.from = NOCT1(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip);
1224                 map.to = NOCT1(ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip);
1225         } else {
1226                 /* DNAT replies */
1227                 map.from = NOCT1(ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip);
1228                 map.to = NOCT1(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip);
1229         }
1230
1231         if (map.from == map.to)
1232                 return NF_ACCEPT;
1233
1234         if (!snmp_parse_mangle((unsigned char *)udph + sizeof(struct udphdr),
1235                                paylen, &map, &udph->check)) {
1236                 printk(KERN_WARNING "bsalg: parser failed\n");
1237                 return NF_DROP;
1238         }
1239         return NF_ACCEPT;
1240 }
1241
1242 /*
1243  * NAT helper function, packets arrive here from NAT code.
1244  */
1245 static unsigned int nat_help(struct ip_conntrack *ct,
1246                              struct ip_conntrack_expect *exp,
1247                              struct ip_nat_info *info,
1248                              enum ip_conntrack_info ctinfo,
1249                              unsigned int hooknum,
1250                              struct sk_buff **pskb)
1251 {
1252         int dir = CTINFO2DIR(ctinfo);
1253         struct iphdr *iph = (*pskb)->nh.iph;
1254         struct udphdr *udph = (struct udphdr *)((u_int32_t *)iph + iph->ihl);
1255
1256         spin_lock_bh(&snmp_lock);
1257
1258         /*
1259          * Translate snmp replies on pre-routing (DNAT) and snmp traps
1260          * on post routing (SNAT).
1261          */
1262         if (!((dir == IP_CT_DIR_REPLY && hooknum == NF_IP_PRE_ROUTING &&
1263                         udph->source == ntohs(SNMP_PORT)) ||
1264               (dir == IP_CT_DIR_ORIGINAL && hooknum == NF_IP_POST_ROUTING &&
1265                         udph->dest == ntohs(SNMP_TRAP_PORT)))) {
1266                 spin_unlock_bh(&snmp_lock);
1267                 return NF_ACCEPT;
1268         }
1269
1270         if (debug > 1) {
1271                 printk(KERN_DEBUG "bsalg: dir=%s hook=%d manip=%s len=%d "
1272                        "src=%u.%u.%u.%u:%u dst=%u.%u.%u.%u:%u "
1273                        "osrc=%u.%u.%u.%u odst=%u.%u.%u.%u "
1274                        "rsrc=%u.%u.%u.%u rdst=%u.%u.%u.%u "
1275                        "\n",
1276                        dir == IP_CT_DIR_REPLY ? "reply" : "orig", hooknum,
1277                        HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC ? "snat" :
1278                        "dnat", (*pskb)->len,
1279                        NIPQUAD(iph->saddr), ntohs(udph->source),
1280                        NIPQUAD(iph->daddr), ntohs(udph->dest),
1281                        NIPQUAD(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip),
1282                        NIPQUAD(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip),
1283                        NIPQUAD(ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip),
1284                        NIPQUAD(ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip));
1285         }
1286
1287         /*
1288          * Make sure the packet length is ok.  So far, we were only guaranteed
1289          * to have a valid length IP header plus 8 bytes, which means we have
1290          * enough room for a UDP header.  Just verify the UDP length field so we
1291          * can mess around with the payload.
1292          */
1293          if (ntohs(udph->len) == (*pskb)->len - (iph->ihl << 2)) {
1294                 int ret = snmp_translate(ct, info, ctinfo, hooknum, pskb);
1295                 spin_unlock_bh(&snmp_lock);
1296                 return ret;
1297         }
1298
1299         if (net_ratelimit())
1300                 printk(KERN_WARNING "bsalg: dropping malformed packet "
1301                        "src=%u.%u.%u.%u dst=%u.%u.%u.%u\n",
1302                        NIPQUAD(iph->saddr), NIPQUAD(iph->daddr));
1303         spin_unlock_bh(&snmp_lock);
1304         return NF_DROP;
1305 }
1306
1307 static struct ip_nat_helper snmp = {
1308         { NULL, NULL },
1309         "snmp",
1310         0,
1311         THIS_MODULE,
1312         { { 0, { .udp = { __constant_htons(SNMP_PORT) } } },
1313           { 0, { 0 }, IPPROTO_UDP } },
1314         { { 0, { .udp = { 0xFFFF } } },
1315           { 0, { 0 }, 0xFFFF } },
1316         nat_help, NULL };
1317
1318 static struct ip_nat_helper snmp_trap = {
1319         { NULL, NULL },
1320         "snmp_trap",
1321         0,
1322         THIS_MODULE,
1323         { { 0, { .udp = { __constant_htons(SNMP_TRAP_PORT) } } },
1324           { 0, { 0 }, IPPROTO_UDP } },
1325         { { 0, { .udp = { 0xFFFF } } },
1326           { 0, { 0 }, 0xFFFF } },
1327         nat_help, NULL };
1328
1329 /*****************************************************************************
1330  *
1331  * Module stuff.
1332  *
1333  *****************************************************************************/
1334
1335 static int __init init(void)
1336 {
1337         int ret = 0;
1338
1339         ret = ip_nat_helper_register(&snmp);
1340         if (ret < 0)
1341                 return ret;
1342         ret = ip_nat_helper_register(&snmp_trap);
1343         if (ret < 0) {
1344                 ip_nat_helper_unregister(&snmp);
1345                 return ret;
1346         }
1347         return ret;
1348 }
1349
1350 static void __exit fini(void)
1351 {
1352         ip_nat_helper_unregister(&snmp);
1353         ip_nat_helper_unregister(&snmp_trap);
1354         synchronize_net();
1355 }
1356
1357 module_init(init);
1358 module_exit(fini);
1359
1360 MODULE_PARM(debug, "i");