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/moduleparam.h>
  51 #include <linux/netfilter_ipv4.h>
  52 #include <linux/netfilter_ipv4/ip_nat.h>
  53 #include <linux/netfilter_ipv4/ip_nat_helper.h>
  54 #include <linux/ip.h>
  55 #include <net/checksum.h>
  56 #include <net/udp.h>
  57 #include <asm/uaccess.h>
  58
  59 MODULE_LICENSE("GPL");
  60 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
  61 MODULE_DESCRIPTION("Basic SNMP Application Layer Gateway");
  62
  63 #define SNMP_PORT 161
  64 #define SNMP_TRAP_PORT 162
  65 #define NOCT1(n) (u_int8_t )((n) & 0xff)
  66
  67 static int debug;
  68 static spinlock_t snmp_lock = SPIN_LOCK_UNLOCKED;
  69
  70 /*
  71  * Application layer address mapping mimics the NAT mapping, but
  72  * only for the first octet in this case (a more flexible system
  73  * can be implemented if needed).
  74  */
  75 struct oct1_map
  76 {
  77         u_int8_t from;
  78         u_int8_t to;
  79 };
  80
  81
  82 /*****************************************************************************
  83  *
  84  * Basic ASN.1 decoding routines (gxsnmp author Dirk Wisse)
  85  *
  86  *****************************************************************************/
  87
  88 /* Class */
  89 #define ASN1_UNI        0       /* Universal */
  90 #define ASN1_APL        1       /* Application */
  91 #define ASN1_CTX        2       /* Context */
  92 #define ASN1_PRV        3       /* Private */
  93
  94 /* Tag */
  95 #define ASN1_EOC        0       /* End Of Contents */
  96 #define ASN1_BOL        1       /* Boolean */
  97 #define ASN1_INT        2       /* Integer */
  98 #define ASN1_BTS        3       /* Bit String */
  99 #define ASN1_OTS        4       /* Octet String */
 100 #define ASN1_NUL        5       /* Null */
 101 #define ASN1_OJI        6       /* Object Identifier  */
 102 #define ASN1_OJD        7       /* Object Description */
 103 #define ASN1_EXT        8       /* External */
 104 #define ASN1_SEQ        16      /* Sequence */
 105 #define ASN1_SET        17      /* Set */
 106 #define ASN1_NUMSTR     18      /* Numerical String */
 107 #define ASN1_PRNSTR     19      /* Printable String */
 108 #define ASN1_TEXSTR     20      /* Teletext String */
 109 #define ASN1_VIDSTR     21      /* Video String */
 110 #define ASN1_IA5STR     22      /* IA5 String */
 111 #define ASN1_UNITIM     23      /* Universal Time */
 112 #define ASN1_GENTIM     24      /* General Time */
 113 #define ASN1_GRASTR     25      /* Graphical String */
 114 #define ASN1_VISSTR     26      /* Visible String */
 115 #define ASN1_GENSTR     27      /* General String */
 116
 117 /* Primitive / Constructed methods*/
 118 #define ASN1_PRI        0       /* Primitive */
 119 #define ASN1_CON        1       /* Constructed */
 120
 121 /*
 122  * Error codes.
 123  */
 124 #define ASN1_ERR_NOERROR                0
 125 #define ASN1_ERR_DEC_EMPTY              2
 126 #define ASN1_ERR_DEC_EOC_MISMATCH       3
 127 #define ASN1_ERR_DEC_LENGTH_MISMATCH    4
 128 #define ASN1_ERR_DEC_BADVALUE           5
 129
 130 /*
 131  * ASN.1 context.
 132  */
 133 struct asn1_ctx
 134 {
 135         int error;                      /* Error condition */
 136         unsigned char *pointer;         /* Octet just to be decoded */
 137         unsigned char *begin;           /* First octet */
 138         unsigned char *end;             /* Octet after last octet */
 139 };
 140
 141 /*
 142  * Octet string (not null terminated)
 143  */
 144 struct asn1_octstr
 145 {
 146         unsigned char *data;
 147         unsigned int len;
 148 };
 149
 150 static void asn1_open(struct asn1_ctx *ctx,
 151                       unsigned char *buf,
 152                       unsigned int len)
 153 {
 154         ctx->begin = buf;
 155         ctx->end = buf + len;
 156         ctx->pointer = buf;
 157         ctx->error = ASN1_ERR_NOERROR;
 158 }
 159
 160 static unsigned char asn1_octet_decode(struct asn1_ctx *ctx, unsigned char *ch)
 161 {
 162         if (ctx->pointer >= ctx->end) {
 163                 ctx->error = ASN1_ERR_DEC_EMPTY;
 164                 return 0;
 165         }
 166         *ch = *(ctx->pointer)++;
 167         return 1;
 168 }
 169
 170 static unsigned char asn1_tag_decode(struct asn1_ctx *ctx, unsigned int *tag)
 171 {
 172         unsigned char ch;
 173
 174         *tag = 0;
 175
 176         do
 177         {
 178                 if (!asn1_octet_decode(ctx, &ch))
 179                         return 0;
 180                 *tag <<= 7;
 181                 *tag |= ch & 0x7F;
 182         } while ((ch & 0x80) == 0x80);
 183         return 1;
 184 }
 185
 186 static unsigned char asn1_id_decode(struct asn1_ctx *ctx,
 187                                     unsigned int *cls,
 188                                     unsigned int *con,
 189                                     unsigned int *tag)
 190 {
 191         unsigned char ch;
 192
 193         if (!asn1_octet_decode(ctx, &ch))
 194                 return 0;
 195
 196         *cls = (ch & 0xC0) >> 6;
 197         *con = (ch & 0x20) >> 5;
 198         *tag = (ch & 0x1F);
 199
 200         if (*tag == 0x1F) {
 201                 if (!asn1_tag_decode(ctx, tag))
 202                         return 0;
 203         }
 204         return 1;
 205 }
 206
 207 static unsigned char asn1_length_decode(struct asn1_ctx *ctx,
 208                                         unsigned int *def,
 209                                         unsigned int *len)
 210 {
 211         unsigned char ch, cnt;
 212
 213         if (!asn1_octet_decode(ctx, &ch))
 214                 return 0;
 215
 216         if (ch == 0x80)
 217                 *def = 0;
 218         else {
 219                 *def = 1;
 220
 221                 if (ch < 0x80)
 222                         *len = ch;
 223                 else {
 224                         cnt = (unsigned char) (ch & 0x7F);
 225                         *len = 0;
 226
 227                         while (cnt > 0) {
 228                                 if (!asn1_octet_decode(ctx, &ch))
 229                                         return 0;
 230                                 *len <<= 8;
 231                                 *len |= ch;
 232                                 cnt--;
 233                         }
 234                 }
 235         }
 236         return 1;
 237 }
 238
 239 static unsigned char asn1_header_decode(struct asn1_ctx *ctx,
 240                                         unsigned char **eoc,
 241                                         unsigned int *cls,
 242                                         unsigned int *con,
 243                                         unsigned int *tag)
 244 {
 245         unsigned int def, len;
 246
 247         if (!asn1_id_decode(ctx, cls, con, tag))
 248                 return 0;
 249
 250         if (!asn1_length_decode(ctx, &def, &len))
 251                 return 0;
 252
 253         if (def)
 254                 *eoc = ctx->pointer + len;
 255         else
 256                 *eoc = NULL;
 257         return 1;
 258 }
 259
 260 static unsigned char asn1_eoc_decode(struct asn1_ctx *ctx, unsigned char *eoc)
 261 {
 262         unsigned char ch;
 263
 264         if (eoc == 0) {
 265                 if (!asn1_octet_decode(ctx, &ch))
 266                         return 0;
 267
 268                 if (ch != 0x00) {
 269                         ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
 270                         return 0;
 271                 }
 272
 273                 if (!asn1_octet_decode(ctx, &ch))
 274                         return 0;
 275
 276                 if (ch != 0x00) {
 277                         ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
 278                         return 0;
 279                 }
 280                 return 1;
 281         } else {
 282                 if (ctx->pointer != eoc) {
 283                         ctx->error = ASN1_ERR_DEC_LENGTH_MISMATCH;
 284                         return 0;
 285                 }
 286                 return 1;
 287         }
 288 }
 289
 290 static unsigned char asn1_null_decode(struct asn1_ctx *ctx, unsigned char *eoc)
 291 {
 292         ctx->pointer = eoc;
 293         return 1;
 294 }
 295
 296 static unsigned char asn1_long_decode(struct asn1_ctx *ctx,
 297                                       unsigned char *eoc,
 298                                       long *integer)
 299 {
 300         unsigned char ch;
 301         unsigned int  len;
 302
 303         if (!asn1_octet_decode(ctx, &ch))
 304                 return 0;
 305
 306         *integer = (signed char) ch;
 307         len = 1;
 308
 309         while (ctx->pointer < eoc) {
 310                 if (++len > sizeof (long)) {
 311                         ctx->error = ASN1_ERR_DEC_BADVALUE;
 312                         return 0;
 313                 }
 314
 315                 if (!asn1_octet_decode(ctx, &ch))
 316                         return 0;
 317
 318                 *integer <<= 8;
 319                 *integer |= ch;
 320         }
 321         return 1;
 322 }
 323
 324 static unsigned char asn1_uint_decode(struct asn1_ctx *ctx,
 325                                       unsigned char *eoc,
 326                                       unsigned int *integer)
 327 {
 328         unsigned char ch;
 329         unsigned int  len;
 330
 331         if (!asn1_octet_decode(ctx, &ch))
 332                 return 0;
 333
 334         *integer = ch;
 335         if (ch == 0) len = 0;
 336         else len = 1;
 337
 338         while (ctx->pointer < eoc) {
 339                 if (++len > sizeof (unsigned int)) {
 340                         ctx->error = ASN1_ERR_DEC_BADVALUE;
 341                         return 0;
 342                 }
 343
 344                 if (!asn1_octet_decode(ctx, &ch))
 345                         return 0;
 346
 347                 *integer <<= 8;
 348                 *integer |= ch;
 349         }
 350         return 1;
 351 }
 352
 353 static unsigned char asn1_ulong_decode(struct asn1_ctx *ctx,
 354                                        unsigned char *eoc,
 355                                        unsigned long *integer)
 356 {
 357         unsigned char ch;
 358         unsigned int  len;
 359
 360         if (!asn1_octet_decode(ctx, &ch))
 361                 return 0;
 362
 363         *integer = ch;
 364         if (ch == 0) len = 0;
 365         else len = 1;
 366
 367         while (ctx->pointer < eoc) {
 368                 if (++len > sizeof (unsigned long)) {
 369                         ctx->error = ASN1_ERR_DEC_BADVALUE;
 370                         return 0;
 371                 }
 372
 373                 if (!asn1_octet_decode(ctx, &ch))
 374                         return 0;
 375
 376                 *integer <<= 8;
 377                 *integer |= ch;
 378         }
 379         return 1;
 380 }
 381
 382 static unsigned char asn1_octets_decode(struct asn1_ctx *ctx,
 383                                         unsigned char *eoc,
 384                                         unsigned char **octets,
 385                                         unsigned int *len)
 386 {
 387         unsigned char *ptr;
 388
 389         *len = 0;
 390
 391         *octets = kmalloc(eoc - ctx->pointer, GFP_ATOMIC);
 392         if (*octets == NULL) {
 393                 if (net_ratelimit())
 394                         printk("OOM in bsalg (%d)\n", __LINE__);
 395                 return 0;
 396         }
 397
 398         ptr = *octets;
 399         while (ctx->pointer < eoc) {
 400                 if (!asn1_octet_decode(ctx, (unsigned char *)ptr++)) {
 401                         kfree(*octets);
 402                         *octets = NULL;
 403                         return 0;
 404                 }
 405                 (*len)++;
 406         }
 407         return 1;
 408 }
 409
 410 static unsigned char asn1_subid_decode(struct asn1_ctx *ctx,
 411                                        unsigned long *subid)
 412 {
 413         unsigned char ch;
 414
 415         *subid = 0;
 416
 417         do {
 418                 if (!asn1_octet_decode(ctx, &ch))
 419                         return 0;
 420
 421                 *subid <<= 7;
 422                 *subid |= ch & 0x7F;
 423         } while ((ch & 0x80) == 0x80);
 424         return 1;
 425 }
 426
 427 static unsigned char asn1_oid_decode(struct asn1_ctx *ctx,
 428                                      unsigned char *eoc,
 429                                      unsigned long **oid,
 430                                      unsigned int *len)
 431 {
 432         unsigned long subid;
 433         unsigned int  size;
 434         unsigned long *optr;
 435
 436         size = eoc - ctx->pointer + 1;
 437         *oid = kmalloc(size * sizeof(unsigned long), GFP_ATOMIC);
 438         if (*oid == NULL) {
 439                 if (net_ratelimit())
 440                         printk("OOM in bsalg (%d)\n", __LINE__);
 441                 return 0;
 442         }
 443
 444         optr = *oid;
 445
 446         if (!asn1_subid_decode(ctx, &subid)) {
 447                 kfree(*oid);
 448                 *oid = NULL;
 449                 return 0;
 450         }
 451
 452         if (subid < 40) {
 453                 optr [0] = 0;
 454                 optr [1] = subid;
 455         } else if (subid < 80) {
 456                 optr [0] = 1;
 457                 optr [1] = subid - 40;
 458         } else {
 459                 optr [0] = 2;
 460                 optr [1] = subid - 80;
 461         }
 462
 463         *len = 2;
 464         optr += 2;
 465
 466         while (ctx->pointer < eoc) {
 467                 if (++(*len) > size) {
 468                         ctx->error = ASN1_ERR_DEC_BADVALUE;
 469                         kfree(*oid);
 470                         *oid = NULL;
 471                         return 0;
 472                 }
 473
 474                 if (!asn1_subid_decode(ctx, optr++)) {
 475                         kfree(*oid);
 476                         *oid = NULL;
 477                         return 0;
 478                 }
 479         }
 480         return 1;
 481 }
 482
 483 /*****************************************************************************
 484  *
 485  * SNMP decoding routines (gxsnmp author Dirk Wisse)
 486  *
 487  *****************************************************************************/
 488
 489 /* SNMP Versions */
 490 #define SNMP_V1                         0
 491 #define SNMP_V2C                        1
 492 #define SNMP_V2                         2
 493 #define SNMP_V3                         3
 494
 495 /* Default Sizes */
 496 #define SNMP_SIZE_COMM                  256
 497 #define SNMP_SIZE_OBJECTID              128
 498 #define SNMP_SIZE_BUFCHR                256
 499 #define SNMP_SIZE_BUFINT                128
 500 #define SNMP_SIZE_SMALLOBJECTID         16
 501
 502 /* Requests */
 503 #define SNMP_PDU_GET                    0
 504 #define SNMP_PDU_NEXT                   1
 505 #define SNMP_PDU_RESPONSE               2
 506 #define SNMP_PDU_SET                    3
 507 #define SNMP_PDU_TRAP1                  4
 508 #define SNMP_PDU_BULK                   5
 509 #define SNMP_PDU_INFORM                 6
 510 #define SNMP_PDU_TRAP2                  7
 511
 512 /* Errors */
 513 #define SNMP_NOERROR                    0
 514 #define SNMP_TOOBIG                     1
 515 #define SNMP_NOSUCHNAME                 2
 516 #define SNMP_BADVALUE                   3
 517 #define SNMP_READONLY                   4
 518 #define SNMP_GENERROR                   5
 519 #define SNMP_NOACCESS                   6
 520 #define SNMP_WRONGTYPE                  7
 521 #define SNMP_WRONGLENGTH                8
 522 #define SNMP_WRONGENCODING              9
 523 #define SNMP_WRONGVALUE                 10
 524 #define SNMP_NOCREATION                 11
 525 #define SNMP_INCONSISTENTVALUE          12
 526 #define SNMP_RESOURCEUNAVAILABLE        13
 527 #define SNMP_COMMITFAILED               14
 528 #define SNMP_UNDOFAILED                 15
 529 #define SNMP_AUTHORIZATIONERROR         16
 530 #define SNMP_NOTWRITABLE                17
 531 #define SNMP_INCONSISTENTNAME           18
 532
 533 /* General SNMP V1 Traps */
 534 #define SNMP_TRAP_COLDSTART             0
 535 #define SNMP_TRAP_WARMSTART             1
 536 #define SNMP_TRAP_LINKDOWN              2
 537 #define SNMP_TRAP_LINKUP                3
 538 #define SNMP_TRAP_AUTFAILURE            4
 539 #define SNMP_TRAP_EQPNEIGHBORLOSS       5
 540 #define SNMP_TRAP_ENTSPECIFIC           6
 541
 542 /* SNMPv1 Types */
 543 #define SNMP_NULL                0
 544 #define SNMP_INTEGER             1    /* l  */
 545 #define SNMP_OCTETSTR            2    /* c  */
 546 #define SNMP_DISPLAYSTR          2    /* c  */
 547 #define SNMP_OBJECTID            3    /* ul */
 548 #define SNMP_IPADDR              4    /* uc */
 549 #define SNMP_COUNTER             5    /* ul */
 550 #define SNMP_GAUGE               6    /* ul */
 551 #define SNMP_TIMETICKS           7    /* ul */
 552 #define SNMP_OPAQUE              8    /* c  */
 553
 554 /* Additional SNMPv2 Types */
 555 #define SNMP_UINTEGER            5    /* ul */
 556 #define SNMP_BITSTR              9    /* uc */
 557 #define SNMP_NSAP               10    /* uc */
 558 #define SNMP_COUNTER64          11    /* ul */
 559 #define SNMP_NOSUCHOBJECT       12
 560 #define SNMP_NOSUCHINSTANCE     13
 561 #define SNMP_ENDOFMIBVIEW       14
 562
 563 union snmp_syntax
 564 {
 565         unsigned char uc[0];    /* 8 bit unsigned */
 566         char c[0];              /* 8 bit signed */
 567         unsigned long ul[0];    /* 32 bit unsigned */
 568         long l[0];              /* 32 bit signed */
 569 };
 570
 571 struct snmp_object
 572 {
 573         unsigned long *id;
 574         unsigned int id_len;
 575         unsigned short type;
 576         unsigned int syntax_len;
 577         union snmp_syntax syntax;
 578 };
 579
 580 struct snmp_request
 581 {
 582         unsigned long id;
 583         unsigned int error_status;
 584         unsigned int error_index;
 585 };
 586
 587 struct snmp_v1_trap
 588 {
 589         unsigned long *id;
 590         unsigned int id_len;
 591         unsigned long ip_address;       /* pointer  */
 592         unsigned int general;
 593         unsigned int specific;
 594         unsigned long time;
 595 };
 596
 597 /* SNMP types */
 598 #define SNMP_IPA    0
 599 #define SNMP_CNT    1
 600 #define SNMP_GGE    2
 601 #define SNMP_TIT    3
 602 #define SNMP_OPQ    4
 603 #define SNMP_C64    6
 604
 605 /* SNMP errors */
 606 #define SERR_NSO    0
 607 #define SERR_NSI    1
 608 #define SERR_EOM    2
 609
 610 static inline void mangle_address(unsigned char *begin,
 611                                   unsigned char *addr,
 612                                   const struct oct1_map *map,
 613                                   u_int16_t *check);
 614 struct snmp_cnv
 615 {
 616         unsigned int class;
 617         unsigned int tag;
 618         int syntax;
 619 };
 620
 621 static struct snmp_cnv snmp_conv [] =
 622 {
 623         {ASN1_UNI, ASN1_NUL, SNMP_NULL},
 624         {ASN1_UNI, ASN1_INT, SNMP_INTEGER},
 625         {ASN1_UNI, ASN1_OTS, SNMP_OCTETSTR},
 626         {ASN1_UNI, ASN1_OTS, SNMP_DISPLAYSTR},
 627         {ASN1_UNI, ASN1_OJI, SNMP_OBJECTID},
 628         {ASN1_APL, SNMP_IPA, SNMP_IPADDR},
 629         {ASN1_APL, SNMP_CNT, SNMP_COUNTER},     /* Counter32 */
 630         {ASN1_APL, SNMP_GGE, SNMP_GAUGE},       /* Gauge32 == Unsigned32  */
 631         {ASN1_APL, SNMP_TIT, SNMP_TIMETICKS},
 632         {ASN1_APL, SNMP_OPQ, SNMP_OPAQUE},
 633
 634         /* SNMPv2 data types and errors */
 635         {ASN1_UNI, ASN1_BTS, SNMP_BITSTR},
 636         {ASN1_APL, SNMP_C64, SNMP_COUNTER64},
 637         {ASN1_CTX, SERR_NSO, SNMP_NOSUCHOBJECT},
 638         {ASN1_CTX, SERR_NSI, SNMP_NOSUCHINSTANCE},
 639         {ASN1_CTX, SERR_EOM, SNMP_ENDOFMIBVIEW},
 640         {0,       0,       -1}
 641 };
 642
 643 static unsigned char snmp_tag_cls2syntax(unsigned int tag,
 644                                          unsigned int cls,
 645                                          unsigned short *syntax)
 646 {
 647         struct snmp_cnv *cnv;
 648
 649         cnv = snmp_conv;
 650
 651         while (cnv->syntax != -1) {
 652                 if (cnv->tag == tag && cnv->class == cls) {
 653                         *syntax = cnv->syntax;
 654                         return 1;
 655                 }
 656                 cnv++;
 657         }
 658         return 0;
 659 }
 660
 661 static unsigned char snmp_object_decode(struct asn1_ctx *ctx,
 662                                         struct snmp_object **obj)
 663 {
 664         unsigned int cls, con, tag, len, idlen;
 665         unsigned short type;
 666         unsigned char *eoc, *end, *p;
 667         unsigned long *lp, *id;
 668         unsigned long ul;
 669         long  l;
 670
 671         *obj = NULL;
 672         id = NULL;
 673
 674         if (!asn1_header_decode(ctx, &eoc, &cls, &con, &tag))
 675                 return 0;
 676
 677         if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
 678                 return 0;
 679
 680         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 681                 return 0;
 682
 683         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
 684                 return 0;
 685
 686         if (!asn1_oid_decode(ctx, end, &id, &idlen))
 687                 return 0;
 688
 689         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag)) {
 690                 kfree(id);
 691                 return 0;
 692         }
 693
 694         if (con != ASN1_PRI) {
 695                 kfree(id);
 696                 return 0;
 697         }
 698
 699         if (!snmp_tag_cls2syntax(tag, cls, &type)) {
 700                 kfree(id);
 701                 return 0;
 702         }
 703
 704         switch (type) {
 705                 case SNMP_INTEGER:
 706                         len = sizeof(long);
 707                         if (!asn1_long_decode(ctx, end, &l)) {
 708                                 kfree(id);
 709                                 return 0;
 710                         }
 711                         *obj = kmalloc(sizeof(struct snmp_object) + len,
 712                                        GFP_ATOMIC);
 713                         if (*obj == NULL) {
 714                                 kfree(id);
 715                                 if (net_ratelimit())
 716                                         printk("OOM in bsalg (%d)\n", __LINE__);
 717                                 return 0;
 718                         }
 719                         (*obj)->syntax.l[0] = l;
 720                         break;
 721                 case SNMP_OCTETSTR:
 722                 case SNMP_OPAQUE:
 723                         if (!asn1_octets_decode(ctx, end, &p, &len)) {
 724                                 kfree(id);
 725                                 return 0;
 726                         }
 727                         *obj = kmalloc(sizeof(struct snmp_object) + len,
 728                                        GFP_ATOMIC);
 729                         if (*obj == NULL) {
 730                                 kfree(id);
 731                                 if (net_ratelimit())
 732                                         printk("OOM in bsalg (%d)\n", __LINE__);
 733                                 return 0;
 734                         }
 735                         memcpy((*obj)->syntax.c, p, len);
 736                         kfree(p);
 737                         break;
 738                 case SNMP_NULL:
 739                 case SNMP_NOSUCHOBJECT:
 740                 case SNMP_NOSUCHINSTANCE:
 741                 case SNMP_ENDOFMIBVIEW:
 742                         len = 0;
 743                         *obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
 744                         if (*obj == NULL) {
 745                                 kfree(id);
 746                                 if (net_ratelimit())
 747                                         printk("OOM in bsalg (%d)\n", __LINE__);
 748                                 return 0;
 749                         }
 750                         if (!asn1_null_decode(ctx, end)) {
 751                                 kfree(id);
 752                                 kfree(*obj);
 753                                 *obj = NULL;
 754                                 return 0;
 755                         }
 756                         break;
 757                 case SNMP_OBJECTID:
 758                         if (!asn1_oid_decode(ctx, end, (unsigned long **)&lp, &len)) {
 759                                 kfree(id);
 760                                 return 0;
 761                         }
 762                         len *= sizeof(unsigned long);
 763                         *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
 764                         if (*obj == NULL) {
 765                                 kfree(id);
 766                                 if (net_ratelimit())
 767                                         printk("OOM in bsalg (%d)\n", __LINE__);
 768                                 return 0;
 769                         }
 770                         memcpy((*obj)->syntax.ul, lp, len);
 771                         kfree(lp);
 772                         break;
 773                 case SNMP_IPADDR:
 774                         if (!asn1_octets_decode(ctx, end, &p, &len)) {
 775                                 kfree(id);
 776                                 return 0;
 777                         }
 778                         if (len != 4) {
 779                                 kfree(p);
 780                                 kfree(id);
 781                                 return 0;
 782                         }
 783                         *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
 784                         if (*obj == NULL) {
 785                                 kfree(p);
 786                                 kfree(id);
 787                                 if (net_ratelimit())
 788                                         printk("OOM in bsalg (%d)\n", __LINE__);
 789                                 return 0;
 790                         }
 791                         memcpy((*obj)->syntax.uc, p, len);
 792                         kfree(p);
 793                         break;
 794                 case SNMP_COUNTER:
 795                 case SNMP_GAUGE:
 796                 case SNMP_TIMETICKS:
 797                         len = sizeof(unsigned long);
 798                         if (!asn1_ulong_decode(ctx, end, &ul)) {
 799                                 kfree(id);
 800                                 return 0;
 801                         }
 802                         *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
 803                         if (*obj == NULL) {
 804                                 kfree(id);
 805                                 if (net_ratelimit())
 806                                         printk("OOM in bsalg (%d)\n", __LINE__);
 807                                 return 0;
 808                         }
 809                         (*obj)->syntax.ul[0] = ul;
 810                         break;
 811                 default:
 812                         kfree(id);
 813                         return 0;
 814         }
 815
 816         (*obj)->syntax_len = len;
 817         (*obj)->type = type;
 818         (*obj)->id = id;
 819         (*obj)->id_len = idlen;
 820
 821         if (!asn1_eoc_decode(ctx, eoc)) {
 822                 kfree(id);
 823                 kfree(*obj);
 824                 *obj = NULL;
 825                 return 0;
 826         }
 827         return 1;
 828 }
 829
 830 static unsigned char snmp_request_decode(struct asn1_ctx *ctx,
 831                                          struct snmp_request *request)
 832 {
 833         unsigned int cls, con, tag;
 834         unsigned char *end;
 835
 836         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 837                 return 0;
 838
 839         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
 840                 return 0;
 841
 842         if (!asn1_ulong_decode(ctx, end, &request->id))
 843                 return 0;
 844
 845         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 846                 return 0;
 847
 848         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
 849                 return 0;
 850
 851         if (!asn1_uint_decode(ctx, end, &request->error_status))
 852                 return 0;
 853
 854         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 855                 return 0;
 856
 857         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
 858                 return 0;
 859
 860         if (!asn1_uint_decode(ctx, end, &request->error_index))
 861                 return 0;
 862
 863         return 1;
 864 }
 865
 866 /*
 867  * Fast checksum update for possibly oddly-aligned UDP byte, from the
 868  * code example in the draft.
 869  */
 870 static void fast_csum(unsigned char *csum,
 871                       const unsigned char *optr,
 872                       const unsigned char *nptr,
 873                       int odd)
 874 {
 875         long x, old, new;
 876
 877         x = csum[0] * 256 + csum[1];
 878
 879         x =~ x & 0xFFFF;
 880
 881         if (odd) old = optr[0] * 256;
 882         else old = optr[0];
 883
 884         x -= old & 0xFFFF;
 885         if (x <= 0) {
 886                 x--;
 887                 x &= 0xFFFF;
 888         }
 889
 890         if (odd) new = nptr[0] * 256;
 891         else new = nptr[0];
 892
 893         x += new & 0xFFFF;
 894         if (x & 0x10000) {
 895                 x++;
 896                 x &= 0xFFFF;
 897         }
 898
 899         x =~ x & 0xFFFF;
 900         csum[0] = x / 256;
 901         csum[1] = x & 0xFF;
 902 }
 903
 904 /*
 905  * Mangle IP address.
 906  *      - begin points to the start of the snmp messgae
 907  *      - addr points to the start of the address
 908  */
 909 static inline void mangle_address(unsigned char *begin,
 910                                   unsigned char *addr,
 911                                   const struct oct1_map *map,
 912                                   u_int16_t *check)
 913 {
 914         if (map->from == NOCT1(*addr)) {
 915                 u_int32_t old;
 916
 917                 if (debug)
 918                         memcpy(&old, (unsigned char *)addr, sizeof(old));
 919
 920                 *addr = map->to;
 921
 922                 /* Update UDP checksum if being used */
 923                 if (*check) {
 924                         unsigned char odd = !((addr - begin) % 2);
 925
 926                         fast_csum((unsigned char *)check,
 927                                   &map->from, &map->to, odd);
 928
 929                 }
 930
 931                 if (debug)
 932                         printk(KERN_DEBUG "bsalg: mapped %u.%u.%u.%u to "
 933                                "%u.%u.%u.%u\n", NIPQUAD(old), NIPQUAD(*addr));
 934         }
 935 }
 936
 937 static unsigned char snmp_trap_decode(struct asn1_ctx *ctx,
 938                                       struct snmp_v1_trap *trap,
 939                                       const struct oct1_map *map,
 940                                       u_int16_t *check)
 941 {
 942         unsigned int cls, con, tag, len;
 943         unsigned char *end;
 944
 945         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 946                 return 0;
 947
 948         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
 949                 return 0;
 950
 951         if (!asn1_oid_decode(ctx, end, &trap->id, &trap->id_len))
 952                 return 0;
 953
 954         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 955                 goto err_id_free;
 956
 957         if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_IPA) ||
 958               (cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_OTS)))
 959                 goto err_id_free;
 960
 961         if (!asn1_octets_decode(ctx, end, (unsigned char **)&trap->ip_address, &len))
 962                 goto err_id_free;
 963
 964         /* IPv4 only */
 965         if (len != 4)
 966                 goto err_addr_free;
 967
 968         mangle_address(ctx->begin, ctx->pointer - 4, map, check);
 969
 970         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 971                 goto err_addr_free;
 972
 973         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
 974                 goto err_addr_free;
 975
 976         if (!asn1_uint_decode(ctx, end, &trap->general))
 977                 goto err_addr_free;
 978
 979         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 980                 goto err_addr_free;
 981
 982         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
 983                 goto err_addr_free;
 984
 985         if (!asn1_uint_decode(ctx, end, &trap->specific))
 986                 goto err_addr_free;
 987
 988         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 989                 goto err_addr_free;
 990
 991         if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_TIT) ||
 992               (cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_INT)))
 993                 goto err_addr_free;
 994
 995         if (!asn1_ulong_decode(ctx, end, &trap->time))
 996                 goto err_addr_free;
 997
 998         return 1;
 999
1000 err_id_free:
1001         kfree(trap->id);
1002
1003 err_addr_free:
1004         kfree((unsigned long *)trap->ip_address);
1005
1006         return 0;
1007 }
1008
1009 /*****************************************************************************
1010  *
1011  * Misc. routines
1012  *
1013  *****************************************************************************/
1014
1015 static void hex_dump(unsigned char *buf, size_t len)
1016 {
1017         size_t i;
1018
1019         for (i = 0; i < len; i++) {
1020                 if (i && !(i % 16))
1021                         printk("\n");
1022                 printk("%02x ", *(buf + i));
1023         }
1024         printk("\n");
1025 }
1026
1027 /*
1028  * Parse and mangle SNMP message according to mapping.
1029  * (And this is the fucking 'basic' method).
1030  */
1031 static int snmp_parse_mangle(unsigned char *msg,
1032                              u_int16_t len,
1033                              const struct oct1_map *map,
1034                              u_int16_t *check)
1035 {
1036         unsigned char *eoc, *end;
1037         unsigned int cls, con, tag, vers, pdutype;
1038         struct asn1_ctx ctx;
1039         struct asn1_octstr comm;
1040         struct snmp_object **obj;
1041
1042         if (debug > 1)
1043                 hex_dump(msg, len);
1044
1045         asn1_open(&ctx, msg, len);
1046
1047         /*
1048          * Start of SNMP message.
1049          */
1050         if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
1051                 return 0;
1052         if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
1053                 return 0;
1054
1055         /*
1056          * Version 1 or 2 handled.
1057          */
1058         if (!asn1_header_decode(&ctx, &end, &cls, &con, &tag))
1059                 return 0;
1060         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
1061                 return 0;
1062         if (!asn1_uint_decode (&ctx, end, &vers))
1063                 return 0;
1064         if (debug > 1)
1065                 printk(KERN_DEBUG "bsalg: snmp version: %u\n", vers + 1);
1066         if (vers > 1)
1067                 return 1;
1068
1069         /*
1070          * Community.
1071          */
1072         if (!asn1_header_decode (&ctx, &end, &cls, &con, &tag))
1073                 return 0;
1074         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OTS)
1075                 return 0;
1076         if (!asn1_octets_decode(&ctx, end, &comm.data, &comm.len))
1077                 return 0;
1078         if (debug > 1) {
1079                 unsigned int i;
1080
1081                 printk(KERN_DEBUG "bsalg: community: ");
1082                 for (i = 0; i < comm.len; i++)
1083                         printk("%c", comm.data[i]);
1084                 printk("\n");
1085         }
1086         kfree(comm.data);
1087
1088         /*
1089          * PDU type
1090          */
1091         if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &pdutype))
1092                 return 0;
1093         if (cls != ASN1_CTX || con != ASN1_CON)
1094                 return 0;
1095         if (debug > 1) {
1096                 unsigned char *pdus[] = {
1097                         [SNMP_PDU_GET] = "get",
1098                         [SNMP_PDU_NEXT] = "get-next",
1099                         [SNMP_PDU_RESPONSE] = "response",
1100                         [SNMP_PDU_SET] = "set",
1101                         [SNMP_PDU_TRAP1] = "trapv1",
1102                         [SNMP_PDU_BULK] = "bulk",
1103                         [SNMP_PDU_INFORM] = "inform",
1104                         [SNMP_PDU_TRAP2] = "trapv2"
1105                 };
1106
1107                 if (pdutype > SNMP_PDU_TRAP2)
1108                         printk(KERN_DEBUG "bsalg: bad pdu type %u\n", pdutype);
1109                 else
1110                         printk(KERN_DEBUG "bsalg: pdu: %s\n", pdus[pdutype]);
1111         }
1112         if (pdutype != SNMP_PDU_RESPONSE &&
1113             pdutype != SNMP_PDU_TRAP1 && pdutype != SNMP_PDU_TRAP2)
1114                 return 1;
1115
1116         /*
1117          * Request header or v1 trap
1118          */
1119         if (pdutype == SNMP_PDU_TRAP1) {
1120                 struct snmp_v1_trap trap;
1121                 unsigned char ret = snmp_trap_decode(&ctx, &trap, map, check);
1122
1123                 /* Discard trap allocations regardless */
1124                 kfree(trap.id);
1125                 kfree((unsigned long *)trap.ip_address);
1126
1127                 if (!ret)
1128                         return ret;
1129
1130         } else {
1131                 struct snmp_request req;
1132
1133                 if (!snmp_request_decode(&ctx, &req))
1134                         return 0;
1135
1136                 if (debug > 1)
1137                         printk(KERN_DEBUG "bsalg: request: id=0x%lx error_status=%u "
1138                         "error_index=%u\n", req.id, req.error_status,
1139                         req.error_index);
1140         }
1141
1142         /*
1143          * Loop through objects, look for IP addresses to mangle.
1144          */
1145         if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
1146                 return 0;
1147
1148         if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
1149                 return 0;
1150
1151         obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
1152         if (obj == NULL) {
1153                 if (net_ratelimit())
1154                         printk(KERN_WARNING "OOM in bsalg(%d)\n", __LINE__);
1155                 return 0;
1156         }
1157
1158         while (!asn1_eoc_decode(&ctx, eoc)) {
1159                 unsigned int i;
1160
1161                 if (!snmp_object_decode(&ctx, obj)) {
1162                         if (*obj) {
1163                                 if ((*obj)->id)
1164                                         kfree((*obj)->id);
1165                                 kfree(*obj);
1166                         }
1167                         kfree(obj);
1168                         return 0;
1169                 }
1170
1171                 if (debug > 1) {
1172                         printk(KERN_DEBUG "bsalg: object: ");
1173                         for (i = 0; i < (*obj)->id_len; i++) {
1174                                 if (i > 0)
1175                                         printk(".");
1176                                 printk("%lu", (*obj)->id[i]);
1177                         }
1178                         printk(": type=%u\n", (*obj)->type);
1179
1180                 }
1181
1182                 if ((*obj)->type == SNMP_IPADDR)
1183                         mangle_address(ctx.begin, ctx.pointer - 4 , map, check);
1184
1185                 kfree((*obj)->id);
1186                 kfree(*obj);
1187         }
1188         kfree(obj);
1189
1190         if (!asn1_eoc_decode(&ctx, eoc))
1191                 return 0;
1192
1193         return 1;
1194 }
1195
1196 /*****************************************************************************
1197  *
1198  * NAT routines.
1199  *
1200  *****************************************************************************/
1201
1202 /*
1203  * SNMP translation routine.
1204  */
1205 static int snmp_translate(struct ip_conntrack *ct,
1206                           struct ip_nat_info *info,
1207                           enum ip_conntrack_info ctinfo,
1208                           unsigned int hooknum,
1209                           struct sk_buff **pskb)
1210 {
1211         struct iphdr *iph = (*pskb)->nh.iph;
1212         struct udphdr *udph = (struct udphdr *)((u_int32_t *)iph + iph->ihl);
1213         u_int16_t udplen = ntohs(udph->len);
1214         u_int16_t paylen = udplen - sizeof(struct udphdr);
1215         int dir = CTINFO2DIR(ctinfo);
1216         struct oct1_map map;
1217
1218         /*
1219          * Determine mappping for application layer addresses based
1220          * on NAT manipulations for the packet.
1221          */
1222         if (dir == IP_CT_DIR_ORIGINAL) {
1223                 /* SNAT traps */
1224                 map.from = NOCT1(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip);
1225                 map.to = NOCT1(ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip);
1226         } else {
1227                 /* DNAT replies */
1228                 map.from = NOCT1(ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip);
1229                 map.to = NOCT1(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip);
1230         }
1231
1232         if (map.from == map.to)
1233                 return NF_ACCEPT;
1234
1235         if (!snmp_parse_mangle((unsigned char *)udph + sizeof(struct udphdr),
1236                                paylen, &map, &udph->check)) {
1237                 printk(KERN_WARNING "bsalg: parser failed\n");
1238                 return NF_DROP;
1239         }
1240         return NF_ACCEPT;
1241 }
1242
1243 /*
1244  * NAT helper function, packets arrive here from NAT code.
1245  */
1246 static unsigned int nat_help(struct ip_conntrack *ct,
1247                              struct ip_conntrack_expect *exp,
1248                              struct ip_nat_info *info,
1249                              enum ip_conntrack_info ctinfo,
1250                              unsigned int hooknum,
1251                              struct sk_buff **pskb)
1252 {
1253         int dir = CTINFO2DIR(ctinfo);
1254         struct iphdr *iph = (*pskb)->nh.iph;
1255         struct udphdr *udph = (struct udphdr *)((u_int32_t *)iph + iph->ihl);
1256
1257         if (!skb_ip_make_writable(pskb, (*pskb)->len))
1258                 return NF_DROP;
1259
1260         spin_lock_bh(&snmp_lock);
1261
1262         /*
1263          * Translate snmp replies on pre-routing (DNAT) and snmp traps
1264          * on post routing (SNAT).
1265          */
1266         if (!((dir == IP_CT_DIR_REPLY && hooknum == NF_IP_PRE_ROUTING &&
1267                         udph->source == ntohs(SNMP_PORT)) ||
1268               (dir == IP_CT_DIR_ORIGINAL && hooknum == NF_IP_POST_ROUTING &&
1269                         udph->dest == ntohs(SNMP_TRAP_PORT)))) {
1270                 spin_unlock_bh(&snmp_lock);
1271                 return NF_ACCEPT;
1272         }
1273
1274         if (debug > 1) {
1275                 printk(KERN_DEBUG "bsalg: dir=%s hook=%d manip=%s len=%d "
1276                        "src=%u.%u.%u.%u:%u dst=%u.%u.%u.%u:%u "
1277                        "osrc=%u.%u.%u.%u odst=%u.%u.%u.%u "
1278                        "rsrc=%u.%u.%u.%u rdst=%u.%u.%u.%u "
1279                        "\n",
1280                        dir == IP_CT_DIR_REPLY ? "reply" : "orig", hooknum,
1281                        HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC ? "snat" :
1282                        "dnat", (*pskb)->len,
1283                        NIPQUAD(iph->saddr), ntohs(udph->source),
1284                        NIPQUAD(iph->daddr), ntohs(udph->dest),
1285                        NIPQUAD(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip),
1286                        NIPQUAD(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip),
1287                        NIPQUAD(ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip),
1288                        NIPQUAD(ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip));
1289         }
1290
1291         /*
1292          * Make sure the packet length is ok.  So far, we were only guaranteed
1293          * to have a valid length IP header plus 8 bytes, which means we have
1294          * enough room for a UDP header.  Just verify the UDP length field so we
1295          * can mess around with the payload.
1296          */
1297          if (ntohs(udph->len) == (*pskb)->len - (iph->ihl << 2)) {
1298                 int ret = snmp_translate(ct, info, ctinfo, hooknum, pskb);
1299                 spin_unlock_bh(&snmp_lock);
1300                 return ret;
1301         }
1302
1303         if (net_ratelimit())
1304                 printk(KERN_WARNING "bsalg: dropping malformed packet "
1305                        "src=%u.%u.%u.%u dst=%u.%u.%u.%u\n",
1306                        NIPQUAD(iph->saddr), NIPQUAD(iph->daddr));
1307         spin_unlock_bh(&snmp_lock);
1308         return NF_DROP;
1309 }
1310
1311 static struct ip_nat_helper snmp = {
1312         { NULL, NULL },
1313         "snmp",
1314         0,
1315         THIS_MODULE,
1316         { { 0, { .udp = { __constant_htons(SNMP_PORT) } } },
1317           { 0, { 0 }, IPPROTO_UDP } },
1318         { { 0, { .udp = { 0xFFFF } } },
1319           { 0, { 0 }, 0xFFFF } },
1320         nat_help, NULL };
1321
1322 static struct ip_nat_helper snmp_trap = {
1323         { NULL, NULL },
1324         "snmp_trap",
1325         0,
1326         THIS_MODULE,
1327         { { 0, { .udp = { __constant_htons(SNMP_TRAP_PORT) } } },
1328           { 0, { 0 }, IPPROTO_UDP } },
1329         { { 0, { .udp = { 0xFFFF } } },
1330           { 0, { 0 }, 0xFFFF } },
1331         nat_help, NULL };
1332
1333 /*****************************************************************************
1334  *
1335  * Module stuff.
1336  *
1337  *****************************************************************************/
1338
1339 static int __init init(void)
1340 {
1341         int ret = 0;
1342
1343         ret = ip_nat_helper_register(&snmp);
1344         if (ret < 0)
1345                 return ret;
1346         ret = ip_nat_helper_register(&snmp_trap);
1347         if (ret < 0) {
1348                 ip_nat_helper_unregister(&snmp);
1349                 return ret;
1350         }
1351         return ret;
1352 }
1353
1354 static void __exit fini(void)
1355 {
1356         ip_nat_helper_unregister(&snmp);
1357         ip_nat_helper_unregister(&snmp_trap);
1358         synchronize_net();
1359 }
1360
1361 module_init(init);
1362 module_exit(fini);
1363
1364 module_param(debug, bool, 0600);