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/brlock.h>
  54 #include <linux/types.h>
  55 #include <linux/ip.h>
  56 #include <net/checksum.h>
  57 #include <net/udp.h>
  58 #include <asm/uaccess.h>
  59
  60
  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 = 0;
  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
 236         /* don't trust len bigger than ctx buffer */
 237         if (*len > ctx->end - ctx->pointer)
 238                 return 0;
 239
 240         return 1;
 241 }
 242
 243 static unsigned char asn1_header_decode(struct asn1_ctx *ctx,
 244                                         unsigned char **eoc,
 245                                         unsigned int *cls,
 246                                         unsigned int *con,
 247                                         unsigned int *tag)
 248 {
 249         unsigned int def, len;
 250
 251         if (!asn1_id_decode(ctx, cls, con, tag))
 252                 return 0;
 253
 254         if (!asn1_length_decode(ctx, &def, &len))
 255                 return 0;
 256
 257         /* primitive shall be definite, indefinite shall be constructed */
 258         if (*con == ASN1_PRI && !def)
 259                 return 0;
 260
 261         if (def)
 262                 *eoc = ctx->pointer + len;
 263         else
 264                 *eoc = 0;
 265         return 1;
 266 }
 267
 268 static unsigned char asn1_eoc_decode(struct asn1_ctx *ctx, unsigned char *eoc)
 269 {
 270         unsigned char ch;
 271
 272         if (eoc == 0) {
 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
 281                 if (!asn1_octet_decode(ctx, &ch))
 282                         return 0;
 283
 284                 if (ch != 0x00) {
 285                         ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
 286                         return 0;
 287                 }
 288                 return 1;
 289         } else {
 290                 if (ctx->pointer != eoc) {
 291                         ctx->error = ASN1_ERR_DEC_LENGTH_MISMATCH;
 292                         return 0;
 293                 }
 294                 return 1;
 295         }
 296 }
 297
 298 static unsigned char asn1_null_decode(struct asn1_ctx *ctx, unsigned char *eoc)
 299 {
 300         ctx->pointer = eoc;
 301         return 1;
 302 }
 303
 304 static unsigned char asn1_long_decode(struct asn1_ctx *ctx,
 305                                       unsigned char *eoc,
 306                                       long *integer)
 307 {
 308         unsigned char ch;
 309         unsigned int  len;
 310
 311         if (!asn1_octet_decode(ctx, &ch))
 312                 return 0;
 313
 314         *integer = (signed char) ch;
 315         len = 1;
 316
 317         while (ctx->pointer < eoc) {
 318                 if (++len > sizeof (long)) {
 319                         ctx->error = ASN1_ERR_DEC_BADVALUE;
 320                         return 0;
 321                 }
 322
 323                 if (!asn1_octet_decode(ctx, &ch))
 324                         return 0;
 325
 326                 *integer <<= 8;
 327                 *integer |= ch;
 328         }
 329         return 1;
 330 }
 331
 332 static unsigned char asn1_uint_decode(struct asn1_ctx *ctx,
 333                                       unsigned char *eoc,
 334                                       unsigned int *integer)
 335 {
 336         unsigned char ch;
 337         unsigned int  len;
 338
 339         if (!asn1_octet_decode(ctx, &ch))
 340                 return 0;
 341
 342         *integer = ch;
 343         if (ch == 0) len = 0;
 344         else len = 1;
 345
 346         while (ctx->pointer < eoc) {
 347                 if (++len > sizeof (unsigned int)) {
 348                         ctx->error = ASN1_ERR_DEC_BADVALUE;
 349                         return 0;
 350                 }
 351
 352                 if (!asn1_octet_decode(ctx, &ch))
 353                         return 0;
 354
 355                 *integer <<= 8;
 356                 *integer |= ch;
 357         }
 358         return 1;
 359 }
 360
 361 static unsigned char asn1_ulong_decode(struct asn1_ctx *ctx,
 362                                        unsigned char *eoc,
 363                                        unsigned long *integer)
 364 {
 365         unsigned char ch;
 366         unsigned int  len;
 367
 368         if (!asn1_octet_decode(ctx, &ch))
 369                 return 0;
 370
 371         *integer = ch;
 372         if (ch == 0) len = 0;
 373         else len = 1;
 374
 375         while (ctx->pointer < eoc) {
 376                 if (++len > sizeof (unsigned long)) {
 377                         ctx->error = ASN1_ERR_DEC_BADVALUE;
 378                         return 0;
 379                 }
 380
 381                 if (!asn1_octet_decode(ctx, &ch))
 382                         return 0;
 383
 384                 *integer <<= 8;
 385                 *integer |= ch;
 386         }
 387         return 1;
 388 }
 389
 390 static unsigned char asn1_octets_decode(struct asn1_ctx *ctx,
 391                                         unsigned char *eoc,
 392                                         unsigned char **octets,
 393                                         unsigned int *len)
 394 {
 395         unsigned char *ptr;
 396
 397         *len = 0;
 398
 399         *octets = kmalloc(eoc - ctx->pointer, GFP_ATOMIC);
 400         if (*octets == NULL) {
 401                 if (net_ratelimit())
 402                         printk("OOM in bsalg (%d)\n", __LINE__);
 403                 return 0;
 404         }
 405
 406         ptr = *octets;
 407         while (ctx->pointer < eoc) {
 408                 if (!asn1_octet_decode(ctx, (unsigned char *)ptr++)) {
 409                         kfree(*octets);
 410                         *octets = NULL;
 411                         return 0;
 412                 }
 413                 (*len)++;
 414         }
 415         return 1;
 416 }
 417
 418 static unsigned char asn1_subid_decode(struct asn1_ctx *ctx,
 419                                        unsigned long *subid)
 420 {
 421         unsigned char ch;
 422
 423         *subid = 0;
 424
 425         do {
 426                 if (!asn1_octet_decode(ctx, &ch))
 427                         return 0;
 428
 429                 *subid <<= 7;
 430                 *subid |= ch & 0x7F;
 431         } while ((ch & 0x80) == 0x80);
 432         return 1;
 433 }
 434
 435 static unsigned char asn1_oid_decode(struct asn1_ctx *ctx,
 436                                      unsigned char *eoc,
 437                                      unsigned long **oid,
 438                                      unsigned int *len)
 439 {
 440         unsigned long subid;
 441         unsigned int  size;
 442         unsigned long *optr;
 443
 444         size = eoc - ctx->pointer + 1;
 445
 446         /* first subid actually encodes first two subids */
 447         if (size < 2 || size > ULONG_MAX/sizeof(unsigned long))
 448                 return 0;
 449
 450         *oid = kmalloc(size * sizeof(unsigned long), GFP_ATOMIC);
 451         if (*oid == NULL) {
 452                 if (net_ratelimit())
 453                         printk("OOM in bsalg (%d)\n", __LINE__);
 454                 return 0;
 455         }
 456
 457         optr = *oid;
 458
 459         if (!asn1_subid_decode(ctx, &subid)) {
 460                 kfree(*oid);
 461                 *oid = NULL;
 462                 return 0;
 463         }
 464
 465         if (subid < 40) {
 466                 optr [0] = 0;
 467                 optr [1] = subid;
 468         } else if (subid < 80) {
 469                 optr [0] = 1;
 470                 optr [1] = subid - 40;
 471         } else {
 472                 optr [0] = 2;
 473                 optr [1] = subid - 80;
 474         }
 475
 476         *len = 2;
 477         optr += 2;
 478
 479         while (ctx->pointer < eoc) {
 480                 if (++(*len) > size) {
 481                         ctx->error = ASN1_ERR_DEC_BADVALUE;
 482                         kfree(*oid);
 483                         *oid = NULL;
 484                         return 0;
 485                 }
 486
 487                 if (!asn1_subid_decode(ctx, optr++)) {
 488                         kfree(*oid);
 489                         *oid = NULL;
 490                         return 0;
 491                 }
 492         }
 493         return 1;
 494 }
 495
 496 /*****************************************************************************
 497  *
 498  * SNMP decoding routines (gxsnmp author Dirk Wisse)
 499  *
 500  *****************************************************************************/
 501
 502 /* SNMP Versions */
 503 #define SNMP_V1                         0
 504 #define SNMP_V2C                        1
 505 #define SNMP_V2                         2
 506 #define SNMP_V3                         3
 507
 508 /* Default Sizes */
 509 #define SNMP_SIZE_COMM                  256
 510 #define SNMP_SIZE_OBJECTID              128
 511 #define SNMP_SIZE_BUFCHR                256
 512 #define SNMP_SIZE_BUFINT                128
 513 #define SNMP_SIZE_SMALLOBJECTID         16
 514
 515 /* Requests */
 516 #define SNMP_PDU_GET                    0
 517 #define SNMP_PDU_NEXT                   1
 518 #define SNMP_PDU_RESPONSE               2
 519 #define SNMP_PDU_SET                    3
 520 #define SNMP_PDU_TRAP1                  4
 521 #define SNMP_PDU_BULK                   5
 522 #define SNMP_PDU_INFORM                 6
 523 #define SNMP_PDU_TRAP2                  7
 524
 525 /* Errors */
 526 #define SNMP_NOERROR                    0
 527 #define SNMP_TOOBIG                     1
 528 #define SNMP_NOSUCHNAME                 2
 529 #define SNMP_BADVALUE                   3
 530 #define SNMP_READONLY                   4
 531 #define SNMP_GENERROR                   5
 532 #define SNMP_NOACCESS                   6
 533 #define SNMP_WRONGTYPE                  7
 534 #define SNMP_WRONGLENGTH                8
 535 #define SNMP_WRONGENCODING              9
 536 #define SNMP_WRONGVALUE                 10
 537 #define SNMP_NOCREATION                 11
 538 #define SNMP_INCONSISTENTVALUE          12
 539 #define SNMP_RESOURCEUNAVAILABLE        13
 540 #define SNMP_COMMITFAILED               14
 541 #define SNMP_UNDOFAILED                 15
 542 #define SNMP_AUTHORIZATIONERROR         16
 543 #define SNMP_NOTWRITABLE                17
 544 #define SNMP_INCONSISTENTNAME           18
 545
 546 /* General SNMP V1 Traps */
 547 #define SNMP_TRAP_COLDSTART             0
 548 #define SNMP_TRAP_WARMSTART             1
 549 #define SNMP_TRAP_LINKDOWN              2
 550 #define SNMP_TRAP_LINKUP                3
 551 #define SNMP_TRAP_AUTFAILURE            4
 552 #define SNMP_TRAP_EQPNEIGHBORLOSS       5
 553 #define SNMP_TRAP_ENTSPECIFIC           6
 554
 555 /* SNMPv1 Types */
 556 #define SNMP_NULL                0
 557 #define SNMP_INTEGER             1    /* l  */
 558 #define SNMP_OCTETSTR            2    /* c  */
 559 #define SNMP_DISPLAYSTR          2    /* c  */
 560 #define SNMP_OBJECTID            3    /* ul */
 561 #define SNMP_IPADDR              4    /* uc */
 562 #define SNMP_COUNTER             5    /* ul */
 563 #define SNMP_GAUGE               6    /* ul */
 564 #define SNMP_TIMETICKS           7    /* ul */
 565 #define SNMP_OPAQUE              8    /* c  */
 566
 567 /* Additional SNMPv2 Types */
 568 #define SNMP_UINTEGER            5    /* ul */
 569 #define SNMP_BITSTR              9    /* uc */
 570 #define SNMP_NSAP               10    /* uc */
 571 #define SNMP_COUNTER64          11    /* ul */
 572 #define SNMP_NOSUCHOBJECT       12
 573 #define SNMP_NOSUCHINSTANCE     13
 574 #define SNMP_ENDOFMIBVIEW       14
 575
 576 union snmp_syntax
 577 {
 578         unsigned char uc[0];    /* 8 bit unsigned */
 579         char c[0];              /* 8 bit signed */
 580         unsigned long ul[0];    /* 32 bit unsigned */
 581         long l[0];              /* 32 bit signed */
 582 };
 583
 584 struct snmp_object
 585 {
 586         unsigned long *id;
 587         unsigned int id_len;
 588         unsigned short type;
 589         unsigned int syntax_len;
 590         union snmp_syntax syntax;
 591 };
 592
 593 struct snmp_request
 594 {
 595         unsigned long id;
 596         unsigned int error_status;
 597         unsigned int error_index;
 598 };
 599
 600 struct snmp_v1_trap
 601 {
 602         unsigned long *id;
 603         unsigned int id_len;
 604         unsigned long ip_address;       /* pointer  */
 605         unsigned int general;
 606         unsigned int specific;
 607         unsigned long time;
 608 };
 609
 610 /* SNMP types */
 611 #define SNMP_IPA    0
 612 #define SNMP_CNT    1
 613 #define SNMP_GGE    2
 614 #define SNMP_TIT    3
 615 #define SNMP_OPQ    4
 616 #define SNMP_C64    6
 617
 618 /* SNMP errors */
 619 #define SERR_NSO    0
 620 #define SERR_NSI    1
 621 #define SERR_EOM    2
 622
 623 static void inline mangle_address(unsigned char *begin,
 624                                   unsigned char *addr,
 625                                   const struct oct1_map *map,
 626                                   u_int16_t *check);
 627 struct snmp_cnv
 628 {
 629         unsigned int class;
 630         unsigned int tag;
 631         int syntax;
 632 };
 633
 634 static struct snmp_cnv snmp_conv [] =
 635 {
 636         {ASN1_UNI, ASN1_NUL, SNMP_NULL},
 637         {ASN1_UNI, ASN1_INT, SNMP_INTEGER},
 638         {ASN1_UNI, ASN1_OTS, SNMP_OCTETSTR},
 639         {ASN1_UNI, ASN1_OTS, SNMP_DISPLAYSTR},
 640         {ASN1_UNI, ASN1_OJI, SNMP_OBJECTID},
 641         {ASN1_APL, SNMP_IPA, SNMP_IPADDR},
 642         {ASN1_APL, SNMP_CNT, SNMP_COUNTER},     /* Counter32 */
 643         {ASN1_APL, SNMP_GGE, SNMP_GAUGE},       /* Gauge32 == Unsigned32  */
 644         {ASN1_APL, SNMP_TIT, SNMP_TIMETICKS},
 645         {ASN1_APL, SNMP_OPQ, SNMP_OPAQUE},
 646
 647         /* SNMPv2 data types and errors */
 648         {ASN1_UNI, ASN1_BTS, SNMP_BITSTR},
 649         {ASN1_APL, SNMP_C64, SNMP_COUNTER64},
 650         {ASN1_CTX, SERR_NSO, SNMP_NOSUCHOBJECT},
 651         {ASN1_CTX, SERR_NSI, SNMP_NOSUCHINSTANCE},
 652         {ASN1_CTX, SERR_EOM, SNMP_ENDOFMIBVIEW},
 653         {0,       0,       -1}
 654 };
 655
 656 static unsigned char snmp_tag_cls2syntax(unsigned int tag,
 657                                          unsigned int cls,
 658                                          unsigned short *syntax)
 659 {
 660         struct snmp_cnv *cnv;
 661
 662         cnv = snmp_conv;
 663
 664         while (cnv->syntax != -1) {
 665                 if (cnv->tag == tag && cnv->class == cls) {
 666                         *syntax = cnv->syntax;
 667                         return 1;
 668                 }
 669                 cnv++;
 670         }
 671         return 0;
 672 }
 673
 674 static unsigned char snmp_object_decode(struct asn1_ctx *ctx,
 675                                         struct snmp_object **obj)
 676 {
 677         unsigned int cls, con, tag, len, idlen;
 678         unsigned short type;
 679         unsigned char *eoc, *end, *p;
 680         unsigned long *lp, *id;
 681         unsigned long ul;
 682         long  l;
 683
 684         *obj = NULL;
 685         id = NULL;
 686
 687         if (!asn1_header_decode(ctx, &eoc, &cls, &con, &tag))
 688                 return 0;
 689
 690         if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
 691                 return 0;
 692
 693         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 694                 return 0;
 695
 696         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
 697                 return 0;
 698
 699         if (!asn1_oid_decode(ctx, end, &id, &idlen))
 700                 return 0;
 701
 702         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag)) {
 703                 kfree(id);
 704                 return 0;
 705         }
 706
 707         if (con != ASN1_PRI) {
 708                 kfree(id);
 709                 return 0;
 710         }
 711
 712         if (!snmp_tag_cls2syntax(tag, cls, &type)) {
 713                 kfree(id);
 714                 return 0;
 715         }
 716
 717         switch (type) {
 718                 case SNMP_INTEGER:
 719                         len = sizeof(long);
 720                         if (!asn1_long_decode(ctx, end, &l)) {
 721                                 kfree(id);
 722                                 return 0;
 723                         }
 724                         *obj = kmalloc(sizeof(struct snmp_object) + len,
 725                                        GFP_ATOMIC);
 726                         if (*obj == NULL) {
 727                                 kfree(id);
 728                                 if (net_ratelimit())
 729                                         printk("OOM in bsalg (%d)\n", __LINE__);
 730                                 return 0;
 731                         }
 732                         (*obj)->syntax.l[0] = l;
 733                         break;
 734                 case SNMP_OCTETSTR:
 735                 case SNMP_OPAQUE:
 736                         if (!asn1_octets_decode(ctx, end, &p, &len)) {
 737                                 kfree(id);
 738                                 return 0;
 739                         }
 740                         *obj = kmalloc(sizeof(struct snmp_object) + len,
 741                                        GFP_ATOMIC);
 742                         if (*obj == NULL) {
 743                                 kfree(p);
 744                                 kfree(id);
 745                                 if (net_ratelimit())
 746                                         printk("OOM in bsalg (%d)\n", __LINE__);
 747                                 return 0;
 748                         }
 749                         memcpy((*obj)->syntax.c, p, len);
 750                         kfree(p);
 751                         break;
 752                 case SNMP_NULL:
 753                 case SNMP_NOSUCHOBJECT:
 754                 case SNMP_NOSUCHINSTANCE:
 755                 case SNMP_ENDOFMIBVIEW:
 756                         len = 0;
 757                         *obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
 758                         if (*obj == NULL) {
 759                                 kfree(id);
 760                                 if (net_ratelimit())
 761                                         printk("OOM in bsalg (%d)\n", __LINE__);
 762                                 return 0;
 763                         }
 764                         if (!asn1_null_decode(ctx, end)) {
 765                                 kfree(id);
 766                                 kfree(*obj);
 767                                 *obj = NULL;
 768                                 return 0;
 769                         }
 770                         break;
 771                 case SNMP_OBJECTID:
 772                         if (!asn1_oid_decode(ctx, end, (unsigned long **)&lp, &len)) {
 773                                 kfree(id);
 774                                 return 0;
 775                         }
 776                         len *= sizeof(unsigned long);
 777                         *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
 778                         if (*obj == NULL) {
 779                                 kfree(id);
 780                                 if (net_ratelimit())
 781                                         printk("OOM in bsalg (%d)\n", __LINE__);
 782                                 return 0;
 783                         }
 784                         memcpy((*obj)->syntax.ul, lp, len);
 785                         kfree(lp);
 786                         break;
 787                 case SNMP_IPADDR:
 788                         if (!asn1_octets_decode(ctx, end, &p, &len)) {
 789                                 kfree(id);
 790                                 return 0;
 791                         }
 792                         if (len != 4) {
 793                                 kfree(p);
 794                                 kfree(id);
 795                                 return 0;
 796                         }
 797                         *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
 798                         if (*obj == NULL) {
 799                                 kfree(p);
 800                                 kfree(id);
 801                                 if (net_ratelimit())
 802                                         printk("OOM in bsalg (%d)\n", __LINE__);
 803                                 return 0;
 804                         }
 805                         memcpy((*obj)->syntax.uc, p, len);
 806                         kfree(p);
 807                         break;
 808                 case SNMP_COUNTER:
 809                 case SNMP_GAUGE:
 810                 case SNMP_TIMETICKS:
 811                         len = sizeof(unsigned long);
 812                         if (!asn1_ulong_decode(ctx, end, &ul)) {
 813                                 kfree(id);
 814                                 return 0;
 815                         }
 816                         *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
 817                         if (*obj == NULL) {
 818                                 kfree(id);
 819                                 if (net_ratelimit())
 820                                         printk("OOM in bsalg (%d)\n", __LINE__);
 821                                 return 0;
 822                         }
 823                         (*obj)->syntax.ul[0] = ul;
 824                         break;
 825                 default:
 826                         kfree(id);
 827                         return 0;
 828         }
 829
 830         (*obj)->syntax_len = len;
 831         (*obj)->type = type;
 832         (*obj)->id = id;
 833         (*obj)->id_len = idlen;
 834
 835         if (!asn1_eoc_decode(ctx, eoc)) {
 836                 kfree(id);
 837                 kfree(*obj);
 838                 *obj = NULL;
 839                 return 0;
 840         }
 841         return 1;
 842 }
 843
 844 static unsigned char snmp_request_decode(struct asn1_ctx *ctx,
 845                                          struct snmp_request *request)
 846 {
 847         unsigned int cls, con, tag;
 848         unsigned char *end;
 849
 850         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 851                 return 0;
 852
 853         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
 854                 return 0;
 855
 856         if (!asn1_ulong_decode(ctx, end, &request->id))
 857                 return 0;
 858
 859         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 860                 return 0;
 861
 862         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
 863                 return 0;
 864
 865         if (!asn1_uint_decode(ctx, end, &request->error_status))
 866                 return 0;
 867
 868         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 869                 return 0;
 870
 871         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
 872                 return 0;
 873
 874         if (!asn1_uint_decode(ctx, end, &request->error_index))
 875                 return 0;
 876
 877         return 1;
 878 }
 879
 880 /*
 881  * Fast checksum update for possibly oddly-aligned UDP byte, from the
 882  * code example in the draft.
 883  */
 884 static void fast_csum(unsigned char *csum,
 885                       const unsigned char *optr,
 886                       const unsigned char *nptr,
 887                       int odd)
 888 {
 889         long x, old, new;
 890
 891         x = csum[0] * 256 + csum[1];
 892
 893         x =~ x & 0xFFFF;
 894
 895         if (odd) old = optr[0] * 256;
 896         else old = optr[0];
 897
 898         x -= old & 0xFFFF;
 899         if (x <= 0) {
 900                 x--;
 901                 x &= 0xFFFF;
 902         }
 903
 904         if (odd) new = nptr[0] * 256;
 905         else new = nptr[0];
 906
 907         x += new & 0xFFFF;
 908         if (x & 0x10000) {
 909                 x++;
 910                 x &= 0xFFFF;
 911         }
 912
 913         x =~ x & 0xFFFF;
 914         csum[0] = x / 256;
 915         csum[1] = x & 0xFF;
 916 }
 917
 918 /*
 919  * Mangle IP address.
 920  *      - begin points to the start of the snmp messgae
 921  *      - addr points to the start of the address
 922  */
 923 static void inline mangle_address(unsigned char *begin,
 924                                   unsigned char *addr,
 925                                   const struct oct1_map *map,
 926                                   u_int16_t *check)
 927 {
 928         if (map->from == NOCT1(*addr)) {
 929                 u_int32_t old;
 930
 931                 if (debug)
 932                         memcpy(&old, (unsigned char *)addr, sizeof(old));
 933
 934                 *addr = map->to;
 935
 936                 /* Update UDP checksum if being used */
 937                 if (*check) {
 938                         unsigned char odd = !((addr - begin) % 2);
 939
 940                         fast_csum((unsigned char *)check,
 941                                   &map->from, &map->to, odd);
 942
 943                 }
 944
 945                 if (debug)
 946                         printk(KERN_DEBUG "bsalg: mapped %u.%u.%u.%u to "
 947                                "%u.%u.%u.%u\n", NIPQUAD(old), NIPQUAD(*addr));
 948         }
 949 }
 950
 951 static unsigned char snmp_trap_decode(struct asn1_ctx *ctx,
 952                                       struct snmp_v1_trap *trap,
 953                                       const struct oct1_map *map,
 954                                       u_int16_t *check)
 955 {
 956         unsigned int cls, con, tag, len;
 957         unsigned char *end;
 958
 959         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 960                 return 0;
 961
 962         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
 963                 return 0;
 964
 965         if (!asn1_oid_decode(ctx, end, &trap->id, &trap->id_len))
 966                 return 0;
 967
 968         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 969                 goto err_id_free;
 970
 971         if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_IPA) ||
 972               (cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_OTS)))
 973                 goto err_id_free;
 974
 975         if (!asn1_octets_decode(ctx, end, (unsigned char **)&trap->ip_address, &len))
 976                 goto err_id_free;
 977
 978         /* IPv4 only */
 979         if (len != 4)
 980                 goto err_addr_free;
 981
 982         mangle_address(ctx->begin, ctx->pointer - 4, map, check);
 983
 984         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 985                 goto err_addr_free;
 986
 987         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
 988                 goto err_addr_free;;
 989
 990         if (!asn1_uint_decode(ctx, end, &trap->general))
 991                 goto err_addr_free;;
 992
 993         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
 994                 goto err_addr_free;
 995
 996         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
 997                 goto err_addr_free;
 998
 999         if (!asn1_uint_decode(ctx, end, &trap->specific))
1000                 goto err_addr_free;
1001
1002         if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
1003                 goto err_addr_free;
1004
1005         if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_TIT) ||
1006               (cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_INT)))
1007                 goto err_addr_free;
1008
1009         if (!asn1_ulong_decode(ctx, end, &trap->time))
1010                 goto err_addr_free;
1011
1012         return 1;
1013
1014 err_addr_free:
1015         kfree((unsigned long *)trap->ip_address);
1016
1017 err_id_free:
1018         kfree(trap->id);
1019
1020         return 0;
1021 }
1022
1023 /*****************************************************************************
1024  *
1025  * Misc. routines
1026  *
1027  *****************************************************************************/
1028
1029 static void hex_dump(unsigned char *buf, size_t len)
1030 {
1031         size_t i;
1032
1033         for (i = 0; i < len; i++) {
1034                 if (i && !(i % 16))
1035                         printk("\n");
1036                 printk("%02x ", *(buf + i));
1037         }
1038         printk("\n");
1039 }
1040
1041 /*
1042  * Parse and mangle SNMP message according to mapping.
1043  * (And this is the fucking 'basic' method).
1044  */
1045 static int snmp_parse_mangle(unsigned char *msg,
1046                              u_int16_t len,
1047                              const struct oct1_map *map,
1048                              u_int16_t *check)
1049 {
1050         unsigned char *eoc, *end;
1051         unsigned int cls, con, tag, vers, pdutype;
1052         struct asn1_ctx ctx;
1053         struct asn1_octstr comm;
1054         struct snmp_object **obj;
1055
1056         if (debug > 1)
1057                 hex_dump(msg, len);
1058
1059         asn1_open(&ctx, msg, len);
1060
1061         /*
1062          * Start of SNMP message.
1063          */
1064         if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
1065                 return 0;
1066         if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
1067                 return 0;
1068
1069         /*
1070          * Version 1 or 2 handled.
1071          */
1072         if (!asn1_header_decode(&ctx, &end, &cls, &con, &tag))
1073                 return 0;
1074         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
1075                 return 0;
1076         if (!asn1_uint_decode (&ctx, end, &vers))
1077                 return 0;
1078         if (debug > 1)
1079                 printk(KERN_DEBUG "bsalg: snmp version: %u\n", vers + 1);
1080         if (vers > 1)
1081                 return 1;
1082
1083         /*
1084          * Community.
1085          */
1086         if (!asn1_header_decode (&ctx, &end, &cls, &con, &tag))
1087                 return 0;
1088         if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OTS)
1089                 return 0;
1090         if (!asn1_octets_decode(&ctx, end, &comm.data, &comm.len))
1091                 return 0;
1092         if (debug > 1) {
1093                 unsigned int i;
1094
1095                 printk(KERN_DEBUG "bsalg: community: ");
1096                 for (i = 0; i < comm.len; i++)
1097                         printk("%c", comm.data[i]);
1098                 printk("\n");
1099         }
1100         kfree(comm.data);
1101
1102         /*
1103          * PDU type
1104          */
1105         if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &pdutype))
1106                 return 0;
1107         if (cls != ASN1_CTX || con != ASN1_CON)
1108                 return 0;
1109         if (debug > 1) {
1110                 unsigned char *pdus[] = {
1111                         [SNMP_PDU_GET] = "get",
1112                         [SNMP_PDU_NEXT] = "get-next",
1113                         [SNMP_PDU_RESPONSE] = "response",
1114                         [SNMP_PDU_SET] = "set",
1115                         [SNMP_PDU_TRAP1] = "trapv1",
1116                         [SNMP_PDU_BULK] = "bulk",
1117                         [SNMP_PDU_INFORM] = "inform",
1118                         [SNMP_PDU_TRAP2] = "trapv2"
1119                 };
1120
1121                 if (pdutype > SNMP_PDU_TRAP2)
1122                         printk(KERN_DEBUG "bsalg: bad pdu type %u\n", pdutype);
1123                 else
1124                         printk(KERN_DEBUG "bsalg: pdu: %s\n", pdus[pdutype]);
1125         }
1126         if (pdutype != SNMP_PDU_RESPONSE &&
1127             pdutype != SNMP_PDU_TRAP1 && pdutype != SNMP_PDU_TRAP2)
1128                 return 1;
1129
1130         /*
1131          * Request header or v1 trap
1132          */
1133         if (pdutype == SNMP_PDU_TRAP1) {
1134                 struct snmp_v1_trap trap;
1135                 unsigned char ret = snmp_trap_decode(&ctx, &trap, map, check);
1136
1137                 if (ret) {
1138                         kfree(trap.id);
1139                         kfree((unsigned long *)trap.ip_address);
1140                 } else
1141                         return ret;
1142
1143         } else {
1144                 struct snmp_request req;
1145
1146                 if (!snmp_request_decode(&ctx, &req))
1147                         return 0;
1148
1149                 if (debug > 1)
1150                         printk(KERN_DEBUG "bsalg: request: id=0x%lx error_status=%u "
1151                         "error_index=%u\n", req.id, req.error_status,
1152                         req.error_index);
1153         }
1154
1155         /*
1156          * Loop through objects, look for IP addresses to mangle.
1157          */
1158         if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
1159                 return 0;
1160
1161         if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
1162                 return 0;
1163
1164         obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
1165         if (obj == NULL) {
1166                 if (net_ratelimit())
1167                         printk(KERN_WARNING "OOM in bsalg(%d)\n", __LINE__);
1168                 return 0;
1169         }
1170
1171         while (!asn1_eoc_decode(&ctx, eoc)) {
1172                 unsigned int i;
1173
1174                 if (!snmp_object_decode(&ctx, obj)) {
1175                         if (*obj) {
1176                                 if ((*obj)->id)
1177                                         kfree((*obj)->id);
1178                                 kfree(*obj);
1179                         }
1180                         kfree(obj);
1181                         return 0;
1182                 }
1183
1184                 if (debug > 1) {
1185                         printk(KERN_DEBUG "bsalg: object: ");
1186                         for (i = 0; i < (*obj)->id_len; i++) {
1187                                 if (i > 0)
1188                                         printk(".");
1189                                 printk("%lu", (*obj)->id[i]);
1190                         }
1191                         printk(": type=%u\n", (*obj)->type);
1192
1193                 }
1194
1195                 if ((*obj)->type == SNMP_IPADDR)
1196                         mangle_address(ctx.begin, ctx.pointer - 4 , map, check);
1197
1198                 kfree((*obj)->id);
1199                 kfree(*obj);
1200         }
1201         kfree(obj);
1202
1203         if (!asn1_eoc_decode(&ctx, eoc))
1204                 return 0;
1205
1206         return 1;
1207 }
1208
1209 /*****************************************************************************
1210  *
1211  * NAT routines.
1212  *
1213  *****************************************************************************/
1214
1215 /*
1216  * SNMP translation routine.
1217  */
1218 static int snmp_translate(struct ip_conntrack *ct,
1219                           struct ip_nat_info *info,
1220                           enum ip_conntrack_info ctinfo,
1221                           unsigned int hooknum,
1222                           struct sk_buff **pskb)
1223 {
1224         struct iphdr *iph = (*pskb)->nh.iph;
1225         struct udphdr *udph = (struct udphdr *)((u_int32_t *)iph + iph->ihl);
1226         u_int16_t udplen = ntohs(udph->len);
1227         u_int16_t paylen = udplen - sizeof(struct udphdr);
1228         int dir = CTINFO2DIR(ctinfo);
1229         struct oct1_map map;
1230
1231         /*
1232          * Determine mappping for application layer addresses based
1233          * on NAT manipulations for the packet.
1234          */
1235         if (dir == IP_CT_DIR_ORIGINAL) {
1236                 /* SNAT traps */
1237                 map.from = NOCT1(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip);
1238                 map.to = NOCT1(ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip);
1239         } else {
1240                 /* DNAT replies */
1241                 map.from = NOCT1(ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip);
1242                 map.to = NOCT1(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip);
1243         }
1244
1245         if (map.from == map.to)
1246                 return NF_ACCEPT;
1247
1248         if (!snmp_parse_mangle((unsigned char *)udph + sizeof(struct udphdr),
1249                                paylen, &map, &udph->check)) {
1250                 printk(KERN_WARNING "bsalg: parser failed\n");
1251                 return NF_DROP;
1252         }
1253         return NF_ACCEPT;
1254 }
1255
1256 /*
1257  * NAT helper function, packets arrive here from NAT code.
1258  */
1259 static unsigned int nat_help(struct ip_conntrack *ct,
1260                              struct ip_conntrack_expect *exp,
1261                              struct ip_nat_info *info,
1262                              enum ip_conntrack_info ctinfo,
1263                              unsigned int hooknum,
1264                              struct sk_buff **pskb)
1265 {
1266         int dir = CTINFO2DIR(ctinfo);
1267         struct iphdr *iph = (*pskb)->nh.iph;
1268         struct udphdr *udph = (struct udphdr *)((u_int32_t *)iph + iph->ihl);
1269
1270         spin_lock_bh(&snmp_lock);
1271
1272         /*
1273          * Translate snmp replies on pre-routing (DNAT) and snmp traps
1274          * on post routing (SNAT).
1275          */
1276         if (!((dir == IP_CT_DIR_REPLY && hooknum == NF_IP_PRE_ROUTING &&
1277                         udph->source == ntohs(SNMP_PORT)) ||
1278               (dir == IP_CT_DIR_ORIGINAL && hooknum == NF_IP_POST_ROUTING &&
1279                         udph->dest == ntohs(SNMP_TRAP_PORT)))) {
1280                 spin_unlock_bh(&snmp_lock);
1281                 return NF_ACCEPT;
1282         }
1283
1284         if (debug > 1) {
1285                 printk(KERN_DEBUG "bsalg: dir=%s hook=%d manip=%s len=%d "
1286                        "src=%u.%u.%u.%u:%u dst=%u.%u.%u.%u:%u "
1287                        "osrc=%u.%u.%u.%u odst=%u.%u.%u.%u "
1288                        "rsrc=%u.%u.%u.%u rdst=%u.%u.%u.%u "
1289                        "\n",
1290                        dir == IP_CT_DIR_REPLY ? "reply" : "orig", hooknum,
1291                        HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC ? "snat" :
1292                        "dnat", (*pskb)->len,
1293                        NIPQUAD(iph->saddr), ntohs(udph->source),
1294                        NIPQUAD(iph->daddr), ntohs(udph->dest),
1295                        NIPQUAD(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip),
1296                        NIPQUAD(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip),
1297                        NIPQUAD(ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip),
1298                        NIPQUAD(ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip));
1299         }
1300
1301         /*
1302          * Make sure the packet length is ok.  So far, we were only guaranteed
1303          * to have a valid length IP header plus 8 bytes, which means we have
1304          * enough room for a UDP header.  Just verify the UDP length field so we
1305          * can mess around with the payload.
1306          */
1307          if (ntohs(udph->len) == (*pskb)->len - (iph->ihl << 2)) {
1308                 int ret = snmp_translate(ct, info, ctinfo, hooknum, pskb);
1309                 spin_unlock_bh(&snmp_lock);
1310                 return ret;
1311         }
1312
1313         if (net_ratelimit())
1314                 printk(KERN_WARNING "bsalg: dropping malformed packet "
1315                        "src=%u.%u.%u.%u dst=%u.%u.%u.%u\n",
1316                        NIPQUAD(iph->saddr), NIPQUAD(iph->daddr));
1317         spin_unlock_bh(&snmp_lock);
1318         return NF_DROP;
1319 }
1320
1321 static struct ip_nat_helper snmp = {
1322         { NULL, NULL },
1323         "snmp",
1324         IP_NAT_HELPER_F_STANDALONE,
1325         THIS_MODULE,
1326         { { 0, { .udp = { __constant_htons(SNMP_PORT) } } },
1327           { 0, { 0 }, IPPROTO_UDP } },
1328         { { 0, { .udp = { 0xFFFF } } },
1329           { 0, { 0 }, 0xFFFF } },
1330         nat_help, NULL };
1331
1332 static struct ip_nat_helper snmp_trap = {
1333         { NULL, NULL },
1334         "snmp_trap",
1335         IP_NAT_HELPER_F_STANDALONE,
1336         THIS_MODULE,
1337         { { 0, { .udp = { __constant_htons(SNMP_TRAP_PORT) } } },
1338           { 0, { 0 }, IPPROTO_UDP } },
1339         { { 0, { .udp = { 0xFFFF } } },
1340           { 0, { 0 }, 0xFFFF } },
1341         nat_help, NULL };
1342
1343 /*****************************************************************************
1344  *
1345  * Module stuff.
1346  *
1347  *****************************************************************************/
1348
1349 static int __init init(void)
1350 {
1351         int ret = 0;
1352
1353         ret = ip_nat_helper_register(&snmp);
1354         if (ret < 0)
1355                 return ret;
1356         ret = ip_nat_helper_register(&snmp_trap);
1357         if (ret < 0) {
1358                 ip_nat_helper_unregister(&snmp);
1359                 return ret;
1360         }
1361         return ret;
1362 }
1363
1364 static void __exit fini(void)
1365 {
1366         ip_nat_helper_unregister(&snmp);
1367         ip_nat_helper_unregister(&snmp_trap);
1368         br_write_lock_bh(BR_NETPROTO_LOCK);
1369         br_write_unlock_bh(BR_NETPROTO_LOCK);
1370 }
1371
1372 module_init(init);
1373 module_exit(fini);
1374
1375 MODULE_PARM(debug, "i");
1376 MODULE_DESCRIPTION("Basic SNMP Application Layer Gateway");
1377 MODULE_LICENSE("GPL");