4 * Basic SNMP Application Layer Gateway
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.
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.
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.
18 * Currently, only SNMPv1 and SNMPv2 are supported.
20 * More information on ALG and associated issues can be found in
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.
26 * Copyright (c) 2000 RP Internet (www.rpi.net.au).
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
40 * Author: James Morris <jmorris@intercode.com.au>
43 * 2000-08-06: Convert to new helper API (Harald Welte).
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>
54 #include <net/checksum.h>
56 #include <asm/uaccess.h>
58 MODULE_LICENSE("GPL");
59 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
60 MODULE_DESCRIPTION("Basic SNMP Application Layer Gateway");
63 #define SNMP_TRAP_PORT 162
64 #define NOCT1(n) (u_int8_t )((n) & 0xff)
67 static spinlock_t snmp_lock = SPIN_LOCK_UNLOCKED;
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).
81 /*****************************************************************************
83 * Basic ASN.1 decoding routines (gxsnmp author Dirk Wisse)
85 *****************************************************************************/
88 #define ASN1_UNI 0 /* Universal */
89 #define ASN1_APL 1 /* Application */
90 #define ASN1_CTX 2 /* Context */
91 #define ASN1_PRV 3 /* Private */
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 */
116 /* Primitive / Constructed methods*/
117 #define ASN1_PRI 0 /* Primitive */
118 #define ASN1_CON 1 /* Constructed */
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
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 */
141 * Octet string (not null terminated)
149 static void asn1_open(struct asn1_ctx *ctx,
154 ctx->end = buf + len;
156 ctx->error = ASN1_ERR_NOERROR;
159 static unsigned char asn1_octet_decode(struct asn1_ctx *ctx, unsigned char *ch)
161 if (ctx->pointer >= ctx->end) {
162 ctx->error = ASN1_ERR_DEC_EMPTY;
165 *ch = *(ctx->pointer)++;
169 static unsigned char asn1_tag_decode(struct asn1_ctx *ctx, unsigned int *tag)
177 if (!asn1_octet_decode(ctx, &ch))
181 } while ((ch & 0x80) == 0x80);
185 static unsigned char asn1_id_decode(struct asn1_ctx *ctx,
192 if (!asn1_octet_decode(ctx, &ch))
195 *cls = (ch & 0xC0) >> 6;
196 *con = (ch & 0x20) >> 5;
200 if (!asn1_tag_decode(ctx, tag))
206 static unsigned char asn1_length_decode(struct asn1_ctx *ctx,
210 unsigned char ch, cnt;
212 if (!asn1_octet_decode(ctx, &ch))
223 cnt = (unsigned char) (ch & 0x7F);
227 if (!asn1_octet_decode(ctx, &ch))
238 static unsigned char asn1_header_decode(struct asn1_ctx *ctx,
244 unsigned int def, len;
246 if (!asn1_id_decode(ctx, cls, con, tag))
249 if (!asn1_length_decode(ctx, &def, &len))
253 *eoc = ctx->pointer + len;
259 static unsigned char asn1_eoc_decode(struct asn1_ctx *ctx, unsigned char *eoc)
264 if (!asn1_octet_decode(ctx, &ch))
268 ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
272 if (!asn1_octet_decode(ctx, &ch))
276 ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
281 if (ctx->pointer != eoc) {
282 ctx->error = ASN1_ERR_DEC_LENGTH_MISMATCH;
289 static unsigned char asn1_null_decode(struct asn1_ctx *ctx, unsigned char *eoc)
295 static unsigned char asn1_long_decode(struct asn1_ctx *ctx,
302 if (!asn1_octet_decode(ctx, &ch))
305 *integer = (signed char) ch;
308 while (ctx->pointer < eoc) {
309 if (++len > sizeof (long)) {
310 ctx->error = ASN1_ERR_DEC_BADVALUE;
314 if (!asn1_octet_decode(ctx, &ch))
323 static unsigned char asn1_uint_decode(struct asn1_ctx *ctx,
325 unsigned int *integer)
330 if (!asn1_octet_decode(ctx, &ch))
334 if (ch == 0) len = 0;
337 while (ctx->pointer < eoc) {
338 if (++len > sizeof (unsigned int)) {
339 ctx->error = ASN1_ERR_DEC_BADVALUE;
343 if (!asn1_octet_decode(ctx, &ch))
352 static unsigned char asn1_ulong_decode(struct asn1_ctx *ctx,
354 unsigned long *integer)
359 if (!asn1_octet_decode(ctx, &ch))
363 if (ch == 0) len = 0;
366 while (ctx->pointer < eoc) {
367 if (++len > sizeof (unsigned long)) {
368 ctx->error = ASN1_ERR_DEC_BADVALUE;
372 if (!asn1_octet_decode(ctx, &ch))
381 static unsigned char asn1_octets_decode(struct asn1_ctx *ctx,
383 unsigned char **octets,
390 *octets = kmalloc(eoc - ctx->pointer, GFP_ATOMIC);
391 if (*octets == NULL) {
393 printk("OOM in bsalg (%d)\n", __LINE__);
398 while (ctx->pointer < eoc) {
399 if (!asn1_octet_decode(ctx, (unsigned char *)ptr++)) {
409 static unsigned char asn1_subid_decode(struct asn1_ctx *ctx,
410 unsigned long *subid)
417 if (!asn1_octet_decode(ctx, &ch))
422 } while ((ch & 0x80) == 0x80);
426 static unsigned char asn1_oid_decode(struct asn1_ctx *ctx,
435 size = eoc - ctx->pointer + 1;
436 *oid = kmalloc(size * sizeof(unsigned long), GFP_ATOMIC);
439 printk("OOM in bsalg (%d)\n", __LINE__);
445 if (!asn1_subid_decode(ctx, &subid)) {
454 } else if (subid < 80) {
456 optr [1] = subid - 40;
459 optr [1] = subid - 80;
465 while (ctx->pointer < eoc) {
466 if (++(*len) > size) {
467 ctx->error = ASN1_ERR_DEC_BADVALUE;
473 if (!asn1_subid_decode(ctx, optr++)) {
482 /*****************************************************************************
484 * SNMP decoding routines (gxsnmp author Dirk Wisse)
486 *****************************************************************************/
495 #define SNMP_SIZE_COMM 256
496 #define SNMP_SIZE_OBJECTID 128
497 #define SNMP_SIZE_BUFCHR 256
498 #define SNMP_SIZE_BUFINT 128
499 #define SNMP_SIZE_SMALLOBJECTID 16
502 #define SNMP_PDU_GET 0
503 #define SNMP_PDU_NEXT 1
504 #define SNMP_PDU_RESPONSE 2
505 #define SNMP_PDU_SET 3
506 #define SNMP_PDU_TRAP1 4
507 #define SNMP_PDU_BULK 5
508 #define SNMP_PDU_INFORM 6
509 #define SNMP_PDU_TRAP2 7
512 #define SNMP_NOERROR 0
513 #define SNMP_TOOBIG 1
514 #define SNMP_NOSUCHNAME 2
515 #define SNMP_BADVALUE 3
516 #define SNMP_READONLY 4
517 #define SNMP_GENERROR 5
518 #define SNMP_NOACCESS 6
519 #define SNMP_WRONGTYPE 7
520 #define SNMP_WRONGLENGTH 8
521 #define SNMP_WRONGENCODING 9
522 #define SNMP_WRONGVALUE 10
523 #define SNMP_NOCREATION 11
524 #define SNMP_INCONSISTENTVALUE 12
525 #define SNMP_RESOURCEUNAVAILABLE 13
526 #define SNMP_COMMITFAILED 14
527 #define SNMP_UNDOFAILED 15
528 #define SNMP_AUTHORIZATIONERROR 16
529 #define SNMP_NOTWRITABLE 17
530 #define SNMP_INCONSISTENTNAME 18
532 /* General SNMP V1 Traps */
533 #define SNMP_TRAP_COLDSTART 0
534 #define SNMP_TRAP_WARMSTART 1
535 #define SNMP_TRAP_LINKDOWN 2
536 #define SNMP_TRAP_LINKUP 3
537 #define SNMP_TRAP_AUTFAILURE 4
538 #define SNMP_TRAP_EQPNEIGHBORLOSS 5
539 #define SNMP_TRAP_ENTSPECIFIC 6
543 #define SNMP_INTEGER 1 /* l */
544 #define SNMP_OCTETSTR 2 /* c */
545 #define SNMP_DISPLAYSTR 2 /* c */
546 #define SNMP_OBJECTID 3 /* ul */
547 #define SNMP_IPADDR 4 /* uc */
548 #define SNMP_COUNTER 5 /* ul */
549 #define SNMP_GAUGE 6 /* ul */
550 #define SNMP_TIMETICKS 7 /* ul */
551 #define SNMP_OPAQUE 8 /* c */
553 /* Additional SNMPv2 Types */
554 #define SNMP_UINTEGER 5 /* ul */
555 #define SNMP_BITSTR 9 /* uc */
556 #define SNMP_NSAP 10 /* uc */
557 #define SNMP_COUNTER64 11 /* ul */
558 #define SNMP_NOSUCHOBJECT 12
559 #define SNMP_NOSUCHINSTANCE 13
560 #define SNMP_ENDOFMIBVIEW 14
564 unsigned char uc[0]; /* 8 bit unsigned */
565 char c[0]; /* 8 bit signed */
566 unsigned long ul[0]; /* 32 bit unsigned */
567 long l[0]; /* 32 bit signed */
575 unsigned int syntax_len;
576 union snmp_syntax syntax;
582 unsigned int error_status;
583 unsigned int error_index;
590 unsigned long ip_address; /* pointer */
591 unsigned int general;
592 unsigned int specific;
609 static inline void mangle_address(unsigned char *begin,
611 const struct oct1_map *map,
620 static struct snmp_cnv snmp_conv [] =
622 {ASN1_UNI, ASN1_NUL, SNMP_NULL},
623 {ASN1_UNI, ASN1_INT, SNMP_INTEGER},
624 {ASN1_UNI, ASN1_OTS, SNMP_OCTETSTR},
625 {ASN1_UNI, ASN1_OTS, SNMP_DISPLAYSTR},
626 {ASN1_UNI, ASN1_OJI, SNMP_OBJECTID},
627 {ASN1_APL, SNMP_IPA, SNMP_IPADDR},
628 {ASN1_APL, SNMP_CNT, SNMP_COUNTER}, /* Counter32 */
629 {ASN1_APL, SNMP_GGE, SNMP_GAUGE}, /* Gauge32 == Unsigned32 */
630 {ASN1_APL, SNMP_TIT, SNMP_TIMETICKS},
631 {ASN1_APL, SNMP_OPQ, SNMP_OPAQUE},
633 /* SNMPv2 data types and errors */
634 {ASN1_UNI, ASN1_BTS, SNMP_BITSTR},
635 {ASN1_APL, SNMP_C64, SNMP_COUNTER64},
636 {ASN1_CTX, SERR_NSO, SNMP_NOSUCHOBJECT},
637 {ASN1_CTX, SERR_NSI, SNMP_NOSUCHINSTANCE},
638 {ASN1_CTX, SERR_EOM, SNMP_ENDOFMIBVIEW},
642 static unsigned char snmp_tag_cls2syntax(unsigned int tag,
644 unsigned short *syntax)
646 struct snmp_cnv *cnv;
650 while (cnv->syntax != -1) {
651 if (cnv->tag == tag && cnv->class == cls) {
652 *syntax = cnv->syntax;
660 static unsigned char snmp_object_decode(struct asn1_ctx *ctx,
661 struct snmp_object **obj)
663 unsigned int cls, con, tag, len, idlen;
665 unsigned char *eoc, *end, *p;
666 unsigned long *lp, *id;
673 if (!asn1_header_decode(ctx, &eoc, &cls, &con, &tag))
676 if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
679 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
682 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
685 if (!asn1_oid_decode(ctx, end, &id, &idlen))
688 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag)) {
693 if (con != ASN1_PRI) {
698 if (!snmp_tag_cls2syntax(tag, cls, &type)) {
706 if (!asn1_long_decode(ctx, end, &l)) {
710 *obj = kmalloc(sizeof(struct snmp_object) + len,
715 printk("OOM in bsalg (%d)\n", __LINE__);
718 (*obj)->syntax.l[0] = l;
722 if (!asn1_octets_decode(ctx, end, &p, &len)) {
726 *obj = kmalloc(sizeof(struct snmp_object) + len,
731 printk("OOM in bsalg (%d)\n", __LINE__);
734 memcpy((*obj)->syntax.c, p, len);
738 case SNMP_NOSUCHOBJECT:
739 case SNMP_NOSUCHINSTANCE:
740 case SNMP_ENDOFMIBVIEW:
742 *obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
746 printk("OOM in bsalg (%d)\n", __LINE__);
749 if (!asn1_null_decode(ctx, end)) {
757 if (!asn1_oid_decode(ctx, end, (unsigned long **)&lp, &len)) {
761 len *= sizeof(unsigned long);
762 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
766 printk("OOM in bsalg (%d)\n", __LINE__);
769 memcpy((*obj)->syntax.ul, lp, len);
773 if (!asn1_octets_decode(ctx, end, &p, &len)) {
782 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
787 printk("OOM in bsalg (%d)\n", __LINE__);
790 memcpy((*obj)->syntax.uc, p, len);
796 len = sizeof(unsigned long);
797 if (!asn1_ulong_decode(ctx, end, &ul)) {
801 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
805 printk("OOM in bsalg (%d)\n", __LINE__);
808 (*obj)->syntax.ul[0] = ul;
815 (*obj)->syntax_len = len;
818 (*obj)->id_len = idlen;
820 if (!asn1_eoc_decode(ctx, eoc)) {
829 static unsigned char snmp_request_decode(struct asn1_ctx *ctx,
830 struct snmp_request *request)
832 unsigned int cls, con, tag;
835 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
838 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
841 if (!asn1_ulong_decode(ctx, end, &request->id))
844 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
847 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
850 if (!asn1_uint_decode(ctx, end, &request->error_status))
853 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
856 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
859 if (!asn1_uint_decode(ctx, end, &request->error_index))
866 * Fast checksum update for possibly oddly-aligned UDP byte, from the
867 * code example in the draft.
869 static void fast_csum(unsigned char *csum,
870 const unsigned char *optr,
871 const unsigned char *nptr,
876 x = csum[0] * 256 + csum[1];
880 if (odd) old = optr[0] * 256;
889 if (odd) new = nptr[0] * 256;
905 * - begin points to the start of the snmp messgae
906 * - addr points to the start of the address
908 static inline void mangle_address(unsigned char *begin,
910 const struct oct1_map *map,
913 if (map->from == NOCT1(*addr)) {
917 memcpy(&old, (unsigned char *)addr, sizeof(old));
921 /* Update UDP checksum if being used */
923 unsigned char odd = !((addr - begin) % 2);
925 fast_csum((unsigned char *)check,
926 &map->from, &map->to, odd);
931 printk(KERN_DEBUG "bsalg: mapped %u.%u.%u.%u to "
932 "%u.%u.%u.%u\n", NIPQUAD(old), NIPQUAD(*addr));
936 static unsigned char snmp_trap_decode(struct asn1_ctx *ctx,
937 struct snmp_v1_trap *trap,
938 const struct oct1_map *map,
941 unsigned int cls, con, tag, len;
944 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
947 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
950 if (!asn1_oid_decode(ctx, end, &trap->id, &trap->id_len))
953 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
956 if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_IPA) ||
957 (cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_OTS)))
960 if (!asn1_octets_decode(ctx, end, (unsigned char **)&trap->ip_address, &len))
967 mangle_address(ctx->begin, ctx->pointer - 4, map, check);
969 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
972 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
975 if (!asn1_uint_decode(ctx, end, &trap->general))
978 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
981 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
984 if (!asn1_uint_decode(ctx, end, &trap->specific))
987 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
990 if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_TIT) ||
991 (cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_INT)))
994 if (!asn1_ulong_decode(ctx, end, &trap->time))
1003 kfree((unsigned long *)trap->ip_address);
1008 /*****************************************************************************
1012 *****************************************************************************/
1014 static void hex_dump(unsigned char *buf, size_t len)
1018 for (i = 0; i < len; i++) {
1021 printk("%02x ", *(buf + i));
1027 * Parse and mangle SNMP message according to mapping.
1028 * (And this is the fucking 'basic' method).
1030 static int snmp_parse_mangle(unsigned char *msg,
1032 const struct oct1_map *map,
1035 unsigned char *eoc, *end;
1036 unsigned int cls, con, tag, vers, pdutype;
1037 struct asn1_ctx ctx;
1038 struct asn1_octstr comm;
1039 struct snmp_object **obj;
1044 asn1_open(&ctx, msg, len);
1047 * Start of SNMP message.
1049 if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
1051 if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
1055 * Version 1 or 2 handled.
1057 if (!asn1_header_decode(&ctx, &end, &cls, &con, &tag))
1059 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
1061 if (!asn1_uint_decode (&ctx, end, &vers))
1064 printk(KERN_DEBUG "bsalg: snmp version: %u\n", vers + 1);
1071 if (!asn1_header_decode (&ctx, &end, &cls, &con, &tag))
1073 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OTS)
1075 if (!asn1_octets_decode(&ctx, end, &comm.data, &comm.len))
1080 printk(KERN_DEBUG "bsalg: community: ");
1081 for (i = 0; i < comm.len; i++)
1082 printk("%c", comm.data[i]);
1090 if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &pdutype))
1092 if (cls != ASN1_CTX || con != ASN1_CON)
1095 unsigned char *pdus[] = {
1096 [SNMP_PDU_GET] = "get",
1097 [SNMP_PDU_NEXT] = "get-next",
1098 [SNMP_PDU_RESPONSE] = "response",
1099 [SNMP_PDU_SET] = "set",
1100 [SNMP_PDU_TRAP1] = "trapv1",
1101 [SNMP_PDU_BULK] = "bulk",
1102 [SNMP_PDU_INFORM] = "inform",
1103 [SNMP_PDU_TRAP2] = "trapv2"
1106 if (pdutype > SNMP_PDU_TRAP2)
1107 printk(KERN_DEBUG "bsalg: bad pdu type %u\n", pdutype);
1109 printk(KERN_DEBUG "bsalg: pdu: %s\n", pdus[pdutype]);
1111 if (pdutype != SNMP_PDU_RESPONSE &&
1112 pdutype != SNMP_PDU_TRAP1 && pdutype != SNMP_PDU_TRAP2)
1116 * Request header or v1 trap
1118 if (pdutype == SNMP_PDU_TRAP1) {
1119 struct snmp_v1_trap trap;
1120 unsigned char ret = snmp_trap_decode(&ctx, &trap, map, check);
1122 /* Discard trap allocations regardless */
1124 kfree((unsigned long *)trap.ip_address);
1130 struct snmp_request req;
1132 if (!snmp_request_decode(&ctx, &req))
1136 printk(KERN_DEBUG "bsalg: request: id=0x%lx error_status=%u "
1137 "error_index=%u\n", req.id, req.error_status,
1142 * Loop through objects, look for IP addresses to mangle.
1144 if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
1147 if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
1150 obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
1152 if (net_ratelimit())
1153 printk(KERN_WARNING "OOM in bsalg(%d)\n", __LINE__);
1157 while (!asn1_eoc_decode(&ctx, eoc)) {
1160 if (!snmp_object_decode(&ctx, obj)) {
1171 printk(KERN_DEBUG "bsalg: object: ");
1172 for (i = 0; i < (*obj)->id_len; i++) {
1175 printk("%lu", (*obj)->id[i]);
1177 printk(": type=%u\n", (*obj)->type);
1181 if ((*obj)->type == SNMP_IPADDR)
1182 mangle_address(ctx.begin, ctx.pointer - 4 , map, check);
1189 if (!asn1_eoc_decode(&ctx, eoc))
1195 /*****************************************************************************
1199 *****************************************************************************/
1202 * SNMP translation routine.
1204 static int snmp_translate(struct ip_conntrack *ct,
1205 struct ip_nat_info *info,
1206 enum ip_conntrack_info ctinfo,
1207 unsigned int hooknum,
1208 struct sk_buff **pskb)
1210 struct iphdr *iph = (*pskb)->nh.iph;
1211 struct udphdr *udph = (struct udphdr *)((u_int32_t *)iph + iph->ihl);
1212 u_int16_t udplen = ntohs(udph->len);
1213 u_int16_t paylen = udplen - sizeof(struct udphdr);
1214 int dir = CTINFO2DIR(ctinfo);
1215 struct oct1_map map;
1218 * Determine mappping for application layer addresses based
1219 * on NAT manipulations for the packet.
1221 if (dir == IP_CT_DIR_ORIGINAL) {
1223 map.from = NOCT1(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip);
1224 map.to = NOCT1(ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip);
1227 map.from = NOCT1(ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip);
1228 map.to = NOCT1(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip);
1231 if (map.from == map.to)
1234 if (!snmp_parse_mangle((unsigned char *)udph + sizeof(struct udphdr),
1235 paylen, &map, &udph->check)) {
1236 printk(KERN_WARNING "bsalg: parser failed\n");
1243 * NAT helper function, packets arrive here from NAT code.
1245 static unsigned int nat_help(struct ip_conntrack *ct,
1246 struct ip_conntrack_expect *exp,
1247 struct ip_nat_info *info,
1248 enum ip_conntrack_info ctinfo,
1249 unsigned int hooknum,
1250 struct sk_buff **pskb)
1252 int dir = CTINFO2DIR(ctinfo);
1253 struct iphdr *iph = (*pskb)->nh.iph;
1254 struct udphdr *udph = (struct udphdr *)((u_int32_t *)iph + iph->ihl);
1256 spin_lock_bh(&snmp_lock);
1259 * Translate snmp replies on pre-routing (DNAT) and snmp traps
1260 * on post routing (SNAT).
1262 if (!((dir == IP_CT_DIR_REPLY && hooknum == NF_IP_PRE_ROUTING &&
1263 udph->source == ntohs(SNMP_PORT)) ||
1264 (dir == IP_CT_DIR_ORIGINAL && hooknum == NF_IP_POST_ROUTING &&
1265 udph->dest == ntohs(SNMP_TRAP_PORT)))) {
1266 spin_unlock_bh(&snmp_lock);
1271 printk(KERN_DEBUG "bsalg: dir=%s hook=%d manip=%s len=%d "
1272 "src=%u.%u.%u.%u:%u dst=%u.%u.%u.%u:%u "
1273 "osrc=%u.%u.%u.%u odst=%u.%u.%u.%u "
1274 "rsrc=%u.%u.%u.%u rdst=%u.%u.%u.%u "
1276 dir == IP_CT_DIR_REPLY ? "reply" : "orig", hooknum,
1277 HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC ? "snat" :
1278 "dnat", (*pskb)->len,
1279 NIPQUAD(iph->saddr), ntohs(udph->source),
1280 NIPQUAD(iph->daddr), ntohs(udph->dest),
1281 NIPQUAD(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip),
1282 NIPQUAD(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip),
1283 NIPQUAD(ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip),
1284 NIPQUAD(ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip));
1288 * Make sure the packet length is ok. So far, we were only guaranteed
1289 * to have a valid length IP header plus 8 bytes, which means we have
1290 * enough room for a UDP header. Just verify the UDP length field so we
1291 * can mess around with the payload.
1293 if (ntohs(udph->len) == (*pskb)->len - (iph->ihl << 2)) {
1294 int ret = snmp_translate(ct, info, ctinfo, hooknum, pskb);
1295 spin_unlock_bh(&snmp_lock);
1299 if (net_ratelimit())
1300 printk(KERN_WARNING "bsalg: dropping malformed packet "
1301 "src=%u.%u.%u.%u dst=%u.%u.%u.%u\n",
1302 NIPQUAD(iph->saddr), NIPQUAD(iph->daddr));
1303 spin_unlock_bh(&snmp_lock);
1307 static struct ip_nat_helper snmp = {
1312 { { 0, { .udp = { __constant_htons(SNMP_PORT) } } },
1313 { 0, { 0 }, IPPROTO_UDP } },
1314 { { 0, { .udp = { 0xFFFF } } },
1315 { 0, { 0 }, 0xFFFF } },
1318 static struct ip_nat_helper snmp_trap = {
1323 { { 0, { .udp = { __constant_htons(SNMP_TRAP_PORT) } } },
1324 { 0, { 0 }, IPPROTO_UDP } },
1325 { { 0, { .udp = { 0xFFFF } } },
1326 { 0, { 0 }, 0xFFFF } },
1329 /*****************************************************************************
1333 *****************************************************************************/
1335 static int __init init(void)
1339 ret = ip_nat_helper_register(&snmp);
1342 ret = ip_nat_helper_register(&snmp_trap);
1344 ip_nat_helper_unregister(&snmp);
1350 static void __exit fini(void)
1352 ip_nat_helper_unregister(&snmp);
1353 ip_nat_helper_unregister(&snmp_trap);
1360 MODULE_PARM(debug, "i");