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).
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_conntrack_helper.h>
54 #include <linux/netfilter_ipv4/ip_nat_helper.h>
56 #include <linux/udp.h>
57 #include <net/checksum.h>
59 #include <asm/uaccess.h>
61 MODULE_LICENSE("GPL");
62 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
63 MODULE_DESCRIPTION("Basic SNMP Application Layer Gateway");
66 #define SNMP_TRAP_PORT 162
67 #define NOCT1(n) (*(u8 *)n)
70 static DEFINE_SPINLOCK(snmp_lock);
73 * Application layer address mapping mimics the NAT mapping, but
74 * only for the first octet in this case (a more flexible system
75 * can be implemented if needed).
84 /*****************************************************************************
86 * Basic ASN.1 decoding routines (gxsnmp author Dirk Wisse)
88 *****************************************************************************/
91 #define ASN1_UNI 0 /* Universal */
92 #define ASN1_APL 1 /* Application */
93 #define ASN1_CTX 2 /* Context */
94 #define ASN1_PRV 3 /* Private */
97 #define ASN1_EOC 0 /* End Of Contents */
98 #define ASN1_BOL 1 /* Boolean */
99 #define ASN1_INT 2 /* Integer */
100 #define ASN1_BTS 3 /* Bit String */
101 #define ASN1_OTS 4 /* Octet String */
102 #define ASN1_NUL 5 /* Null */
103 #define ASN1_OJI 6 /* Object Identifier */
104 #define ASN1_OJD 7 /* Object Description */
105 #define ASN1_EXT 8 /* External */
106 #define ASN1_SEQ 16 /* Sequence */
107 #define ASN1_SET 17 /* Set */
108 #define ASN1_NUMSTR 18 /* Numerical String */
109 #define ASN1_PRNSTR 19 /* Printable String */
110 #define ASN1_TEXSTR 20 /* Teletext String */
111 #define ASN1_VIDSTR 21 /* Video String */
112 #define ASN1_IA5STR 22 /* IA5 String */
113 #define ASN1_UNITIM 23 /* Universal Time */
114 #define ASN1_GENTIM 24 /* General Time */
115 #define ASN1_GRASTR 25 /* Graphical String */
116 #define ASN1_VISSTR 26 /* Visible String */
117 #define ASN1_GENSTR 27 /* General String */
119 /* Primitive / Constructed methods*/
120 #define ASN1_PRI 0 /* Primitive */
121 #define ASN1_CON 1 /* Constructed */
126 #define ASN1_ERR_NOERROR 0
127 #define ASN1_ERR_DEC_EMPTY 2
128 #define ASN1_ERR_DEC_EOC_MISMATCH 3
129 #define ASN1_ERR_DEC_LENGTH_MISMATCH 4
130 #define ASN1_ERR_DEC_BADVALUE 5
137 int error; /* Error condition */
138 unsigned char *pointer; /* Octet just to be decoded */
139 unsigned char *begin; /* First octet */
140 unsigned char *end; /* Octet after last octet */
144 * Octet string (not null terminated)
152 static void asn1_open(struct asn1_ctx *ctx,
157 ctx->end = buf + len;
159 ctx->error = ASN1_ERR_NOERROR;
162 static unsigned char asn1_octet_decode(struct asn1_ctx *ctx, unsigned char *ch)
164 if (ctx->pointer >= ctx->end) {
165 ctx->error = ASN1_ERR_DEC_EMPTY;
168 *ch = *(ctx->pointer)++;
172 static unsigned char asn1_tag_decode(struct asn1_ctx *ctx, unsigned int *tag)
180 if (!asn1_octet_decode(ctx, &ch))
184 } while ((ch & 0x80) == 0x80);
188 static unsigned char asn1_id_decode(struct asn1_ctx *ctx,
195 if (!asn1_octet_decode(ctx, &ch))
198 *cls = (ch & 0xC0) >> 6;
199 *con = (ch & 0x20) >> 5;
203 if (!asn1_tag_decode(ctx, tag))
209 static unsigned char asn1_length_decode(struct asn1_ctx *ctx,
213 unsigned char ch, cnt;
215 if (!asn1_octet_decode(ctx, &ch))
226 cnt = (unsigned char) (ch & 0x7F);
230 if (!asn1_octet_decode(ctx, &ch))
241 static unsigned char asn1_header_decode(struct asn1_ctx *ctx,
247 unsigned int def, len;
249 if (!asn1_id_decode(ctx, cls, con, tag))
253 if (!asn1_length_decode(ctx, &def, &len))
257 *eoc = ctx->pointer + len;
263 static unsigned char asn1_eoc_decode(struct asn1_ctx *ctx, unsigned char *eoc)
268 if (!asn1_octet_decode(ctx, &ch))
272 ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
276 if (!asn1_octet_decode(ctx, &ch))
280 ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
285 if (ctx->pointer != eoc) {
286 ctx->error = ASN1_ERR_DEC_LENGTH_MISMATCH;
293 static unsigned char asn1_null_decode(struct asn1_ctx *ctx, unsigned char *eoc)
299 static unsigned char asn1_long_decode(struct asn1_ctx *ctx,
306 if (!asn1_octet_decode(ctx, &ch))
309 *integer = (signed char) ch;
312 while (ctx->pointer < eoc) {
313 if (++len > sizeof (long)) {
314 ctx->error = ASN1_ERR_DEC_BADVALUE;
318 if (!asn1_octet_decode(ctx, &ch))
327 static unsigned char asn1_uint_decode(struct asn1_ctx *ctx,
329 unsigned int *integer)
334 if (!asn1_octet_decode(ctx, &ch))
338 if (ch == 0) len = 0;
341 while (ctx->pointer < eoc) {
342 if (++len > sizeof (unsigned int)) {
343 ctx->error = ASN1_ERR_DEC_BADVALUE;
347 if (!asn1_octet_decode(ctx, &ch))
356 static unsigned char asn1_ulong_decode(struct asn1_ctx *ctx,
358 unsigned long *integer)
363 if (!asn1_octet_decode(ctx, &ch))
367 if (ch == 0) len = 0;
370 while (ctx->pointer < eoc) {
371 if (++len > sizeof (unsigned long)) {
372 ctx->error = ASN1_ERR_DEC_BADVALUE;
376 if (!asn1_octet_decode(ctx, &ch))
385 static unsigned char asn1_octets_decode(struct asn1_ctx *ctx,
387 unsigned char **octets,
394 *octets = kmalloc(eoc - ctx->pointer, GFP_ATOMIC);
395 if (*octets == NULL) {
397 printk("OOM in bsalg (%d)\n", __LINE__);
402 while (ctx->pointer < eoc) {
403 if (!asn1_octet_decode(ctx, (unsigned char *)ptr++)) {
413 static unsigned char asn1_subid_decode(struct asn1_ctx *ctx,
414 unsigned long *subid)
421 if (!asn1_octet_decode(ctx, &ch))
426 } while ((ch & 0x80) == 0x80);
430 static unsigned char asn1_oid_decode(struct asn1_ctx *ctx,
439 size = eoc - ctx->pointer + 1;
440 *oid = kmalloc(size * sizeof(unsigned long), GFP_ATOMIC);
443 printk("OOM in bsalg (%d)\n", __LINE__);
449 if (!asn1_subid_decode(ctx, &subid)) {
458 } else if (subid < 80) {
460 optr [1] = subid - 40;
463 optr [1] = subid - 80;
469 while (ctx->pointer < eoc) {
470 if (++(*len) > size) {
471 ctx->error = ASN1_ERR_DEC_BADVALUE;
477 if (!asn1_subid_decode(ctx, optr++)) {
486 /*****************************************************************************
488 * SNMP decoding routines (gxsnmp author Dirk Wisse)
490 *****************************************************************************/
499 #define SNMP_SIZE_COMM 256
500 #define SNMP_SIZE_OBJECTID 128
501 #define SNMP_SIZE_BUFCHR 256
502 #define SNMP_SIZE_BUFINT 128
503 #define SNMP_SIZE_SMALLOBJECTID 16
506 #define SNMP_PDU_GET 0
507 #define SNMP_PDU_NEXT 1
508 #define SNMP_PDU_RESPONSE 2
509 #define SNMP_PDU_SET 3
510 #define SNMP_PDU_TRAP1 4
511 #define SNMP_PDU_BULK 5
512 #define SNMP_PDU_INFORM 6
513 #define SNMP_PDU_TRAP2 7
516 #define SNMP_NOERROR 0
517 #define SNMP_TOOBIG 1
518 #define SNMP_NOSUCHNAME 2
519 #define SNMP_BADVALUE 3
520 #define SNMP_READONLY 4
521 #define SNMP_GENERROR 5
522 #define SNMP_NOACCESS 6
523 #define SNMP_WRONGTYPE 7
524 #define SNMP_WRONGLENGTH 8
525 #define SNMP_WRONGENCODING 9
526 #define SNMP_WRONGVALUE 10
527 #define SNMP_NOCREATION 11
528 #define SNMP_INCONSISTENTVALUE 12
529 #define SNMP_RESOURCEUNAVAILABLE 13
530 #define SNMP_COMMITFAILED 14
531 #define SNMP_UNDOFAILED 15
532 #define SNMP_AUTHORIZATIONERROR 16
533 #define SNMP_NOTWRITABLE 17
534 #define SNMP_INCONSISTENTNAME 18
536 /* General SNMP V1 Traps */
537 #define SNMP_TRAP_COLDSTART 0
538 #define SNMP_TRAP_WARMSTART 1
539 #define SNMP_TRAP_LINKDOWN 2
540 #define SNMP_TRAP_LINKUP 3
541 #define SNMP_TRAP_AUTFAILURE 4
542 #define SNMP_TRAP_EQPNEIGHBORLOSS 5
543 #define SNMP_TRAP_ENTSPECIFIC 6
547 #define SNMP_INTEGER 1 /* l */
548 #define SNMP_OCTETSTR 2 /* c */
549 #define SNMP_DISPLAYSTR 2 /* c */
550 #define SNMP_OBJECTID 3 /* ul */
551 #define SNMP_IPADDR 4 /* uc */
552 #define SNMP_COUNTER 5 /* ul */
553 #define SNMP_GAUGE 6 /* ul */
554 #define SNMP_TIMETICKS 7 /* ul */
555 #define SNMP_OPAQUE 8 /* c */
557 /* Additional SNMPv2 Types */
558 #define SNMP_UINTEGER 5 /* ul */
559 #define SNMP_BITSTR 9 /* uc */
560 #define SNMP_NSAP 10 /* uc */
561 #define SNMP_COUNTER64 11 /* ul */
562 #define SNMP_NOSUCHOBJECT 12
563 #define SNMP_NOSUCHINSTANCE 13
564 #define SNMP_ENDOFMIBVIEW 14
568 unsigned char uc[0]; /* 8 bit unsigned */
569 char c[0]; /* 8 bit signed */
570 unsigned long ul[0]; /* 32 bit unsigned */
571 long l[0]; /* 32 bit signed */
579 unsigned int syntax_len;
580 union snmp_syntax syntax;
586 unsigned int error_status;
587 unsigned int error_index;
594 unsigned long ip_address; /* pointer */
595 unsigned int general;
596 unsigned int specific;
613 static inline void mangle_address(unsigned char *begin,
615 const struct oct1_map *map,
624 static struct snmp_cnv snmp_conv [] =
626 {ASN1_UNI, ASN1_NUL, SNMP_NULL},
627 {ASN1_UNI, ASN1_INT, SNMP_INTEGER},
628 {ASN1_UNI, ASN1_OTS, SNMP_OCTETSTR},
629 {ASN1_UNI, ASN1_OTS, SNMP_DISPLAYSTR},
630 {ASN1_UNI, ASN1_OJI, SNMP_OBJECTID},
631 {ASN1_APL, SNMP_IPA, SNMP_IPADDR},
632 {ASN1_APL, SNMP_CNT, SNMP_COUNTER}, /* Counter32 */
633 {ASN1_APL, SNMP_GGE, SNMP_GAUGE}, /* Gauge32 == Unsigned32 */
634 {ASN1_APL, SNMP_TIT, SNMP_TIMETICKS},
635 {ASN1_APL, SNMP_OPQ, SNMP_OPAQUE},
637 /* SNMPv2 data types and errors */
638 {ASN1_UNI, ASN1_BTS, SNMP_BITSTR},
639 {ASN1_APL, SNMP_C64, SNMP_COUNTER64},
640 {ASN1_CTX, SERR_NSO, SNMP_NOSUCHOBJECT},
641 {ASN1_CTX, SERR_NSI, SNMP_NOSUCHINSTANCE},
642 {ASN1_CTX, SERR_EOM, SNMP_ENDOFMIBVIEW},
646 static unsigned char snmp_tag_cls2syntax(unsigned int tag,
648 unsigned short *syntax)
650 struct snmp_cnv *cnv;
654 while (cnv->syntax != -1) {
655 if (cnv->tag == tag && cnv->class == cls) {
656 *syntax = cnv->syntax;
664 static unsigned char snmp_object_decode(struct asn1_ctx *ctx,
665 struct snmp_object **obj)
667 unsigned int cls, con, tag, len, idlen;
669 unsigned char *eoc, *end, *p;
670 unsigned long *lp, *id;
677 if (!asn1_header_decode(ctx, &eoc, &cls, &con, &tag))
680 if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
683 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
686 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
689 if (!asn1_oid_decode(ctx, end, &id, &idlen))
692 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag)) {
697 if (con != ASN1_PRI) {
703 if (!snmp_tag_cls2syntax(tag, cls, &type)) {
712 if (!asn1_long_decode(ctx, end, &l)) {
716 *obj = kmalloc(sizeof(struct snmp_object) + len,
721 printk("OOM in bsalg (%d)\n", __LINE__);
724 (*obj)->syntax.l[0] = l;
728 if (!asn1_octets_decode(ctx, end, &p, &len)) {
732 *obj = kmalloc(sizeof(struct snmp_object) + len,
737 printk("OOM in bsalg (%d)\n", __LINE__);
740 memcpy((*obj)->syntax.c, p, len);
744 case SNMP_NOSUCHOBJECT:
745 case SNMP_NOSUCHINSTANCE:
746 case SNMP_ENDOFMIBVIEW:
748 *obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
752 printk("OOM in bsalg (%d)\n", __LINE__);
755 if (!asn1_null_decode(ctx, end)) {
763 if (!asn1_oid_decode(ctx, end, (unsigned long **)&lp, &len)) {
767 len *= sizeof(unsigned long);
768 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
773 printk("OOM in bsalg (%d)\n", __LINE__);
776 memcpy((*obj)->syntax.ul, lp, len);
780 if (!asn1_octets_decode(ctx, end, &p, &len)) {
789 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
794 printk("OOM in bsalg (%d)\n", __LINE__);
797 memcpy((*obj)->syntax.uc, p, len);
803 len = sizeof(unsigned long);
804 if (!asn1_ulong_decode(ctx, end, &ul)) {
808 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
812 printk("OOM in bsalg (%d)\n", __LINE__);
815 (*obj)->syntax.ul[0] = ul;
822 (*obj)->syntax_len = len;
825 (*obj)->id_len = idlen;
827 if (!asn1_eoc_decode(ctx, eoc)) {
836 static unsigned char snmp_request_decode(struct asn1_ctx *ctx,
837 struct snmp_request *request)
839 unsigned int cls, con, tag;
842 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
845 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
848 if (!asn1_ulong_decode(ctx, end, &request->id))
851 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
854 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
857 if (!asn1_uint_decode(ctx, end, &request->error_status))
860 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
863 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
866 if (!asn1_uint_decode(ctx, end, &request->error_index))
873 * Fast checksum update for possibly oddly-aligned UDP byte, from the
874 * code example in the draft.
876 static void fast_csum(__sum16 *csum,
877 const unsigned char *optr,
878 const unsigned char *nptr,
893 *csum = csum_fold(csum_partial(s, 4, ~csum_unfold(*csum)));
898 * - begin points to the start of the snmp messgae
899 * - addr points to the start of the address
901 static inline void mangle_address(unsigned char *begin,
903 const struct oct1_map *map,
906 if (map->from == NOCT1(addr)) {
910 memcpy(&old, (unsigned char *)addr, sizeof(old));
914 /* Update UDP checksum if being used */
917 &map->from, &map->to, addr - begin);
921 printk(KERN_DEBUG "bsalg: mapped %u.%u.%u.%u to "
922 "%u.%u.%u.%u\n", NIPQUAD(old), NIPQUAD(*addr));
926 static unsigned char snmp_trap_decode(struct asn1_ctx *ctx,
927 struct snmp_v1_trap *trap,
928 const struct oct1_map *map,
931 unsigned int cls, con, tag, len;
934 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
937 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
940 if (!asn1_oid_decode(ctx, end, &trap->id, &trap->id_len))
943 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
946 if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_IPA) ||
947 (cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_OTS)))
950 if (!asn1_octets_decode(ctx, end, (unsigned char **)&trap->ip_address, &len))
957 mangle_address(ctx->begin, ctx->pointer - 4, map, check);
959 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
962 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
965 if (!asn1_uint_decode(ctx, end, &trap->general))
968 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
971 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
974 if (!asn1_uint_decode(ctx, end, &trap->specific))
977 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
980 if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_TIT) ||
981 (cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_INT)))
984 if (!asn1_ulong_decode(ctx, end, &trap->time))
990 kfree((unsigned long *)trap->ip_address);
998 /*****************************************************************************
1002 *****************************************************************************/
1004 static void hex_dump(unsigned char *buf, size_t len)
1008 for (i = 0; i < len; i++) {
1011 printk("%02x ", *(buf + i));
1017 * Parse and mangle SNMP message according to mapping.
1018 * (And this is the fucking 'basic' method).
1020 static int snmp_parse_mangle(unsigned char *msg,
1022 const struct oct1_map *map,
1025 unsigned char *eoc, *end;
1026 unsigned int cls, con, tag, vers, pdutype;
1027 struct asn1_ctx ctx;
1028 struct asn1_octstr comm;
1029 struct snmp_object **obj;
1034 asn1_open(&ctx, msg, len);
1037 * Start of SNMP message.
1039 if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
1041 if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
1045 * Version 1 or 2 handled.
1047 if (!asn1_header_decode(&ctx, &end, &cls, &con, &tag))
1049 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
1051 if (!asn1_uint_decode (&ctx, end, &vers))
1054 printk(KERN_DEBUG "bsalg: snmp version: %u\n", vers + 1);
1061 if (!asn1_header_decode (&ctx, &end, &cls, &con, &tag))
1063 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OTS)
1065 if (!asn1_octets_decode(&ctx, end, &comm.data, &comm.len))
1070 printk(KERN_DEBUG "bsalg: community: ");
1071 for (i = 0; i < comm.len; i++)
1072 printk("%c", comm.data[i]);
1080 if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &pdutype))
1082 if (cls != ASN1_CTX || con != ASN1_CON)
1085 unsigned char *pdus[] = {
1086 [SNMP_PDU_GET] = "get",
1087 [SNMP_PDU_NEXT] = "get-next",
1088 [SNMP_PDU_RESPONSE] = "response",
1089 [SNMP_PDU_SET] = "set",
1090 [SNMP_PDU_TRAP1] = "trapv1",
1091 [SNMP_PDU_BULK] = "bulk",
1092 [SNMP_PDU_INFORM] = "inform",
1093 [SNMP_PDU_TRAP2] = "trapv2"
1096 if (pdutype > SNMP_PDU_TRAP2)
1097 printk(KERN_DEBUG "bsalg: bad pdu type %u\n", pdutype);
1099 printk(KERN_DEBUG "bsalg: pdu: %s\n", pdus[pdutype]);
1101 if (pdutype != SNMP_PDU_RESPONSE &&
1102 pdutype != SNMP_PDU_TRAP1 && pdutype != SNMP_PDU_TRAP2)
1106 * Request header or v1 trap
1108 if (pdutype == SNMP_PDU_TRAP1) {
1109 struct snmp_v1_trap trap;
1110 unsigned char ret = snmp_trap_decode(&ctx, &trap, map, check);
1114 kfree((unsigned long *)trap.ip_address);
1119 struct snmp_request req;
1121 if (!snmp_request_decode(&ctx, &req))
1125 printk(KERN_DEBUG "bsalg: request: id=0x%lx error_status=%u "
1126 "error_index=%u\n", req.id, req.error_status,
1131 * Loop through objects, look for IP addresses to mangle.
1133 if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
1136 if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
1139 obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
1141 if (net_ratelimit())
1142 printk(KERN_WARNING "OOM in bsalg(%d)\n", __LINE__);
1146 while (!asn1_eoc_decode(&ctx, eoc)) {
1149 if (!snmp_object_decode(&ctx, obj)) {
1159 printk(KERN_DEBUG "bsalg: object: ");
1160 for (i = 0; i < (*obj)->id_len; i++) {
1163 printk("%lu", (*obj)->id[i]);
1165 printk(": type=%u\n", (*obj)->type);
1169 if ((*obj)->type == SNMP_IPADDR)
1170 mangle_address(ctx.begin, ctx.pointer - 4 , map, check);
1177 if (!asn1_eoc_decode(&ctx, eoc))
1183 /*****************************************************************************
1187 *****************************************************************************/
1190 * SNMP translation routine.
1192 static int snmp_translate(struct ip_conntrack *ct,
1193 enum ip_conntrack_info ctinfo,
1194 struct sk_buff **pskb)
1196 struct iphdr *iph = (*pskb)->nh.iph;
1197 struct udphdr *udph = (struct udphdr *)((__be32 *)iph + iph->ihl);
1198 u_int16_t udplen = ntohs(udph->len);
1199 u_int16_t paylen = udplen - sizeof(struct udphdr);
1200 int dir = CTINFO2DIR(ctinfo);
1201 struct oct1_map map;
1204 * Determine mappping for application layer addresses based
1205 * on NAT manipulations for the packet.
1207 if (dir == IP_CT_DIR_ORIGINAL) {
1209 map.from = NOCT1(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip);
1210 map.to = NOCT1(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip);
1213 map.from = NOCT1(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip);
1214 map.to = NOCT1(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip);
1217 if (map.from == map.to)
1220 if (!snmp_parse_mangle((unsigned char *)udph + sizeof(struct udphdr),
1221 paylen, &map, &udph->check)) {
1222 if (net_ratelimit())
1223 printk(KERN_WARNING "bsalg: parser failed\n");
1229 /* We don't actually set up expectations, just adjust internal IP
1230 * addresses if this is being NATted */
1231 static int help(struct sk_buff **pskb,
1232 struct ip_conntrack *ct,
1233 enum ip_conntrack_info ctinfo)
1235 int dir = CTINFO2DIR(ctinfo);
1237 struct iphdr *iph = (*pskb)->nh.iph;
1238 struct udphdr *udph = (struct udphdr *)((u_int32_t *)iph + iph->ihl);
1240 /* SNMP replies and originating SNMP traps get mangled */
1241 if (udph->source == htons(SNMP_PORT) && dir != IP_CT_DIR_REPLY)
1243 if (udph->dest == htons(SNMP_TRAP_PORT) && dir != IP_CT_DIR_ORIGINAL)
1247 if (!(ct->status & IPS_NAT_MASK))
1251 * Make sure the packet length is ok. So far, we were only guaranteed
1252 * to have a valid length IP header plus 8 bytes, which means we have
1253 * enough room for a UDP header. Just verify the UDP length field so we
1254 * can mess around with the payload.
1256 if (ntohs(udph->len) != (*pskb)->len - (iph->ihl << 2)) {
1257 if (net_ratelimit())
1258 printk(KERN_WARNING "SNMP: dropping malformed packet "
1259 "src=%u.%u.%u.%u dst=%u.%u.%u.%u\n",
1260 NIPQUAD(iph->saddr), NIPQUAD(iph->daddr));
1264 if (!skb_make_writable(pskb, (*pskb)->len))
1267 spin_lock_bh(&snmp_lock);
1268 ret = snmp_translate(ct, ctinfo, pskb);
1269 spin_unlock_bh(&snmp_lock);
1273 static struct ip_conntrack_helper snmp_helper = {
1280 .tuple = {.src = {.u = {.udp = {.port = __constant_htons(SNMP_PORT)}}},
1281 .dst = {.protonum = IPPROTO_UDP},
1283 .mask = {.src = {.u = {0xFFFF}},
1284 .dst = {.protonum = 0xFF},
1288 static struct ip_conntrack_helper snmp_trap_helper = {
1293 .name = "snmp_trap",
1295 .tuple = {.src = {.u = {.udp = {.port = __constant_htons(SNMP_TRAP_PORT)}}},
1296 .dst = {.protonum = IPPROTO_UDP},
1298 .mask = {.src = {.u = {0xFFFF}},
1299 .dst = {.protonum = 0xFF},
1303 /*****************************************************************************
1307 *****************************************************************************/
1309 static int __init ip_nat_snmp_basic_init(void)
1313 ret = ip_conntrack_helper_register(&snmp_helper);
1316 ret = ip_conntrack_helper_register(&snmp_trap_helper);
1318 ip_conntrack_helper_unregister(&snmp_helper);
1324 static void __exit ip_nat_snmp_basic_fini(void)
1326 ip_conntrack_helper_unregister(&snmp_helper);
1327 ip_conntrack_helper_unregister(&snmp_trap_helper);
1330 module_init(ip_nat_snmp_basic_init);
1331 module_exit(ip_nat_snmp_basic_fini);
1333 module_param(debug, int, 0600);