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/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 <net/checksum.h>
58 #include <asm/uaccess.h>
60 MODULE_LICENSE("GPL");
61 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
62 MODULE_DESCRIPTION("Basic SNMP Application Layer Gateway");
65 #define SNMP_TRAP_PORT 162
66 #define NOCT1(n) (u_int8_t )((n) & 0xff)
69 static DEFINE_SPINLOCK(snmp_lock);
72 * Application layer address mapping mimics the NAT mapping, but
73 * only for the first octet in this case (a more flexible system
74 * can be implemented if needed).
83 /*****************************************************************************
85 * Basic ASN.1 decoding routines (gxsnmp author Dirk Wisse)
87 *****************************************************************************/
90 #define ASN1_UNI 0 /* Universal */
91 #define ASN1_APL 1 /* Application */
92 #define ASN1_CTX 2 /* Context */
93 #define ASN1_PRV 3 /* Private */
96 #define ASN1_EOC 0 /* End Of Contents */
97 #define ASN1_BOL 1 /* Boolean */
98 #define ASN1_INT 2 /* Integer */
99 #define ASN1_BTS 3 /* Bit String */
100 #define ASN1_OTS 4 /* Octet String */
101 #define ASN1_NUL 5 /* Null */
102 #define ASN1_OJI 6 /* Object Identifier */
103 #define ASN1_OJD 7 /* Object Description */
104 #define ASN1_EXT 8 /* External */
105 #define ASN1_SEQ 16 /* Sequence */
106 #define ASN1_SET 17 /* Set */
107 #define ASN1_NUMSTR 18 /* Numerical String */
108 #define ASN1_PRNSTR 19 /* Printable String */
109 #define ASN1_TEXSTR 20 /* Teletext String */
110 #define ASN1_VIDSTR 21 /* Video String */
111 #define ASN1_IA5STR 22 /* IA5 String */
112 #define ASN1_UNITIM 23 /* Universal Time */
113 #define ASN1_GENTIM 24 /* General Time */
114 #define ASN1_GRASTR 25 /* Graphical String */
115 #define ASN1_VISSTR 26 /* Visible String */
116 #define ASN1_GENSTR 27 /* General String */
118 /* Primitive / Constructed methods*/
119 #define ASN1_PRI 0 /* Primitive */
120 #define ASN1_CON 1 /* Constructed */
125 #define ASN1_ERR_NOERROR 0
126 #define ASN1_ERR_DEC_EMPTY 2
127 #define ASN1_ERR_DEC_EOC_MISMATCH 3
128 #define ASN1_ERR_DEC_LENGTH_MISMATCH 4
129 #define ASN1_ERR_DEC_BADVALUE 5
136 int error; /* Error condition */
137 unsigned char *pointer; /* Octet just to be decoded */
138 unsigned char *begin; /* First octet */
139 unsigned char *end; /* Octet after last octet */
143 * Octet string (not null terminated)
151 static void asn1_open(struct asn1_ctx *ctx,
156 ctx->end = buf + len;
158 ctx->error = ASN1_ERR_NOERROR;
161 static unsigned char asn1_octet_decode(struct asn1_ctx *ctx, unsigned char *ch)
163 if (ctx->pointer >= ctx->end) {
164 ctx->error = ASN1_ERR_DEC_EMPTY;
167 *ch = *(ctx->pointer)++;
171 static unsigned char asn1_tag_decode(struct asn1_ctx *ctx, unsigned int *tag)
179 if (!asn1_octet_decode(ctx, &ch))
183 } while ((ch & 0x80) == 0x80);
187 static unsigned char asn1_id_decode(struct asn1_ctx *ctx,
194 if (!asn1_octet_decode(ctx, &ch))
197 *cls = (ch & 0xC0) >> 6;
198 *con = (ch & 0x20) >> 5;
202 if (!asn1_tag_decode(ctx, tag))
208 static unsigned char asn1_length_decode(struct asn1_ctx *ctx,
212 unsigned char ch, cnt;
214 if (!asn1_octet_decode(ctx, &ch))
225 cnt = (unsigned char) (ch & 0x7F);
229 if (!asn1_octet_decode(ctx, &ch))
240 static unsigned char asn1_header_decode(struct asn1_ctx *ctx,
246 unsigned int def, len;
248 if (!asn1_id_decode(ctx, cls, con, tag))
251 if (!asn1_length_decode(ctx, &def, &len))
255 *eoc = ctx->pointer + len;
261 static unsigned char asn1_eoc_decode(struct asn1_ctx *ctx, unsigned char *eoc)
266 if (!asn1_octet_decode(ctx, &ch))
270 ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
274 if (!asn1_octet_decode(ctx, &ch))
278 ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
283 if (ctx->pointer != eoc) {
284 ctx->error = ASN1_ERR_DEC_LENGTH_MISMATCH;
291 static unsigned char asn1_null_decode(struct asn1_ctx *ctx, unsigned char *eoc)
297 static unsigned char asn1_long_decode(struct asn1_ctx *ctx,
304 if (!asn1_octet_decode(ctx, &ch))
307 *integer = (signed char) ch;
310 while (ctx->pointer < eoc) {
311 if (++len > sizeof (long)) {
312 ctx->error = ASN1_ERR_DEC_BADVALUE;
316 if (!asn1_octet_decode(ctx, &ch))
325 static unsigned char asn1_uint_decode(struct asn1_ctx *ctx,
327 unsigned int *integer)
332 if (!asn1_octet_decode(ctx, &ch))
336 if (ch == 0) len = 0;
339 while (ctx->pointer < eoc) {
340 if (++len > sizeof (unsigned int)) {
341 ctx->error = ASN1_ERR_DEC_BADVALUE;
345 if (!asn1_octet_decode(ctx, &ch))
354 static unsigned char asn1_ulong_decode(struct asn1_ctx *ctx,
356 unsigned long *integer)
361 if (!asn1_octet_decode(ctx, &ch))
365 if (ch == 0) len = 0;
368 while (ctx->pointer < eoc) {
369 if (++len > sizeof (unsigned long)) {
370 ctx->error = ASN1_ERR_DEC_BADVALUE;
374 if (!asn1_octet_decode(ctx, &ch))
383 static unsigned char asn1_octets_decode(struct asn1_ctx *ctx,
385 unsigned char **octets,
392 *octets = kmalloc(eoc - ctx->pointer, GFP_ATOMIC);
393 if (*octets == NULL) {
395 printk("OOM in bsalg (%d)\n", __LINE__);
400 while (ctx->pointer < eoc) {
401 if (!asn1_octet_decode(ctx, (unsigned char *)ptr++)) {
411 static unsigned char asn1_subid_decode(struct asn1_ctx *ctx,
412 unsigned long *subid)
419 if (!asn1_octet_decode(ctx, &ch))
424 } while ((ch & 0x80) == 0x80);
428 static unsigned char asn1_oid_decode(struct asn1_ctx *ctx,
437 size = eoc - ctx->pointer + 1;
438 *oid = kmalloc(size * sizeof(unsigned long), GFP_ATOMIC);
441 printk("OOM in bsalg (%d)\n", __LINE__);
447 if (!asn1_subid_decode(ctx, &subid)) {
456 } else if (subid < 80) {
458 optr [1] = subid - 40;
461 optr [1] = subid - 80;
467 while (ctx->pointer < eoc) {
468 if (++(*len) > size) {
469 ctx->error = ASN1_ERR_DEC_BADVALUE;
475 if (!asn1_subid_decode(ctx, optr++)) {
484 /*****************************************************************************
486 * SNMP decoding routines (gxsnmp author Dirk Wisse)
488 *****************************************************************************/
497 #define SNMP_SIZE_COMM 256
498 #define SNMP_SIZE_OBJECTID 128
499 #define SNMP_SIZE_BUFCHR 256
500 #define SNMP_SIZE_BUFINT 128
501 #define SNMP_SIZE_SMALLOBJECTID 16
504 #define SNMP_PDU_GET 0
505 #define SNMP_PDU_NEXT 1
506 #define SNMP_PDU_RESPONSE 2
507 #define SNMP_PDU_SET 3
508 #define SNMP_PDU_TRAP1 4
509 #define SNMP_PDU_BULK 5
510 #define SNMP_PDU_INFORM 6
511 #define SNMP_PDU_TRAP2 7
514 #define SNMP_NOERROR 0
515 #define SNMP_TOOBIG 1
516 #define SNMP_NOSUCHNAME 2
517 #define SNMP_BADVALUE 3
518 #define SNMP_READONLY 4
519 #define SNMP_GENERROR 5
520 #define SNMP_NOACCESS 6
521 #define SNMP_WRONGTYPE 7
522 #define SNMP_WRONGLENGTH 8
523 #define SNMP_WRONGENCODING 9
524 #define SNMP_WRONGVALUE 10
525 #define SNMP_NOCREATION 11
526 #define SNMP_INCONSISTENTVALUE 12
527 #define SNMP_RESOURCEUNAVAILABLE 13
528 #define SNMP_COMMITFAILED 14
529 #define SNMP_UNDOFAILED 15
530 #define SNMP_AUTHORIZATIONERROR 16
531 #define SNMP_NOTWRITABLE 17
532 #define SNMP_INCONSISTENTNAME 18
534 /* General SNMP V1 Traps */
535 #define SNMP_TRAP_COLDSTART 0
536 #define SNMP_TRAP_WARMSTART 1
537 #define SNMP_TRAP_LINKDOWN 2
538 #define SNMP_TRAP_LINKUP 3
539 #define SNMP_TRAP_AUTFAILURE 4
540 #define SNMP_TRAP_EQPNEIGHBORLOSS 5
541 #define SNMP_TRAP_ENTSPECIFIC 6
545 #define SNMP_INTEGER 1 /* l */
546 #define SNMP_OCTETSTR 2 /* c */
547 #define SNMP_DISPLAYSTR 2 /* c */
548 #define SNMP_OBJECTID 3 /* ul */
549 #define SNMP_IPADDR 4 /* uc */
550 #define SNMP_COUNTER 5 /* ul */
551 #define SNMP_GAUGE 6 /* ul */
552 #define SNMP_TIMETICKS 7 /* ul */
553 #define SNMP_OPAQUE 8 /* c */
555 /* Additional SNMPv2 Types */
556 #define SNMP_UINTEGER 5 /* ul */
557 #define SNMP_BITSTR 9 /* uc */
558 #define SNMP_NSAP 10 /* uc */
559 #define SNMP_COUNTER64 11 /* ul */
560 #define SNMP_NOSUCHOBJECT 12
561 #define SNMP_NOSUCHINSTANCE 13
562 #define SNMP_ENDOFMIBVIEW 14
566 unsigned char uc[0]; /* 8 bit unsigned */
567 char c[0]; /* 8 bit signed */
568 unsigned long ul[0]; /* 32 bit unsigned */
569 long l[0]; /* 32 bit signed */
577 unsigned int syntax_len;
578 union snmp_syntax syntax;
584 unsigned int error_status;
585 unsigned int error_index;
592 unsigned long ip_address; /* pointer */
593 unsigned int general;
594 unsigned int specific;
611 static inline void mangle_address(unsigned char *begin,
613 const struct oct1_map *map,
622 static struct snmp_cnv snmp_conv [] =
624 {ASN1_UNI, ASN1_NUL, SNMP_NULL},
625 {ASN1_UNI, ASN1_INT, SNMP_INTEGER},
626 {ASN1_UNI, ASN1_OTS, SNMP_OCTETSTR},
627 {ASN1_UNI, ASN1_OTS, SNMP_DISPLAYSTR},
628 {ASN1_UNI, ASN1_OJI, SNMP_OBJECTID},
629 {ASN1_APL, SNMP_IPA, SNMP_IPADDR},
630 {ASN1_APL, SNMP_CNT, SNMP_COUNTER}, /* Counter32 */
631 {ASN1_APL, SNMP_GGE, SNMP_GAUGE}, /* Gauge32 == Unsigned32 */
632 {ASN1_APL, SNMP_TIT, SNMP_TIMETICKS},
633 {ASN1_APL, SNMP_OPQ, SNMP_OPAQUE},
635 /* SNMPv2 data types and errors */
636 {ASN1_UNI, ASN1_BTS, SNMP_BITSTR},
637 {ASN1_APL, SNMP_C64, SNMP_COUNTER64},
638 {ASN1_CTX, SERR_NSO, SNMP_NOSUCHOBJECT},
639 {ASN1_CTX, SERR_NSI, SNMP_NOSUCHINSTANCE},
640 {ASN1_CTX, SERR_EOM, SNMP_ENDOFMIBVIEW},
644 static unsigned char snmp_tag_cls2syntax(unsigned int tag,
646 unsigned short *syntax)
648 struct snmp_cnv *cnv;
652 while (cnv->syntax != -1) {
653 if (cnv->tag == tag && cnv->class == cls) {
654 *syntax = cnv->syntax;
662 static unsigned char snmp_object_decode(struct asn1_ctx *ctx,
663 struct snmp_object **obj)
665 unsigned int cls, con, tag, len, idlen;
667 unsigned char *eoc, *end, *p;
668 unsigned long *lp, *id;
675 if (!asn1_header_decode(ctx, &eoc, &cls, &con, &tag))
678 if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
681 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
684 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
687 if (!asn1_oid_decode(ctx, end, &id, &idlen))
690 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag)) {
695 if (con != ASN1_PRI) {
700 if (!snmp_tag_cls2syntax(tag, cls, &type)) {
708 if (!asn1_long_decode(ctx, end, &l)) {
712 *obj = kmalloc(sizeof(struct snmp_object) + len,
717 printk("OOM in bsalg (%d)\n", __LINE__);
720 (*obj)->syntax.l[0] = l;
724 if (!asn1_octets_decode(ctx, end, &p, &len)) {
728 *obj = kmalloc(sizeof(struct snmp_object) + len,
733 printk("OOM in bsalg (%d)\n", __LINE__);
736 memcpy((*obj)->syntax.c, p, len);
740 case SNMP_NOSUCHOBJECT:
741 case SNMP_NOSUCHINSTANCE:
742 case SNMP_ENDOFMIBVIEW:
744 *obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
748 printk("OOM in bsalg (%d)\n", __LINE__);
751 if (!asn1_null_decode(ctx, end)) {
759 if (!asn1_oid_decode(ctx, end, (unsigned long **)&lp, &len)) {
763 len *= sizeof(unsigned long);
764 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
768 printk("OOM in bsalg (%d)\n", __LINE__);
771 memcpy((*obj)->syntax.ul, lp, len);
775 if (!asn1_octets_decode(ctx, end, &p, &len)) {
784 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
789 printk("OOM in bsalg (%d)\n", __LINE__);
792 memcpy((*obj)->syntax.uc, p, len);
798 len = sizeof(unsigned long);
799 if (!asn1_ulong_decode(ctx, end, &ul)) {
803 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
807 printk("OOM in bsalg (%d)\n", __LINE__);
810 (*obj)->syntax.ul[0] = ul;
817 (*obj)->syntax_len = len;
820 (*obj)->id_len = idlen;
822 if (!asn1_eoc_decode(ctx, eoc)) {
831 static unsigned char snmp_request_decode(struct asn1_ctx *ctx,
832 struct snmp_request *request)
834 unsigned int cls, con, tag;
837 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
840 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
843 if (!asn1_ulong_decode(ctx, end, &request->id))
846 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
849 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
852 if (!asn1_uint_decode(ctx, end, &request->error_status))
855 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
858 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
861 if (!asn1_uint_decode(ctx, end, &request->error_index))
868 * Fast checksum update for possibly oddly-aligned UDP byte, from the
869 * code example in the draft.
871 static void fast_csum(unsigned char *csum,
872 const unsigned char *optr,
873 const unsigned char *nptr,
878 x = csum[0] * 256 + csum[1];
882 if (odd) old = optr[0] * 256;
891 if (odd) new = nptr[0] * 256;
907 * - begin points to the start of the snmp messgae
908 * - addr points to the start of the address
910 static inline void mangle_address(unsigned char *begin,
912 const struct oct1_map *map,
915 if (map->from == NOCT1(*addr)) {
919 memcpy(&old, (unsigned char *)addr, sizeof(old));
923 /* Update UDP checksum if being used */
925 unsigned char odd = !((addr - begin) % 2);
927 fast_csum((unsigned char *)check,
928 &map->from, &map->to, odd);
933 printk(KERN_DEBUG "bsalg: mapped %u.%u.%u.%u to "
934 "%u.%u.%u.%u\n", NIPQUAD(old), NIPQUAD(*addr));
938 static unsigned char snmp_trap_decode(struct asn1_ctx *ctx,
939 struct snmp_v1_trap *trap,
940 const struct oct1_map *map,
943 unsigned int cls, con, tag, len;
946 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
949 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
952 if (!asn1_oid_decode(ctx, end, &trap->id, &trap->id_len))
955 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
958 if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_IPA) ||
959 (cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_OTS)))
962 if (!asn1_octets_decode(ctx, end, (unsigned char **)&trap->ip_address, &len))
969 mangle_address(ctx->begin, ctx->pointer - 4, map, check);
971 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
974 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
977 if (!asn1_uint_decode(ctx, end, &trap->general))
980 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
983 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
986 if (!asn1_uint_decode(ctx, end, &trap->specific))
989 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
992 if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_TIT) ||
993 (cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_INT)))
996 if (!asn1_ulong_decode(ctx, end, &trap->time))
1005 kfree((unsigned long *)trap->ip_address);
1010 /*****************************************************************************
1014 *****************************************************************************/
1016 static void hex_dump(unsigned char *buf, size_t len)
1020 for (i = 0; i < len; i++) {
1023 printk("%02x ", *(buf + i));
1029 * Parse and mangle SNMP message according to mapping.
1030 * (And this is the fucking 'basic' method).
1032 static int snmp_parse_mangle(unsigned char *msg,
1034 const struct oct1_map *map,
1037 unsigned char *eoc, *end;
1038 unsigned int cls, con, tag, vers, pdutype;
1039 struct asn1_ctx ctx;
1040 struct asn1_octstr comm;
1041 struct snmp_object **obj;
1046 asn1_open(&ctx, msg, len);
1049 * Start of SNMP message.
1051 if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
1053 if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
1057 * Version 1 or 2 handled.
1059 if (!asn1_header_decode(&ctx, &end, &cls, &con, &tag))
1061 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
1063 if (!asn1_uint_decode (&ctx, end, &vers))
1066 printk(KERN_DEBUG "bsalg: snmp version: %u\n", vers + 1);
1073 if (!asn1_header_decode (&ctx, &end, &cls, &con, &tag))
1075 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OTS)
1077 if (!asn1_octets_decode(&ctx, end, &comm.data, &comm.len))
1082 printk(KERN_DEBUG "bsalg: community: ");
1083 for (i = 0; i < comm.len; i++)
1084 printk("%c", comm.data[i]);
1092 if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &pdutype))
1094 if (cls != ASN1_CTX || con != ASN1_CON)
1097 unsigned char *pdus[] = {
1098 [SNMP_PDU_GET] = "get",
1099 [SNMP_PDU_NEXT] = "get-next",
1100 [SNMP_PDU_RESPONSE] = "response",
1101 [SNMP_PDU_SET] = "set",
1102 [SNMP_PDU_TRAP1] = "trapv1",
1103 [SNMP_PDU_BULK] = "bulk",
1104 [SNMP_PDU_INFORM] = "inform",
1105 [SNMP_PDU_TRAP2] = "trapv2"
1108 if (pdutype > SNMP_PDU_TRAP2)
1109 printk(KERN_DEBUG "bsalg: bad pdu type %u\n", pdutype);
1111 printk(KERN_DEBUG "bsalg: pdu: %s\n", pdus[pdutype]);
1113 if (pdutype != SNMP_PDU_RESPONSE &&
1114 pdutype != SNMP_PDU_TRAP1 && pdutype != SNMP_PDU_TRAP2)
1118 * Request header or v1 trap
1120 if (pdutype == SNMP_PDU_TRAP1) {
1121 struct snmp_v1_trap trap;
1122 unsigned char ret = snmp_trap_decode(&ctx, &trap, map, check);
1124 /* Discard trap allocations regardless */
1126 kfree((unsigned long *)trap.ip_address);
1132 struct snmp_request req;
1134 if (!snmp_request_decode(&ctx, &req))
1138 printk(KERN_DEBUG "bsalg: request: id=0x%lx error_status=%u "
1139 "error_index=%u\n", req.id, req.error_status,
1144 * Loop through objects, look for IP addresses to mangle.
1146 if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
1149 if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
1152 obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
1154 if (net_ratelimit())
1155 printk(KERN_WARNING "OOM in bsalg(%d)\n", __LINE__);
1159 while (!asn1_eoc_decode(&ctx, eoc)) {
1162 if (!snmp_object_decode(&ctx, obj)) {
1173 printk(KERN_DEBUG "bsalg: object: ");
1174 for (i = 0; i < (*obj)->id_len; i++) {
1177 printk("%lu", (*obj)->id[i]);
1179 printk(": type=%u\n", (*obj)->type);
1183 if ((*obj)->type == SNMP_IPADDR)
1184 mangle_address(ctx.begin, ctx.pointer - 4 , map, check);
1191 if (!asn1_eoc_decode(&ctx, eoc))
1197 /*****************************************************************************
1201 *****************************************************************************/
1204 * SNMP translation routine.
1206 static int snmp_translate(struct ip_conntrack *ct,
1207 enum ip_conntrack_info ctinfo,
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 if (net_ratelimit())
1237 printk(KERN_WARNING "bsalg: parser failed\n");
1243 /* We don't actually set up expectations, just adjust internal IP
1244 * addresses if this is being NATted */
1245 static int help(struct sk_buff **pskb,
1246 struct ip_conntrack *ct,
1247 enum ip_conntrack_info ctinfo)
1249 int dir = CTINFO2DIR(ctinfo);
1251 struct iphdr *iph = (*pskb)->nh.iph;
1252 struct udphdr *udph = (struct udphdr *)((u_int32_t *)iph + iph->ihl);
1254 /* SNMP replies and originating SNMP traps get mangled */
1255 if (udph->source == ntohs(SNMP_PORT) && dir != IP_CT_DIR_REPLY)
1257 if (udph->dest == ntohs(SNMP_TRAP_PORT) && dir != IP_CT_DIR_ORIGINAL)
1261 if (!(ct->status & IPS_NAT_MASK))
1265 * Make sure the packet length is ok. So far, we were only guaranteed
1266 * to have a valid length IP header plus 8 bytes, which means we have
1267 * enough room for a UDP header. Just verify the UDP length field so we
1268 * can mess around with the payload.
1270 if (ntohs(udph->len) != (*pskb)->len - (iph->ihl << 2)) {
1271 if (net_ratelimit())
1272 printk(KERN_WARNING "SNMP: dropping malformed packet "
1273 "src=%u.%u.%u.%u dst=%u.%u.%u.%u\n",
1274 NIPQUAD(iph->saddr), NIPQUAD(iph->daddr));
1278 if (!skb_ip_make_writable(pskb, (*pskb)->len))
1281 spin_lock_bh(&snmp_lock);
1282 ret = snmp_translate(ct, ctinfo, pskb);
1283 spin_unlock_bh(&snmp_lock);
1287 static struct ip_conntrack_helper snmp_helper = {
1294 .tuple = { .src = { .u = { __constant_htons(SNMP_PORT) } },
1295 .dst = { .protonum = IPPROTO_UDP },
1297 .mask = { .src = { .u = { 0xFFFF } },
1298 .dst = { .protonum = 0xFF },
1302 static struct ip_conntrack_helper snmp_trap_helper = {
1307 .name = "snmp_trap",
1309 .tuple = { .src = { .u = { __constant_htons(SNMP_TRAP_PORT) } },
1310 .dst = { .protonum = IPPROTO_UDP },
1312 .mask = { .src = { .u = { 0xFFFF } },
1313 .dst = { .protonum = 0xFF },
1317 /*****************************************************************************
1321 *****************************************************************************/
1323 static int __init init(void)
1327 ret = ip_conntrack_helper_register(&snmp_helper);
1330 ret = ip_conntrack_helper_register(&snmp_trap_helper);
1332 ip_conntrack_helper_unregister(&snmp_helper);
1338 static void __exit fini(void)
1340 ip_conntrack_helper_unregister(&snmp_helper);
1341 ip_conntrack_helper_unregister(&snmp_trap_helper);
1347 module_param(debug, bool, 0600);