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>
42 #include <linux/module.h>
43 #include <linux/moduleparam.h>
44 #include <linux/types.h>
45 #include <linux/kernel.h>
46 #include <linux/slab.h>
49 #include <linux/udp.h>
50 #include <net/checksum.h>
53 #include <net/netfilter/nf_nat.h>
54 #include <net/netfilter/nf_conntrack_expect.h>
55 #include <net/netfilter/nf_conntrack_helper.h>
56 #include <net/netfilter/nf_nat_helper.h>
58 MODULE_LICENSE("GPL");
59 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
60 MODULE_DESCRIPTION("Basic SNMP Application Layer Gateway");
61 MODULE_ALIAS("ip_nat_snmp_basic");
64 #define SNMP_TRAP_PORT 162
65 #define NOCT1(n) (*(u8 *)(n))
68 static DEFINE_SPINLOCK(snmp_lock);
71 * Application layer address mapping mimics the NAT mapping, but
72 * only for the first octet in this case (a more flexible system
73 * can be implemented if needed).
82 /*****************************************************************************
84 * Basic ASN.1 decoding routines (gxsnmp author Dirk Wisse)
86 *****************************************************************************/
89 #define ASN1_UNI 0 /* Universal */
90 #define ASN1_APL 1 /* Application */
91 #define ASN1_CTX 2 /* Context */
92 #define ASN1_PRV 3 /* Private */
95 #define ASN1_EOC 0 /* End Of Contents */
96 #define ASN1_BOL 1 /* Boolean */
97 #define ASN1_INT 2 /* Integer */
98 #define ASN1_BTS 3 /* Bit String */
99 #define ASN1_OTS 4 /* Octet String */
100 #define ASN1_NUL 5 /* Null */
101 #define ASN1_OJI 6 /* Object Identifier */
102 #define ASN1_OJD 7 /* Object Description */
103 #define ASN1_EXT 8 /* External */
104 #define ASN1_SEQ 16 /* Sequence */
105 #define ASN1_SET 17 /* Set */
106 #define ASN1_NUMSTR 18 /* Numerical String */
107 #define ASN1_PRNSTR 19 /* Printable String */
108 #define ASN1_TEXSTR 20 /* Teletext String */
109 #define ASN1_VIDSTR 21 /* Video String */
110 #define ASN1_IA5STR 22 /* IA5 String */
111 #define ASN1_UNITIM 23 /* Universal Time */
112 #define ASN1_GENTIM 24 /* General Time */
113 #define ASN1_GRASTR 25 /* Graphical String */
114 #define ASN1_VISSTR 26 /* Visible String */
115 #define ASN1_GENSTR 27 /* General String */
117 /* Primitive / Constructed methods*/
118 #define ASN1_PRI 0 /* Primitive */
119 #define ASN1_CON 1 /* Constructed */
124 #define ASN1_ERR_NOERROR 0
125 #define ASN1_ERR_DEC_EMPTY 2
126 #define ASN1_ERR_DEC_EOC_MISMATCH 3
127 #define ASN1_ERR_DEC_LENGTH_MISMATCH 4
128 #define ASN1_ERR_DEC_BADVALUE 5
135 int error; /* Error condition */
136 unsigned char *pointer; /* Octet just to be decoded */
137 unsigned char *begin; /* First octet */
138 unsigned char *end; /* Octet after last octet */
142 * Octet string (not null terminated)
150 static void asn1_open(struct asn1_ctx *ctx,
155 ctx->end = buf + len;
157 ctx->error = ASN1_ERR_NOERROR;
160 static unsigned char asn1_octet_decode(struct asn1_ctx *ctx, unsigned char *ch)
162 if (ctx->pointer >= ctx->end) {
163 ctx->error = ASN1_ERR_DEC_EMPTY;
166 *ch = *(ctx->pointer)++;
170 static unsigned char asn1_tag_decode(struct asn1_ctx *ctx, unsigned int *tag)
178 if (!asn1_octet_decode(ctx, &ch))
182 } while ((ch & 0x80) == 0x80);
186 static unsigned char asn1_id_decode(struct asn1_ctx *ctx,
193 if (!asn1_octet_decode(ctx, &ch))
196 *cls = (ch & 0xC0) >> 6;
197 *con = (ch & 0x20) >> 5;
201 if (!asn1_tag_decode(ctx, tag))
207 static unsigned char asn1_length_decode(struct asn1_ctx *ctx,
211 unsigned char ch, cnt;
213 if (!asn1_octet_decode(ctx, &ch))
228 if (!asn1_octet_decode(ctx, &ch))
237 /* don't trust len bigger than ctx buffer */
238 if (*len > ctx->end - ctx->pointer)
244 static unsigned char asn1_header_decode(struct asn1_ctx *ctx,
250 unsigned int def, len;
252 if (!asn1_id_decode(ctx, cls, con, tag))
256 if (!asn1_length_decode(ctx, &def, &len))
259 /* primitive shall be definite, indefinite shall be constructed */
260 if (*con == ASN1_PRI && !def)
264 *eoc = ctx->pointer + len;
270 static unsigned char asn1_eoc_decode(struct asn1_ctx *ctx, unsigned char *eoc)
275 if (!asn1_octet_decode(ctx, &ch))
279 ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
283 if (!asn1_octet_decode(ctx, &ch))
287 ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
292 if (ctx->pointer != eoc) {
293 ctx->error = ASN1_ERR_DEC_LENGTH_MISMATCH;
300 static unsigned char asn1_null_decode(struct asn1_ctx *ctx, unsigned char *eoc)
306 static unsigned char asn1_long_decode(struct asn1_ctx *ctx,
313 if (!asn1_octet_decode(ctx, &ch))
316 *integer = (signed char) ch;
319 while (ctx->pointer < eoc) {
320 if (++len > sizeof (long)) {
321 ctx->error = ASN1_ERR_DEC_BADVALUE;
325 if (!asn1_octet_decode(ctx, &ch))
334 static unsigned char asn1_uint_decode(struct asn1_ctx *ctx,
336 unsigned int *integer)
341 if (!asn1_octet_decode(ctx, &ch))
345 if (ch == 0) len = 0;
348 while (ctx->pointer < eoc) {
349 if (++len > sizeof (unsigned int)) {
350 ctx->error = ASN1_ERR_DEC_BADVALUE;
354 if (!asn1_octet_decode(ctx, &ch))
363 static unsigned char asn1_ulong_decode(struct asn1_ctx *ctx,
365 unsigned long *integer)
370 if (!asn1_octet_decode(ctx, &ch))
374 if (ch == 0) len = 0;
377 while (ctx->pointer < eoc) {
378 if (++len > sizeof (unsigned long)) {
379 ctx->error = ASN1_ERR_DEC_BADVALUE;
383 if (!asn1_octet_decode(ctx, &ch))
392 static unsigned char asn1_octets_decode(struct asn1_ctx *ctx,
394 unsigned char **octets,
401 *octets = kmalloc(eoc - ctx->pointer, GFP_ATOMIC);
402 if (*octets == NULL) {
404 pr_notice("OOM in bsalg (%d)\n", __LINE__);
409 while (ctx->pointer < eoc) {
410 if (!asn1_octet_decode(ctx, (unsigned char *)ptr++)) {
420 static unsigned char asn1_subid_decode(struct asn1_ctx *ctx,
421 unsigned long *subid)
428 if (!asn1_octet_decode(ctx, &ch))
433 } while ((ch & 0x80) == 0x80);
437 static unsigned char asn1_oid_decode(struct asn1_ctx *ctx,
446 size = eoc - ctx->pointer + 1;
448 /* first subid actually encodes first two subids */
449 if (size < 2 || size > ULONG_MAX/sizeof(unsigned long))
452 *oid = kmalloc(size * sizeof(unsigned long), GFP_ATOMIC);
455 pr_notice("OOM in bsalg (%d)\n", __LINE__);
461 if (!asn1_subid_decode(ctx, &subid)) {
470 } else if (subid < 80) {
472 optr [1] = subid - 40;
475 optr [1] = subid - 80;
481 while (ctx->pointer < eoc) {
482 if (++(*len) > size) {
483 ctx->error = ASN1_ERR_DEC_BADVALUE;
489 if (!asn1_subid_decode(ctx, optr++)) {
498 /*****************************************************************************
500 * SNMP decoding routines (gxsnmp author Dirk Wisse)
502 *****************************************************************************/
511 #define SNMP_SIZE_COMM 256
512 #define SNMP_SIZE_OBJECTID 128
513 #define SNMP_SIZE_BUFCHR 256
514 #define SNMP_SIZE_BUFINT 128
515 #define SNMP_SIZE_SMALLOBJECTID 16
518 #define SNMP_PDU_GET 0
519 #define SNMP_PDU_NEXT 1
520 #define SNMP_PDU_RESPONSE 2
521 #define SNMP_PDU_SET 3
522 #define SNMP_PDU_TRAP1 4
523 #define SNMP_PDU_BULK 5
524 #define SNMP_PDU_INFORM 6
525 #define SNMP_PDU_TRAP2 7
528 #define SNMP_NOERROR 0
529 #define SNMP_TOOBIG 1
530 #define SNMP_NOSUCHNAME 2
531 #define SNMP_BADVALUE 3
532 #define SNMP_READONLY 4
533 #define SNMP_GENERROR 5
534 #define SNMP_NOACCESS 6
535 #define SNMP_WRONGTYPE 7
536 #define SNMP_WRONGLENGTH 8
537 #define SNMP_WRONGENCODING 9
538 #define SNMP_WRONGVALUE 10
539 #define SNMP_NOCREATION 11
540 #define SNMP_INCONSISTENTVALUE 12
541 #define SNMP_RESOURCEUNAVAILABLE 13
542 #define SNMP_COMMITFAILED 14
543 #define SNMP_UNDOFAILED 15
544 #define SNMP_AUTHORIZATIONERROR 16
545 #define SNMP_NOTWRITABLE 17
546 #define SNMP_INCONSISTENTNAME 18
548 /* General SNMP V1 Traps */
549 #define SNMP_TRAP_COLDSTART 0
550 #define SNMP_TRAP_WARMSTART 1
551 #define SNMP_TRAP_LINKDOWN 2
552 #define SNMP_TRAP_LINKUP 3
553 #define SNMP_TRAP_AUTFAILURE 4
554 #define SNMP_TRAP_EQPNEIGHBORLOSS 5
555 #define SNMP_TRAP_ENTSPECIFIC 6
559 #define SNMP_INTEGER 1 /* l */
560 #define SNMP_OCTETSTR 2 /* c */
561 #define SNMP_DISPLAYSTR 2 /* c */
562 #define SNMP_OBJECTID 3 /* ul */
563 #define SNMP_IPADDR 4 /* uc */
564 #define SNMP_COUNTER 5 /* ul */
565 #define SNMP_GAUGE 6 /* ul */
566 #define SNMP_TIMETICKS 7 /* ul */
567 #define SNMP_OPAQUE 8 /* c */
569 /* Additional SNMPv2 Types */
570 #define SNMP_UINTEGER 5 /* ul */
571 #define SNMP_BITSTR 9 /* uc */
572 #define SNMP_NSAP 10 /* uc */
573 #define SNMP_COUNTER64 11 /* ul */
574 #define SNMP_NOSUCHOBJECT 12
575 #define SNMP_NOSUCHINSTANCE 13
576 #define SNMP_ENDOFMIBVIEW 14
580 unsigned char uc[0]; /* 8 bit unsigned */
581 char c[0]; /* 8 bit signed */
582 unsigned long ul[0]; /* 32 bit unsigned */
583 long l[0]; /* 32 bit signed */
591 unsigned int syntax_len;
592 union snmp_syntax syntax;
598 unsigned int error_status;
599 unsigned int error_index;
606 unsigned long ip_address; /* pointer */
607 unsigned int general;
608 unsigned int specific;
625 static inline void mangle_address(unsigned char *begin,
627 const struct oct1_map *map,
636 static const struct snmp_cnv snmp_conv[] = {
637 {ASN1_UNI, ASN1_NUL, SNMP_NULL},
638 {ASN1_UNI, ASN1_INT, SNMP_INTEGER},
639 {ASN1_UNI, ASN1_OTS, SNMP_OCTETSTR},
640 {ASN1_UNI, ASN1_OTS, SNMP_DISPLAYSTR},
641 {ASN1_UNI, ASN1_OJI, SNMP_OBJECTID},
642 {ASN1_APL, SNMP_IPA, SNMP_IPADDR},
643 {ASN1_APL, SNMP_CNT, SNMP_COUNTER}, /* Counter32 */
644 {ASN1_APL, SNMP_GGE, SNMP_GAUGE}, /* Gauge32 == Unsigned32 */
645 {ASN1_APL, SNMP_TIT, SNMP_TIMETICKS},
646 {ASN1_APL, SNMP_OPQ, SNMP_OPAQUE},
648 /* SNMPv2 data types and errors */
649 {ASN1_UNI, ASN1_BTS, SNMP_BITSTR},
650 {ASN1_APL, SNMP_C64, SNMP_COUNTER64},
651 {ASN1_CTX, SERR_NSO, SNMP_NOSUCHOBJECT},
652 {ASN1_CTX, SERR_NSI, SNMP_NOSUCHINSTANCE},
653 {ASN1_CTX, SERR_EOM, SNMP_ENDOFMIBVIEW},
657 static unsigned char snmp_tag_cls2syntax(unsigned int tag,
659 unsigned short *syntax)
661 const struct snmp_cnv *cnv;
665 while (cnv->syntax != -1) {
666 if (cnv->tag == tag && cnv->class == cls) {
667 *syntax = cnv->syntax;
675 static unsigned char snmp_object_decode(struct asn1_ctx *ctx,
676 struct snmp_object **obj)
678 unsigned int cls, con, tag, len, idlen;
680 unsigned char *eoc, *end, *p;
681 unsigned long *lp, *id;
688 if (!asn1_header_decode(ctx, &eoc, &cls, &con, &tag))
691 if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
694 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
697 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
700 if (!asn1_oid_decode(ctx, end, &id, &idlen))
703 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag)) {
708 if (con != ASN1_PRI) {
714 if (!snmp_tag_cls2syntax(tag, cls, &type)) {
723 if (!asn1_long_decode(ctx, end, &l)) {
727 *obj = kmalloc(sizeof(struct snmp_object) + len,
732 pr_notice("OOM in bsalg (%d)\n", __LINE__);
735 (*obj)->syntax.l[0] = l;
739 if (!asn1_octets_decode(ctx, end, &p, &len)) {
743 *obj = kmalloc(sizeof(struct snmp_object) + len,
749 pr_notice("OOM in bsalg (%d)\n", __LINE__);
752 memcpy((*obj)->syntax.c, p, len);
756 case SNMP_NOSUCHOBJECT:
757 case SNMP_NOSUCHINSTANCE:
758 case SNMP_ENDOFMIBVIEW:
760 *obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
764 pr_notice("OOM in bsalg (%d)\n", __LINE__);
767 if (!asn1_null_decode(ctx, end)) {
775 if (!asn1_oid_decode(ctx, end, (unsigned long **)&lp, &len)) {
779 len *= sizeof(unsigned long);
780 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
785 pr_notice("OOM in bsalg (%d)\n", __LINE__);
788 memcpy((*obj)->syntax.ul, lp, len);
792 if (!asn1_octets_decode(ctx, end, &p, &len)) {
801 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
806 pr_notice("OOM in bsalg (%d)\n", __LINE__);
809 memcpy((*obj)->syntax.uc, p, len);
815 len = sizeof(unsigned long);
816 if (!asn1_ulong_decode(ctx, end, &ul)) {
820 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
824 pr_notice("OOM in bsalg (%d)\n", __LINE__);
827 (*obj)->syntax.ul[0] = ul;
834 (*obj)->syntax_len = len;
837 (*obj)->id_len = idlen;
839 if (!asn1_eoc_decode(ctx, eoc)) {
848 static unsigned char snmp_request_decode(struct asn1_ctx *ctx,
849 struct snmp_request *request)
851 unsigned int cls, con, tag;
854 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
857 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
860 if (!asn1_ulong_decode(ctx, end, &request->id))
863 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
866 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
869 if (!asn1_uint_decode(ctx, end, &request->error_status))
872 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
875 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
878 if (!asn1_uint_decode(ctx, end, &request->error_index))
885 * Fast checksum update for possibly oddly-aligned UDP byte, from the
886 * code example in the draft.
888 static void fast_csum(__sum16 *csum,
889 const unsigned char *optr,
890 const unsigned char *nptr,
905 *csum = csum_fold(csum_partial(s, 4, ~csum_unfold(*csum)));
910 * - begin points to the start of the snmp messgae
911 * - addr points to the start of the address
913 static inline void mangle_address(unsigned char *begin,
915 const struct oct1_map *map,
918 if (map->from == NOCT1(addr)) {
922 memcpy(&old, addr, sizeof(old));
926 /* Update UDP checksum if being used */
929 &map->from, &map->to, addr - begin);
934 printk(KERN_DEBUG "bsalg: mapped %pI4 to %pI4\n",
939 static unsigned char snmp_trap_decode(struct asn1_ctx *ctx,
940 struct snmp_v1_trap *trap,
941 const struct oct1_map *map,
944 unsigned int cls, con, tag, len;
947 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
950 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
953 if (!asn1_oid_decode(ctx, end, &trap->id, &trap->id_len))
956 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
959 if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_IPA) ||
960 (cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_OTS)))
963 if (!asn1_octets_decode(ctx, end, (unsigned char **)&trap->ip_address, &len))
970 mangle_address(ctx->begin, ctx->pointer - 4, map, check);
972 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
975 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
978 if (!asn1_uint_decode(ctx, end, &trap->general))
981 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
984 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
987 if (!asn1_uint_decode(ctx, end, &trap->specific))
990 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
993 if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_TIT) ||
994 (cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_INT)))
997 if (!asn1_ulong_decode(ctx, end, &trap->time))
1003 kfree((unsigned long *)trap->ip_address);
1011 /*****************************************************************************
1015 *****************************************************************************/
1017 static void hex_dump(const unsigned char *buf, size_t len)
1021 for (i = 0; i < len; i++) {
1024 printk("%02x ", *(buf + i));
1030 * Parse and mangle SNMP message according to mapping.
1031 * (And this is the fucking 'basic' method).
1033 static int snmp_parse_mangle(unsigned char *msg,
1035 const struct oct1_map *map,
1038 unsigned char *eoc, *end;
1039 unsigned int cls, con, tag, vers, pdutype;
1040 struct asn1_ctx ctx;
1041 struct asn1_octstr comm;
1042 struct snmp_object *obj;
1047 asn1_open(&ctx, msg, len);
1050 * Start of SNMP message.
1052 if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
1054 if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
1058 * Version 1 or 2 handled.
1060 if (!asn1_header_decode(&ctx, &end, &cls, &con, &tag))
1062 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
1064 if (!asn1_uint_decode (&ctx, end, &vers))
1067 printk(KERN_DEBUG "bsalg: snmp version: %u\n", vers + 1);
1074 if (!asn1_header_decode (&ctx, &end, &cls, &con, &tag))
1076 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OTS)
1078 if (!asn1_octets_decode(&ctx, end, &comm.data, &comm.len))
1083 printk(KERN_DEBUG "bsalg: community: ");
1084 for (i = 0; i < comm.len; i++)
1085 printk("%c", comm.data[i]);
1093 if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &pdutype))
1095 if (cls != ASN1_CTX || con != ASN1_CON)
1098 static const unsigned char *const pdus[] = {
1099 [SNMP_PDU_GET] = "get",
1100 [SNMP_PDU_NEXT] = "get-next",
1101 [SNMP_PDU_RESPONSE] = "response",
1102 [SNMP_PDU_SET] = "set",
1103 [SNMP_PDU_TRAP1] = "trapv1",
1104 [SNMP_PDU_BULK] = "bulk",
1105 [SNMP_PDU_INFORM] = "inform",
1106 [SNMP_PDU_TRAP2] = "trapv2"
1109 if (pdutype > SNMP_PDU_TRAP2)
1110 printk(KERN_DEBUG "bsalg: bad pdu type %u\n", pdutype);
1112 printk(KERN_DEBUG "bsalg: pdu: %s\n", pdus[pdutype]);
1114 if (pdutype != SNMP_PDU_RESPONSE &&
1115 pdutype != SNMP_PDU_TRAP1 && pdutype != SNMP_PDU_TRAP2)
1119 * Request header or v1 trap
1121 if (pdutype == SNMP_PDU_TRAP1) {
1122 struct snmp_v1_trap trap;
1123 unsigned char ret = snmp_trap_decode(&ctx, &trap, map, check);
1127 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 while (!asn1_eoc_decode(&ctx, eoc)) {
1155 if (!snmp_object_decode(&ctx, &obj)) {
1164 printk(KERN_DEBUG "bsalg: object: ");
1165 for (i = 0; i < obj->id_len; i++) {
1168 printk("%lu", obj->id[i]);
1170 printk(": type=%u\n", obj->type);
1174 if (obj->type == SNMP_IPADDR)
1175 mangle_address(ctx.begin, ctx.pointer - 4 , map, check);
1181 if (!asn1_eoc_decode(&ctx, eoc))
1187 /*****************************************************************************
1191 *****************************************************************************/
1194 * SNMP translation routine.
1196 static int snmp_translate(struct nf_conn *ct,
1197 enum ip_conntrack_info ctinfo,
1198 struct sk_buff *skb)
1200 struct iphdr *iph = ip_hdr(skb);
1201 struct udphdr *udph = (struct udphdr *)((__be32 *)iph + iph->ihl);
1202 u_int16_t udplen = ntohs(udph->len);
1203 u_int16_t paylen = udplen - sizeof(struct udphdr);
1204 int dir = CTINFO2DIR(ctinfo);
1205 struct oct1_map map;
1208 * Determine mappping for application layer addresses based
1209 * on NAT manipulations for the packet.
1211 if (dir == IP_CT_DIR_ORIGINAL) {
1213 map.from = NOCT1(&ct->tuplehash[dir].tuple.src.u3.ip);
1214 map.to = NOCT1(&ct->tuplehash[!dir].tuple.dst.u3.ip);
1217 map.from = NOCT1(&ct->tuplehash[dir].tuple.src.u3.ip);
1218 map.to = NOCT1(&ct->tuplehash[!dir].tuple.dst.u3.ip);
1221 if (map.from == map.to)
1224 if (!snmp_parse_mangle((unsigned char *)udph + sizeof(struct udphdr),
1225 paylen, &map, &udph->check)) {
1226 if (net_ratelimit())
1227 printk(KERN_WARNING "bsalg: parser failed\n");
1233 /* We don't actually set up expectations, just adjust internal IP
1234 * addresses if this is being NATted */
1235 static int help(struct sk_buff *skb, unsigned int protoff,
1237 enum ip_conntrack_info ctinfo)
1239 int dir = CTINFO2DIR(ctinfo);
1241 const struct iphdr *iph = ip_hdr(skb);
1242 const struct udphdr *udph = (struct udphdr *)((__be32 *)iph + iph->ihl);
1244 /* SNMP replies and originating SNMP traps get mangled */
1245 if (udph->source == htons(SNMP_PORT) && dir != IP_CT_DIR_REPLY)
1247 if (udph->dest == htons(SNMP_TRAP_PORT) && dir != IP_CT_DIR_ORIGINAL)
1251 if (!(ct->status & IPS_NAT_MASK))
1255 * Make sure the packet length is ok. So far, we were only guaranteed
1256 * to have a valid length IP header plus 8 bytes, which means we have
1257 * enough room for a UDP header. Just verify the UDP length field so we
1258 * can mess around with the payload.
1260 if (ntohs(udph->len) != skb->len - (iph->ihl << 2)) {
1261 if (net_ratelimit())
1262 printk(KERN_WARNING "SNMP: dropping malformed packet src=%pI4 dst=%pI4\n",
1263 &iph->saddr, &iph->daddr);
1267 if (!skb_make_writable(skb, skb->len))
1270 spin_lock_bh(&snmp_lock);
1271 ret = snmp_translate(ct, ctinfo, skb);
1272 spin_unlock_bh(&snmp_lock);
1276 static const struct nf_conntrack_expect_policy snmp_exp_policy = {
1281 static struct nf_conntrack_helper snmp_helper __read_mostly = {
1284 .expect_policy = &snmp_exp_policy,
1286 .tuple.src.l3num = AF_INET,
1287 .tuple.src.u.udp.port = cpu_to_be16(SNMP_PORT),
1288 .tuple.dst.protonum = IPPROTO_UDP,
1291 static struct nf_conntrack_helper snmp_trap_helper __read_mostly = {
1294 .expect_policy = &snmp_exp_policy,
1295 .name = "snmp_trap",
1296 .tuple.src.l3num = AF_INET,
1297 .tuple.src.u.udp.port = cpu_to_be16(SNMP_TRAP_PORT),
1298 .tuple.dst.protonum = IPPROTO_UDP,
1301 /*****************************************************************************
1305 *****************************************************************************/
1307 static int __init nf_nat_snmp_basic_init(void)
1311 ret = nf_conntrack_helper_register(&snmp_helper);
1314 ret = nf_conntrack_helper_register(&snmp_trap_helper);
1316 nf_conntrack_helper_unregister(&snmp_helper);
1322 static void __exit nf_nat_snmp_basic_fini(void)
1324 nf_conntrack_helper_unregister(&snmp_helper);
1325 nf_conntrack_helper_unregister(&snmp_trap_helper);
1328 module_init(nf_nat_snmp_basic_init);
1329 module_exit(nf_nat_snmp_basic_fini);
1331 module_param(debug, int, 0600);