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>
48 #include <linux/module.h>
49 #include <linux/types.h>
50 #include <linux/kernel.h>
51 #include <linux/moduleparam.h>
52 #include <linux/netfilter_ipv4.h>
53 #include <linux/netfilter_ipv4/ip_nat.h>
54 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
55 #include <linux/netfilter_ipv4/ip_nat_helper.h>
57 #include <linux/udp.h>
58 #include <net/checksum.h>
60 #include <asm/uaccess.h>
62 MODULE_LICENSE("GPL");
63 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
64 MODULE_DESCRIPTION("Basic SNMP Application Layer Gateway");
67 #define SNMP_TRAP_PORT 162
68 #define NOCT1(n) (u_int8_t )((n) & 0xff)
71 static DEFINE_SPINLOCK(snmp_lock);
74 * Application layer address mapping mimics the NAT mapping, but
75 * only for the first octet in this case (a more flexible system
76 * can be implemented if needed).
85 /*****************************************************************************
87 * Basic ASN.1 decoding routines (gxsnmp author Dirk Wisse)
89 *****************************************************************************/
92 #define ASN1_UNI 0 /* Universal */
93 #define ASN1_APL 1 /* Application */
94 #define ASN1_CTX 2 /* Context */
95 #define ASN1_PRV 3 /* Private */
98 #define ASN1_EOC 0 /* End Of Contents */
99 #define ASN1_BOL 1 /* Boolean */
100 #define ASN1_INT 2 /* Integer */
101 #define ASN1_BTS 3 /* Bit String */
102 #define ASN1_OTS 4 /* Octet String */
103 #define ASN1_NUL 5 /* Null */
104 #define ASN1_OJI 6 /* Object Identifier */
105 #define ASN1_OJD 7 /* Object Description */
106 #define ASN1_EXT 8 /* External */
107 #define ASN1_SEQ 16 /* Sequence */
108 #define ASN1_SET 17 /* Set */
109 #define ASN1_NUMSTR 18 /* Numerical String */
110 #define ASN1_PRNSTR 19 /* Printable String */
111 #define ASN1_TEXSTR 20 /* Teletext String */
112 #define ASN1_VIDSTR 21 /* Video String */
113 #define ASN1_IA5STR 22 /* IA5 String */
114 #define ASN1_UNITIM 23 /* Universal Time */
115 #define ASN1_GENTIM 24 /* General Time */
116 #define ASN1_GRASTR 25 /* Graphical String */
117 #define ASN1_VISSTR 26 /* Visible String */
118 #define ASN1_GENSTR 27 /* General String */
120 /* Primitive / Constructed methods*/
121 #define ASN1_PRI 0 /* Primitive */
122 #define ASN1_CON 1 /* Constructed */
127 #define ASN1_ERR_NOERROR 0
128 #define ASN1_ERR_DEC_EMPTY 2
129 #define ASN1_ERR_DEC_EOC_MISMATCH 3
130 #define ASN1_ERR_DEC_LENGTH_MISMATCH 4
131 #define ASN1_ERR_DEC_BADVALUE 5
138 int error; /* Error condition */
139 unsigned char *pointer; /* Octet just to be decoded */
140 unsigned char *begin; /* First octet */
141 unsigned char *end; /* Octet after last octet */
145 * Octet string (not null terminated)
153 static void asn1_open(struct asn1_ctx *ctx,
158 ctx->end = buf + len;
160 ctx->error = ASN1_ERR_NOERROR;
163 static unsigned char asn1_octet_decode(struct asn1_ctx *ctx, unsigned char *ch)
165 if (ctx->pointer >= ctx->end) {
166 ctx->error = ASN1_ERR_DEC_EMPTY;
169 *ch = *(ctx->pointer)++;
173 static unsigned char asn1_tag_decode(struct asn1_ctx *ctx, unsigned int *tag)
181 if (!asn1_octet_decode(ctx, &ch))
185 } while ((ch & 0x80) == 0x80);
189 static unsigned char asn1_id_decode(struct asn1_ctx *ctx,
196 if (!asn1_octet_decode(ctx, &ch))
199 *cls = (ch & 0xC0) >> 6;
200 *con = (ch & 0x20) >> 5;
204 if (!asn1_tag_decode(ctx, tag))
210 static unsigned char asn1_length_decode(struct asn1_ctx *ctx,
214 unsigned char ch, cnt;
216 if (!asn1_octet_decode(ctx, &ch))
227 cnt = (unsigned char) (ch & 0x7F);
231 if (!asn1_octet_decode(ctx, &ch))
242 static unsigned char asn1_header_decode(struct asn1_ctx *ctx,
248 unsigned int def, len;
250 if (!asn1_id_decode(ctx, cls, con, tag))
254 if (!asn1_length_decode(ctx, &def, &len))
258 *eoc = ctx->pointer + len;
264 static unsigned char asn1_eoc_decode(struct asn1_ctx *ctx, unsigned char *eoc)
269 if (!asn1_octet_decode(ctx, &ch))
273 ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
277 if (!asn1_octet_decode(ctx, &ch))
281 ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
286 if (ctx->pointer != eoc) {
287 ctx->error = ASN1_ERR_DEC_LENGTH_MISMATCH;
294 static unsigned char asn1_null_decode(struct asn1_ctx *ctx, unsigned char *eoc)
300 static unsigned char asn1_long_decode(struct asn1_ctx *ctx,
307 if (!asn1_octet_decode(ctx, &ch))
310 *integer = (signed char) ch;
313 while (ctx->pointer < eoc) {
314 if (++len > sizeof (long)) {
315 ctx->error = ASN1_ERR_DEC_BADVALUE;
319 if (!asn1_octet_decode(ctx, &ch))
328 static unsigned char asn1_uint_decode(struct asn1_ctx *ctx,
330 unsigned int *integer)
335 if (!asn1_octet_decode(ctx, &ch))
339 if (ch == 0) len = 0;
342 while (ctx->pointer < eoc) {
343 if (++len > sizeof (unsigned int)) {
344 ctx->error = ASN1_ERR_DEC_BADVALUE;
348 if (!asn1_octet_decode(ctx, &ch))
357 static unsigned char asn1_ulong_decode(struct asn1_ctx *ctx,
359 unsigned long *integer)
364 if (!asn1_octet_decode(ctx, &ch))
368 if (ch == 0) len = 0;
371 while (ctx->pointer < eoc) {
372 if (++len > sizeof (unsigned long)) {
373 ctx->error = ASN1_ERR_DEC_BADVALUE;
377 if (!asn1_octet_decode(ctx, &ch))
386 static unsigned char asn1_octets_decode(struct asn1_ctx *ctx,
388 unsigned char **octets,
395 *octets = kmalloc(eoc - ctx->pointer, GFP_ATOMIC);
396 if (*octets == NULL) {
398 printk("OOM in bsalg (%d)\n", __LINE__);
403 while (ctx->pointer < eoc) {
404 if (!asn1_octet_decode(ctx, (unsigned char *)ptr++)) {
414 static unsigned char asn1_subid_decode(struct asn1_ctx *ctx,
415 unsigned long *subid)
422 if (!asn1_octet_decode(ctx, &ch))
427 } while ((ch & 0x80) == 0x80);
431 static unsigned char asn1_oid_decode(struct asn1_ctx *ctx,
440 size = eoc - ctx->pointer + 1;
441 *oid = kmalloc(size * sizeof(unsigned long), GFP_ATOMIC);
444 printk("OOM in bsalg (%d)\n", __LINE__);
450 if (!asn1_subid_decode(ctx, &subid)) {
459 } else if (subid < 80) {
461 optr [1] = subid - 40;
464 optr [1] = subid - 80;
470 while (ctx->pointer < eoc) {
471 if (++(*len) > size) {
472 ctx->error = ASN1_ERR_DEC_BADVALUE;
478 if (!asn1_subid_decode(ctx, optr++)) {
487 /*****************************************************************************
489 * SNMP decoding routines (gxsnmp author Dirk Wisse)
491 *****************************************************************************/
500 #define SNMP_SIZE_COMM 256
501 #define SNMP_SIZE_OBJECTID 128
502 #define SNMP_SIZE_BUFCHR 256
503 #define SNMP_SIZE_BUFINT 128
504 #define SNMP_SIZE_SMALLOBJECTID 16
507 #define SNMP_PDU_GET 0
508 #define SNMP_PDU_NEXT 1
509 #define SNMP_PDU_RESPONSE 2
510 #define SNMP_PDU_SET 3
511 #define SNMP_PDU_TRAP1 4
512 #define SNMP_PDU_BULK 5
513 #define SNMP_PDU_INFORM 6
514 #define SNMP_PDU_TRAP2 7
517 #define SNMP_NOERROR 0
518 #define SNMP_TOOBIG 1
519 #define SNMP_NOSUCHNAME 2
520 #define SNMP_BADVALUE 3
521 #define SNMP_READONLY 4
522 #define SNMP_GENERROR 5
523 #define SNMP_NOACCESS 6
524 #define SNMP_WRONGTYPE 7
525 #define SNMP_WRONGLENGTH 8
526 #define SNMP_WRONGENCODING 9
527 #define SNMP_WRONGVALUE 10
528 #define SNMP_NOCREATION 11
529 #define SNMP_INCONSISTENTVALUE 12
530 #define SNMP_RESOURCEUNAVAILABLE 13
531 #define SNMP_COMMITFAILED 14
532 #define SNMP_UNDOFAILED 15
533 #define SNMP_AUTHORIZATIONERROR 16
534 #define SNMP_NOTWRITABLE 17
535 #define SNMP_INCONSISTENTNAME 18
537 /* General SNMP V1 Traps */
538 #define SNMP_TRAP_COLDSTART 0
539 #define SNMP_TRAP_WARMSTART 1
540 #define SNMP_TRAP_LINKDOWN 2
541 #define SNMP_TRAP_LINKUP 3
542 #define SNMP_TRAP_AUTFAILURE 4
543 #define SNMP_TRAP_EQPNEIGHBORLOSS 5
544 #define SNMP_TRAP_ENTSPECIFIC 6
548 #define SNMP_INTEGER 1 /* l */
549 #define SNMP_OCTETSTR 2 /* c */
550 #define SNMP_DISPLAYSTR 2 /* c */
551 #define SNMP_OBJECTID 3 /* ul */
552 #define SNMP_IPADDR 4 /* uc */
553 #define SNMP_COUNTER 5 /* ul */
554 #define SNMP_GAUGE 6 /* ul */
555 #define SNMP_TIMETICKS 7 /* ul */
556 #define SNMP_OPAQUE 8 /* c */
558 /* Additional SNMPv2 Types */
559 #define SNMP_UINTEGER 5 /* ul */
560 #define SNMP_BITSTR 9 /* uc */
561 #define SNMP_NSAP 10 /* uc */
562 #define SNMP_COUNTER64 11 /* ul */
563 #define SNMP_NOSUCHOBJECT 12
564 #define SNMP_NOSUCHINSTANCE 13
565 #define SNMP_ENDOFMIBVIEW 14
569 unsigned char uc[0]; /* 8 bit unsigned */
570 char c[0]; /* 8 bit signed */
571 unsigned long ul[0]; /* 32 bit unsigned */
572 long l[0]; /* 32 bit signed */
580 unsigned int syntax_len;
581 union snmp_syntax syntax;
587 unsigned int error_status;
588 unsigned int error_index;
595 unsigned long ip_address; /* pointer */
596 unsigned int general;
597 unsigned int specific;
614 static inline void mangle_address(unsigned char *begin,
616 const struct oct1_map *map,
625 static struct snmp_cnv snmp_conv [] =
627 {ASN1_UNI, ASN1_NUL, SNMP_NULL},
628 {ASN1_UNI, ASN1_INT, SNMP_INTEGER},
629 {ASN1_UNI, ASN1_OTS, SNMP_OCTETSTR},
630 {ASN1_UNI, ASN1_OTS, SNMP_DISPLAYSTR},
631 {ASN1_UNI, ASN1_OJI, SNMP_OBJECTID},
632 {ASN1_APL, SNMP_IPA, SNMP_IPADDR},
633 {ASN1_APL, SNMP_CNT, SNMP_COUNTER}, /* Counter32 */
634 {ASN1_APL, SNMP_GGE, SNMP_GAUGE}, /* Gauge32 == Unsigned32 */
635 {ASN1_APL, SNMP_TIT, SNMP_TIMETICKS},
636 {ASN1_APL, SNMP_OPQ, SNMP_OPAQUE},
638 /* SNMPv2 data types and errors */
639 {ASN1_UNI, ASN1_BTS, SNMP_BITSTR},
640 {ASN1_APL, SNMP_C64, SNMP_COUNTER64},
641 {ASN1_CTX, SERR_NSO, SNMP_NOSUCHOBJECT},
642 {ASN1_CTX, SERR_NSI, SNMP_NOSUCHINSTANCE},
643 {ASN1_CTX, SERR_EOM, SNMP_ENDOFMIBVIEW},
647 static unsigned char snmp_tag_cls2syntax(unsigned int tag,
649 unsigned short *syntax)
651 struct snmp_cnv *cnv;
655 while (cnv->syntax != -1) {
656 if (cnv->tag == tag && cnv->class == cls) {
657 *syntax = cnv->syntax;
665 static unsigned char snmp_object_decode(struct asn1_ctx *ctx,
666 struct snmp_object **obj)
668 unsigned int cls, con, tag, len, idlen;
670 unsigned char *eoc, *end, *p;
671 unsigned long *lp, *id;
678 if (!asn1_header_decode(ctx, &eoc, &cls, &con, &tag))
681 if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
684 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
687 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
690 if (!asn1_oid_decode(ctx, end, &id, &idlen))
693 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag)) {
698 if (con != ASN1_PRI) {
704 if (!snmp_tag_cls2syntax(tag, cls, &type)) {
713 if (!asn1_long_decode(ctx, end, &l)) {
717 *obj = kmalloc(sizeof(struct snmp_object) + len,
722 printk("OOM in bsalg (%d)\n", __LINE__);
725 (*obj)->syntax.l[0] = l;
729 if (!asn1_octets_decode(ctx, end, &p, &len)) {
733 *obj = kmalloc(sizeof(struct snmp_object) + len,
738 printk("OOM in bsalg (%d)\n", __LINE__);
741 memcpy((*obj)->syntax.c, p, len);
745 case SNMP_NOSUCHOBJECT:
746 case SNMP_NOSUCHINSTANCE:
747 case SNMP_ENDOFMIBVIEW:
749 *obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
753 printk("OOM in bsalg (%d)\n", __LINE__);
756 if (!asn1_null_decode(ctx, end)) {
764 if (!asn1_oid_decode(ctx, end, (unsigned long **)&lp, &len)) {
768 len *= sizeof(unsigned long);
769 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
774 printk("OOM in bsalg (%d)\n", __LINE__);
777 memcpy((*obj)->syntax.ul, lp, len);
781 if (!asn1_octets_decode(ctx, end, &p, &len)) {
790 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
795 printk("OOM in bsalg (%d)\n", __LINE__);
798 memcpy((*obj)->syntax.uc, p, len);
804 len = sizeof(unsigned long);
805 if (!asn1_ulong_decode(ctx, end, &ul)) {
809 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
813 printk("OOM in bsalg (%d)\n", __LINE__);
816 (*obj)->syntax.ul[0] = ul;
823 (*obj)->syntax_len = len;
826 (*obj)->id_len = idlen;
828 if (!asn1_eoc_decode(ctx, eoc)) {
837 static unsigned char snmp_request_decode(struct asn1_ctx *ctx,
838 struct snmp_request *request)
840 unsigned int cls, con, tag;
843 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
846 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
849 if (!asn1_ulong_decode(ctx, end, &request->id))
852 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
855 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
858 if (!asn1_uint_decode(ctx, end, &request->error_status))
861 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
864 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
867 if (!asn1_uint_decode(ctx, end, &request->error_index))
874 * Fast checksum update for possibly oddly-aligned UDP byte, from the
875 * code example in the draft.
877 static void fast_csum(unsigned char *csum,
878 const unsigned char *optr,
879 const unsigned char *nptr,
884 x = csum[0] * 256 + csum[1];
888 if (odd) old = optr[0] * 256;
897 if (odd) new = nptr[0] * 256;
913 * - begin points to the start of the snmp messgae
914 * - addr points to the start of the address
916 static inline void mangle_address(unsigned char *begin,
918 const struct oct1_map *map,
921 if (map->from == NOCT1(*addr)) {
925 memcpy(&old, (unsigned char *)addr, sizeof(old));
929 /* Update UDP checksum if being used */
931 unsigned char odd = !((addr - begin) % 2);
933 fast_csum((unsigned char *)check,
934 &map->from, &map->to, odd);
939 printk(KERN_DEBUG "bsalg: mapped %u.%u.%u.%u to "
940 "%u.%u.%u.%u\n", NIPQUAD(old), NIPQUAD(*addr));
944 static unsigned char snmp_trap_decode(struct asn1_ctx *ctx,
945 struct snmp_v1_trap *trap,
946 const struct oct1_map *map,
949 unsigned int cls, con, tag, len;
952 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
955 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
958 if (!asn1_oid_decode(ctx, end, &trap->id, &trap->id_len))
961 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
964 if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_IPA) ||
965 (cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_OTS)))
968 if (!asn1_octets_decode(ctx, end, (unsigned char **)&trap->ip_address, &len))
975 mangle_address(ctx->begin, ctx->pointer - 4, map, check);
977 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
980 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
983 if (!asn1_uint_decode(ctx, end, &trap->general))
986 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
989 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
992 if (!asn1_uint_decode(ctx, end, &trap->specific))
995 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
998 if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_TIT) ||
999 (cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_INT)))
1002 if (!asn1_ulong_decode(ctx, end, &trap->time))
1008 kfree((unsigned long *)trap->ip_address);
1016 /*****************************************************************************
1020 *****************************************************************************/
1022 static void hex_dump(unsigned char *buf, size_t len)
1026 for (i = 0; i < len; i++) {
1029 printk("%02x ", *(buf + i));
1035 * Parse and mangle SNMP message according to mapping.
1036 * (And this is the fucking 'basic' method).
1038 static int snmp_parse_mangle(unsigned char *msg,
1040 const struct oct1_map *map,
1043 unsigned char *eoc, *end;
1044 unsigned int cls, con, tag, vers, pdutype;
1045 struct asn1_ctx ctx;
1046 struct asn1_octstr comm;
1047 struct snmp_object **obj;
1052 asn1_open(&ctx, msg, len);
1055 * Start of SNMP message.
1057 if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
1059 if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
1063 * Version 1 or 2 handled.
1065 if (!asn1_header_decode(&ctx, &end, &cls, &con, &tag))
1067 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
1069 if (!asn1_uint_decode (&ctx, end, &vers))
1072 printk(KERN_DEBUG "bsalg: snmp version: %u\n", vers + 1);
1079 if (!asn1_header_decode (&ctx, &end, &cls, &con, &tag))
1081 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OTS)
1083 if (!asn1_octets_decode(&ctx, end, &comm.data, &comm.len))
1088 printk(KERN_DEBUG "bsalg: community: ");
1089 for (i = 0; i < comm.len; i++)
1090 printk("%c", comm.data[i]);
1098 if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &pdutype))
1100 if (cls != ASN1_CTX || con != ASN1_CON)
1103 unsigned char *pdus[] = {
1104 [SNMP_PDU_GET] = "get",
1105 [SNMP_PDU_NEXT] = "get-next",
1106 [SNMP_PDU_RESPONSE] = "response",
1107 [SNMP_PDU_SET] = "set",
1108 [SNMP_PDU_TRAP1] = "trapv1",
1109 [SNMP_PDU_BULK] = "bulk",
1110 [SNMP_PDU_INFORM] = "inform",
1111 [SNMP_PDU_TRAP2] = "trapv2"
1114 if (pdutype > SNMP_PDU_TRAP2)
1115 printk(KERN_DEBUG "bsalg: bad pdu type %u\n", pdutype);
1117 printk(KERN_DEBUG "bsalg: pdu: %s\n", pdus[pdutype]);
1119 if (pdutype != SNMP_PDU_RESPONSE &&
1120 pdutype != SNMP_PDU_TRAP1 && pdutype != SNMP_PDU_TRAP2)
1124 * Request header or v1 trap
1126 if (pdutype == SNMP_PDU_TRAP1) {
1127 struct snmp_v1_trap trap;
1128 unsigned char ret = snmp_trap_decode(&ctx, &trap, map, check);
1132 kfree((unsigned long *)trap.ip_address);
1137 struct snmp_request req;
1139 if (!snmp_request_decode(&ctx, &req))
1143 printk(KERN_DEBUG "bsalg: request: id=0x%lx error_status=%u "
1144 "error_index=%u\n", req.id, req.error_status,
1149 * Loop through objects, look for IP addresses to mangle.
1151 if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
1154 if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
1157 obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
1159 if (net_ratelimit())
1160 printk(KERN_WARNING "OOM in bsalg(%d)\n", __LINE__);
1164 while (!asn1_eoc_decode(&ctx, eoc)) {
1167 if (!snmp_object_decode(&ctx, obj)) {
1177 printk(KERN_DEBUG "bsalg: object: ");
1178 for (i = 0; i < (*obj)->id_len; i++) {
1181 printk("%lu", (*obj)->id[i]);
1183 printk(": type=%u\n", (*obj)->type);
1187 if ((*obj)->type == SNMP_IPADDR)
1188 mangle_address(ctx.begin, ctx.pointer - 4 , map, check);
1195 if (!asn1_eoc_decode(&ctx, eoc))
1201 /*****************************************************************************
1205 *****************************************************************************/
1208 * SNMP translation routine.
1210 static int snmp_translate(struct ip_conntrack *ct,
1211 enum ip_conntrack_info ctinfo,
1212 struct sk_buff **pskb)
1214 struct iphdr *iph = (*pskb)->nh.iph;
1215 struct udphdr *udph = (struct udphdr *)((u_int32_t *)iph + iph->ihl);
1216 u_int16_t udplen = ntohs(udph->len);
1217 u_int16_t paylen = udplen - sizeof(struct udphdr);
1218 int dir = CTINFO2DIR(ctinfo);
1219 struct oct1_map map;
1222 * Determine mappping for application layer addresses based
1223 * on NAT manipulations for the packet.
1225 if (dir == IP_CT_DIR_ORIGINAL) {
1227 map.from = NOCT1(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip);
1228 map.to = NOCT1(ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip);
1231 map.from = NOCT1(ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip);
1232 map.to = NOCT1(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip);
1235 if (map.from == map.to)
1238 if (!snmp_parse_mangle((unsigned char *)udph + sizeof(struct udphdr),
1239 paylen, &map, &udph->check)) {
1240 if (net_ratelimit())
1241 printk(KERN_WARNING "bsalg: parser failed\n");
1247 /* We don't actually set up expectations, just adjust internal IP
1248 * addresses if this is being NATted */
1249 static int help(struct sk_buff **pskb,
1250 struct ip_conntrack *ct,
1251 enum ip_conntrack_info ctinfo)
1253 int dir = CTINFO2DIR(ctinfo);
1255 struct iphdr *iph = (*pskb)->nh.iph;
1256 struct udphdr *udph = (struct udphdr *)((u_int32_t *)iph + iph->ihl);
1258 /* SNMP replies and originating SNMP traps get mangled */
1259 if (udph->source == ntohs(SNMP_PORT) && dir != IP_CT_DIR_REPLY)
1261 if (udph->dest == ntohs(SNMP_TRAP_PORT) && dir != IP_CT_DIR_ORIGINAL)
1265 if (!(ct->status & IPS_NAT_MASK))
1269 * Make sure the packet length is ok. So far, we were only guaranteed
1270 * to have a valid length IP header plus 8 bytes, which means we have
1271 * enough room for a UDP header. Just verify the UDP length field so we
1272 * can mess around with the payload.
1274 if (ntohs(udph->len) != (*pskb)->len - (iph->ihl << 2)) {
1275 if (net_ratelimit())
1276 printk(KERN_WARNING "SNMP: dropping malformed packet "
1277 "src=%u.%u.%u.%u dst=%u.%u.%u.%u\n",
1278 NIPQUAD(iph->saddr), NIPQUAD(iph->daddr));
1282 if (!skb_make_writable(pskb, (*pskb)->len))
1285 spin_lock_bh(&snmp_lock);
1286 ret = snmp_translate(ct, ctinfo, pskb);
1287 spin_unlock_bh(&snmp_lock);
1291 static struct ip_conntrack_helper snmp_helper = {
1298 .tuple = { .src = { .u = { __constant_htons(SNMP_PORT) } },
1299 .dst = { .protonum = IPPROTO_UDP },
1301 .mask = { .src = { .u = { 0xFFFF } },
1302 .dst = { .protonum = 0xFF },
1306 static struct ip_conntrack_helper snmp_trap_helper = {
1311 .name = "snmp_trap",
1313 .tuple = { .src = { .u = { __constant_htons(SNMP_TRAP_PORT) } },
1314 .dst = { .protonum = IPPROTO_UDP },
1316 .mask = { .src = { .u = { 0xFFFF } },
1317 .dst = { .protonum = 0xFF },
1321 /*****************************************************************************
1325 *****************************************************************************/
1327 static int __init ip_nat_snmp_basic_init(void)
1331 ret = ip_conntrack_helper_register(&snmp_helper);
1334 ret = ip_conntrack_helper_register(&snmp_trap_helper);
1336 ip_conntrack_helper_unregister(&snmp_helper);
1342 static void __exit ip_nat_snmp_basic_fini(void)
1344 ip_conntrack_helper_unregister(&snmp_helper);
1345 ip_conntrack_helper_unregister(&snmp_trap_helper);
1348 module_init(ip_nat_snmp_basic_init);
1349 module_exit(ip_nat_snmp_basic_fini);
1351 module_param(debug, bool, 0600);