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 * Copyright (c) 2006-2010 Patrick McHardy <kaber@trash.net>
44 #include <linux/module.h>
45 #include <linux/moduleparam.h>
46 #include <linux/types.h>
47 #include <linux/kernel.h>
48 #include <linux/slab.h>
51 #include <linux/udp.h>
52 #include <net/checksum.h>
55 #include <net/netfilter/nf_nat.h>
56 #include <net/netfilter/nf_conntrack_expect.h>
57 #include <net/netfilter/nf_conntrack_helper.h>
58 #include <net/netfilter/nf_nat_helper.h>
59 #include <linux/netfilter/nf_conntrack_snmp.h>
61 MODULE_LICENSE("GPL");
62 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
63 MODULE_DESCRIPTION("Basic SNMP Application Layer Gateway");
64 MODULE_ALIAS("ip_nat_snmp_basic");
67 #define SNMP_TRAP_PORT 162
68 #define NOCT1(n) (*(u8 *)(n))
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))
231 if (!asn1_octet_decode(ctx, &ch))
240 /* don't trust len bigger than ctx buffer */
241 if (*len > ctx->end - ctx->pointer)
247 static unsigned char asn1_header_decode(struct asn1_ctx *ctx,
253 unsigned int def, len;
255 if (!asn1_id_decode(ctx, cls, con, tag))
259 if (!asn1_length_decode(ctx, &def, &len))
262 /* primitive shall be definite, indefinite shall be constructed */
263 if (*con == ASN1_PRI && !def)
267 *eoc = ctx->pointer + len;
273 static unsigned char asn1_eoc_decode(struct asn1_ctx *ctx, unsigned char *eoc)
278 if (!asn1_octet_decode(ctx, &ch))
282 ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
286 if (!asn1_octet_decode(ctx, &ch))
290 ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
295 if (ctx->pointer != eoc) {
296 ctx->error = ASN1_ERR_DEC_LENGTH_MISMATCH;
303 static unsigned char asn1_null_decode(struct asn1_ctx *ctx, unsigned char *eoc)
309 static unsigned char asn1_long_decode(struct asn1_ctx *ctx,
316 if (!asn1_octet_decode(ctx, &ch))
319 *integer = (signed char) ch;
322 while (ctx->pointer < eoc) {
323 if (++len > sizeof (long)) {
324 ctx->error = ASN1_ERR_DEC_BADVALUE;
328 if (!asn1_octet_decode(ctx, &ch))
337 static unsigned char asn1_uint_decode(struct asn1_ctx *ctx,
339 unsigned int *integer)
344 if (!asn1_octet_decode(ctx, &ch))
348 if (ch == 0) len = 0;
351 while (ctx->pointer < eoc) {
352 if (++len > sizeof (unsigned int)) {
353 ctx->error = ASN1_ERR_DEC_BADVALUE;
357 if (!asn1_octet_decode(ctx, &ch))
366 static unsigned char asn1_ulong_decode(struct asn1_ctx *ctx,
368 unsigned long *integer)
373 if (!asn1_octet_decode(ctx, &ch))
377 if (ch == 0) len = 0;
380 while (ctx->pointer < eoc) {
381 if (++len > sizeof (unsigned long)) {
382 ctx->error = ASN1_ERR_DEC_BADVALUE;
386 if (!asn1_octet_decode(ctx, &ch))
395 static unsigned char asn1_octets_decode(struct asn1_ctx *ctx,
397 unsigned char **octets,
404 *octets = kmalloc(eoc - ctx->pointer, GFP_ATOMIC);
409 while (ctx->pointer < eoc) {
410 if (!asn1_octet_decode(ctx, 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);
458 if (!asn1_subid_decode(ctx, &subid)) {
467 } else if (subid < 80) {
469 optr [1] = subid - 40;
472 optr [1] = subid - 80;
478 while (ctx->pointer < eoc) {
479 if (++(*len) > size) {
480 ctx->error = ASN1_ERR_DEC_BADVALUE;
486 if (!asn1_subid_decode(ctx, optr++)) {
495 /*****************************************************************************
497 * SNMP decoding routines (gxsnmp author Dirk Wisse)
499 *****************************************************************************/
508 #define SNMP_SIZE_COMM 256
509 #define SNMP_SIZE_OBJECTID 128
510 #define SNMP_SIZE_BUFCHR 256
511 #define SNMP_SIZE_BUFINT 128
512 #define SNMP_SIZE_SMALLOBJECTID 16
515 #define SNMP_PDU_GET 0
516 #define SNMP_PDU_NEXT 1
517 #define SNMP_PDU_RESPONSE 2
518 #define SNMP_PDU_SET 3
519 #define SNMP_PDU_TRAP1 4
520 #define SNMP_PDU_BULK 5
521 #define SNMP_PDU_INFORM 6
522 #define SNMP_PDU_TRAP2 7
525 #define SNMP_NOERROR 0
526 #define SNMP_TOOBIG 1
527 #define SNMP_NOSUCHNAME 2
528 #define SNMP_BADVALUE 3
529 #define SNMP_READONLY 4
530 #define SNMP_GENERROR 5
531 #define SNMP_NOACCESS 6
532 #define SNMP_WRONGTYPE 7
533 #define SNMP_WRONGLENGTH 8
534 #define SNMP_WRONGENCODING 9
535 #define SNMP_WRONGVALUE 10
536 #define SNMP_NOCREATION 11
537 #define SNMP_INCONSISTENTVALUE 12
538 #define SNMP_RESOURCEUNAVAILABLE 13
539 #define SNMP_COMMITFAILED 14
540 #define SNMP_UNDOFAILED 15
541 #define SNMP_AUTHORIZATIONERROR 16
542 #define SNMP_NOTWRITABLE 17
543 #define SNMP_INCONSISTENTNAME 18
545 /* General SNMP V1 Traps */
546 #define SNMP_TRAP_COLDSTART 0
547 #define SNMP_TRAP_WARMSTART 1
548 #define SNMP_TRAP_LINKDOWN 2
549 #define SNMP_TRAP_LINKUP 3
550 #define SNMP_TRAP_AUTFAILURE 4
551 #define SNMP_TRAP_EQPNEIGHBORLOSS 5
552 #define SNMP_TRAP_ENTSPECIFIC 6
556 #define SNMP_INTEGER 1 /* l */
557 #define SNMP_OCTETSTR 2 /* c */
558 #define SNMP_DISPLAYSTR 2 /* c */
559 #define SNMP_OBJECTID 3 /* ul */
560 #define SNMP_IPADDR 4 /* uc */
561 #define SNMP_COUNTER 5 /* ul */
562 #define SNMP_GAUGE 6 /* ul */
563 #define SNMP_TIMETICKS 7 /* ul */
564 #define SNMP_OPAQUE 8 /* c */
566 /* Additional SNMPv2 Types */
567 #define SNMP_UINTEGER 5 /* ul */
568 #define SNMP_BITSTR 9 /* uc */
569 #define SNMP_NSAP 10 /* uc */
570 #define SNMP_COUNTER64 11 /* ul */
571 #define SNMP_NOSUCHOBJECT 12
572 #define SNMP_NOSUCHINSTANCE 13
573 #define SNMP_ENDOFMIBVIEW 14
577 unsigned char uc[0]; /* 8 bit unsigned */
578 char c[0]; /* 8 bit signed */
579 unsigned long ul[0]; /* 32 bit unsigned */
580 long l[0]; /* 32 bit signed */
588 unsigned int syntax_len;
589 union snmp_syntax syntax;
595 unsigned int error_status;
596 unsigned int error_index;
603 unsigned long ip_address; /* pointer */
604 unsigned int general;
605 unsigned int specific;
622 static inline void mangle_address(unsigned char *begin,
624 const struct oct1_map *map,
633 static const struct snmp_cnv snmp_conv[] = {
634 {ASN1_UNI, ASN1_NUL, SNMP_NULL},
635 {ASN1_UNI, ASN1_INT, SNMP_INTEGER},
636 {ASN1_UNI, ASN1_OTS, SNMP_OCTETSTR},
637 {ASN1_UNI, ASN1_OTS, SNMP_DISPLAYSTR},
638 {ASN1_UNI, ASN1_OJI, SNMP_OBJECTID},
639 {ASN1_APL, SNMP_IPA, SNMP_IPADDR},
640 {ASN1_APL, SNMP_CNT, SNMP_COUNTER}, /* Counter32 */
641 {ASN1_APL, SNMP_GGE, SNMP_GAUGE}, /* Gauge32 == Unsigned32 */
642 {ASN1_APL, SNMP_TIT, SNMP_TIMETICKS},
643 {ASN1_APL, SNMP_OPQ, SNMP_OPAQUE},
645 /* SNMPv2 data types and errors */
646 {ASN1_UNI, ASN1_BTS, SNMP_BITSTR},
647 {ASN1_APL, SNMP_C64, SNMP_COUNTER64},
648 {ASN1_CTX, SERR_NSO, SNMP_NOSUCHOBJECT},
649 {ASN1_CTX, SERR_NSI, SNMP_NOSUCHINSTANCE},
650 {ASN1_CTX, SERR_EOM, SNMP_ENDOFMIBVIEW},
654 static unsigned char snmp_tag_cls2syntax(unsigned int tag,
656 unsigned short *syntax)
658 const struct snmp_cnv *cnv;
662 while (cnv->syntax != -1) {
663 if (cnv->tag == tag && cnv->class == cls) {
664 *syntax = cnv->syntax;
672 static unsigned char snmp_object_decode(struct asn1_ctx *ctx,
673 struct snmp_object **obj)
675 unsigned int cls, con, tag, len, idlen;
677 unsigned char *eoc, *end, *p;
678 unsigned long *lp, *id;
685 if (!asn1_header_decode(ctx, &eoc, &cls, &con, &tag))
688 if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
691 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
694 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
697 if (!asn1_oid_decode(ctx, end, &id, &idlen))
700 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag)) {
705 if (con != ASN1_PRI) {
711 if (!snmp_tag_cls2syntax(tag, cls, &type)) {
720 if (!asn1_long_decode(ctx, end, &l)) {
724 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
729 (*obj)->syntax.l[0] = l;
733 if (!asn1_octets_decode(ctx, end, &p, &len)) {
737 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
743 memcpy((*obj)->syntax.c, p, len);
747 case SNMP_NOSUCHOBJECT:
748 case SNMP_NOSUCHINSTANCE:
749 case SNMP_ENDOFMIBVIEW:
751 *obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
756 if (!asn1_null_decode(ctx, end)) {
764 if (!asn1_oid_decode(ctx, end, &lp, &len)) {
768 len *= sizeof(unsigned long);
769 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
775 memcpy((*obj)->syntax.ul, lp, len);
779 if (!asn1_octets_decode(ctx, end, &p, &len)) {
788 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
794 memcpy((*obj)->syntax.uc, p, len);
800 len = sizeof(unsigned long);
801 if (!asn1_ulong_decode(ctx, end, &ul)) {
805 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
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(__sum16 *csum,
872 const unsigned char *optr,
873 const unsigned char *nptr,
890 *csum = csum_fold(csum_partial(s, 4, ~csum_unfold(*csum)));
895 * - begin points to the start of the snmp messgae
896 * - addr points to the start of the address
898 static inline void mangle_address(unsigned char *begin,
900 const struct oct1_map *map,
903 if (map->from == NOCT1(addr)) {
907 memcpy(&old, addr, sizeof(old));
911 /* Update UDP checksum if being used */
914 &map->from, &map->to, addr - begin);
919 printk(KERN_DEBUG "bsalg: mapped %pI4 to %pI4\n",
924 static unsigned char snmp_trap_decode(struct asn1_ctx *ctx,
925 struct snmp_v1_trap *trap,
926 const struct oct1_map *map,
929 unsigned int cls, con, tag, len;
932 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
935 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
938 if (!asn1_oid_decode(ctx, end, &trap->id, &trap->id_len))
941 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
944 if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_IPA) ||
945 (cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_OTS)))
948 if (!asn1_octets_decode(ctx, end, (unsigned char **)&trap->ip_address, &len))
955 mangle_address(ctx->begin, ctx->pointer - 4, map, check);
957 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
960 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
963 if (!asn1_uint_decode(ctx, end, &trap->general))
966 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
969 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
972 if (!asn1_uint_decode(ctx, end, &trap->specific))
975 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
978 if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_TIT) ||
979 (cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_INT)))
982 if (!asn1_ulong_decode(ctx, end, &trap->time))
988 kfree((unsigned long *)trap->ip_address);
996 /*****************************************************************************
1000 *****************************************************************************/
1002 static void hex_dump(const unsigned char *buf, size_t len)
1006 for (i = 0; i < len; i++) {
1009 printk("%02x ", *(buf + i));
1015 * Parse and mangle SNMP message according to mapping.
1016 * (And this is the fucking 'basic' method).
1018 static int snmp_parse_mangle(unsigned char *msg,
1020 const struct oct1_map *map,
1023 unsigned char *eoc, *end;
1024 unsigned int cls, con, tag, vers, pdutype;
1025 struct asn1_ctx ctx;
1026 struct asn1_octstr comm;
1027 struct snmp_object *obj;
1032 asn1_open(&ctx, msg, len);
1035 * Start of SNMP message.
1037 if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
1039 if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
1043 * Version 1 or 2 handled.
1045 if (!asn1_header_decode(&ctx, &end, &cls, &con, &tag))
1047 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
1049 if (!asn1_uint_decode (&ctx, end, &vers))
1052 printk(KERN_DEBUG "bsalg: snmp version: %u\n", vers + 1);
1059 if (!asn1_header_decode (&ctx, &end, &cls, &con, &tag))
1061 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OTS)
1063 if (!asn1_octets_decode(&ctx, end, &comm.data, &comm.len))
1068 printk(KERN_DEBUG "bsalg: community: ");
1069 for (i = 0; i < comm.len; i++)
1070 printk("%c", comm.data[i]);
1078 if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &pdutype))
1080 if (cls != ASN1_CTX || con != ASN1_CON)
1083 static const unsigned char *const pdus[] = {
1084 [SNMP_PDU_GET] = "get",
1085 [SNMP_PDU_NEXT] = "get-next",
1086 [SNMP_PDU_RESPONSE] = "response",
1087 [SNMP_PDU_SET] = "set",
1088 [SNMP_PDU_TRAP1] = "trapv1",
1089 [SNMP_PDU_BULK] = "bulk",
1090 [SNMP_PDU_INFORM] = "inform",
1091 [SNMP_PDU_TRAP2] = "trapv2"
1094 if (pdutype > SNMP_PDU_TRAP2)
1095 printk(KERN_DEBUG "bsalg: bad pdu type %u\n", pdutype);
1097 printk(KERN_DEBUG "bsalg: pdu: %s\n", pdus[pdutype]);
1099 if (pdutype != SNMP_PDU_RESPONSE &&
1100 pdutype != SNMP_PDU_TRAP1 && pdutype != SNMP_PDU_TRAP2)
1104 * Request header or v1 trap
1106 if (pdutype == SNMP_PDU_TRAP1) {
1107 struct snmp_v1_trap trap;
1108 unsigned char ret = snmp_trap_decode(&ctx, &trap, map, check);
1112 kfree((unsigned long *)trap.ip_address);
1117 struct snmp_request req;
1119 if (!snmp_request_decode(&ctx, &req))
1123 printk(KERN_DEBUG "bsalg: request: id=0x%lx error_status=%u "
1124 "error_index=%u\n", req.id, req.error_status,
1129 * Loop through objects, look for IP addresses to mangle.
1131 if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
1134 if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
1137 while (!asn1_eoc_decode(&ctx, eoc)) {
1140 if (!snmp_object_decode(&ctx, &obj)) {
1149 printk(KERN_DEBUG "bsalg: object: ");
1150 for (i = 0; i < obj->id_len; i++) {
1153 printk("%lu", obj->id[i]);
1155 printk(": type=%u\n", obj->type);
1159 if (obj->type == SNMP_IPADDR)
1160 mangle_address(ctx.begin, ctx.pointer - 4 , map, check);
1166 if (!asn1_eoc_decode(&ctx, eoc))
1172 /*****************************************************************************
1176 *****************************************************************************/
1179 * SNMP translation routine.
1181 static int snmp_translate(struct nf_conn *ct,
1182 enum ip_conntrack_info ctinfo,
1183 struct sk_buff *skb)
1185 struct iphdr *iph = ip_hdr(skb);
1186 struct udphdr *udph = (struct udphdr *)((__be32 *)iph + iph->ihl);
1187 u_int16_t udplen = ntohs(udph->len);
1188 u_int16_t paylen = udplen - sizeof(struct udphdr);
1189 int dir = CTINFO2DIR(ctinfo);
1190 struct oct1_map map;
1193 * Determine mappping for application layer addresses based
1194 * on NAT manipulations for the packet.
1196 if (dir == IP_CT_DIR_ORIGINAL) {
1198 map.from = NOCT1(&ct->tuplehash[dir].tuple.src.u3.ip);
1199 map.to = NOCT1(&ct->tuplehash[!dir].tuple.dst.u3.ip);
1202 map.from = NOCT1(&ct->tuplehash[dir].tuple.src.u3.ip);
1203 map.to = NOCT1(&ct->tuplehash[!dir].tuple.dst.u3.ip);
1206 if (map.from == map.to)
1209 if (!snmp_parse_mangle((unsigned char *)udph + sizeof(struct udphdr),
1210 paylen, &map, &udph->check)) {
1211 net_warn_ratelimited("bsalg: parser failed\n");
1217 /* We don't actually set up expectations, just adjust internal IP
1218 * addresses if this is being NATted */
1219 static int help(struct sk_buff *skb, unsigned int protoff,
1221 enum ip_conntrack_info ctinfo)
1223 int dir = CTINFO2DIR(ctinfo);
1225 const struct iphdr *iph = ip_hdr(skb);
1226 const struct udphdr *udph = (struct udphdr *)((__be32 *)iph + iph->ihl);
1228 /* SNMP replies and originating SNMP traps get mangled */
1229 if (udph->source == htons(SNMP_PORT) && dir != IP_CT_DIR_REPLY)
1231 if (udph->dest == htons(SNMP_TRAP_PORT) && dir != IP_CT_DIR_ORIGINAL)
1235 if (!(ct->status & IPS_NAT_MASK))
1239 * Make sure the packet length is ok. So far, we were only guaranteed
1240 * to have a valid length IP header plus 8 bytes, which means we have
1241 * enough room for a UDP header. Just verify the UDP length field so we
1242 * can mess around with the payload.
1244 if (ntohs(udph->len) != skb->len - (iph->ihl << 2)) {
1245 net_warn_ratelimited("SNMP: dropping malformed packet src=%pI4 dst=%pI4\n",
1246 &iph->saddr, &iph->daddr);
1250 if (!skb_make_writable(skb, skb->len))
1253 spin_lock_bh(&snmp_lock);
1254 ret = snmp_translate(ct, ctinfo, skb);
1255 spin_unlock_bh(&snmp_lock);
1259 static const struct nf_conntrack_expect_policy snmp_exp_policy = {
1264 static struct nf_conntrack_helper snmp_helper __read_mostly = {
1267 .expect_policy = &snmp_exp_policy,
1269 .tuple.src.l3num = AF_INET,
1270 .tuple.src.u.udp.port = cpu_to_be16(SNMP_PORT),
1271 .tuple.dst.protonum = IPPROTO_UDP,
1274 static struct nf_conntrack_helper snmp_trap_helper __read_mostly = {
1277 .expect_policy = &snmp_exp_policy,
1278 .name = "snmp_trap",
1279 .tuple.src.l3num = AF_INET,
1280 .tuple.src.u.udp.port = cpu_to_be16(SNMP_TRAP_PORT),
1281 .tuple.dst.protonum = IPPROTO_UDP,
1284 /*****************************************************************************
1288 *****************************************************************************/
1290 static int __init nf_nat_snmp_basic_init(void)
1294 BUG_ON(nf_nat_snmp_hook != NULL);
1295 RCU_INIT_POINTER(nf_nat_snmp_hook, help);
1297 ret = nf_conntrack_helper_register(&snmp_trap_helper);
1299 nf_conntrack_helper_unregister(&snmp_helper);
1305 static void __exit nf_nat_snmp_basic_fini(void)
1307 RCU_INIT_POINTER(nf_nat_snmp_hook, NULL);
1308 nf_conntrack_helper_unregister(&snmp_trap_helper);
1311 module_init(nf_nat_snmp_basic_init);
1312 module_exit(nf_nat_snmp_basic_fini);
1314 module_param(debug, int, 0600);