net/netfilter/nf_conntrack_ftp.c

   1 /* FTP extension for connection tracking. */
   2
   3 /* (C) 1999-2001 Paul `Rusty' Russell
   4  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   5  * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/moduleparam.h>
  14 #include <linux/netfilter.h>
  15 #include <linux/ip.h>
  16 #include <linux/slab.h>
  17 #include <linux/ipv6.h>
  18 #include <linux/ctype.h>
  19 #include <linux/inet.h>
  20 #include <net/checksum.h>
  21 #include <net/tcp.h>
  22
  23 #include <net/netfilter/nf_conntrack.h>
  24 #include <net/netfilter/nf_conntrack_expect.h>
  25 #include <net/netfilter/nf_conntrack_ecache.h>
  26 #include <net/netfilter/nf_conntrack_helper.h>
  27 #include <linux/netfilter/nf_conntrack_ftp.h>
  28
  29 MODULE_LICENSE("GPL");
  30 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
  31 MODULE_DESCRIPTION("ftp connection tracking helper");
  32 MODULE_ALIAS("ip_conntrack_ftp");
  33 MODULE_ALIAS_NFCT_HELPER("ftp");
  34
  35 /* This is slow, but it's simple. --RR */
  36 static char *ftp_buffer;
  37
  38 static DEFINE_SPINLOCK(nf_ftp_lock);
  39
  40 #define MAX_PORTS 8
  41 static u_int16_t ports[MAX_PORTS];
  42 static unsigned int ports_c;
  43 module_param_array(ports, ushort, &ports_c, 0400);
  44
  45 static bool loose;
  46 module_param(loose, bool, 0600);
  47
  48 unsigned int (*nf_nat_ftp_hook)(struct sk_buff *skb,
  49                                 enum ip_conntrack_info ctinfo,
  50                                 enum nf_ct_ftp_type type,
  51                                 unsigned int protoff,
  52                                 unsigned int matchoff,
  53                                 unsigned int matchlen,
  54                                 struct nf_conntrack_expect *exp);
  55 EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
  56
  57 static int try_rfc959(const char *, size_t, struct nf_conntrack_man *, char);
  58 static int try_eprt(const char *, size_t, struct nf_conntrack_man *, char);
  59 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
  60                              char);
  61
  62 static struct ftp_search {
  63         const char *pattern;
  64         size_t plen;
  65         char skip;
  66         char term;
  67         enum nf_ct_ftp_type ftptype;
  68         int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char);
  69 } search[IP_CT_DIR_MAX][2] = {
  70         [IP_CT_DIR_ORIGINAL] = {
  71                 {
  72                         .pattern        = "PORT",
  73                         .plen           = sizeof("PORT") - 1,
  74                         .skip           = ' ',
  75                         .term           = '\r',
  76                         .ftptype        = NF_CT_FTP_PORT,
  77                         .getnum         = try_rfc959,
  78                 },
  79                 {
  80                         .pattern        = "EPRT",
  81                         .plen           = sizeof("EPRT") - 1,
  82                         .skip           = ' ',
  83                         .term           = '\r',
  84                         .ftptype        = NF_CT_FTP_EPRT,
  85                         .getnum         = try_eprt,
  86                 },
  87         },
  88         [IP_CT_DIR_REPLY] = {
  89                 {
  90                         .pattern        = "227 ",
  91                         .plen           = sizeof("227 ") - 1,
  92                         .skip           = '(',
  93                         .term           = ')',
  94                         .ftptype        = NF_CT_FTP_PASV,
  95                         .getnum         = try_rfc959,
  96                 },
  97                 {
  98                         .pattern        = "229 ",
  99                         .plen           = sizeof("229 ") - 1,
 100                         .skip           = '(',
 101                         .term           = ')',
 102                         .ftptype        = NF_CT_FTP_EPSV,
 103                         .getnum         = try_epsv_response,
 104                 },
 105         },
 106 };
 107
 108 static int
 109 get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
 110 {
 111         const char *end;
 112         int ret = in6_pton(src, min_t(size_t, dlen, 0xffff), (u8 *)dst, term, &end);
 113         if (ret > 0)
 114                 return (int)(end - src);
 115         return 0;
 116 }
 117
 118 static int try_number(const char *data, size_t dlen, u_int32_t array[],
 119                       int array_size, char sep, char term)
 120 {
 121         u_int32_t i, len;
 122
 123         memset(array, 0, sizeof(array[0])*array_size);
 124
 125         /* Keep data pointing at next char. */
 126         for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
 127                 if (*data >= '0' && *data <= '9') {
 128                         array[i] = array[i]*10 + *data - '0';
 129                 }
 130                 else if (*data == sep)
 131                         i++;
 132                 else {
 133                         /* Unexpected character; true if it's the
 134                            terminator and we're finished. */
 135                         if (*data == term && i == array_size - 1)
 136                                 return len;
 137
 138                         pr_debug("Char %u (got %u nums) `%u' unexpected\n",
 139                                  len, i, *data);
 140                         return 0;
 141                 }
 142         }
 143         pr_debug("Failed to fill %u numbers separated by %c\n",
 144                  array_size, sep);
 145         return 0;
 146 }
 147
 148 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
 149 static int try_rfc959(const char *data, size_t dlen,
 150                       struct nf_conntrack_man *cmd, char term)
 151 {
 152         int length;
 153         u_int32_t array[6];
 154
 155         length = try_number(data, dlen, array, 6, ',', term);
 156         if (length == 0)
 157                 return 0;
 158
 159         cmd->u3.ip =  htonl((array[0] << 24) | (array[1] << 16) |
 160                                     (array[2] << 8) | array[3]);
 161         cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
 162         return length;
 163 }
 164
 165 /* Grab port: number up to delimiter */
 166 static int get_port(const char *data, int start, size_t dlen, char delim,
 167                     __be16 *port)
 168 {
 169         u_int16_t tmp_port = 0;
 170         int i;
 171
 172         for (i = start; i < dlen; i++) {
 173                 /* Finished? */
 174                 if (data[i] == delim) {
 175                         if (tmp_port == 0)
 176                                 break;
 177                         *port = htons(tmp_port);
 178                         pr_debug("get_port: return %d\n", tmp_port);
 179                         return i + 1;
 180                 }
 181                 else if (data[i] >= '0' && data[i] <= '9')
 182                         tmp_port = tmp_port*10 + data[i] - '0';
 183                 else { /* Some other crap */
 184                         pr_debug("get_port: invalid char.\n");
 185                         break;
 186                 }
 187         }
 188         return 0;
 189 }
 190
 191 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
 192 static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
 193                     char term)
 194 {
 195         char delim;
 196         int length;
 197
 198         /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
 199            then delimiter again. */
 200         if (dlen <= 3) {
 201                 pr_debug("EPRT: too short\n");
 202                 return 0;
 203         }
 204         delim = data[0];
 205         if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
 206                 pr_debug("try_eprt: invalid delimitter.\n");
 207                 return 0;
 208         }
 209
 210         if ((cmd->l3num == PF_INET && data[1] != '1') ||
 211             (cmd->l3num == PF_INET6 && data[1] != '2')) {
 212                 pr_debug("EPRT: invalid protocol number.\n");
 213                 return 0;
 214         }
 215
 216         pr_debug("EPRT: Got %c%c%c\n", delim, data[1], delim);
 217
 218         if (data[1] == '1') {
 219                 u_int32_t array[4];
 220
 221                 /* Now we have IP address. */
 222                 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
 223                 if (length != 0)
 224                         cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
 225                                            | (array[2] << 8) | array[3]);
 226         } else {
 227                 /* Now we have IPv6 address. */
 228                 length = get_ipv6_addr(data + 3, dlen - 3,
 229                                        (struct in6_addr *)cmd->u3.ip6, delim);
 230         }
 231
 232         if (length == 0)
 233                 return 0;
 234         pr_debug("EPRT: Got IP address!\n");
 235         /* Start offset includes initial "|1|", and trailing delimiter */
 236         return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
 237 }
 238
 239 /* Returns 0, or length of numbers: |||6446| */
 240 static int try_epsv_response(const char *data, size_t dlen,
 241                              struct nf_conntrack_man *cmd, char term)
 242 {
 243         char delim;
 244
 245         /* Three delimiters. */
 246         if (dlen <= 3) return 0;
 247         delim = data[0];
 248         if (isdigit(delim) || delim < 33 || delim > 126 ||
 249             data[1] != delim || data[2] != delim)
 250                 return 0;
 251
 252         return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
 253 }
 254
 255 /* Return 1 for match, 0 for accept, -1 for partial. */
 256 static int find_pattern(const char *data, size_t dlen,
 257                         const char *pattern, size_t plen,
 258                         char skip, char term,
 259                         unsigned int *numoff,
 260                         unsigned int *numlen,
 261                         struct nf_conntrack_man *cmd,
 262                         int (*getnum)(const char *, size_t,
 263                                       struct nf_conntrack_man *, char))
 264 {
 265         size_t i;
 266
 267         pr_debug("find_pattern `%s': dlen = %Zu\n", pattern, dlen);
 268         if (dlen == 0)
 269                 return 0;
 270
 271         if (dlen <= plen) {
 272                 /* Short packet: try for partial? */
 273                 if (strnicmp(data, pattern, dlen) == 0)
 274                         return -1;
 275                 else return 0;
 276         }
 277
 278         if (strnicmp(data, pattern, plen) != 0) {
 279 #if 0
 280                 size_t i;
 281
 282                 pr_debug("ftp: string mismatch\n");
 283                 for (i = 0; i < plen; i++) {
 284                         pr_debug("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
 285                                  i, data[i], data[i],
 286                                  pattern[i], pattern[i]);
 287                 }
 288 #endif
 289                 return 0;
 290         }
 291
 292         pr_debug("Pattern matches!\n");
 293         /* Now we've found the constant string, try to skip
 294            to the 'skip' character */
 295         for (i = plen; data[i] != skip; i++)
 296                 if (i == dlen - 1) return -1;
 297
 298         /* Skip over the last character */
 299         i++;
 300
 301         pr_debug("Skipped up to `%c'!\n", skip);
 302
 303         *numoff = i;
 304         *numlen = getnum(data + i, dlen - i, cmd, term);
 305         if (!*numlen)
 306                 return -1;
 307
 308         pr_debug("Match succeeded!\n");
 309         return 1;
 310 }
 311
 312 /* Look up to see if we're just after a \n. */
 313 static int find_nl_seq(u32 seq, const struct nf_ct_ftp_master *info, int dir)
 314 {
 315         unsigned int i;
 316
 317         for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
 318                 if (info->seq_aft_nl[dir][i] == seq)
 319                         return 1;
 320         return 0;
 321 }
 322
 323 /* We don't update if it's older than what we have. */
 324 static void update_nl_seq(struct nf_conn *ct, u32 nl_seq,
 325                           struct nf_ct_ftp_master *info, int dir,
 326                           struct sk_buff *skb)
 327 {
 328         unsigned int i, oldest;
 329
 330         /* Look for oldest: if we find exact match, we're done. */
 331         for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
 332                 if (info->seq_aft_nl[dir][i] == nl_seq)
 333                         return;
 334         }
 335
 336         if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
 337                 info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
 338         } else {
 339                 if (before(info->seq_aft_nl[dir][0], info->seq_aft_nl[dir][1]))
 340                         oldest = 0;
 341                 else
 342                         oldest = 1;
 343
 344                 if (after(nl_seq, info->seq_aft_nl[dir][oldest]))
 345                         info->seq_aft_nl[dir][oldest] = nl_seq;
 346         }
 347 }
 348
 349 static int help(struct sk_buff *skb,
 350                 unsigned int protoff,
 351                 struct nf_conn *ct,
 352                 enum ip_conntrack_info ctinfo)
 353 {
 354         unsigned int dataoff, datalen;
 355         const struct tcphdr *th;
 356         struct tcphdr _tcph;
 357         const char *fb_ptr;
 358         int ret;
 359         u32 seq;
 360         int dir = CTINFO2DIR(ctinfo);
 361         unsigned int uninitialized_var(matchlen), uninitialized_var(matchoff);
 362         struct nf_ct_ftp_master *ct_ftp_info = nfct_help_data(ct);
 363         struct nf_conntrack_expect *exp;
 364         union nf_inet_addr *daddr;
 365         struct nf_conntrack_man cmd = {};
 366         unsigned int i;
 367         int found = 0, ends_in_nl;
 368         typeof(nf_nat_ftp_hook) nf_nat_ftp;
 369
 370         /* Until there's been traffic both ways, don't look in packets. */
 371         if (ctinfo != IP_CT_ESTABLISHED &&
 372             ctinfo != IP_CT_ESTABLISHED_REPLY) {
 373                 pr_debug("ftp: Conntrackinfo = %u\n", ctinfo);
 374                 return NF_ACCEPT;
 375         }
 376
 377         th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
 378         if (th == NULL)
 379                 return NF_ACCEPT;
 380
 381         dataoff = protoff + th->doff * 4;
 382         /* No data? */
 383         if (dataoff >= skb->len) {
 384                 pr_debug("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
 385                          skb->len);
 386                 return NF_ACCEPT;
 387         }
 388         datalen = skb->len - dataoff;
 389
 390         spin_lock_bh(&nf_ftp_lock);
 391         fb_ptr = skb_header_pointer(skb, dataoff, datalen, ftp_buffer);
 392         BUG_ON(fb_ptr == NULL);
 393
 394         ends_in_nl = (fb_ptr[datalen - 1] == '\n');
 395         seq = ntohl(th->seq) + datalen;
 396
 397         /* Look up to see if we're just after a \n. */
 398         if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
 399                 /* We're picking up this, clear flags and let it continue */
 400                 if (unlikely(ct_ftp_info->flags[dir] & NF_CT_FTP_SEQ_PICKUP)) {
 401                         ct_ftp_info->flags[dir] ^= NF_CT_FTP_SEQ_PICKUP;
 402                         goto skip_nl_seq;
 403                 }
 404
 405                 /* Now if this ends in \n, update ftp info. */
 406                 pr_debug("nf_conntrack_ftp: wrong seq pos %s(%u) or %s(%u)\n",
 407                          ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
 408                          ct_ftp_info->seq_aft_nl[dir][0],
 409                          ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
 410                          ct_ftp_info->seq_aft_nl[dir][1]);
 411                 ret = NF_ACCEPT;
 412                 goto out_update_nl;
 413         }
 414
 415 skip_nl_seq:
 416         /* Initialize IP/IPv6 addr to expected address (it's not mentioned
 417            in EPSV responses) */
 418         cmd.l3num = nf_ct_l3num(ct);
 419         memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
 420                sizeof(cmd.u3.all));
 421
 422         for (i = 0; i < ARRAY_SIZE(search[dir]); i++) {
 423                 found = find_pattern(fb_ptr, datalen,
 424                                      search[dir][i].pattern,
 425                                      search[dir][i].plen,
 426                                      search[dir][i].skip,
 427                                      search[dir][i].term,
 428                                      &matchoff, &matchlen,
 429                                      &cmd,
 430                                      search[dir][i].getnum);
 431                 if (found) break;
 432         }
 433         if (found == -1) {
 434                 /* We don't usually drop packets.  After all, this is
 435                    connection tracking, not packet filtering.
 436                    However, it is necessary for accurate tracking in
 437                    this case. */
 438                 nf_ct_helper_log(skb, ct, "partial matching of `%s'",
 439                                  search[dir][i].pattern);
 440                 ret = NF_DROP;
 441                 goto out;
 442         } else if (found == 0) { /* No match */
 443                 ret = NF_ACCEPT;
 444                 goto out_update_nl;
 445         }
 446
 447         pr_debug("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
 448                  matchlen, fb_ptr + matchoff,
 449                  matchlen, ntohl(th->seq) + matchoff);
 450
 451         exp = nf_ct_expect_alloc(ct);
 452         if (exp == NULL) {
 453                 nf_ct_helper_log(skb, ct, "cannot alloc expectation");
 454                 ret = NF_DROP;
 455                 goto out;
 456         }
 457
 458         /* We refer to the reverse direction ("!dir") tuples here,
 459          * because we're expecting something in the other direction.
 460          * Doesn't matter unless NAT is happening.  */
 461         daddr = &ct->tuplehash[!dir].tuple.dst.u3;
 462
 463         /* Update the ftp info */
 464         if ((cmd.l3num == nf_ct_l3num(ct)) &&
 465             memcmp(&cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
 466                      sizeof(cmd.u3.all))) {
 467                 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
 468                    server: it really wants us to connect to a
 469                    different IP address.  Simply don't record it for
 470                    NAT. */
 471                 if (cmd.l3num == PF_INET) {
 472                         pr_debug("conntrack_ftp: NOT RECORDING: %pI4 != %pI4\n",
 473                                  &cmd.u3.ip,
 474                                  &ct->tuplehash[dir].tuple.src.u3.ip);
 475                 } else {
 476                         pr_debug("conntrack_ftp: NOT RECORDING: %pI6 != %pI6\n",
 477                                  cmd.u3.ip6,
 478                                  ct->tuplehash[dir].tuple.src.u3.ip6);
 479                 }
 480
 481                 /* Thanks to Cristiano Lincoln Mattos
 482                    <lincoln@cesar.org.br> for reporting this potential
 483                    problem (DMZ machines opening holes to internal
 484                    networks, or the packet filter itself). */
 485                 if (!loose) {
 486                         ret = NF_ACCEPT;
 487                         goto out_put_expect;
 488                 }
 489                 daddr = &cmd.u3;
 490         }
 491
 492         nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, cmd.l3num,
 493                           &ct->tuplehash[!dir].tuple.src.u3, daddr,
 494                           IPPROTO_TCP, NULL, &cmd.u.tcp.port);
 495
 496         /* Now, NAT might want to mangle the packet, and register the
 497          * (possibly changed) expectation itself. */
 498         nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
 499         if (nf_nat_ftp && ct->status & IPS_NAT_MASK)
 500                 ret = nf_nat_ftp(skb, ctinfo, search[dir][i].ftptype,
 501                                  protoff, matchoff, matchlen, exp);
 502         else {
 503                 /* Can't expect this?  Best to drop packet now. */
 504                 if (nf_ct_expect_related(exp) != 0) {
 505                         nf_ct_helper_log(skb, ct, "cannot add expectation");
 506                         ret = NF_DROP;
 507                 } else
 508                         ret = NF_ACCEPT;
 509         }
 510
 511 out_put_expect:
 512         nf_ct_expect_put(exp);
 513
 514 out_update_nl:
 515         /* Now if this ends in \n, update ftp info.  Seq may have been
 516          * adjusted by NAT code. */
 517         if (ends_in_nl)
 518                 update_nl_seq(ct, seq, ct_ftp_info, dir, skb);
 519  out:
 520         spin_unlock_bh(&nf_ftp_lock);
 521         return ret;
 522 }
 523
 524 static int nf_ct_ftp_from_nlattr(struct nlattr *attr, struct nf_conn *ct)
 525 {
 526         struct nf_ct_ftp_master *ftp = nfct_help_data(ct);
 527
 528         /* This conntrack has been injected from user-space, always pick up
 529          * sequence tracking. Otherwise, the first FTP command after the
 530          * failover breaks.
 531          */
 532         ftp->flags[IP_CT_DIR_ORIGINAL] |= NF_CT_FTP_SEQ_PICKUP;
 533         ftp->flags[IP_CT_DIR_REPLY] |= NF_CT_FTP_SEQ_PICKUP;
 534         return 0;
 535 }
 536
 537 static struct nf_conntrack_helper ftp[MAX_PORTS][2] __read_mostly;
 538
 539 static const struct nf_conntrack_expect_policy ftp_exp_policy = {
 540         .max_expected   = 1,
 541         .timeout        = 5 * 60,
 542 };
 543
 544 /* don't make this __exit, since it's called from __init ! */
 545 static void nf_conntrack_ftp_fini(void)
 546 {
 547         int i, j;
 548         for (i = 0; i < ports_c; i++) {
 549                 for (j = 0; j < 2; j++) {
 550                         if (ftp[i][j].me == NULL)
 551                                 continue;
 552
 553                         pr_debug("nf_ct_ftp: unregistering helper for pf: %d "
 554                                  "port: %d\n",
 555                                  ftp[i][j].tuple.src.l3num, ports[i]);
 556                         nf_conntrack_helper_unregister(&ftp[i][j]);
 557                 }
 558         }
 559
 560         kfree(ftp_buffer);
 561 }
 562
 563 static int __init nf_conntrack_ftp_init(void)
 564 {
 565         int i, j = -1, ret = 0;
 566
 567         ftp_buffer = kmalloc(65536, GFP_KERNEL);
 568         if (!ftp_buffer)
 569                 return -ENOMEM;
 570
 571         if (ports_c == 0)
 572                 ports[ports_c++] = FTP_PORT;
 573
 574         /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
 575                  are tracked or not - YK */
 576         for (i = 0; i < ports_c; i++) {
 577                 ftp[i][0].tuple.src.l3num = PF_INET;
 578                 ftp[i][1].tuple.src.l3num = PF_INET6;
 579                 for (j = 0; j < 2; j++) {
 580                         ftp[i][j].data_len = sizeof(struct nf_ct_ftp_master);
 581                         ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
 582                         ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
 583                         ftp[i][j].expect_policy = &ftp_exp_policy;
 584                         ftp[i][j].me = THIS_MODULE;
 585                         ftp[i][j].help = help;
 586                         ftp[i][j].from_nlattr = nf_ct_ftp_from_nlattr;
 587                         if (ports[i] == FTP_PORT)
 588                                 sprintf(ftp[i][j].name, "ftp");
 589                         else
 590                                 sprintf(ftp[i][j].name, "ftp-%d", ports[i]);
 591
 592                         pr_debug("nf_ct_ftp: registering helper for pf: %d "
 593                                  "port: %d\n",
 594                                  ftp[i][j].tuple.src.l3num, ports[i]);
 595                         ret = nf_conntrack_helper_register(&ftp[i][j]);
 596                         if (ret) {
 597                                 printk(KERN_ERR "nf_ct_ftp: failed to register"
 598                                        " helper for pf: %d port: %d\n",
 599                                         ftp[i][j].tuple.src.l3num, ports[i]);
 600                                 nf_conntrack_ftp_fini();
 601                                 return ret;
 602                         }
 603                 }
 604         }
 605
 606         return 0;
 607 }
 608
 609 module_init(nf_conntrack_ftp_init);
 610 module_exit(nf_conntrack_ftp_fini);