net/netfilter/nf_conntrack_ftp.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* FTP extension for connection tracking. */
   3
   4 /* (C) 1999-2001 Paul `Rusty' Russell
   5  * (C) 2002-2004 Netfilter Core Team <[email protected]>
   6  * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
   7  * (C) 2006-2012 Patrick McHardy <[email protected]>
   8  */
   9
  10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  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 #define HELPER_NAME "ftp"
  30
  31 MODULE_LICENSE("GPL");
  32 MODULE_AUTHOR("Rusty Russell <[email protected]>");
  33 MODULE_DESCRIPTION("ftp connection tracking helper");
  34 MODULE_ALIAS("ip_conntrack_ftp");
  35 MODULE_ALIAS_NFCT_HELPER(HELPER_NAME);
  36 static DEFINE_SPINLOCK(nf_ftp_lock);
  37
  38 #define MAX_PORTS 8
  39 static u_int16_t ports[MAX_PORTS];
  40 static unsigned int ports_c;
  41 module_param_array(ports, ushort, &ports_c, 0400);
  42
  43 static bool loose;
  44 module_param(loose, bool, 0600);
  45
  46 unsigned int (*nf_nat_ftp_hook)(struct sk_buff *skb,
  47                                 enum ip_conntrack_info ctinfo,
  48                                 enum nf_ct_ftp_type type,
  49                                 unsigned int protoff,
  50                                 unsigned int matchoff,
  51                                 unsigned int matchlen,
  52                                 struct nf_conntrack_expect *exp);
  53 EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
  54
  55 static int try_rfc959(const char *, size_t, struct nf_conntrack_man *,
  56                       char, unsigned int *);
  57 static int try_rfc1123(const char *, size_t, struct nf_conntrack_man *,
  58                        char, unsigned int *);
  59 static int try_eprt(const char *, size_t, struct nf_conntrack_man *,
  60                     char, unsigned int *);
  61 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
  62                              char, unsigned int *);
  63
  64 static struct ftp_search {
  65         const char *pattern;
  66         size_t plen;
  67         char skip;
  68         char term;
  69         enum nf_ct_ftp_type ftptype;
  70         int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char, unsigned int *);
  71 } search[IP_CT_DIR_MAX][2] = {
  72         [IP_CT_DIR_ORIGINAL] = {
  73                 {
  74                         .pattern        = "PORT",
  75                         .plen           = sizeof("PORT") - 1,
  76                         .skip           = ' ',
  77                         .term           = '\r',
  78                         .ftptype        = NF_CT_FTP_PORT,
  79                         .getnum         = try_rfc959,
  80                 },
  81                 {
  82                         .pattern        = "EPRT",
  83                         .plen           = sizeof("EPRT") - 1,
  84                         .skip           = ' ',
  85                         .term           = '\r',
  86                         .ftptype        = NF_CT_FTP_EPRT,
  87                         .getnum         = try_eprt,
  88                 },
  89         },
  90         [IP_CT_DIR_REPLY] = {
  91                 {
  92                         .pattern        = "227 ",
  93                         .plen           = sizeof("227 ") - 1,
  94                         .ftptype        = NF_CT_FTP_PASV,
  95                         .getnum         = try_rfc1123,
  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 (or we don't care about one)
 135                            and we're finished. */
 136                         if ((*data == term || !term) && i == array_size - 1)
 137                                 return len;
 138
 139                         pr_debug("Char %u (got %u nums) `%u' unexpected\n",
 140                                  len, i, *data);
 141                         return 0;
 142                 }
 143         }
 144         pr_debug("Failed to fill %u numbers separated by %c\n",
 145                  array_size, sep);
 146         return 0;
 147 }
 148
 149 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
 150 static int try_rfc959(const char *data, size_t dlen,
 151                       struct nf_conntrack_man *cmd, char term,
 152                       unsigned int *offset)
 153 {
 154         int length;
 155         u_int32_t array[6];
 156
 157         length = try_number(data, dlen, array, 6, ',', term);
 158         if (length == 0)
 159                 return 0;
 160
 161         cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16) |
 162                                     (array[2] << 8) | array[3]);
 163         cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
 164         return length;
 165 }
 166
 167 /*
 168  * From RFC 1123:
 169  * The format of the 227 reply to a PASV command is not
 170  * well standardized.  In particular, an FTP client cannot
 171  * assume that the parentheses shown on page 40 of RFC-959
 172  * will be present (and in fact, Figure 3 on page 43 omits
 173  * them).  Therefore, a User-FTP program that interprets
 174  * the PASV reply must scan the reply for the first digit
 175  * of the host and port numbers.
 176  */
 177 static int try_rfc1123(const char *data, size_t dlen,
 178                        struct nf_conntrack_man *cmd, char term,
 179                        unsigned int *offset)
 180 {
 181         int i;
 182         for (i = 0; i < dlen; i++)
 183                 if (isdigit(data[i]))
 184                         break;
 185
 186         if (i == dlen)
 187                 return 0;
 188
 189         *offset += i;
 190
 191         return try_rfc959(data + i, dlen - i, cmd, 0, offset);
 192 }
 193
 194 /* Grab port: number up to delimiter */
 195 static int get_port(const char *data, int start, size_t dlen, char delim,
 196                     __be16 *port)
 197 {
 198         u_int16_t tmp_port = 0;
 199         int i;
 200
 201         for (i = start; i < dlen; i++) {
 202                 /* Finished? */
 203                 if (data[i] == delim) {
 204                         if (tmp_port == 0)
 205                                 break;
 206                         *port = htons(tmp_port);
 207                         pr_debug("get_port: return %d\n", tmp_port);
 208                         return i + 1;
 209                 }
 210                 else if (data[i] >= '0' && data[i] <= '9')
 211                         tmp_port = tmp_port*10 + data[i] - '0';
 212                 else { /* Some other crap */
 213                         pr_debug("get_port: invalid char.\n");
 214                         break;
 215                 }
 216         }
 217         return 0;
 218 }
 219
 220 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
 221 static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
 222                     char term, unsigned int *offset)
 223 {
 224         char delim;
 225         int length;
 226
 227         /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
 228            then delimiter again. */
 229         if (dlen <= 3) {
 230                 pr_debug("EPRT: too short\n");
 231                 return 0;
 232         }
 233         delim = data[0];
 234         if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
 235                 pr_debug("try_eprt: invalid delimiter.\n");
 236                 return 0;
 237         }
 238
 239         if ((cmd->l3num == PF_INET && data[1] != '1') ||
 240             (cmd->l3num == PF_INET6 && data[1] != '2')) {
 241                 pr_debug("EPRT: invalid protocol number.\n");
 242                 return 0;
 243         }
 244
 245         pr_debug("EPRT: Got %c%c%c\n", delim, data[1], delim);
 246
 247         if (data[1] == '1') {
 248                 u_int32_t array[4];
 249
 250                 /* Now we have IP address. */
 251                 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
 252                 if (length != 0)
 253                         cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
 254                                            | (array[2] << 8) | array[3]);
 255         } else {
 256                 /* Now we have IPv6 address. */
 257                 length = get_ipv6_addr(data + 3, dlen - 3,
 258                                        (struct in6_addr *)cmd->u3.ip6, delim);
 259         }
 260
 261         if (length == 0)
 262                 return 0;
 263         pr_debug("EPRT: Got IP address!\n");
 264         /* Start offset includes initial "|1|", and trailing delimiter */
 265         return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
 266 }
 267
 268 /* Returns 0, or length of numbers: |||6446| */
 269 static int try_epsv_response(const char *data, size_t dlen,
 270                              struct nf_conntrack_man *cmd, char term,
 271                              unsigned int *offset)
 272 {
 273         char delim;
 274
 275         /* Three delimiters. */
 276         if (dlen <= 3) return 0;
 277         delim = data[0];
 278         if (isdigit(delim) || delim < 33 || delim > 126 ||
 279             data[1] != delim || data[2] != delim)
 280                 return 0;
 281
 282         return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
 283 }
 284
 285 /* Return 1 for match, 0 for accept, -1 for partial. */
 286 static int find_pattern(const char *data, size_t dlen,
 287                         const char *pattern, size_t plen,
 288                         char skip, char term,
 289                         unsigned int *numoff,
 290                         unsigned int *numlen,
 291                         struct nf_conntrack_man *cmd,
 292                         int (*getnum)(const char *, size_t,
 293                                       struct nf_conntrack_man *, char,
 294                                       unsigned int *))
 295 {
 296         size_t i = plen;
 297
 298         pr_debug("find_pattern `%s': dlen = %zu\n", pattern, dlen);
 299
 300         if (dlen <= plen) {
 301                 /* Short packet: try for partial? */
 302                 if (strncasecmp(data, pattern, dlen) == 0)
 303                         return -1;
 304                 else return 0;
 305         }
 306
 307         if (strncasecmp(data, pattern, plen) != 0)
 308                 return 0;
 309
 310         pr_debug("Pattern matches!\n");
 311         /* Now we've found the constant string, try to skip
 312            to the 'skip' character */
 313         if (skip) {
 314                 for (i = plen; data[i] != skip; i++)
 315                         if (i == dlen - 1) return -1;
 316
 317                 /* Skip over the last character */
 318                 i++;
 319         }
 320
 321         pr_debug("Skipped up to 0x%hhx delimiter!\n", skip);
 322
 323         *numoff = i;
 324         *numlen = getnum(data + i, dlen - i, cmd, term, numoff);
 325         if (!*numlen)
 326                 return -1;
 327
 328         pr_debug("Match succeeded!\n");
 329         return 1;
 330 }
 331
 332 /* Look up to see if we're just after a \n. */
 333 static int find_nl_seq(u32 seq, const struct nf_ct_ftp_master *info, int dir)
 334 {
 335         unsigned int i;
 336
 337         for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
 338                 if (info->seq_aft_nl[dir][i] == seq)
 339                         return 1;
 340         return 0;
 341 }
 342
 343 /* We don't update if it's older than what we have. */
 344 static void update_nl_seq(struct nf_conn *ct, u32 nl_seq,
 345                           struct nf_ct_ftp_master *info, int dir,
 346                           struct sk_buff *skb)
 347 {
 348         unsigned int i, oldest;
 349
 350         /* Look for oldest: if we find exact match, we're done. */
 351         for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
 352                 if (info->seq_aft_nl[dir][i] == nl_seq)
 353                         return;
 354         }
 355
 356         if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
 357                 info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
 358         } else {
 359                 if (before(info->seq_aft_nl[dir][0], info->seq_aft_nl[dir][1]))
 360                         oldest = 0;
 361                 else
 362                         oldest = 1;
 363
 364                 if (after(nl_seq, info->seq_aft_nl[dir][oldest]))
 365                         info->seq_aft_nl[dir][oldest] = nl_seq;
 366         }
 367 }
 368
 369 static int help(struct sk_buff *skb,
 370                 unsigned int protoff,
 371                 struct nf_conn *ct,
 372                 enum ip_conntrack_info ctinfo)
 373 {
 374         unsigned int dataoff, datalen;
 375         const struct tcphdr *th;
 376         struct tcphdr _tcph;
 377         const char *fb_ptr;
 378         int ret;
 379         u32 seq;
 380         int dir = CTINFO2DIR(ctinfo);
 381         unsigned int matchlen, matchoff;
 382         struct nf_ct_ftp_master *ct_ftp_info = nfct_help_data(ct);
 383         struct nf_conntrack_expect *exp;
 384         union nf_inet_addr *daddr;
 385         struct nf_conntrack_man cmd = {};
 386         unsigned int i;
 387         int found = 0, ends_in_nl;
 388         typeof(nf_nat_ftp_hook) nf_nat_ftp;
 389
 390         /* Until there's been traffic both ways, don't look in packets. */
 391         if (ctinfo != IP_CT_ESTABLISHED &&
 392             ctinfo != IP_CT_ESTABLISHED_REPLY) {
 393                 pr_debug("ftp: Conntrackinfo = %u\n", ctinfo);
 394                 return NF_ACCEPT;
 395         }
 396
 397         if (unlikely(skb_linearize(skb)))
 398                 return NF_DROP;
 399
 400         th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
 401         if (th == NULL)
 402                 return NF_ACCEPT;
 403
 404         dataoff = protoff + th->doff * 4;
 405         /* No data? */
 406         if (dataoff >= skb->len) {
 407                 pr_debug("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
 408                          skb->len);
 409                 return NF_ACCEPT;
 410         }
 411         datalen = skb->len - dataoff;
 412
 413         /* seqadj (nat) uses ct->lock internally, nf_nat_ftp would cause deadlock */
 414         spin_lock_bh(&nf_ftp_lock);
 415         fb_ptr = skb->data + dataoff;
 416
 417         ends_in_nl = (fb_ptr[datalen - 1] == '\n');
 418         seq = ntohl(th->seq) + datalen;
 419
 420         /* Look up to see if we're just after a \n. */
 421         if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
 422                 /* We're picking up this, clear flags and let it continue */
 423                 if (unlikely(ct_ftp_info->flags[dir] & NF_CT_FTP_SEQ_PICKUP)) {
 424                         ct_ftp_info->flags[dir] ^= NF_CT_FTP_SEQ_PICKUP;
 425                         goto skip_nl_seq;
 426                 }
 427
 428                 /* Now if this ends in \n, update ftp info. */
 429                 pr_debug("nf_conntrack_ftp: wrong seq pos %s(%u) or %s(%u)\n",
 430                          ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
 431                          ct_ftp_info->seq_aft_nl[dir][0],
 432                          ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
 433                          ct_ftp_info->seq_aft_nl[dir][1]);
 434                 ret = NF_ACCEPT;
 435                 goto out_update_nl;
 436         }
 437
 438 skip_nl_seq:
 439         /* Initialize IP/IPv6 addr to expected address (it's not mentioned
 440            in EPSV responses) */
 441         cmd.l3num = nf_ct_l3num(ct);
 442         memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
 443                sizeof(cmd.u3.all));
 444
 445         for (i = 0; i < ARRAY_SIZE(search[dir]); i++) {
 446                 found = find_pattern(fb_ptr, datalen,
 447                                      search[dir][i].pattern,
 448                                      search[dir][i].plen,
 449                                      search[dir][i].skip,
 450                                      search[dir][i].term,
 451                                      &matchoff, &matchlen,
 452                                      &cmd,
 453                                      search[dir][i].getnum);
 454                 if (found) break;
 455         }
 456         if (found == -1) {
 457                 /* We don't usually drop packets.  After all, this is
 458                    connection tracking, not packet filtering.
 459                    However, it is necessary for accurate tracking in
 460                    this case. */
 461                 nf_ct_helper_log(skb, ct, "partial matching of `%s'",
 462                                  search[dir][i].pattern);
 463                 ret = NF_DROP;
 464                 goto out;
 465         } else if (found == 0) { /* No match */
 466                 ret = NF_ACCEPT;
 467                 goto out_update_nl;
 468         }
 469
 470         pr_debug("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
 471                  matchlen, fb_ptr + matchoff,
 472                  matchlen, ntohl(th->seq) + matchoff);
 473
 474         exp = nf_ct_expect_alloc(ct);
 475         if (exp == NULL) {
 476                 nf_ct_helper_log(skb, ct, "cannot alloc expectation");
 477                 ret = NF_DROP;
 478                 goto out;
 479         }
 480
 481         /* We refer to the reverse direction ("!dir") tuples here,
 482          * because we're expecting something in the other direction.
 483          * Doesn't matter unless NAT is happening.  */
 484         daddr = &ct->tuplehash[!dir].tuple.dst.u3;
 485
 486         /* Update the ftp info */
 487         if ((cmd.l3num == nf_ct_l3num(ct)) &&
 488             memcmp(&cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
 489                      sizeof(cmd.u3.all))) {
 490                 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
 491                    server: it really wants us to connect to a
 492                    different IP address.  Simply don't record it for
 493                    NAT. */
 494                 if (cmd.l3num == PF_INET) {
 495                         pr_debug("NOT RECORDING: %pI4 != %pI4\n",
 496                                  &cmd.u3.ip,
 497                                  &ct->tuplehash[dir].tuple.src.u3.ip);
 498                 } else {
 499                         pr_debug("NOT RECORDING: %pI6 != %pI6\n",
 500                                  cmd.u3.ip6,
 501                                  ct->tuplehash[dir].tuple.src.u3.ip6);
 502                 }
 503
 504                 /* Thanks to Cristiano Lincoln Mattos
 505                    <[email protected]> for reporting this potential
 506                    problem (DMZ machines opening holes to internal
 507                    networks, or the packet filter itself). */
 508                 if (!loose) {
 509                         ret = NF_ACCEPT;
 510                         goto out_put_expect;
 511                 }
 512                 daddr = &cmd.u3;
 513         }
 514
 515         nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, cmd.l3num,
 516                           &ct->tuplehash[!dir].tuple.src.u3, daddr,
 517                           IPPROTO_TCP, NULL, &cmd.u.tcp.port);
 518
 519         /* Now, NAT might want to mangle the packet, and register the
 520          * (possibly changed) expectation itself. */
 521         nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
 522         if (nf_nat_ftp && ct->status & IPS_NAT_MASK)
 523                 ret = nf_nat_ftp(skb, ctinfo, search[dir][i].ftptype,
 524                                  protoff, matchoff, matchlen, exp);
 525         else {
 526                 /* Can't expect this?  Best to drop packet now. */
 527                 if (nf_ct_expect_related(exp, 0) != 0) {
 528                         nf_ct_helper_log(skb, ct, "cannot add expectation");
 529                         ret = NF_DROP;
 530                 } else
 531                         ret = NF_ACCEPT;
 532         }
 533
 534 out_put_expect:
 535         nf_ct_expect_put(exp);
 536
 537 out_update_nl:
 538         /* Now if this ends in \n, update ftp info.  Seq may have been
 539          * adjusted by NAT code. */
 540         if (ends_in_nl)
 541                 update_nl_seq(ct, seq, ct_ftp_info, dir, skb);
 542  out:
 543         spin_unlock_bh(&nf_ftp_lock);
 544         return ret;
 545 }
 546
 547 static int nf_ct_ftp_from_nlattr(struct nlattr *attr, struct nf_conn *ct)
 548 {
 549         struct nf_ct_ftp_master *ftp = nfct_help_data(ct);
 550
 551         /* This conntrack has been injected from user-space, always pick up
 552          * sequence tracking. Otherwise, the first FTP command after the
 553          * failover breaks.
 554          */
 555         ftp->flags[IP_CT_DIR_ORIGINAL] |= NF_CT_FTP_SEQ_PICKUP;
 556         ftp->flags[IP_CT_DIR_REPLY] |= NF_CT_FTP_SEQ_PICKUP;
 557         return 0;
 558 }
 559
 560 static struct nf_conntrack_helper ftp[MAX_PORTS * 2] __read_mostly;
 561
 562 static const struct nf_conntrack_expect_policy ftp_exp_policy = {
 563         .max_expected   = 1,
 564         .timeout        = 5 * 60,
 565 };
 566
 567 static void __exit nf_conntrack_ftp_fini(void)
 568 {
 569         nf_conntrack_helpers_unregister(ftp, ports_c * 2);
 570 }
 571
 572 static int __init nf_conntrack_ftp_init(void)
 573 {
 574         int i, ret = 0;
 575
 576         NF_CT_HELPER_BUILD_BUG_ON(sizeof(struct nf_ct_ftp_master));
 577
 578         if (ports_c == 0)
 579                 ports[ports_c++] = FTP_PORT;
 580
 581         /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
 582                  are tracked or not - YK */
 583         for (i = 0; i < ports_c; i++) {
 584                 nf_ct_helper_init(&ftp[2 * i], AF_INET, IPPROTO_TCP,
 585                                   HELPER_NAME, FTP_PORT, ports[i], ports[i],
 586                                   &ftp_exp_policy, 0, help,
 587                                   nf_ct_ftp_from_nlattr, THIS_MODULE);
 588                 nf_ct_helper_init(&ftp[2 * i + 1], AF_INET6, IPPROTO_TCP,
 589                                   HELPER_NAME, FTP_PORT, ports[i], ports[i],
 590                                   &ftp_exp_policy, 0, help,
 591                                   nf_ct_ftp_from_nlattr, THIS_MODULE);
 592         }
 593
 594         ret = nf_conntrack_helpers_register(ftp, ports_c * 2);
 595         if (ret < 0) {
 596                 pr_err("failed to register helpers\n");
 597                 return ret;
 598         }
 599
 600         return 0;
 601 }
 602
 603 module_init(nf_conntrack_ftp_init);
 604 module_exit(nf_conntrack_ftp_fini);