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  * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  */
  12
  13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  14
  15 #include <linux/module.h>
  16 #include <linux/moduleparam.h>
  17 #include <linux/netfilter.h>
  18 #include <linux/ip.h>
  19 #include <linux/slab.h>
  20 #include <linux/ipv6.h>
  21 #include <linux/ctype.h>
  22 #include <linux/inet.h>
  23 #include <net/checksum.h>
  24 #include <net/tcp.h>
  25
  26 #include <net/netfilter/nf_conntrack.h>
  27 #include <net/netfilter/nf_conntrack_expect.h>
  28 #include <net/netfilter/nf_conntrack_ecache.h>
  29 #include <net/netfilter/nf_conntrack_helper.h>
  30 #include <linux/netfilter/nf_conntrack_ftp.h>
  31
  32 #define HELPER_NAME "ftp"
  33
  34 MODULE_LICENSE("GPL");
  35 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
  36 MODULE_DESCRIPTION("ftp connection tracking helper");
  37 MODULE_ALIAS("ip_conntrack_ftp");
  38 MODULE_ALIAS_NFCT_HELPER(HELPER_NAME);
  39
  40 /* This is slow, but it's simple. --RR */
  41 static char *ftp_buffer;
  42
  43 static DEFINE_SPINLOCK(nf_ftp_lock);
  44
  45 #define MAX_PORTS 8
  46 static u_int16_t ports[MAX_PORTS];
  47 static unsigned int ports_c;
  48 module_param_array(ports, ushort, &ports_c, 0400);
  49
  50 static bool loose;
  51 module_param(loose, bool, 0600);
  52
  53 unsigned int (*nf_nat_ftp_hook)(struct sk_buff *skb,
  54                                 enum ip_conntrack_info ctinfo,
  55                                 enum nf_ct_ftp_type type,
  56                                 unsigned int protoff,
  57                                 unsigned int matchoff,
  58                                 unsigned int matchlen,
  59                                 struct nf_conntrack_expect *exp);
  60 EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
  61
  62 static int try_rfc959(const char *, size_t, struct nf_conntrack_man *,
  63                       char, unsigned int *);
  64 static int try_rfc1123(const char *, size_t, struct nf_conntrack_man *,
  65                        char, unsigned int *);
  66 static int try_eprt(const char *, size_t, struct nf_conntrack_man *,
  67                     char, unsigned int *);
  68 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
  69                              char, unsigned int *);
  70
  71 static struct ftp_search {
  72         const char *pattern;
  73         size_t plen;
  74         char skip;
  75         char term;
  76         enum nf_ct_ftp_type ftptype;
  77         int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char, unsigned int *);
  78 } search[IP_CT_DIR_MAX][2] = {
  79         [IP_CT_DIR_ORIGINAL] = {
  80                 {
  81                         .pattern        = "PORT",
  82                         .plen           = sizeof("PORT") - 1,
  83                         .skip           = ' ',
  84                         .term           = '\r',
  85                         .ftptype        = NF_CT_FTP_PORT,
  86                         .getnum         = try_rfc959,
  87                 },
  88                 {
  89                         .pattern        = "EPRT",
  90                         .plen           = sizeof("EPRT") - 1,
  91                         .skip           = ' ',
  92                         .term           = '\r',
  93                         .ftptype        = NF_CT_FTP_EPRT,
  94                         .getnum         = try_eprt,
  95                 },
  96         },
  97         [IP_CT_DIR_REPLY] = {
  98                 {
  99                         .pattern        = "227 ",
 100                         .plen           = sizeof("227 ") - 1,
 101                         .ftptype        = NF_CT_FTP_PASV,
 102                         .getnum         = try_rfc1123,
 103                 },
 104                 {
 105                         .pattern        = "229 ",
 106                         .plen           = sizeof("229 ") - 1,
 107                         .skip           = '(',
 108                         .term           = ')',
 109                         .ftptype        = NF_CT_FTP_EPSV,
 110                         .getnum         = try_epsv_response,
 111                 },
 112         },
 113 };
 114
 115 static int
 116 get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
 117 {
 118         const char *end;
 119         int ret = in6_pton(src, min_t(size_t, dlen, 0xffff), (u8 *)dst, term, &end);
 120         if (ret > 0)
 121                 return (int)(end - src);
 122         return 0;
 123 }
 124
 125 static int try_number(const char *data, size_t dlen, u_int32_t array[],
 126                       int array_size, char sep, char term)
 127 {
 128         u_int32_t i, len;
 129
 130         memset(array, 0, sizeof(array[0])*array_size);
 131
 132         /* Keep data pointing at next char. */
 133         for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
 134                 if (*data >= '0' && *data <= '9') {
 135                         array[i] = array[i]*10 + *data - '0';
 136                 }
 137                 else if (*data == sep)
 138                         i++;
 139                 else {
 140                         /* Unexpected character; true if it's the
 141                            terminator (or we don't care about one)
 142                            and we're finished. */
 143                         if ((*data == term || !term) && i == array_size - 1)
 144                                 return len;
 145
 146                         pr_debug("Char %u (got %u nums) `%u' unexpected\n",
 147                                  len, i, *data);
 148                         return 0;
 149                 }
 150         }
 151         pr_debug("Failed to fill %u numbers separated by %c\n",
 152                  array_size, sep);
 153         return 0;
 154 }
 155
 156 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
 157 static int try_rfc959(const char *data, size_t dlen,
 158                       struct nf_conntrack_man *cmd, char term,
 159                       unsigned int *offset)
 160 {
 161         int length;
 162         u_int32_t array[6];
 163
 164         length = try_number(data, dlen, array, 6, ',', term);
 165         if (length == 0)
 166                 return 0;
 167
 168         cmd->u3.ip =  htonl((array[0] << 24) | (array[1] << 16) |
 169                                     (array[2] << 8) | array[3]);
 170         cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
 171         return length;
 172 }
 173
 174 /*
 175  * From RFC 1123:
 176  * The format of the 227 reply to a PASV command is not
 177  * well standardized.  In particular, an FTP client cannot
 178  * assume that the parentheses shown on page 40 of RFC-959
 179  * will be present (and in fact, Figure 3 on page 43 omits
 180  * them).  Therefore, a User-FTP program that interprets
 181  * the PASV reply must scan the reply for the first digit
 182  * of the host and port numbers.
 183  */
 184 static int try_rfc1123(const char *data, size_t dlen,
 185                        struct nf_conntrack_man *cmd, char term,
 186                        unsigned int *offset)
 187 {
 188         int i;
 189         for (i = 0; i < dlen; i++)
 190                 if (isdigit(data[i]))
 191                         break;
 192
 193         if (i == dlen)
 194                 return 0;
 195
 196         *offset += i;
 197
 198         return try_rfc959(data + i, dlen - i, cmd, 0, offset);
 199 }
 200
 201 /* Grab port: number up to delimiter */
 202 static int get_port(const char *data, int start, size_t dlen, char delim,
 203                     __be16 *port)
 204 {
 205         u_int16_t tmp_port = 0;
 206         int i;
 207
 208         for (i = start; i < dlen; i++) {
 209                 /* Finished? */
 210                 if (data[i] == delim) {
 211                         if (tmp_port == 0)
 212                                 break;
 213                         *port = htons(tmp_port);
 214                         pr_debug("get_port: return %d\n", tmp_port);
 215                         return i + 1;
 216                 }
 217                 else if (data[i] >= '0' && data[i] <= '9')
 218                         tmp_port = tmp_port*10 + data[i] - '0';
 219                 else { /* Some other crap */
 220                         pr_debug("get_port: invalid char.\n");
 221                         break;
 222                 }
 223         }
 224         return 0;
 225 }
 226
 227 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
 228 static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
 229                     char term, unsigned int *offset)
 230 {
 231         char delim;
 232         int length;
 233
 234         /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
 235            then delimiter again. */
 236         if (dlen <= 3) {
 237                 pr_debug("EPRT: too short\n");
 238                 return 0;
 239         }
 240         delim = data[0];
 241         if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
 242                 pr_debug("try_eprt: invalid delimiter.\n");
 243                 return 0;
 244         }
 245
 246         if ((cmd->l3num == PF_INET && data[1] != '1') ||
 247             (cmd->l3num == PF_INET6 && data[1] != '2')) {
 248                 pr_debug("EPRT: invalid protocol number.\n");
 249                 return 0;
 250         }
 251
 252         pr_debug("EPRT: Got %c%c%c\n", delim, data[1], delim);
 253
 254         if (data[1] == '1') {
 255                 u_int32_t array[4];
 256
 257                 /* Now we have IP address. */
 258                 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
 259                 if (length != 0)
 260                         cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
 261                                            | (array[2] << 8) | array[3]);
 262         } else {
 263                 /* Now we have IPv6 address. */
 264                 length = get_ipv6_addr(data + 3, dlen - 3,
 265                                        (struct in6_addr *)cmd->u3.ip6, delim);
 266         }
 267
 268         if (length == 0)
 269                 return 0;
 270         pr_debug("EPRT: Got IP address!\n");
 271         /* Start offset includes initial "|1|", and trailing delimiter */
 272         return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
 273 }
 274
 275 /* Returns 0, or length of numbers: |||6446| */
 276 static int try_epsv_response(const char *data, size_t dlen,
 277                              struct nf_conntrack_man *cmd, char term,
 278                              unsigned int *offset)
 279 {
 280         char delim;
 281
 282         /* Three delimiters. */
 283         if (dlen <= 3) return 0;
 284         delim = data[0];
 285         if (isdigit(delim) || delim < 33 || delim > 126 ||
 286             data[1] != delim || data[2] != delim)
 287                 return 0;
 288
 289         return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
 290 }
 291
 292 /* Return 1 for match, 0 for accept, -1 for partial. */
 293 static int find_pattern(const char *data, size_t dlen,
 294                         const char *pattern, size_t plen,
 295                         char skip, char term,
 296                         unsigned int *numoff,
 297                         unsigned int *numlen,
 298                         struct nf_conntrack_man *cmd,
 299                         int (*getnum)(const char *, size_t,
 300                                       struct nf_conntrack_man *, char,
 301                                       unsigned int *))
 302 {
 303         size_t i = plen;
 304
 305         pr_debug("find_pattern `%s': dlen = %zu\n", pattern, dlen);
 306
 307         if (dlen <= plen) {
 308                 /* Short packet: try for partial? */
 309                 if (strncasecmp(data, pattern, dlen) == 0)
 310                         return -1;
 311                 else return 0;
 312         }
 313
 314         if (strncasecmp(data, pattern, plen) != 0)
 315                 return 0;
 316
 317         pr_debug("Pattern matches!\n");
 318         /* Now we've found the constant string, try to skip
 319            to the 'skip' character */
 320         if (skip) {
 321                 for (i = plen; data[i] != skip; i++)
 322                         if (i == dlen - 1) return -1;
 323
 324                 /* Skip over the last character */
 325                 i++;
 326         }
 327
 328         pr_debug("Skipped up to `%c'!\n", skip);
 329
 330         *numoff = i;
 331         *numlen = getnum(data + i, dlen - i, cmd, term, numoff);
 332         if (!*numlen)
 333                 return -1;
 334
 335         pr_debug("Match succeeded!\n");
 336         return 1;
 337 }
 338
 339 /* Look up to see if we're just after a \n. */
 340 static int find_nl_seq(u32 seq, const struct nf_ct_ftp_master *info, int dir)
 341 {
 342         unsigned int i;
 343
 344         for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
 345                 if (info->seq_aft_nl[dir][i] == seq)
 346                         return 1;
 347         return 0;
 348 }
 349
 350 /* We don't update if it's older than what we have. */
 351 static void update_nl_seq(struct nf_conn *ct, u32 nl_seq,
 352                           struct nf_ct_ftp_master *info, int dir,
 353                           struct sk_buff *skb)
 354 {
 355         unsigned int i, oldest;
 356
 357         /* Look for oldest: if we find exact match, we're done. */
 358         for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
 359                 if (info->seq_aft_nl[dir][i] == nl_seq)
 360                         return;
 361         }
 362
 363         if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
 364                 info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
 365         } else {
 366                 if (before(info->seq_aft_nl[dir][0], info->seq_aft_nl[dir][1]))
 367                         oldest = 0;
 368                 else
 369                         oldest = 1;
 370
 371                 if (after(nl_seq, info->seq_aft_nl[dir][oldest]))
 372                         info->seq_aft_nl[dir][oldest] = nl_seq;
 373         }
 374 }
 375
 376 static int help(struct sk_buff *skb,
 377                 unsigned int protoff,
 378                 struct nf_conn *ct,
 379                 enum ip_conntrack_info ctinfo)
 380 {
 381         unsigned int dataoff, datalen;
 382         const struct tcphdr *th;
 383         struct tcphdr _tcph;
 384         const char *fb_ptr;
 385         int ret;
 386         u32 seq;
 387         int dir = CTINFO2DIR(ctinfo);
 388         unsigned int uninitialized_var(matchlen), uninitialized_var(matchoff);
 389         struct nf_ct_ftp_master *ct_ftp_info = nfct_help_data(ct);
 390         struct nf_conntrack_expect *exp;
 391         union nf_inet_addr *daddr;
 392         struct nf_conntrack_man cmd = {};
 393         unsigned int i;
 394         int found = 0, ends_in_nl;
 395         typeof(nf_nat_ftp_hook) nf_nat_ftp;
 396
 397         /* Until there's been traffic both ways, don't look in packets. */
 398         if (ctinfo != IP_CT_ESTABLISHED &&
 399             ctinfo != IP_CT_ESTABLISHED_REPLY) {
 400                 pr_debug("ftp: Conntrackinfo = %u\n", ctinfo);
 401                 return NF_ACCEPT;
 402         }
 403
 404         th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
 405         if (th == NULL)
 406                 return NF_ACCEPT;
 407
 408         dataoff = protoff + th->doff * 4;
 409         /* No data? */
 410         if (dataoff >= skb->len) {
 411                 pr_debug("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
 412                          skb->len);
 413                 return NF_ACCEPT;
 414         }
 415         datalen = skb->len - dataoff;
 416
 417         spin_lock_bh(&nf_ftp_lock);
 418         fb_ptr = skb_header_pointer(skb, dataoff, datalen, ftp_buffer);
 419         BUG_ON(fb_ptr == NULL);
 420
 421         ends_in_nl = (fb_ptr[datalen - 1] == '\n');
 422         seq = ntohl(th->seq) + datalen;
 423
 424         /* Look up to see if we're just after a \n. */
 425         if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
 426                 /* We're picking up this, clear flags and let it continue */
 427                 if (unlikely(ct_ftp_info->flags[dir] & NF_CT_FTP_SEQ_PICKUP)) {
 428                         ct_ftp_info->flags[dir] ^= NF_CT_FTP_SEQ_PICKUP;
 429                         goto skip_nl_seq;
 430                 }
 431
 432                 /* Now if this ends in \n, update ftp info. */
 433                 pr_debug("nf_conntrack_ftp: wrong seq pos %s(%u) or %s(%u)\n",
 434                          ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
 435                          ct_ftp_info->seq_aft_nl[dir][0],
 436                          ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
 437                          ct_ftp_info->seq_aft_nl[dir][1]);
 438                 ret = NF_ACCEPT;
 439                 goto out_update_nl;
 440         }
 441
 442 skip_nl_seq:
 443         /* Initialize IP/IPv6 addr to expected address (it's not mentioned
 444            in EPSV responses) */
 445         cmd.l3num = nf_ct_l3num(ct);
 446         memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
 447                sizeof(cmd.u3.all));
 448
 449         for (i = 0; i < ARRAY_SIZE(search[dir]); i++) {
 450                 found = find_pattern(fb_ptr, datalen,
 451                                      search[dir][i].pattern,
 452                                      search[dir][i].plen,
 453                                      search[dir][i].skip,
 454                                      search[dir][i].term,
 455                                      &matchoff, &matchlen,
 456                                      &cmd,
 457                                      search[dir][i].getnum);
 458                 if (found) break;
 459         }
 460         if (found == -1) {
 461                 /* We don't usually drop packets.  After all, this is
 462                    connection tracking, not packet filtering.
 463                    However, it is necessary for accurate tracking in
 464                    this case. */
 465                 nf_ct_helper_log(skb, ct, "partial matching of `%s'",
 466                                  search[dir][i].pattern);
 467                 ret = NF_DROP;
 468                 goto out;
 469         } else if (found == 0) { /* No match */
 470                 ret = NF_ACCEPT;
 471                 goto out_update_nl;
 472         }
 473
 474         pr_debug("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
 475                  matchlen, fb_ptr + matchoff,
 476                  matchlen, ntohl(th->seq) + matchoff);
 477
 478         exp = nf_ct_expect_alloc(ct);
 479         if (exp == NULL) {
 480                 nf_ct_helper_log(skb, ct, "cannot alloc expectation");
 481                 ret = NF_DROP;
 482                 goto out;
 483         }
 484
 485         /* We refer to the reverse direction ("!dir") tuples here,
 486          * because we're expecting something in the other direction.
 487          * Doesn't matter unless NAT is happening.  */
 488         daddr = &ct->tuplehash[!dir].tuple.dst.u3;
 489
 490         /* Update the ftp info */
 491         if ((cmd.l3num == nf_ct_l3num(ct)) &&
 492             memcmp(&cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
 493                      sizeof(cmd.u3.all))) {
 494                 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
 495                    server: it really wants us to connect to a
 496                    different IP address.  Simply don't record it for
 497                    NAT. */
 498                 if (cmd.l3num == PF_INET) {
 499                         pr_debug("NOT RECORDING: %pI4 != %pI4\n",
 500                                  &cmd.u3.ip,
 501                                  &ct->tuplehash[dir].tuple.src.u3.ip);
 502                 } else {
 503                         pr_debug("NOT RECORDING: %pI6 != %pI6\n",
 504                                  cmd.u3.ip6,
 505                                  ct->tuplehash[dir].tuple.src.u3.ip6);
 506                 }
 507
 508                 /* Thanks to Cristiano Lincoln Mattos
 509                    <lincoln@cesar.org.br> for reporting this potential
 510                    problem (DMZ machines opening holes to internal
 511                    networks, or the packet filter itself). */
 512                 if (!loose) {
 513                         ret = NF_ACCEPT;
 514                         goto out_put_expect;
 515                 }
 516                 daddr = &cmd.u3;
 517         }
 518
 519         nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, cmd.l3num,
 520                           &ct->tuplehash[!dir].tuple.src.u3, daddr,
 521                           IPPROTO_TCP, NULL, &cmd.u.tcp.port);
 522
 523         /* Now, NAT might want to mangle the packet, and register the
 524          * (possibly changed) expectation itself. */
 525         nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
 526         if (nf_nat_ftp && ct->status & IPS_NAT_MASK)
 527                 ret = nf_nat_ftp(skb, ctinfo, search[dir][i].ftptype,
 528                                  protoff, matchoff, matchlen, exp);
 529         else {
 530                 /* Can't expect this?  Best to drop packet now. */
 531                 if (nf_ct_expect_related(exp) != 0) {
 532                         nf_ct_helper_log(skb, ct, "cannot add expectation");
 533                         ret = NF_DROP;
 534                 } else
 535                         ret = NF_ACCEPT;
 536         }
 537
 538 out_put_expect:
 539         nf_ct_expect_put(exp);
 540
 541 out_update_nl:
 542         /* Now if this ends in \n, update ftp info.  Seq may have been
 543          * adjusted by NAT code. */
 544         if (ends_in_nl)
 545                 update_nl_seq(ct, seq, ct_ftp_info, dir, skb);
 546  out:
 547         spin_unlock_bh(&nf_ftp_lock);
 548         return ret;
 549 }
 550
 551 static int nf_ct_ftp_from_nlattr(struct nlattr *attr, struct nf_conn *ct)
 552 {
 553         struct nf_ct_ftp_master *ftp = nfct_help_data(ct);
 554
 555         /* This conntrack has been injected from user-space, always pick up
 556          * sequence tracking. Otherwise, the first FTP command after the
 557          * failover breaks.
 558          */
 559         ftp->flags[IP_CT_DIR_ORIGINAL] |= NF_CT_FTP_SEQ_PICKUP;
 560         ftp->flags[IP_CT_DIR_REPLY] |= NF_CT_FTP_SEQ_PICKUP;
 561         return 0;
 562 }
 563
 564 static struct nf_conntrack_helper ftp[MAX_PORTS * 2] __read_mostly;
 565
 566 static const struct nf_conntrack_expect_policy ftp_exp_policy = {
 567         .max_expected   = 1,
 568         .timeout        = 5 * 60,
 569 };
 570
 571 static void __exit nf_conntrack_ftp_fini(void)
 572 {
 573         nf_conntrack_helpers_unregister(ftp, ports_c * 2);
 574         kfree(ftp_buffer);
 575 }
 576
 577 static int __init nf_conntrack_ftp_init(void)
 578 {
 579         int i, ret = 0;
 580
 581         NF_CT_HELPER_BUILD_BUG_ON(sizeof(struct nf_ct_ftp_master));
 582
 583         ftp_buffer = kmalloc(65536, GFP_KERNEL);
 584         if (!ftp_buffer)
 585                 return -ENOMEM;
 586
 587         if (ports_c == 0)
 588                 ports[ports_c++] = FTP_PORT;
 589
 590         /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
 591                  are tracked or not - YK */
 592         for (i = 0; i < ports_c; i++) {
 593                 nf_ct_helper_init(&ftp[2 * i], AF_INET, IPPROTO_TCP,
 594                                   HELPER_NAME, FTP_PORT, ports[i], ports[i],
 595                                   &ftp_exp_policy, 0, help,
 596                                   nf_ct_ftp_from_nlattr, THIS_MODULE);
 597                 nf_ct_helper_init(&ftp[2 * i + 1], AF_INET6, IPPROTO_TCP,
 598                                   HELPER_NAME, FTP_PORT, ports[i], ports[i],
 599                                   &ftp_exp_policy, 0, help,
 600                                   nf_ct_ftp_from_nlattr, THIS_MODULE);
 601         }
 602
 603         ret = nf_conntrack_helpers_register(ftp, ports_c * 2);
 604         if (ret < 0) {
 605                 pr_err("failed to register helpers\n");
 606                 kfree(ftp_buffer);
 607                 return ret;
 608         }
 609
 610         return 0;
 611 }
 612
 613 module_init(nf_conntrack_ftp_init);
 614 module_exit(nf_conntrack_ftp_fini);