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