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 matchoff,
  52                                 unsigned int matchlen,
  53                                 struct nf_conntrack_expect *exp);
  54 EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
  55
  56 static int try_rfc959(const char *, size_t, struct nf_conntrack_man *,
  57                       char, unsigned int *);
  58 static int try_rfc1123(const char *, size_t, struct nf_conntrack_man *,
  59                        char, unsigned int *);
  60 static int try_eprt(const char *, size_t, struct nf_conntrack_man *,
  61                     char, unsigned int *);
  62 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
  63                              char, unsigned int *);
  64
  65 static struct ftp_search {
  66         const char *pattern;
  67         size_t plen;
  68         char skip;
  69         char term;
  70         enum nf_ct_ftp_type ftptype;
  71         int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char, unsigned int *);
  72 } search[IP_CT_DIR_MAX][2] = {
  73         [IP_CT_DIR_ORIGINAL] = {
  74                 {
  75                         .pattern        = "PORT",
  76                         .plen           = sizeof("PORT") - 1,
  77                         .skip           = ' ',
  78                         .term           = '\r',
  79                         .ftptype        = NF_CT_FTP_PORT,
  80                         .getnum         = try_rfc959,
  81                 },
  82                 {
  83                         .pattern        = "EPRT",
  84                         .plen           = sizeof("EPRT") - 1,
  85                         .skip           = ' ',
  86                         .term           = '\r',
  87                         .ftptype        = NF_CT_FTP_EPRT,
  88                         .getnum         = try_eprt,
  89                 },
  90         },
  91         [IP_CT_DIR_REPLY] = {
  92                 {
  93                         .pattern        = "227 ",
  94                         .plen           = sizeof("227 ") - 1,
  95                         .ftptype        = NF_CT_FTP_PASV,
  96                         .getnum         = try_rfc1123,
  97                 },
  98                 {
  99                         .pattern        = "229 ",
 100                         .plen           = sizeof("229 ") - 1,
 101                         .skip           = '(',
 102                         .term           = ')',
 103                         .ftptype        = NF_CT_FTP_EPSV,
 104                         .getnum         = try_epsv_response,
 105                 },
 106         },
 107 };
 108
 109 static int
 110 get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
 111 {
 112         const char *end;
 113         int ret = in6_pton(src, min_t(size_t, dlen, 0xffff), (u8 *)dst, term, &end);
 114         if (ret > 0)
 115                 return (int)(end - src);
 116         return 0;
 117 }
 118
 119 static int try_number(const char *data, size_t dlen, u_int32_t array[],
 120                       int array_size, char sep, char term)
 121 {
 122         u_int32_t i, len;
 123
 124         memset(array, 0, sizeof(array[0])*array_size);
 125
 126         /* Keep data pointing at next char. */
 127         for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
 128                 if (*data >= '0' && *data <= '9') {
 129                         array[i] = array[i]*10 + *data - '0';
 130                 }
 131                 else if (*data == sep)
 132                         i++;
 133                 else {
 134                         /* Unexpected character; true if it's the
 135                            terminator (or we don't care about one)
 136                            and we're finished. */
 137                         if ((*data == term || !term) && i == array_size - 1)
 138                                 return len;
 139
 140                         pr_debug("Char %u (got %u nums) `%u' unexpected\n",
 141                                  len, i, *data);
 142                         return 0;
 143                 }
 144         }
 145         pr_debug("Failed to fill %u numbers separated by %c\n",
 146                  array_size, sep);
 147         return 0;
 148 }
 149
 150 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
 151 static int try_rfc959(const char *data, size_t dlen,
 152                       struct nf_conntrack_man *cmd, char term,
 153                       unsigned int *offset)
 154 {
 155         int length;
 156         u_int32_t array[6];
 157
 158         length = try_number(data, dlen, array, 6, ',', term);
 159         if (length == 0)
 160                 return 0;
 161
 162         cmd->u3.ip =  htonl((array[0] << 24) | (array[1] << 16) |
 163                                     (array[2] << 8) | array[3]);
 164         cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
 165         return length;
 166 }
 167
 168 /*
 169  * From RFC 1123:
 170  * The format of the 227 reply to a PASV command is not
 171  * well standardized.  In particular, an FTP client cannot
 172  * assume that the parentheses shown on page 40 of RFC-959
 173  * will be present (and in fact, Figure 3 on page 43 omits
 174  * them).  Therefore, a User-FTP program that interprets
 175  * the PASV reply must scan the reply for the first digit
 176  * of the host and port numbers.
 177  */
 178 static int try_rfc1123(const char *data, size_t dlen,
 179                        struct nf_conntrack_man *cmd, char term,
 180                        unsigned int *offset)
 181 {
 182         int i;
 183         for (i = 0; i < dlen; i++)
 184                 if (isdigit(data[i]))
 185                         break;
 186
 187         if (i == dlen)
 188                 return 0;
 189
 190         *offset += i;
 191
 192         return try_rfc959(data + i, dlen - i, cmd, 0, offset);
 193 }
 194
 195 /* Grab port: number up to delimiter */
 196 static int get_port(const char *data, int start, size_t dlen, char delim,
 197                     __be16 *port)
 198 {
 199         u_int16_t tmp_port = 0;
 200         int i;
 201
 202         for (i = start; i < dlen; i++) {
 203                 /* Finished? */
 204                 if (data[i] == delim) {
 205                         if (tmp_port == 0)
 206                                 break;
 207                         *port = htons(tmp_port);
 208                         pr_debug("get_port: return %d\n", tmp_port);
 209                         return i + 1;
 210                 }
 211                 else if (data[i] >= '0' && data[i] <= '9')
 212                         tmp_port = tmp_port*10 + data[i] - '0';
 213                 else { /* Some other crap */
 214                         pr_debug("get_port: invalid char.\n");
 215                         break;
 216                 }
 217         }
 218         return 0;
 219 }
 220
 221 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
 222 static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
 223                     char term, unsigned int *offset)
 224 {
 225         char delim;
 226         int length;
 227
 228         /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
 229            then delimiter again. */
 230         if (dlen <= 3) {
 231                 pr_debug("EPRT: too short\n");
 232                 return 0;
 233         }
 234         delim = data[0];
 235         if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
 236                 pr_debug("try_eprt: invalid delimitter.\n");
 237                 return 0;
 238         }
 239
 240         if ((cmd->l3num == PF_INET && data[1] != '1') ||
 241             (cmd->l3num == PF_INET6 && data[1] != '2')) {
 242                 pr_debug("EPRT: invalid protocol number.\n");
 243                 return 0;
 244         }
 245
 246         pr_debug("EPRT: Got %c%c%c\n", delim, data[1], delim);
 247
 248         if (data[1] == '1') {
 249                 u_int32_t array[4];
 250
 251                 /* Now we have IP address. */
 252                 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
 253                 if (length != 0)
 254                         cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
 255                                            | (array[2] << 8) | array[3]);
 256         } else {
 257                 /* Now we have IPv6 address. */
 258                 length = get_ipv6_addr(data + 3, dlen - 3,
 259                                        (struct in6_addr *)cmd->u3.ip6, delim);
 260         }
 261
 262         if (length == 0)
 263                 return 0;
 264         pr_debug("EPRT: Got IP address!\n");
 265         /* Start offset includes initial "|1|", and trailing delimiter */
 266         return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
 267 }
 268
 269 /* Returns 0, or length of numbers: |||6446| */
 270 static int try_epsv_response(const char *data, size_t dlen,
 271                              struct nf_conntrack_man *cmd, char term,
 272                              unsigned int *offset)
 273 {
 274         char delim;
 275
 276         /* Three delimiters. */
 277         if (dlen <= 3) return 0;
 278         delim = data[0];
 279         if (isdigit(delim) || delim < 33 || delim > 126 ||
 280             data[1] != delim || data[2] != delim)
 281                 return 0;
 282
 283         return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
 284 }
 285
 286 /* Return 1 for match, 0 for accept, -1 for partial. */
 287 static int find_pattern(const char *data, size_t dlen,
 288                         const char *pattern, size_t plen,
 289                         char skip, char term,
 290                         unsigned int *numoff,
 291                         unsigned int *numlen,
 292                         struct nf_conntrack_man *cmd,
 293                         int (*getnum)(const char *, size_t,
 294                                       struct nf_conntrack_man *, char,
 295                                       unsigned int *))
 296 {
 297         size_t i = plen;
 298
 299         pr_debug("find_pattern `%s': dlen = %Zu\n", pattern, dlen);
 300         if (dlen == 0)
 301                 return 0;
 302
 303         if (dlen <= plen) {
 304                 /* Short packet: try for partial? */
 305                 if (strnicmp(data, pattern, dlen) == 0)
 306                         return -1;
 307                 else return 0;
 308         }
 309
 310         if (strnicmp(data, pattern, plen) != 0) {
 311 #if 0
 312                 size_t i;
 313
 314                 pr_debug("ftp: string mismatch\n");
 315                 for (i = 0; i < plen; i++) {
 316                         pr_debug("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
 317                                  i, data[i], data[i],
 318                                  pattern[i], pattern[i]);
 319                 }
 320 #endif
 321                 return 0;
 322         }
 323
 324         pr_debug("Pattern matches!\n");
 325         /* Now we've found the constant string, try to skip
 326            to the 'skip' character */
 327         if (skip) {
 328                 for (i = plen; data[i] != skip; i++)
 329                         if (i == dlen - 1) return -1;
 330
 331                 /* Skip over the last character */
 332                 i++;
 333         }
 334
 335         pr_debug("Skipped up to `%c'!\n", skip);
 336
 337         *numoff = i;
 338         *numlen = getnum(data + i, dlen - i, cmd, term, numoff);
 339         if (!*numlen)
 340                 return -1;
 341
 342         pr_debug("Match succeeded!\n");
 343         return 1;
 344 }
 345
 346 /* Look up to see if we're just after a \n. */
 347 static int find_nl_seq(u32 seq, const struct nf_ct_ftp_master *info, int dir)
 348 {
 349         unsigned int i;
 350
 351         for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
 352                 if (info->seq_aft_nl[dir][i] == seq)
 353                         return 1;
 354         return 0;
 355 }
 356
 357 /* We don't update if it's older than what we have. */
 358 static void update_nl_seq(struct nf_conn *ct, u32 nl_seq,
 359                           struct nf_ct_ftp_master *info, int dir,
 360                           struct sk_buff *skb)
 361 {
 362         unsigned int i, oldest;
 363
 364         /* Look for oldest: if we find exact match, we're done. */
 365         for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
 366                 if (info->seq_aft_nl[dir][i] == nl_seq)
 367                         return;
 368         }
 369
 370         if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
 371                 info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
 372         } else {
 373                 if (before(info->seq_aft_nl[dir][0], info->seq_aft_nl[dir][1]))
 374                         oldest = 0;
 375                 else
 376                         oldest = 1;
 377
 378                 if (after(nl_seq, info->seq_aft_nl[dir][oldest]))
 379                         info->seq_aft_nl[dir][oldest] = nl_seq;
 380         }
 381 }
 382
 383 static int help(struct sk_buff *skb,
 384                 unsigned int protoff,
 385                 struct nf_conn *ct,
 386                 enum ip_conntrack_info ctinfo)
 387 {
 388         unsigned int dataoff, datalen;
 389         const struct tcphdr *th;
 390         struct tcphdr _tcph;
 391         const char *fb_ptr;
 392         int ret;
 393         u32 seq;
 394         int dir = CTINFO2DIR(ctinfo);
 395         unsigned int uninitialized_var(matchlen), uninitialized_var(matchoff);
 396         struct nf_ct_ftp_master *ct_ftp_info = &nfct_help(ct)->help.ct_ftp_info;
 397         struct nf_conntrack_expect *exp;
 398         union nf_inet_addr *daddr;
 399         struct nf_conntrack_man cmd = {};
 400         unsigned int i;
 401         int found = 0, ends_in_nl;
 402         typeof(nf_nat_ftp_hook) nf_nat_ftp;
 403
 404         /* Until there's been traffic both ways, don't look in packets. */
 405         if (ctinfo != IP_CT_ESTABLISHED &&
 406             ctinfo != IP_CT_ESTABLISHED_REPLY) {
 407                 pr_debug("ftp: Conntrackinfo = %u\n", ctinfo);
 408                 return NF_ACCEPT;
 409         }
 410
 411         th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
 412         if (th == NULL)
 413                 return NF_ACCEPT;
 414
 415         dataoff = protoff + th->doff * 4;
 416         /* No data? */
 417         if (dataoff >= skb->len) {
 418                 pr_debug("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
 419                          skb->len);
 420                 return NF_ACCEPT;
 421         }
 422         datalen = skb->len - dataoff;
 423
 424         spin_lock_bh(&nf_ftp_lock);
 425         fb_ptr = skb_header_pointer(skb, dataoff, datalen, ftp_buffer);
 426         BUG_ON(fb_ptr == NULL);
 427
 428         ends_in_nl = (fb_ptr[datalen - 1] == '\n');
 429         seq = ntohl(th->seq) + datalen;
 430
 431         /* Look up to see if we're just after a \n. */
 432         if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
 433                 /* Now if this ends in \n, update ftp info. */
 434                 pr_debug("nf_conntrack_ftp: wrong seq pos %s(%u) or %s(%u)\n",
 435                          ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
 436                          ct_ftp_info->seq_aft_nl[dir][0],
 437                          ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
 438                          ct_ftp_info->seq_aft_nl[dir][1]);
 439                 ret = NF_ACCEPT;
 440                 goto out_update_nl;
 441         }
 442
 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                 pr_debug("conntrack_ftp: partial %s %u+%u\n",
 466                          search[dir][i].pattern,  ntohl(th->seq), datalen);
 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                 ret = NF_DROP;
 481                 goto out;
 482         }
 483
 484         /* We refer to the reverse direction ("!dir") tuples here,
 485          * because we're expecting something in the other direction.
 486          * Doesn't matter unless NAT is happening.  */
 487         daddr = &ct->tuplehash[!dir].tuple.dst.u3;
 488
 489         /* Update the ftp info */
 490         if ((cmd.l3num == nf_ct_l3num(ct)) &&
 491             memcmp(&cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
 492                      sizeof(cmd.u3.all))) {
 493                 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
 494                    server: it really wants us to connect to a
 495                    different IP address.  Simply don't record it for
 496                    NAT. */
 497                 if (cmd.l3num == PF_INET) {
 498                         pr_debug("conntrack_ftp: NOT RECORDING: %pI4 != %pI4\n",
 499                                  &cmd.u3.ip,
 500                                  &ct->tuplehash[dir].tuple.src.u3.ip);
 501                 } else {
 502                         pr_debug("conntrack_ftp: NOT RECORDING: %pI6 != %pI6\n",
 503                                  cmd.u3.ip6,
 504                                  ct->tuplehash[dir].tuple.src.u3.ip6);
 505                 }
 506
 507                 /* Thanks to Cristiano Lincoln Mattos
 508                    <lincoln@cesar.org.br> for reporting this potential
 509                    problem (DMZ machines opening holes to internal
 510                    networks, or the packet filter itself). */
 511                 if (!loose) {
 512                         ret = NF_ACCEPT;
 513                         goto out_put_expect;
 514                 }
 515                 daddr = &cmd.u3;
 516         }
 517
 518         nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, cmd.l3num,
 519                           &ct->tuplehash[!dir].tuple.src.u3, daddr,
 520                           IPPROTO_TCP, NULL, &cmd.u.tcp.port);
 521
 522         /* Now, NAT might want to mangle the packet, and register the
 523          * (possibly changed) expectation itself. */
 524         nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
 525         if (nf_nat_ftp && ct->status & IPS_NAT_MASK)
 526                 ret = nf_nat_ftp(skb, ctinfo, search[dir][i].ftptype,
 527                                  matchoff, matchlen, exp);
 528         else {
 529                 /* Can't expect this?  Best to drop packet now. */
 530                 if (nf_ct_expect_related(exp) != 0)
 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 struct nf_conntrack_helper ftp[MAX_PORTS][2] __read_mostly;
 550 static char ftp_names[MAX_PORTS][2][sizeof("ftp-65535")] __read_mostly;
 551
 552 static const struct nf_conntrack_expect_policy ftp_exp_policy = {
 553         .max_expected   = 1,
 554         .timeout        = 5 * 60,
 555 };
 556
 557 /* don't make this __exit, since it's called from __init ! */
 558 static void nf_conntrack_ftp_fini(void)
 559 {
 560         int i, j;
 561         for (i = 0; i < ports_c; i++) {
 562                 for (j = 0; j < 2; j++) {
 563                         if (ftp[i][j].me == NULL)
 564                                 continue;
 565
 566                         pr_debug("nf_ct_ftp: unregistering helper for pf: %d "
 567                                  "port: %d\n",
 568                                  ftp[i][j].tuple.src.l3num, ports[i]);
 569                         nf_conntrack_helper_unregister(&ftp[i][j]);
 570                 }
 571         }
 572
 573         kfree(ftp_buffer);
 574 }
 575
 576 static int __init nf_conntrack_ftp_init(void)
 577 {
 578         int i, j = -1, ret = 0;
 579         char *tmpname;
 580
 581         ftp_buffer = kmalloc(65536, GFP_KERNEL);
 582         if (!ftp_buffer)
 583                 return -ENOMEM;
 584
 585         if (ports_c == 0)
 586                 ports[ports_c++] = FTP_PORT;
 587
 588         /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
 589                  are tracked or not - YK */
 590         for (i = 0; i < ports_c; i++) {
 591                 ftp[i][0].tuple.src.l3num = PF_INET;
 592                 ftp[i][1].tuple.src.l3num = PF_INET6;
 593                 for (j = 0; j < 2; j++) {
 594                         ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
 595                         ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
 596                         ftp[i][j].expect_policy = &ftp_exp_policy;
 597                         ftp[i][j].me = THIS_MODULE;
 598                         ftp[i][j].help = help;
 599                         tmpname = &ftp_names[i][j][0];
 600                         if (ports[i] == FTP_PORT)
 601                                 sprintf(tmpname, "ftp");
 602                         else
 603                                 sprintf(tmpname, "ftp-%d", ports[i]);
 604                         ftp[i][j].name = tmpname;
 605
 606                         pr_debug("nf_ct_ftp: registering helper for pf: %d "
 607                                  "port: %d\n",
 608                                  ftp[i][j].tuple.src.l3num, ports[i]);
 609                         ret = nf_conntrack_helper_register(&ftp[i][j]);
 610                         if (ret) {
 611                                 printk(KERN_ERR "nf_ct_ftp: failed to register"
 612                                        " helper for pf: %d port: %d\n",
 613                                         ftp[i][j].tuple.src.l3num, ports[i]);
 614                                 nf_conntrack_ftp_fini();
 615                                 return ret;
 616                         }
 617                 }
 618         }
 619
 620         return 0;
 621 }
 622
 623 module_init(nf_conntrack_ftp_init);
 624 module_exit(nf_conntrack_ftp_fini);