linux/net/netfilter/nf_conntrack_ftp.c
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   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
  32MODULE_LICENSE("GPL");
  33MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
  34MODULE_DESCRIPTION("ftp connection tracking helper");
  35MODULE_ALIAS("ip_conntrack_ftp");
  36MODULE_ALIAS_NFCT_HELPER("ftp");
  37
  38/* This is slow, but it's simple. --RR */
  39static char *ftp_buffer;
  40
  41static DEFINE_SPINLOCK(nf_ftp_lock);
  42
  43#define MAX_PORTS 8
  44static u_int16_t ports[MAX_PORTS];
  45static unsigned int ports_c;
  46module_param_array(ports, ushort, &ports_c, 0400);
  47
  48static bool loose;
  49module_param(loose, bool, 0600);
  50
  51unsigned 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);
  58EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
  59
  60static int try_rfc959(const char *, size_t, struct nf_conntrack_man *,
  61                      char, unsigned int *);
  62static int try_rfc1123(const char *, size_t, struct nf_conntrack_man *,
  63                       char, unsigned int *);
  64static int try_eprt(const char *, size_t, struct nf_conntrack_man *,
  65                    char, unsigned int *);
  66static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
  67                             char, unsigned int *);
  68
  69static 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
 113static int
 114get_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
 123static 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 */
 155static 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 */
 182static 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 */
 200static 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| */
 226static 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| */
 274static 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. */
 291static 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. */
 338static 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. */
 349static 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
 374static 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
 440skip_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
 536out_put_expect:
 537        nf_ct_expect_put(exp);
 538
 539out_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
 549static 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
 562static struct nf_conntrack_helper ftp[MAX_PORTS * 2] __read_mostly;
 563
 564static 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 ! */
 570static void nf_conntrack_ftp_fini(void)
 571{
 572        nf_conntrack_helpers_unregister(ftp, ports_c * 2);
 573        kfree(ftp_buffer);
 574}
 575
 576static int __init nf_conntrack_ftp_init(void)
 577{
 578        int i, ret = 0;
 579
 580        NF_CT_HELPER_BUILD_BUG_ON(sizeof(struct nf_ct_ftp_master));
 581
 582        ftp_buffer = kmalloc(65536, GFP_KERNEL);
 583        if (!ftp_buffer)
 584                return -ENOMEM;
 585
 586        if (ports_c == 0)
 587                ports[ports_c++] = FTP_PORT;
 588
 589        /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
 590                 are tracked or not - YK */
 591        for (i = 0; i < ports_c; i++) {
 592                nf_ct_helper_init(&ftp[2 * i], AF_INET, IPPROTO_TCP, "ftp",
 593                                  FTP_PORT, ports[i], ports[i], &ftp_exp_policy,
 594                                  0, help, nf_ct_ftp_from_nlattr, THIS_MODULE);
 595                nf_ct_helper_init(&ftp[2 * i + 1], AF_INET6, IPPROTO_TCP, "ftp",
 596                                  FTP_PORT, ports[i], ports[i], &ftp_exp_policy,
 597                                  0, help, 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
 610module_init(nf_conntrack_ftp_init);
 611module_exit(nf_conntrack_ftp_fini);
 612