linux/net/netfilter/ipvs/ip_vs_ftp.c
<<
>>
Prefs
   1/*
   2 * ip_vs_ftp.c: IPVS ftp application module
   3 *
   4 * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
   5 *
   6 * Changes:
   7 *
   8 *
   9 *      This program is free software; you can redistribute it and/or
  10 *      modify it under the terms of the GNU General Public License
  11 *      as published by the Free Software Foundation; either version
  12 *      2 of the License, or (at your option) any later version.
  13 *
  14 * Most code here is taken from ip_masq_ftp.c in kernel 2.2. The difference
  15 * is that ip_vs_ftp module handles the reverse direction to ip_masq_ftp.
  16 *
  17 *              IP_MASQ_FTP ftp masquerading module
  18 *
  19 * Version:     @(#)ip_masq_ftp.c 0.04   02/05/96
  20 *
  21 * Author:      Wouter Gadeyne
  22 *
  23 */
  24
  25#define KMSG_COMPONENT "IPVS"
  26#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  27
  28#include <linux/module.h>
  29#include <linux/moduleparam.h>
  30#include <linux/kernel.h>
  31#include <linux/skbuff.h>
  32#include <linux/in.h>
  33#include <linux/ip.h>
  34#include <linux/netfilter.h>
  35#include <net/netfilter/nf_conntrack.h>
  36#include <net/netfilter/nf_conntrack_expect.h>
  37#include <net/netfilter/nf_nat.h>
  38#include <net/netfilter/nf_nat_helper.h>
  39#include <linux/gfp.h>
  40#include <net/protocol.h>
  41#include <net/tcp.h>
  42#include <asm/unaligned.h>
  43
  44#include <net/ip_vs.h>
  45
  46
  47#define SERVER_STRING "227 "
  48#define CLIENT_STRING "PORT"
  49
  50
  51/*
  52 * List of ports (up to IP_VS_APP_MAX_PORTS) to be handled by helper
  53 * First port is set to the default port.
  54 */
  55static unsigned int ports_count = 1;
  56static unsigned short ports[IP_VS_APP_MAX_PORTS] = {21, 0};
  57module_param_array(ports, ushort, &ports_count, 0444);
  58MODULE_PARM_DESC(ports, "Ports to monitor for FTP control commands");
  59
  60
  61/*      Dummy variable */
  62static int ip_vs_ftp_pasv;
  63
  64
  65static int
  66ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  67{
  68        /* We use connection tracking for the command connection */
  69        cp->flags |= IP_VS_CONN_F_NFCT;
  70        return 0;
  71}
  72
  73
  74static int
  75ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  76{
  77        return 0;
  78}
  79
  80
  81/*
  82 * Get <addr,port> from the string "xxx.xxx.xxx.xxx,ppp,ppp", started
  83 * with the "pattern", ignoring before "skip" and terminated with
  84 * the "term" character.
  85 * <addr,port> is in network order.
  86 */
  87static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
  88                                  const char *pattern, size_t plen,
  89                                  char skip, char term,
  90                                  __be32 *addr, __be16 *port,
  91                                  char **start, char **end)
  92{
  93        char *s, c;
  94        unsigned char p[6];
  95        int i = 0;
  96
  97        if (data_limit - data < plen) {
  98                /* check if there is partial match */
  99                if (strncasecmp(data, pattern, data_limit - data) == 0)
 100                        return -1;
 101                else
 102                        return 0;
 103        }
 104
 105        if (strncasecmp(data, pattern, plen) != 0) {
 106                return 0;
 107        }
 108        s = data + plen;
 109        if (skip) {
 110                int found = 0;
 111
 112                for (;; s++) {
 113                        if (s == data_limit)
 114                                return -1;
 115                        if (!found) {
 116                                if (*s == skip)
 117                                        found = 1;
 118                        } else if (*s != skip) {
 119                                break;
 120                        }
 121                }
 122        }
 123
 124        for (data = s; ; data++) {
 125                if (data == data_limit)
 126                        return -1;
 127                if (*data == term)
 128                        break;
 129        }
 130        *end = data;
 131
 132        memset(p, 0, sizeof(p));
 133        for (data = s; ; data++) {
 134                c = *data;
 135                if (c == term)
 136                        break;
 137                if (c >= '0' && c <= '9') {
 138                        p[i] = p[i]*10 + c - '0';
 139                } else if (c == ',' && i < 5) {
 140                        i++;
 141                } else {
 142                        /* unexpected character */
 143                        return -1;
 144                }
 145        }
 146
 147        if (i != 5)
 148                return -1;
 149
 150        *start = s;
 151        *addr = get_unaligned((__be32 *) p);
 152        *port = get_unaligned((__be16 *) (p + 4));
 153        return 1;
 154}
 155
 156/*
 157 * Look at outgoing ftp packets to catch the response to a PASV command
 158 * from the server (inside-to-outside).
 159 * When we see one, we build a connection entry with the client address,
 160 * client port 0 (unknown at the moment), the server address and the
 161 * server port.  Mark the current connection entry as a control channel
 162 * of the new entry. All this work is just to make the data connection
 163 * can be scheduled to the right server later.
 164 *
 165 * The outgoing packet should be something like
 166 *   "227 Entering Passive Mode (xxx,xxx,xxx,xxx,ppp,ppp)".
 167 * xxx,xxx,xxx,xxx is the server address, ppp,ppp is the server port number.
 168 */
 169static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
 170                         struct sk_buff *skb, int *diff)
 171{
 172        struct iphdr *iph;
 173        struct tcphdr *th;
 174        char *data, *data_limit;
 175        char *start, *end;
 176        union nf_inet_addr from;
 177        __be16 port;
 178        struct ip_vs_conn *n_cp;
 179        char buf[24];           /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
 180        unsigned int buf_len;
 181        int ret = 0;
 182        enum ip_conntrack_info ctinfo;
 183        struct nf_conn *ct;
 184        struct net *net;
 185
 186        *diff = 0;
 187
 188#ifdef CONFIG_IP_VS_IPV6
 189        /* This application helper doesn't work with IPv6 yet,
 190         * so turn this into a no-op for IPv6 packets
 191         */
 192        if (cp->af == AF_INET6)
 193                return 1;
 194#endif
 195
 196        /* Only useful for established sessions */
 197        if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 198                return 1;
 199
 200        /* Linear packets are much easier to deal with. */
 201        if (!skb_make_writable(skb, skb->len))
 202                return 0;
 203
 204        if (cp->app_data == &ip_vs_ftp_pasv) {
 205                iph = ip_hdr(skb);
 206                th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 207                data = (char *)th + (th->doff << 2);
 208                data_limit = skb_tail_pointer(skb);
 209
 210                if (ip_vs_ftp_get_addrport(data, data_limit,
 211                                           SERVER_STRING,
 212                                           sizeof(SERVER_STRING)-1,
 213                                           '(', ')',
 214                                           &from.ip, &port,
 215                                           &start, &end) != 1)
 216                        return 1;
 217
 218                IP_VS_DBG(7, "PASV response (%pI4:%d) -> %pI4:%d detected\n",
 219                          &from.ip, ntohs(port), &cp->caddr.ip, 0);
 220
 221                /*
 222                 * Now update or create an connection entry for it
 223                 */
 224                {
 225                        struct ip_vs_conn_param p;
 226                        ip_vs_conn_fill_param(ip_vs_conn_net(cp), AF_INET,
 227                                              iph->protocol, &from, port,
 228                                              &cp->caddr, 0, &p);
 229                        n_cp = ip_vs_conn_out_get(&p);
 230                }
 231                if (!n_cp) {
 232                        struct ip_vs_conn_param p;
 233                        ip_vs_conn_fill_param(ip_vs_conn_net(cp),
 234                                              AF_INET, IPPROTO_TCP, &cp->caddr,
 235                                              0, &cp->vaddr, port, &p);
 236                        /* As above, this is ipv4 only */
 237                        n_cp = ip_vs_conn_new(&p, AF_INET, &from, port,
 238                                              IP_VS_CONN_F_NO_CPORT |
 239                                              IP_VS_CONN_F_NFCT,
 240                                              cp->dest, skb->mark);
 241                        if (!n_cp)
 242                                return 0;
 243
 244                        /* add its controller */
 245                        ip_vs_control_add(n_cp, cp);
 246                }
 247
 248                /*
 249                 * Replace the old passive address with the new one
 250                 */
 251                from.ip = n_cp->vaddr.ip;
 252                port = n_cp->vport;
 253                snprintf(buf, sizeof(buf), "%u,%u,%u,%u,%u,%u",
 254                         ((unsigned char *)&from.ip)[0],
 255                         ((unsigned char *)&from.ip)[1],
 256                         ((unsigned char *)&from.ip)[2],
 257                         ((unsigned char *)&from.ip)[3],
 258                         ntohs(port) >> 8,
 259                         ntohs(port) & 0xFF);
 260
 261                buf_len = strlen(buf);
 262
 263                ct = nf_ct_get(skb, &ctinfo);
 264                if (ct && !nf_ct_is_untracked(ct) && nfct_nat(ct)) {
 265                        /* If mangling fails this function will return 0
 266                         * which will cause the packet to be dropped.
 267                         * Mangling can only fail under memory pressure,
 268                         * hopefully it will succeed on the retransmitted
 269                         * packet.
 270                         */
 271                        rcu_read_lock();
 272                        ret = nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
 273                                                       iph->ihl * 4,
 274                                                       start-data, end-start,
 275                                                       buf, buf_len);
 276                        rcu_read_unlock();
 277                        if (ret) {
 278                                ip_vs_nfct_expect_related(skb, ct, n_cp,
 279                                                          IPPROTO_TCP, 0, 0);
 280                                if (skb->ip_summed == CHECKSUM_COMPLETE)
 281                                        skb->ip_summed = CHECKSUM_UNNECESSARY;
 282                                /* csum is updated */
 283                                ret = 1;
 284                        }
 285                }
 286
 287                /*
 288                 * Not setting 'diff' is intentional, otherwise the sequence
 289                 * would be adjusted twice.
 290                 */
 291
 292                net = skb_net(skb);
 293                cp->app_data = NULL;
 294                ip_vs_tcp_conn_listen(net, n_cp);
 295                ip_vs_conn_put(n_cp);
 296                return ret;
 297        }
 298        return 1;
 299}
 300
 301
 302/*
 303 * Look at incoming ftp packets to catch the PASV/PORT command
 304 * (outside-to-inside).
 305 *
 306 * The incoming packet having the PORT command should be something like
 307 *      "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
 308 * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
 309 * In this case, we create a connection entry using the client address and
 310 * port, so that the active ftp data connection from the server can reach
 311 * the client.
 312 */
 313static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
 314                        struct sk_buff *skb, int *diff)
 315{
 316        struct iphdr *iph;
 317        struct tcphdr *th;
 318        char *data, *data_start, *data_limit;
 319        char *start, *end;
 320        union nf_inet_addr to;
 321        __be16 port;
 322        struct ip_vs_conn *n_cp;
 323        struct net *net;
 324
 325        /* no diff required for incoming packets */
 326        *diff = 0;
 327
 328#ifdef CONFIG_IP_VS_IPV6
 329        /* This application helper doesn't work with IPv6 yet,
 330         * so turn this into a no-op for IPv6 packets
 331         */
 332        if (cp->af == AF_INET6)
 333                return 1;
 334#endif
 335
 336        /* Only useful for established sessions */
 337        if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 338                return 1;
 339
 340        /* Linear packets are much easier to deal with. */
 341        if (!skb_make_writable(skb, skb->len))
 342                return 0;
 343
 344        /*
 345         * Detecting whether it is passive
 346         */
 347        iph = ip_hdr(skb);
 348        th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 349
 350        /* Since there may be OPTIONS in the TCP packet and the HLEN is
 351           the length of the header in 32-bit multiples, it is accurate
 352           to calculate data address by th+HLEN*4 */
 353        data = data_start = (char *)th + (th->doff << 2);
 354        data_limit = skb_tail_pointer(skb);
 355
 356        while (data <= data_limit - 6) {
 357                if (strncasecmp(data, "PASV\r\n", 6) == 0) {
 358                        /* Passive mode on */
 359                        IP_VS_DBG(7, "got PASV at %td of %td\n",
 360                                  data - data_start,
 361                                  data_limit - data_start);
 362                        cp->app_data = &ip_vs_ftp_pasv;
 363                        return 1;
 364                }
 365                data++;
 366        }
 367
 368        /*
 369         * To support virtual FTP server, the scenerio is as follows:
 370         *       FTP client ----> Load Balancer ----> FTP server
 371         * First detect the port number in the application data,
 372         * then create a new connection entry for the coming data
 373         * connection.
 374         */
 375        if (ip_vs_ftp_get_addrport(data_start, data_limit,
 376                                   CLIENT_STRING, sizeof(CLIENT_STRING)-1,
 377                                   ' ', '\r', &to.ip, &port,
 378                                   &start, &end) != 1)
 379                return 1;
 380
 381        IP_VS_DBG(7, "PORT %pI4:%d detected\n", &to.ip, ntohs(port));
 382
 383        /* Passive mode off */
 384        cp->app_data = NULL;
 385
 386        /*
 387         * Now update or create a connection entry for it
 388         */
 389        IP_VS_DBG(7, "protocol %s %pI4:%d %pI4:%d\n",
 390                  ip_vs_proto_name(iph->protocol),
 391                  &to.ip, ntohs(port), &cp->vaddr.ip, 0);
 392
 393        {
 394                struct ip_vs_conn_param p;
 395                ip_vs_conn_fill_param(ip_vs_conn_net(cp), AF_INET,
 396                                      iph->protocol, &to, port, &cp->vaddr,
 397                                      htons(ntohs(cp->vport)-1), &p);
 398                n_cp = ip_vs_conn_in_get(&p);
 399                if (!n_cp) {
 400                        /* This is ipv4 only */
 401                        n_cp = ip_vs_conn_new(&p, AF_INET, &cp->daddr,
 402                                              htons(ntohs(cp->dport)-1),
 403                                              IP_VS_CONN_F_NFCT, cp->dest,
 404                                              skb->mark);
 405                        if (!n_cp)
 406                                return 0;
 407
 408                        /* add its controller */
 409                        ip_vs_control_add(n_cp, cp);
 410                }
 411        }
 412
 413        /*
 414         *      Move tunnel to listen state
 415         */
 416        net = skb_net(skb);
 417        ip_vs_tcp_conn_listen(net, n_cp);
 418        ip_vs_conn_put(n_cp);
 419
 420        return 1;
 421}
 422
 423
 424static struct ip_vs_app ip_vs_ftp = {
 425        .name =         "ftp",
 426        .type =         IP_VS_APP_TYPE_FTP,
 427        .protocol =     IPPROTO_TCP,
 428        .module =       THIS_MODULE,
 429        .incs_list =    LIST_HEAD_INIT(ip_vs_ftp.incs_list),
 430        .init_conn =    ip_vs_ftp_init_conn,
 431        .done_conn =    ip_vs_ftp_done_conn,
 432        .bind_conn =    NULL,
 433        .unbind_conn =  NULL,
 434        .pkt_out =      ip_vs_ftp_out,
 435        .pkt_in =       ip_vs_ftp_in,
 436};
 437
 438/*
 439 *      per netns ip_vs_ftp initialization
 440 */
 441static int __net_init __ip_vs_ftp_init(struct net *net)
 442{
 443        int i, ret;
 444        struct ip_vs_app *app;
 445        struct netns_ipvs *ipvs = net_ipvs(net);
 446
 447        if (!ipvs)
 448                return -ENOENT;
 449
 450        app = register_ip_vs_app(net, &ip_vs_ftp);
 451        if (IS_ERR(app))
 452                return PTR_ERR(app);
 453
 454        for (i = 0; i < ports_count; i++) {
 455                if (!ports[i])
 456                        continue;
 457                ret = register_ip_vs_app_inc(net, app, app->protocol, ports[i]);
 458                if (ret)
 459                        goto err_unreg;
 460                pr_info("%s: loaded support on port[%d] = %d\n",
 461                        app->name, i, ports[i]);
 462        }
 463        return 0;
 464
 465err_unreg:
 466        unregister_ip_vs_app(net, &ip_vs_ftp);
 467        return ret;
 468}
 469/*
 470 *      netns exit
 471 */
 472static void __ip_vs_ftp_exit(struct net *net)
 473{
 474        unregister_ip_vs_app(net, &ip_vs_ftp);
 475}
 476
 477static struct pernet_operations ip_vs_ftp_ops = {
 478        .init = __ip_vs_ftp_init,
 479        .exit = __ip_vs_ftp_exit,
 480};
 481
 482static int __init ip_vs_ftp_init(void)
 483{
 484        int rv;
 485
 486        rv = register_pernet_subsys(&ip_vs_ftp_ops);
 487        /* rcu_barrier() is called by netns on error */
 488        return rv;
 489}
 490
 491/*
 492 *      ip_vs_ftp finish.
 493 */
 494static void __exit ip_vs_ftp_exit(void)
 495{
 496        unregister_pernet_subsys(&ip_vs_ftp_ops);
 497        /* rcu_barrier() is called by netns */
 498}
 499
 500
 501module_init(ip_vs_ftp_init);
 502module_exit(ip_vs_ftp_exit);
 503MODULE_LICENSE("GPL");
 504