net/ipv4/ipvs/ip_vs_ftp.c

   1 /*
   2  * ip_vs_ftp.c: IPVS ftp application module
   3  *
   4  * Version:     $Id: ip_vs_ftp.c,v 1.13 2002/09/15 08:14:08 wensong Exp $
   5  *
   6  * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
   7  *
   8  * Changes:
   9  *
  10  *
  11  *      This program is free software; you can redistribute it and/or
  12  *      modify it under the terms of the GNU General Public License
  13  *      as published by the Free Software Foundation; either version
  14  *      2 of the License, or (at your option) any later version.
  15  *
  16  * Most code here is taken from ip_masq_ftp.c in kernel 2.2. The difference
  17  * is that ip_vs_ftp module handles the reverse direction to ip_masq_ftp.
  18  *
  19  *              IP_MASQ_FTP ftp masquerading module
  20  *
  21  * Version:     @(#)ip_masq_ftp.c 0.04   02/05/96
  22  *
  23  * Author:      Wouter Gadeyne
  24  *
  25  */
  26
  27 #include <linux/module.h>
  28 #include <linux/moduleparam.h>
  29 #include <linux/kernel.h>
  30 #include <linux/skbuff.h>
  31 #include <linux/in.h>
  32 #include <linux/ip.h>
  33 #include <linux/netfilter.h>
  34 #include <net/protocol.h>
  35 #include <net/tcp.h>
  36 #include <asm/unaligned.h>
  37
  38 #include <net/ip_vs.h>
  39
  40
  41 #define SERVER_STRING "227 Entering Passive Mode ("
  42 #define CLIENT_STRING "PORT "
  43
  44
  45 /*
  46  * List of ports (up to IP_VS_APP_MAX_PORTS) to be handled by helper
  47  * First port is set to the default port.
  48  */
  49 static unsigned short ports[IP_VS_APP_MAX_PORTS] = {21, 0};
  50 module_param_array(ports, ushort, NULL, 0);
  51 MODULE_PARM_DESC(ports, "Ports to monitor for FTP control commands");
  52
  53
  54 /*      Dummy variable */
  55 static int ip_vs_ftp_pasv;
  56
  57
  58 static int
  59 ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  60 {
  61         return 0;
  62 }
  63
  64
  65 static int
  66 ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  67 {
  68         return 0;
  69 }
  70
  71
  72 /*
  73  * Get <addr,port> from the string "xxx.xxx.xxx.xxx,ppp,ppp", started
  74  * with the "pattern" and terminated with the "term" character.
  75  * <addr,port> is in network order.
  76  */
  77 static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
  78                                   const char *pattern, size_t plen, char term,
  79                                   __be32 *addr, __be16 *port,
  80                                   char **start, char **end)
  81 {
  82         unsigned char p[6];
  83         int i = 0;
  84
  85         if (data_limit - data < plen) {
  86                 /* check if there is partial match */
  87                 if (strnicmp(data, pattern, data_limit - data) == 0)
  88                         return -1;
  89                 else
  90                         return 0;
  91         }
  92
  93         if (strnicmp(data, pattern, plen) != 0) {
  94                 return 0;
  95         }
  96         *start = data + plen;
  97
  98         for (data = *start; *data != term; data++) {
  99                 if (data == data_limit)
 100                         return -1;
 101         }
 102         *end = data;
 103
 104         memset(p, 0, sizeof(p));
 105         for (data = *start; data != *end; data++) {
 106                 if (*data >= '0' && *data <= '9') {
 107                         p[i] = p[i]*10 + *data - '0';
 108                 } else if (*data == ',' && i < 5) {
 109                         i++;
 110                 } else {
 111                         /* unexpected character */
 112                         return -1;
 113                 }
 114         }
 115
 116         if (i != 5)
 117                 return -1;
 118
 119         *addr = get_unaligned((__be32 *)p);
 120         *port = get_unaligned((__be16 *)(p + 4));
 121         return 1;
 122 }
 123
 124
 125 /*
 126  * Look at outgoing ftp packets to catch the response to a PASV command
 127  * from the server (inside-to-outside).
 128  * When we see one, we build a connection entry with the client address,
 129  * client port 0 (unknown at the moment), the server address and the
 130  * server port.  Mark the current connection entry as a control channel
 131  * of the new entry. All this work is just to make the data connection
 132  * can be scheduled to the right server later.
 133  *
 134  * The outgoing packet should be something like
 135  *   "227 Entering Passive Mode (xxx,xxx,xxx,xxx,ppp,ppp)".
 136  * xxx,xxx,xxx,xxx is the server address, ppp,ppp is the server port number.
 137  */
 138 static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
 139                          struct sk_buff *skb, int *diff)
 140 {
 141         struct iphdr *iph;
 142         struct tcphdr *th;
 143         char *data, *data_limit;
 144         char *start, *end;
 145         __be32 from;
 146         __be16 port;
 147         struct ip_vs_conn *n_cp;
 148         char buf[24];           /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
 149         unsigned buf_len;
 150         int ret;
 151
 152         *diff = 0;
 153
 154         /* Only useful for established sessions */
 155         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 156                 return 1;
 157
 158         /* Linear packets are much easier to deal with. */
 159         if (!skb_make_writable(skb, skb->len))
 160                 return 0;
 161
 162         if (cp->app_data == &ip_vs_ftp_pasv) {
 163                 iph = ip_hdr(skb);
 164                 th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 165                 data = (char *)th + (th->doff << 2);
 166                 data_limit = skb_tail_pointer(skb);
 167
 168                 if (ip_vs_ftp_get_addrport(data, data_limit,
 169                                            SERVER_STRING,
 170                                            sizeof(SERVER_STRING)-1, ')',
 171                                            &from, &port,
 172                                            &start, &end) != 1)
 173                         return 1;
 174
 175                 IP_VS_DBG(7, "PASV response (%u.%u.%u.%u:%d) -> "
 176                           "%u.%u.%u.%u:%d detected\n",
 177                           NIPQUAD(from), ntohs(port), NIPQUAD(cp->caddr), 0);
 178
 179                 /*
 180                  * Now update or create an connection entry for it
 181                  */
 182                 n_cp = ip_vs_conn_out_get(iph->protocol, from, port,
 183                                           cp->caddr, 0);
 184                 if (!n_cp) {
 185                         n_cp = ip_vs_conn_new(IPPROTO_TCP,
 186                                               cp->caddr, 0,
 187                                               cp->vaddr, port,
 188                                               from, port,
 189                                               IP_VS_CONN_F_NO_CPORT,
 190                                               cp->dest);
 191                         if (!n_cp)
 192                                 return 0;
 193
 194                         /* add its controller */
 195                         ip_vs_control_add(n_cp, cp);
 196                 }
 197
 198                 /*
 199                  * Replace the old passive address with the new one
 200                  */
 201                 from = n_cp->vaddr;
 202                 port = n_cp->vport;
 203                 sprintf(buf,"%d,%d,%d,%d,%d,%d", NIPQUAD(from),
 204                         (ntohs(port)>>8)&255, ntohs(port)&255);
 205                 buf_len = strlen(buf);
 206
 207                 /*
 208                  * Calculate required delta-offset to keep TCP happy
 209                  */
 210                 *diff = buf_len - (end-start);
 211
 212                 if (*diff == 0) {
 213                         /* simply replace it with new passive address */
 214                         memcpy(start, buf, buf_len);
 215                         ret = 1;
 216                 } else {
 217                         ret = !ip_vs_skb_replace(skb, GFP_ATOMIC, start,
 218                                           end-start, buf, buf_len);
 219                 }
 220
 221                 cp->app_data = NULL;
 222                 ip_vs_tcp_conn_listen(n_cp);
 223                 ip_vs_conn_put(n_cp);
 224                 return ret;
 225         }
 226         return 1;
 227 }
 228
 229
 230 /*
 231  * Look at incoming ftp packets to catch the PASV/PORT command
 232  * (outside-to-inside).
 233  *
 234  * The incoming packet having the PORT command should be something like
 235  *      "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
 236  * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
 237  * In this case, we create a connection entry using the client address and
 238  * port, so that the active ftp data connection from the server can reach
 239  * the client.
 240  */
 241 static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
 242                         struct sk_buff *skb, int *diff)
 243 {
 244         struct iphdr *iph;
 245         struct tcphdr *th;
 246         char *data, *data_start, *data_limit;
 247         char *start, *end;
 248         __be32 to;
 249         __be16 port;
 250         struct ip_vs_conn *n_cp;
 251
 252         /* no diff required for incoming packets */
 253         *diff = 0;
 254
 255         /* Only useful for established sessions */
 256         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 257                 return 1;
 258
 259         /* Linear packets are much easier to deal with. */
 260         if (!skb_make_writable(skb, skb->len))
 261                 return 0;
 262
 263         /*
 264          * Detecting whether it is passive
 265          */
 266         iph = ip_hdr(skb);
 267         th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 268
 269         /* Since there may be OPTIONS in the TCP packet and the HLEN is
 270            the length of the header in 32-bit multiples, it is accurate
 271            to calculate data address by th+HLEN*4 */
 272         data = data_start = (char *)th + (th->doff << 2);
 273         data_limit = skb_tail_pointer(skb);
 274
 275         while (data <= data_limit - 6) {
 276                 if (strnicmp(data, "PASV\r\n", 6) == 0) {
 277                         /* Passive mode on */
 278                         IP_VS_DBG(7, "got PASV at %td of %td\n",
 279                                   data - data_start,
 280                                   data_limit - data_start);
 281                         cp->app_data = &ip_vs_ftp_pasv;
 282                         return 1;
 283                 }
 284                 data++;
 285         }
 286
 287         /*
 288          * To support virtual FTP server, the scenerio is as follows:
 289          *       FTP client ----> Load Balancer ----> FTP server
 290          * First detect the port number in the application data,
 291          * then create a new connection entry for the coming data
 292          * connection.
 293          */
 294         if (ip_vs_ftp_get_addrport(data_start, data_limit,
 295                                    CLIENT_STRING, sizeof(CLIENT_STRING)-1,
 296                                    '\r', &to, &port,
 297                                    &start, &end) != 1)
 298                 return 1;
 299
 300         IP_VS_DBG(7, "PORT %u.%u.%u.%u:%d detected\n",
 301                   NIPQUAD(to), ntohs(port));
 302
 303         /* Passive mode off */
 304         cp->app_data = NULL;
 305
 306         /*
 307          * Now update or create a connection entry for it
 308          */
 309         IP_VS_DBG(7, "protocol %s %u.%u.%u.%u:%d %u.%u.%u.%u:%d\n",
 310                   ip_vs_proto_name(iph->protocol),
 311                   NIPQUAD(to), ntohs(port), NIPQUAD(cp->vaddr), 0);
 312
 313         n_cp = ip_vs_conn_in_get(iph->protocol,
 314                                  to, port,
 315                                  cp->vaddr, htons(ntohs(cp->vport)-1));
 316         if (!n_cp) {
 317                 n_cp = ip_vs_conn_new(IPPROTO_TCP,
 318                                       to, port,
 319                                       cp->vaddr, htons(ntohs(cp->vport)-1),
 320                                       cp->daddr, htons(ntohs(cp->dport)-1),
 321                                       0,
 322                                       cp->dest);
 323                 if (!n_cp)
 324                         return 0;
 325
 326                 /* add its controller */
 327                 ip_vs_control_add(n_cp, cp);
 328         }
 329
 330         /*
 331          *      Move tunnel to listen state
 332          */
 333         ip_vs_tcp_conn_listen(n_cp);
 334         ip_vs_conn_put(n_cp);
 335
 336         return 1;
 337 }
 338
 339
 340 static struct ip_vs_app ip_vs_ftp = {
 341         .name =         "ftp",
 342         .type =         IP_VS_APP_TYPE_FTP,
 343         .protocol =     IPPROTO_TCP,
 344         .module =       THIS_MODULE,
 345         .incs_list =    LIST_HEAD_INIT(ip_vs_ftp.incs_list),
 346         .init_conn =    ip_vs_ftp_init_conn,
 347         .done_conn =    ip_vs_ftp_done_conn,
 348         .bind_conn =    NULL,
 349         .unbind_conn =  NULL,
 350         .pkt_out =      ip_vs_ftp_out,
 351         .pkt_in =       ip_vs_ftp_in,
 352 };
 353
 354
 355 /*
 356  *      ip_vs_ftp initialization
 357  */
 358 static int __init ip_vs_ftp_init(void)
 359 {
 360         int i, ret;
 361         struct ip_vs_app *app = &ip_vs_ftp;
 362
 363         ret = register_ip_vs_app(app);
 364         if (ret)
 365                 return ret;
 366
 367         for (i=0; i<IP_VS_APP_MAX_PORTS; i++) {
 368                 if (!ports[i])
 369                         continue;
 370                 ret = register_ip_vs_app_inc(app, app->protocol, ports[i]);
 371                 if (ret)
 372                         break;
 373                 IP_VS_INFO("%s: loaded support on port[%d] = %d\n",
 374                            app->name, i, ports[i]);
 375         }
 376
 377         if (ret)
 378                 unregister_ip_vs_app(app);
 379
 380         return ret;
 381 }
 382
 383
 384 /*
 385  *      ip_vs_ftp finish.
 386  */
 387 static void __exit ip_vs_ftp_exit(void)
 388 {
 389         unregister_ip_vs_app(&ip_vs_ftp);
 390 }
 391
 392
 393 module_init(ip_vs_ftp_init);
 394 module_exit(ip_vs_ftp_exit);
 395 MODULE_LICENSE("GPL");