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 <net/protocol.h>
  34 #include <net/tcp.h>
  35
  36 #include <net/ip_vs.h>
  37
  38
  39 #define SERVER_STRING "227 Entering Passive Mode ("
  40 #define CLIENT_STRING "PORT "
  41
  42
  43 /*
  44  * List of ports (up to IP_VS_APP_MAX_PORTS) to be handled by helper
  45  * First port is set to the default port.
  46  */
  47 static int ports[IP_VS_APP_MAX_PORTS] = {21, 0};
  48 module_param_array(ports, int, NULL, 0);
  49
  50 /*
  51  *      Debug level
  52  */
  53 #ifdef CONFIG_IP_VS_DEBUG
  54 static int debug=0;
  55 module_param(debug, int, 0);
  56 #endif
  57
  58
  59 /*      Dummy variable */
  60 static int ip_vs_ftp_pasv;
  61
  62
  63 static int
  64 ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  65 {
  66         return 0;
  67 }
  68
  69
  70 static int
  71 ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  72 {
  73         return 0;
  74 }
  75
  76
  77 /*
  78  * Get <addr,port> from the string "xxx.xxx.xxx.xxx,ppp,ppp", started
  79  * with the "pattern" and terminated with the "term" character.
  80  * <addr,port> is in network order.
  81  */
  82 static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
  83                                   const char *pattern, size_t plen, char term,
  84                                   __u32 *addr, __u16 *port,
  85                                   char **start, char **end)
  86 {
  87         unsigned char p[6];
  88         int i = 0;
  89
  90         if (data_limit - data < plen) {
  91                 /* check if there is partial match */
  92                 if (strnicmp(data, pattern, data_limit - data) == 0)
  93                         return -1;
  94                 else
  95                         return 0;
  96         }
  97
  98         if (strnicmp(data, pattern, plen) != 0) {
  99                 return 0;
 100         }
 101         *start = data + plen;
 102
 103         for (data = *start; *data != term; data++) {
 104                 if (data == data_limit)
 105                         return -1;
 106         }
 107         *end = data;
 108
 109         memset(p, 0, sizeof(p));
 110         for (data = *start; data != *end; data++) {
 111                 if (*data >= '0' && *data <= '9') {
 112                         p[i] = p[i]*10 + *data - '0';
 113                 } else if (*data == ',' && i < 5) {
 114                         i++;
 115                 } else {
 116                         /* unexpected character */
 117                         return -1;
 118                 }
 119         }
 120
 121         if (i != 5)
 122                 return -1;
 123
 124         *addr = (p[3]<<24) | (p[2]<<16) | (p[1]<<8) | p[0];
 125         *port = (p[5]<<8) | p[4];
 126         return 1;
 127 }
 128
 129
 130 /*
 131  * Look at outgoing ftp packets to catch the response to a PASV command
 132  * from the server (inside-to-outside).
 133  * When we see one, we build a connection entry with the client address,
 134  * client port 0 (unknown at the moment), the server address and the
 135  * server port.  Mark the current connection entry as a control channel
 136  * of the new entry. All this work is just to make the data connection
 137  * can be scheduled to the right server later.
 138  *
 139  * The outgoing packet should be something like
 140  *   "227 Entering Passive Mode (xxx,xxx,xxx,xxx,ppp,ppp)".
 141  * xxx,xxx,xxx,xxx is the server address, ppp,ppp is the server port number.
 142  */
 143 static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
 144                          struct sk_buff **pskb, int *diff)
 145 {
 146         struct iphdr *iph;
 147         struct tcphdr *th;
 148         char *data, *data_limit;
 149         char *start, *end;
 150         __u32 from;
 151         __u16 port;
 152         struct ip_vs_conn *n_cp;
 153         char buf[24];           /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
 154         unsigned buf_len;
 155         int ret;
 156
 157         *diff = 0;
 158
 159         /* Only useful for established sessions */
 160         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 161                 return 1;
 162
 163         /* Linear packets are much easier to deal with. */
 164         if (!ip_vs_make_skb_writable(pskb, (*pskb)->len))
 165                 return 0;
 166
 167         if (cp->app_data == &ip_vs_ftp_pasv) {
 168                 iph = (*pskb)->nh.iph;
 169                 th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 170                 data = (char *)th + (th->doff << 2);
 171                 data_limit = (*pskb)->tail;
 172
 173                 if (ip_vs_ftp_get_addrport(data, data_limit,
 174                                            SERVER_STRING,
 175                                            sizeof(SERVER_STRING)-1, ')',
 176                                            &from, &port,
 177                                            &start, &end) != 1)
 178                         return 1;
 179
 180                 IP_VS_DBG(1-debug, "PASV response (%u.%u.%u.%u:%d) -> "
 181                           "%u.%u.%u.%u:%d detected\n",
 182                           NIPQUAD(from), ntohs(port), NIPQUAD(cp->caddr), 0);
 183
 184                 /*
 185                  * Now update or create an connection entry for it
 186                  */
 187                 n_cp = ip_vs_conn_out_get(iph->protocol, from, port,
 188                                           cp->caddr, 0);
 189                 if (!n_cp) {
 190                         n_cp = ip_vs_conn_new(IPPROTO_TCP,
 191                                               cp->caddr, 0,
 192                                               cp->vaddr, port,
 193                                               from, port,
 194                                               IP_VS_CONN_F_NO_CPORT,
 195                                               cp->dest);
 196                         if (!n_cp)
 197                                 return 0;
 198
 199                         /* add its controller */
 200                         ip_vs_control_add(n_cp, cp);
 201                 }
 202
 203                 /*
 204                  * Replace the old passive address with the new one
 205                  */
 206                 from = n_cp->vaddr;
 207                 port = n_cp->vport;
 208                 sprintf(buf,"%d,%d,%d,%d,%d,%d", NIPQUAD(from),
 209                         port&255, (port>>8)&255);
 210                 buf_len = strlen(buf);
 211
 212                 /*
 213                  * Calculate required delta-offset to keep TCP happy
 214                  */
 215                 *diff = buf_len - (end-start);
 216
 217                 if (*diff == 0) {
 218                         /* simply replace it with new passive address */
 219                         memcpy(start, buf, buf_len);
 220                         ret = 1;
 221                 } else {
 222                         ret = !ip_vs_skb_replace(*pskb, GFP_ATOMIC, start,
 223                                           end-start, buf, buf_len);
 224                 }
 225
 226                 cp->app_data = NULL;
 227                 ip_vs_tcp_conn_listen(n_cp);
 228                 ip_vs_conn_put(n_cp);
 229                 return ret;
 230         }
 231         return 1;
 232 }
 233
 234
 235 /*
 236  * Look at incoming ftp packets to catch the PASV/PORT command
 237  * (outside-to-inside).
 238  *
 239  * The incoming packet having the PORT command should be something like
 240  *      "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
 241  * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
 242  * In this case, we create a connection entry using the client address and
 243  * port, so that the active ftp data connection from the server can reach
 244  * the client.
 245  */
 246 static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
 247                         struct sk_buff **pskb, int *diff)
 248 {
 249         struct iphdr *iph;
 250         struct tcphdr *th;
 251         char *data, *data_start, *data_limit;
 252         char *start, *end;
 253         __u32 to;
 254         __u16 port;
 255         struct ip_vs_conn *n_cp;
 256
 257         /* no diff required for incoming packets */
 258         *diff = 0;
 259
 260         /* Only useful for established sessions */
 261         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 262                 return 1;
 263
 264         /* Linear packets are much easier to deal with. */
 265         if (!ip_vs_make_skb_writable(pskb, (*pskb)->len))
 266                 return 0;
 267
 268         /*
 269          * Detecting whether it is passive
 270          */
 271         iph = (*pskb)->nh.iph;
 272         th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 273
 274         /* Since there may be OPTIONS in the TCP packet and the HLEN is
 275            the length of the header in 32-bit multiples, it is accurate
 276            to calculate data address by th+HLEN*4 */
 277         data = data_start = (char *)th + (th->doff << 2);
 278         data_limit = (*pskb)->tail;
 279
 280         while (data <= data_limit - 6) {
 281                 if (strnicmp(data, "PASV\r\n", 6) == 0) {
 282                         /* Passive mode on */
 283                         IP_VS_DBG(1-debug, "got PASV at %zd of %zd\n",
 284                                   data - data_start,
 285                                   data_limit - data_start);
 286                         cp->app_data = &ip_vs_ftp_pasv;
 287                         return 1;
 288                 }
 289                 data++;
 290         }
 291
 292         /*
 293          * To support virtual FTP server, the scenerio is as follows:
 294          *       FTP client ----> Load Balancer ----> FTP server
 295          * First detect the port number in the application data,
 296          * then create a new connection entry for the coming data
 297          * connection.
 298          */
 299         if (ip_vs_ftp_get_addrport(data_start, data_limit,
 300                                    CLIENT_STRING, sizeof(CLIENT_STRING)-1,
 301                                    '\r', &to, &port,
 302                                    &start, &end) != 1)
 303                 return 1;
 304
 305         IP_VS_DBG(1-debug, "PORT %u.%u.%u.%u:%d detected\n",
 306                   NIPQUAD(to), ntohs(port));
 307
 308         /* Passive mode off */
 309         cp->app_data = NULL;
 310
 311         /*
 312          * Now update or create a connection entry for it
 313          */
 314         IP_VS_DBG(1-debug, "protocol %s %u.%u.%u.%u:%d %u.%u.%u.%u:%d\n",
 315                   ip_vs_proto_name(iph->protocol),
 316                   NIPQUAD(to), ntohs(port), NIPQUAD(cp->vaddr), 0);
 317
 318         n_cp = ip_vs_conn_in_get(iph->protocol,
 319                                  to, port,
 320                                  cp->vaddr, htons(ntohs(cp->vport)-1));
 321         if (!n_cp) {
 322                 n_cp = ip_vs_conn_new(IPPROTO_TCP,
 323                                       to, port,
 324                                       cp->vaddr, htons(ntohs(cp->vport)-1),
 325                                       cp->daddr, htons(ntohs(cp->dport)-1),
 326                                       0,
 327                                       cp->dest);
 328                 if (!n_cp)
 329                         return 0;
 330
 331                 /* add its controller */
 332                 ip_vs_control_add(n_cp, cp);
 333         }
 334
 335         /*
 336          *      Move tunnel to listen state
 337          */
 338         ip_vs_tcp_conn_listen(n_cp);
 339         ip_vs_conn_put(n_cp);
 340
 341         return 1;
 342 }
 343
 344
 345 static struct ip_vs_app ip_vs_ftp = {
 346         .name =         "ftp",
 347         .type =         IP_VS_APP_TYPE_FTP,
 348         .protocol =     IPPROTO_TCP,
 349         .module =       THIS_MODULE,
 350         .incs_list =    LIST_HEAD_INIT(ip_vs_ftp.incs_list),
 351         .init_conn =    ip_vs_ftp_init_conn,
 352         .done_conn =    ip_vs_ftp_done_conn,
 353         .bind_conn =    NULL,
 354         .unbind_conn =  NULL,
 355         .pkt_out =      ip_vs_ftp_out,
 356         .pkt_in =       ip_vs_ftp_in,
 357 };
 358
 359
 360 /*
 361  *      ip_vs_ftp initialization
 362  */
 363 static int __init ip_vs_ftp_init(void)
 364 {
 365         int i, ret;
 366         struct ip_vs_app *app = &ip_vs_ftp;
 367
 368         ret = register_ip_vs_app(app);
 369         if (ret)
 370                 return ret;
 371
 372         for (i=0; i<IP_VS_APP_MAX_PORTS; i++) {
 373                 if (!ports[i])
 374                         continue;
 375                 ret = register_ip_vs_app_inc(app, app->protocol, ports[i]);
 376                 if (ret)
 377                         break;
 378                 IP_VS_DBG(1-debug, "%s: loaded support on port[%d] = %d\n",
 379                           app->name, i, ports[i]);
 380         }
 381
 382         if (ret)
 383                 unregister_ip_vs_app(app);
 384
 385         return ret;
 386 }
 387
 388
 389 /*
 390  *      ip_vs_ftp finish.
 391  */
 392 static void __exit ip_vs_ftp_exit(void)
 393 {
 394         unregister_ip_vs_app(&ip_vs_ftp);
 395 }
 396
 397
 398 module_init(ip_vs_ftp_init);
 399 module_exit(ip_vs_ftp_exit);
 400 MODULE_LICENSE("GPL");