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