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 MODULE_PARM_DESC(ports, "Ports to monitor for FTP control commands");
  50
  51
  52 /*      Dummy variable */
  53 static int ip_vs_ftp_pasv;
  54
  55
  56 static int
  57 ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  58 {
  59         return 0;
  60 }
  61
  62
  63 static int
  64 ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  65 {
  66         return 0;
  67 }
  68
  69
  70 /*
  71  * Get <addr,port> from the string "xxx.xxx.xxx.xxx,ppp,ppp", started
  72  * with the "pattern" and terminated with the "term" character.
  73  * <addr,port> is in network order.
  74  */
  75 static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
  76                                   const char *pattern, size_t plen, char term,
  77                                   __u32 *addr, __u16 *port,
  78                                   char **start, char **end)
  79 {
  80         unsigned char p[6];
  81         int i = 0;
  82
  83         if (data_limit - data < plen) {
  84                 /* check if there is partial match */
  85                 if (strnicmp(data, pattern, data_limit - data) == 0)
  86                         return -1;
  87                 else
  88                         return 0;
  89         }
  90
  91         if (strnicmp(data, pattern, plen) != 0) {
  92                 return 0;
  93         }
  94         *start = data + plen;
  95
  96         for (data = *start; *data != term; data++) {
  97                 if (data == data_limit)
  98                         return -1;
  99         }
 100         *end = data;
 101
 102         memset(p, 0, sizeof(p));
 103         for (data = *start; data != *end; data++) {
 104                 if (*data >= '0' && *data <= '9') {
 105                         p[i] = p[i]*10 + *data - '0';
 106                 } else if (*data == ',' && i < 5) {
 107                         i++;
 108                 } else {
 109                         /* unexpected character */
 110                         return -1;
 111                 }
 112         }
 113
 114         if (i != 5)
 115                 return -1;
 116
 117         *addr = (p[3]<<24) | (p[2]<<16) | (p[1]<<8) | p[0];
 118         *port = (p[5]<<8) | p[4];
 119         return 1;
 120 }
 121
 122
 123 /*
 124  * Look at outgoing ftp packets to catch the response to a PASV command
 125  * from the server (inside-to-outside).
 126  * When we see one, we build a connection entry with the client address,
 127  * client port 0 (unknown at the moment), the server address and the
 128  * server port.  Mark the current connection entry as a control channel
 129  * of the new entry. All this work is just to make the data connection
 130  * can be scheduled to the right server later.
 131  *
 132  * The outgoing packet should be something like
 133  *   "227 Entering Passive Mode (xxx,xxx,xxx,xxx,ppp,ppp)".
 134  * xxx,xxx,xxx,xxx is the server address, ppp,ppp is the server port number.
 135  */
 136 static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
 137                          struct sk_buff **pskb, int *diff)
 138 {
 139         struct iphdr *iph;
 140         struct tcphdr *th;
 141         char *data, *data_limit;
 142         char *start, *end;
 143         __u32 from;
 144         __u16 port;
 145         struct ip_vs_conn *n_cp;
 146         char buf[24];           /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
 147         unsigned buf_len;
 148         int ret;
 149
 150         *diff = 0;
 151
 152         /* Only useful for established sessions */
 153         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 154                 return 1;
 155
 156         /* Linear packets are much easier to deal with. */
 157         if (!ip_vs_make_skb_writable(pskb, (*pskb)->len))
 158                 return 0;
 159
 160         if (cp->app_data == &ip_vs_ftp_pasv) {
 161                 iph = (*pskb)->nh.iph;
 162                 th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 163                 data = (char *)th + (th->doff << 2);
 164                 data_limit = (*pskb)->tail;
 165
 166                 if (ip_vs_ftp_get_addrport(data, data_limit,
 167                                            SERVER_STRING,
 168                                            sizeof(SERVER_STRING)-1, ')',
 169                                            &from, &port,
 170                                            &start, &end) != 1)
 171                         return 1;
 172
 173                 IP_VS_DBG(7, "PASV response (%u.%u.%u.%u:%d) -> "
 174                           "%u.%u.%u.%u:%d detected\n",
 175                           NIPQUAD(from), ntohs(port), NIPQUAD(cp->caddr), 0);
 176
 177                 /*
 178                  * Now update or create an connection entry for it
 179                  */
 180                 n_cp = ip_vs_conn_out_get(iph->protocol, from, port,
 181                                           cp->caddr, 0);
 182                 if (!n_cp) {
 183                         n_cp = ip_vs_conn_new(IPPROTO_TCP,
 184                                               cp->caddr, 0,
 185                                               cp->vaddr, port,
 186                                               from, port,
 187                                               IP_VS_CONN_F_NO_CPORT,
 188                                               cp->dest);
 189                         if (!n_cp)
 190                                 return 0;
 191
 192                         /* add its controller */
 193                         ip_vs_control_add(n_cp, cp);
 194                 }
 195
 196                 /*
 197                  * Replace the old passive address with the new one
 198                  */
 199                 from = n_cp->vaddr;
 200                 port = n_cp->vport;
 201                 sprintf(buf,"%d,%d,%d,%d,%d,%d", NIPQUAD(from),
 202                         port&255, (port>>8)&255);
 203                 buf_len = strlen(buf);
 204
 205                 /*
 206                  * Calculate required delta-offset to keep TCP happy
 207                  */
 208                 *diff = buf_len - (end-start);
 209
 210                 if (*diff == 0) {
 211                         /* simply replace it with new passive address */
 212                         memcpy(start, buf, buf_len);
 213                         ret = 1;
 214                 } else {
 215                         ret = !ip_vs_skb_replace(*pskb, GFP_ATOMIC, start,
 216                                           end-start, buf, buf_len);
 217                 }
 218
 219                 cp->app_data = NULL;
 220                 ip_vs_tcp_conn_listen(n_cp);
 221                 ip_vs_conn_put(n_cp);
 222                 return ret;
 223         }
 224         return 1;
 225 }
 226
 227
 228 /*
 229  * Look at incoming ftp packets to catch the PASV/PORT command
 230  * (outside-to-inside).
 231  *
 232  * The incoming packet having the PORT command should be something like
 233  *      "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
 234  * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
 235  * In this case, we create a connection entry using the client address and
 236  * port, so that the active ftp data connection from the server can reach
 237  * the client.
 238  */
 239 static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
 240                         struct sk_buff **pskb, int *diff)
 241 {
 242         struct iphdr *iph;
 243         struct tcphdr *th;
 244         char *data, *data_start, *data_limit;
 245         char *start, *end;
 246         __u32 to;
 247         __u16 port;
 248         struct ip_vs_conn *n_cp;
 249
 250         /* no diff required for incoming packets */
 251         *diff = 0;
 252
 253         /* Only useful for established sessions */
 254         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 255                 return 1;
 256
 257         /* Linear packets are much easier to deal with. */
 258         if (!ip_vs_make_skb_writable(pskb, (*pskb)->len))
 259                 return 0;
 260
 261         /*
 262          * Detecting whether it is passive
 263          */
 264         iph = (*pskb)->nh.iph;
 265         th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 266
 267         /* Since there may be OPTIONS in the TCP packet and the HLEN is
 268            the length of the header in 32-bit multiples, it is accurate
 269            to calculate data address by th+HLEN*4 */
 270         data = data_start = (char *)th + (th->doff << 2);
 271         data_limit = (*pskb)->tail;
 272
 273         while (data <= data_limit - 6) {
 274                 if (strnicmp(data, "PASV\r\n", 6) == 0) {
 275                         /* Passive mode on */
 276                         IP_VS_DBG(7, "got PASV at %zd of %zd\n",
 277                                   data - data_start,
 278                                   data_limit - data_start);
 279                         cp->app_data = &ip_vs_ftp_pasv;
 280                         return 1;
 281                 }
 282                 data++;
 283         }
 284
 285         /*
 286          * To support virtual FTP server, the scenerio is as follows:
 287          *       FTP client ----> Load Balancer ----> FTP server
 288          * First detect the port number in the application data,
 289          * then create a new connection entry for the coming data
 290          * connection.
 291          */
 292         if (ip_vs_ftp_get_addrport(data_start, data_limit,
 293                                    CLIENT_STRING, sizeof(CLIENT_STRING)-1,
 294                                    '\r', &to, &port,
 295                                    &start, &end) != 1)
 296                 return 1;
 297
 298         IP_VS_DBG(7, "PORT %u.%u.%u.%u:%d detected\n",
 299                   NIPQUAD(to), ntohs(port));
 300
 301         /* Passive mode off */
 302         cp->app_data = NULL;
 303
 304         /*
 305          * Now update or create a connection entry for it
 306          */
 307         IP_VS_DBG(7, "protocol %s %u.%u.%u.%u:%d %u.%u.%u.%u:%d\n",
 308                   ip_vs_proto_name(iph->protocol),
 309                   NIPQUAD(to), ntohs(port), NIPQUAD(cp->vaddr), 0);
 310
 311         n_cp = ip_vs_conn_in_get(iph->protocol,
 312                                  to, port,
 313                                  cp->vaddr, htons(ntohs(cp->vport)-1));
 314         if (!n_cp) {
 315                 n_cp = ip_vs_conn_new(IPPROTO_TCP,
 316                                       to, port,
 317                                       cp->vaddr, htons(ntohs(cp->vport)-1),
 318                                       cp->daddr, htons(ntohs(cp->dport)-1),
 319                                       0,
 320                                       cp->dest);
 321                 if (!n_cp)
 322                         return 0;
 323
 324                 /* add its controller */
 325                 ip_vs_control_add(n_cp, cp);
 326         }
 327
 328         /*
 329          *      Move tunnel to listen state
 330          */
 331         ip_vs_tcp_conn_listen(n_cp);
 332         ip_vs_conn_put(n_cp);
 333
 334         return 1;
 335 }
 336
 337
 338 static struct ip_vs_app ip_vs_ftp = {
 339         .name =         "ftp",
 340         .type =         IP_VS_APP_TYPE_FTP,
 341         .protocol =     IPPROTO_TCP,
 342         .module =       THIS_MODULE,
 343         .incs_list =    LIST_HEAD_INIT(ip_vs_ftp.incs_list),
 344         .init_conn =    ip_vs_ftp_init_conn,
 345         .done_conn =    ip_vs_ftp_done_conn,
 346         .bind_conn =    NULL,
 347         .unbind_conn =  NULL,
 348         .pkt_out =      ip_vs_ftp_out,
 349         .pkt_in =       ip_vs_ftp_in,
 350 };
 351
 352
 353 /*
 354  *      ip_vs_ftp initialization
 355  */
 356 static int __init ip_vs_ftp_init(void)
 357 {
 358         int i, ret;
 359         struct ip_vs_app *app = &ip_vs_ftp;
 360
 361         ret = register_ip_vs_app(app);
 362         if (ret)
 363                 return ret;
 364
 365         for (i=0; i<IP_VS_APP_MAX_PORTS; i++) {
 366                 if (!ports[i])
 367                         continue;
 368                 if (ports[i] < 0 || ports[i] > 0xffff) {
 369                         IP_VS_WARNING("ip_vs_ftp: Ignoring invalid "
 370                                       "configuration port[%d] = %d\n",
 371                                       i, ports[i]);
 372                         continue;
 373                 }
 374                 ret = register_ip_vs_app_inc(app, app->protocol, ports[i]);
 375                 if (ret)
 376                         break;
 377                 IP_VS_INFO("%s: loaded support on port[%d] = %d\n",
 378                            app->name, i, ports[i]);
 379         }
 380
 381         if (ret)
 382                 unregister_ip_vs_app(app);
 383
 384         return ret;
 385 }
 386
 387
 388 /*
 389  *      ip_vs_ftp finish.
 390  */
 391 static void __exit ip_vs_ftp_exit(void)
 392 {
 393         unregister_ip_vs_app(&ip_vs_ftp);
 394 }
 395
 396
 397 module_init(ip_vs_ftp_init);
 398 module_exit(ip_vs_ftp_exit);
 399 MODULE_LICENSE("GPL");