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  *      Debug level
  53  */
  54 #ifdef CONFIG_IP_VS_DEBUG
  55 static int debug=0;
  56 module_param(debug, int, 0);
  57 #endif
  58
  59
  60 /*      Dummy variable */
  61 static int ip_vs_ftp_pasv;
  62
  63
  64 static int
  65 ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  66 {
  67         return 0;
  68 }
  69
  70
  71 static int
  72 ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  73 {
  74         return 0;
  75 }
  76
  77
  78 /*
  79  * Get <addr,port> from the string "xxx.xxx.xxx.xxx,ppp,ppp", started
  80  * with the "pattern" and terminated with the "term" character.
  81  * <addr,port> is in network order.
  82  */
  83 static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
  84                                   const char *pattern, size_t plen, char term,
  85                                   __u32 *addr, __u16 *port,
  86                                   char **start, char **end)
  87 {
  88         unsigned char p[6];
  89         int i = 0;
  90
  91         if (data_limit - data < plen) {
  92                 /* check if there is partial match */
  93                 if (strnicmp(data, pattern, data_limit - data) == 0)
  94                         return -1;
  95                 else
  96                         return 0;
  97         }
  98
  99         if (strnicmp(data, pattern, plen) != 0) {
 100                 return 0;
 101         }
 102         *start = data + plen;
 103
 104         for (data = *start; *data != term; data++) {
 105                 if (data == data_limit)
 106                         return -1;
 107         }
 108         *end = data;
 109
 110         memset(p, 0, sizeof(p));
 111         for (data = *start; data != *end; data++) {
 112                 if (*data >= '0' && *data <= '9') {
 113                         p[i] = p[i]*10 + *data - '0';
 114                 } else if (*data == ',' && i < 5) {
 115                         i++;
 116                 } else {
 117                         /* unexpected character */
 118                         return -1;
 119                 }
 120         }
 121
 122         if (i != 5)
 123                 return -1;
 124
 125         *addr = (p[3]<<24) | (p[2]<<16) | (p[1]<<8) | p[0];
 126         *port = (p[5]<<8) | p[4];
 127         return 1;
 128 }
 129
 130
 131 /*
 132  * Look at outgoing ftp packets to catch the response to a PASV command
 133  * from the server (inside-to-outside).
 134  * When we see one, we build a connection entry with the client address,
 135  * client port 0 (unknown at the moment), the server address and the
 136  * server port.  Mark the current connection entry as a control channel
 137  * of the new entry. All this work is just to make the data connection
 138  * can be scheduled to the right server later.
 139  *
 140  * The outgoing packet should be something like
 141  *   "227 Entering Passive Mode (xxx,xxx,xxx,xxx,ppp,ppp)".
 142  * xxx,xxx,xxx,xxx is the server address, ppp,ppp is the server port number.
 143  */
 144 static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
 145                          struct sk_buff **pskb, int *diff)
 146 {
 147         struct iphdr *iph;
 148         struct tcphdr *th;
 149         char *data, *data_limit;
 150         char *start, *end;
 151         __u32 from;
 152         __u16 port;
 153         struct ip_vs_conn *n_cp;
 154         char buf[24];           /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
 155         unsigned buf_len;
 156         int ret;
 157
 158         *diff = 0;
 159
 160         /* Only useful for established sessions */
 161         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 162                 return 1;
 163
 164         /* Linear packets are much easier to deal with. */
 165         if (!ip_vs_make_skb_writable(pskb, (*pskb)->len))
 166                 return 0;
 167
 168         if (cp->app_data == &ip_vs_ftp_pasv) {
 169                 iph = (*pskb)->nh.iph;
 170                 th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 171                 data = (char *)th + (th->doff << 2);
 172                 data_limit = (*pskb)->tail;
 173
 174                 if (ip_vs_ftp_get_addrport(data, data_limit,
 175                                            SERVER_STRING,
 176                                            sizeof(SERVER_STRING)-1, ')',
 177                                            &from, &port,
 178                                            &start, &end) != 1)
 179                         return 1;
 180
 181                 IP_VS_DBG(1-debug, "PASV response (%u.%u.%u.%u:%d) -> "
 182                           "%u.%u.%u.%u:%d detected\n",
 183                           NIPQUAD(from), ntohs(port), NIPQUAD(cp->caddr), 0);
 184
 185                 /*
 186                  * Now update or create an connection entry for it
 187                  */
 188                 n_cp = ip_vs_conn_out_get(iph->protocol, from, port,
 189                                           cp->caddr, 0);
 190                 if (!n_cp) {
 191                         n_cp = ip_vs_conn_new(IPPROTO_TCP,
 192                                               cp->caddr, 0,
 193                                               cp->vaddr, port,
 194                                               from, port,
 195                                               IP_VS_CONN_F_NO_CPORT,
 196                                               cp->dest);
 197                         if (!n_cp)
 198                                 return 0;
 199
 200                         /* add its controller */
 201                         ip_vs_control_add(n_cp, cp);
 202                 }
 203
 204                 /*
 205                  * Replace the old passive address with the new one
 206                  */
 207                 from = n_cp->vaddr;
 208                 port = n_cp->vport;
 209                 sprintf(buf,"%d,%d,%d,%d,%d,%d", NIPQUAD(from),
 210                         port&255, (port>>8)&255);
 211                 buf_len = strlen(buf);
 212
 213                 /*
 214                  * Calculate required delta-offset to keep TCP happy
 215                  */
 216                 *diff = buf_len - (end-start);
 217
 218                 if (*diff == 0) {
 219                         /* simply replace it with new passive address */
 220                         memcpy(start, buf, buf_len);
 221                         ret = 1;
 222                 } else {
 223                         ret = !ip_vs_skb_replace(*pskb, GFP_ATOMIC, start,
 224                                           end-start, buf, buf_len);
 225                 }
 226
 227                 cp->app_data = NULL;
 228                 ip_vs_tcp_conn_listen(n_cp);
 229                 ip_vs_conn_put(n_cp);
 230                 return ret;
 231         }
 232         return 1;
 233 }
 234
 235
 236 /*
 237  * Look at incoming ftp packets to catch the PASV/PORT command
 238  * (outside-to-inside).
 239  *
 240  * The incoming packet having the PORT command should be something like
 241  *      "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
 242  * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
 243  * In this case, we create a connection entry using the client address and
 244  * port, so that the active ftp data connection from the server can reach
 245  * the client.
 246  */
 247 static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
 248                         struct sk_buff **pskb, int *diff)
 249 {
 250         struct iphdr *iph;
 251         struct tcphdr *th;
 252         char *data, *data_start, *data_limit;
 253         char *start, *end;
 254         __u32 to;
 255         __u16 port;
 256         struct ip_vs_conn *n_cp;
 257
 258         /* no diff required for incoming packets */
 259         *diff = 0;
 260
 261         /* Only useful for established sessions */
 262         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 263                 return 1;
 264
 265         /* Linear packets are much easier to deal with. */
 266         if (!ip_vs_make_skb_writable(pskb, (*pskb)->len))
 267                 return 0;
 268
 269         /*
 270          * Detecting whether it is passive
 271          */
 272         iph = (*pskb)->nh.iph;
 273         th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 274
 275         /* Since there may be OPTIONS in the TCP packet and the HLEN is
 276            the length of the header in 32-bit multiples, it is accurate
 277            to calculate data address by th+HLEN*4 */
 278         data = data_start = (char *)th + (th->doff << 2);
 279         data_limit = (*pskb)->tail;
 280
 281         while (data <= data_limit - 6) {
 282                 if (strnicmp(data, "PASV\r\n", 6) == 0) {
 283                         /* Passive mode on */
 284                         IP_VS_DBG(1-debug, "got PASV at %zd of %zd\n",
 285                                   data - data_start,
 286                                   data_limit - data_start);
 287                         cp->app_data = &ip_vs_ftp_pasv;
 288                         return 1;
 289                 }
 290                 data++;
 291         }
 292
 293         /*
 294          * To support virtual FTP server, the scenerio is as follows:
 295          *       FTP client ----> Load Balancer ----> FTP server
 296          * First detect the port number in the application data,
 297          * then create a new connection entry for the coming data
 298          * connection.
 299          */
 300         if (ip_vs_ftp_get_addrport(data_start, data_limit,
 301                                    CLIENT_STRING, sizeof(CLIENT_STRING)-1,
 302                                    '\r', &to, &port,
 303                                    &start, &end) != 1)
 304                 return 1;
 305
 306         IP_VS_DBG(1-debug, "PORT %u.%u.%u.%u:%d detected\n",
 307                   NIPQUAD(to), ntohs(port));
 308
 309         /* Passive mode off */
 310         cp->app_data = NULL;
 311
 312         /*
 313          * Now update or create a connection entry for it
 314          */
 315         IP_VS_DBG(1-debug, "protocol %s %u.%u.%u.%u:%d %u.%u.%u.%u:%d\n",
 316                   ip_vs_proto_name(iph->protocol),
 317                   NIPQUAD(to), ntohs(port), NIPQUAD(cp->vaddr), 0);
 318
 319         n_cp = ip_vs_conn_in_get(iph->protocol,
 320                                  to, port,
 321                                  cp->vaddr, htons(ntohs(cp->vport)-1));
 322         if (!n_cp) {
 323                 n_cp = ip_vs_conn_new(IPPROTO_TCP,
 324                                       to, port,
 325                                       cp->vaddr, htons(ntohs(cp->vport)-1),
 326                                       cp->daddr, htons(ntohs(cp->dport)-1),
 327                                       0,
 328                                       cp->dest);
 329                 if (!n_cp)
 330                         return 0;
 331
 332                 /* add its controller */
 333                 ip_vs_control_add(n_cp, cp);
 334         }
 335
 336         /*
 337          *      Move tunnel to listen state
 338          */
 339         ip_vs_tcp_conn_listen(n_cp);
 340         ip_vs_conn_put(n_cp);
 341
 342         return 1;
 343 }
 344
 345
 346 static struct ip_vs_app ip_vs_ftp = {
 347         .name =         "ftp",
 348         .type =         IP_VS_APP_TYPE_FTP,
 349         .protocol =     IPPROTO_TCP,
 350         .module =       THIS_MODULE,
 351         .incs_list =    LIST_HEAD_INIT(ip_vs_ftp.incs_list),
 352         .init_conn =    ip_vs_ftp_init_conn,
 353         .done_conn =    ip_vs_ftp_done_conn,
 354         .bind_conn =    NULL,
 355         .unbind_conn =  NULL,
 356         .pkt_out =      ip_vs_ftp_out,
 357         .pkt_in =       ip_vs_ftp_in,
 358 };
 359
 360
 361 /*
 362  *      ip_vs_ftp initialization
 363  */
 364 static int __init ip_vs_ftp_init(void)
 365 {
 366         int i, ret;
 367         struct ip_vs_app *app = &ip_vs_ftp;
 368
 369         ret = register_ip_vs_app(app);
 370         if (ret)
 371                 return ret;
 372
 373         for (i=0; i<IP_VS_APP_MAX_PORTS; i++) {
 374                 if (!ports[i])
 375                         continue;
 376                 if (ports[i] < 0 || ports[i] > 0xffff) {
 377                         IP_VS_WARNING("ip_vs_ftp: Ignoring invalid "
 378                                       "configuration port[%d] = %d\n",
 379                                       i, ports[i]);
 380                         continue;
 381                 }
 382                 ret = register_ip_vs_app_inc(app, app->protocol, ports[i]);
 383                 if (ret)
 384                         break;
 385                 IP_VS_DBG(1-debug, "%s: loaded support on port[%d] = %d\n",
 386                           app->name, i, ports[i]);
 387         }
 388
 389         if (ret)
 390                 unregister_ip_vs_app(app);
 391
 392         return ret;
 393 }
 394
 395
 396 /*
 397  *      ip_vs_ftp finish.
 398  */
 399 static void __exit ip_vs_ftp_exit(void)
 400 {
 401         unregister_ip_vs_app(&ip_vs_ftp);
 402 }
 403
 404
 405 module_init(ip_vs_ftp_init);
 406 module_exit(ip_vs_ftp_exit);
 407 MODULE_LICENSE("GPL");