2 * ip_vs_ftp.c: IPVS ftp application module
4 * Authors: Wensong Zhang <wensong@linuxvirtualserver.org>
9 * This program is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU General Public License
11 * as published by the Free Software Foundation; either version
12 * 2 of the License, or (at your option) any later version.
14 * Most code here is taken from ip_masq_ftp.c in kernel 2.2. The difference
15 * is that ip_vs_ftp module handles the reverse direction to ip_masq_ftp.
17 * IP_MASQ_FTP ftp masquerading module
19 * Version: @(#)ip_masq_ftp.c 0.04 02/05/96
21 * Author: Wouter Gadeyne
25 #include <linux/module.h>
26 #include <linux/moduleparam.h>
27 #include <linux/kernel.h>
28 #include <linux/skbuff.h>
31 #include <linux/netfilter.h>
32 #include <net/protocol.h>
34 #include <asm/unaligned.h>
36 #include <net/ip_vs.h>
39 #define SERVER_STRING "227 Entering Passive Mode ("
40 #define CLIENT_STRING "PORT "
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.
47 static unsigned short ports[IP_VS_APP_MAX_PORTS] = {21, 0};
48 module_param_array(ports, ushort, NULL, 0);
49 MODULE_PARM_DESC(ports, "Ports to monitor for FTP control commands");
53 static int ip_vs_ftp_pasv;
57 ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
64 ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
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.
75 static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
76 const char *pattern, size_t plen, char term,
77 __be32 *addr, __be16 *port,
78 char **start, char **end)
83 if (data_limit - data < plen) {
84 /* check if there is partial match */
85 if (strnicmp(data, pattern, data_limit - data) == 0)
91 if (strnicmp(data, pattern, plen) != 0) {
96 for (data = *start; *data != term; data++) {
97 if (data == data_limit)
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) {
109 /* unexpected character */
117 *addr = get_unaligned((__be32 *)p);
118 *port = get_unaligned((__be16 *)(p + 4));
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.
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.
136 static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
137 struct sk_buff *skb, int *diff)
141 char *data, *data_limit;
143 union nf_inet_addr from;
145 struct ip_vs_conn *n_cp;
146 char buf[24]; /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
150 #ifdef CONFIG_IP_VS_IPV6
151 /* This application helper doesn't work with IPv6 yet,
152 * so turn this into a no-op for IPv6 packets
154 if (cp->af == AF_INET6)
160 /* Only useful for established sessions */
161 if (cp->state != IP_VS_TCP_S_ESTABLISHED)
164 /* Linear packets are much easier to deal with. */
165 if (!skb_make_writable(skb, skb->len))
168 if (cp->app_data == &ip_vs_ftp_pasv) {
170 th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
171 data = (char *)th + (th->doff << 2);
172 data_limit = skb_tail_pointer(skb);
174 if (ip_vs_ftp_get_addrport(data, data_limit,
176 sizeof(SERVER_STRING)-1, ')',
181 IP_VS_DBG(7, "PASV response (%u.%u.%u.%u:%d) -> "
182 "%u.%u.%u.%u:%d detected\n",
183 NIPQUAD(from.ip), ntohs(port),
184 NIPQUAD(cp->caddr.ip), 0);
187 * Now update or create an connection entry for it
189 n_cp = ip_vs_conn_out_get(AF_INET, iph->protocol, &from, port,
192 n_cp = ip_vs_conn_new(AF_INET, IPPROTO_TCP,
196 IP_VS_CONN_F_NO_CPORT,
201 /* add its controller */
202 ip_vs_control_add(n_cp, cp);
206 * Replace the old passive address with the new one
208 from.ip = n_cp->vaddr.ip;
210 sprintf(buf, "%d,%d,%d,%d,%d,%d", NIPQUAD(from.ip),
211 (ntohs(port)>>8)&255, ntohs(port)&255);
212 buf_len = strlen(buf);
215 * Calculate required delta-offset to keep TCP happy
217 *diff = buf_len - (end-start);
220 /* simply replace it with new passive address */
221 memcpy(start, buf, buf_len);
224 ret = !ip_vs_skb_replace(skb, GFP_ATOMIC, start,
225 end-start, buf, buf_len);
229 ip_vs_tcp_conn_listen(n_cp);
230 ip_vs_conn_put(n_cp);
238 * Look at incoming ftp packets to catch the PASV/PORT command
239 * (outside-to-inside).
241 * The incoming packet having the PORT command should be something like
242 * "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
243 * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
244 * In this case, we create a connection entry using the client address and
245 * port, so that the active ftp data connection from the server can reach
248 static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
249 struct sk_buff *skb, int *diff)
253 char *data, *data_start, *data_limit;
255 union nf_inet_addr to;
257 struct ip_vs_conn *n_cp;
259 #ifdef CONFIG_IP_VS_IPV6
260 /* This application helper doesn't work with IPv6 yet,
261 * so turn this into a no-op for IPv6 packets
263 if (cp->af == AF_INET6)
267 /* no diff required for incoming packets */
270 /* Only useful for established sessions */
271 if (cp->state != IP_VS_TCP_S_ESTABLISHED)
274 /* Linear packets are much easier to deal with. */
275 if (!skb_make_writable(skb, skb->len))
279 * Detecting whether it is passive
282 th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
284 /* Since there may be OPTIONS in the TCP packet and the HLEN is
285 the length of the header in 32-bit multiples, it is accurate
286 to calculate data address by th+HLEN*4 */
287 data = data_start = (char *)th + (th->doff << 2);
288 data_limit = skb_tail_pointer(skb);
290 while (data <= data_limit - 6) {
291 if (strnicmp(data, "PASV\r\n", 6) == 0) {
292 /* Passive mode on */
293 IP_VS_DBG(7, "got PASV at %td of %td\n",
295 data_limit - data_start);
296 cp->app_data = &ip_vs_ftp_pasv;
303 * To support virtual FTP server, the scenerio is as follows:
304 * FTP client ----> Load Balancer ----> FTP server
305 * First detect the port number in the application data,
306 * then create a new connection entry for the coming data
309 if (ip_vs_ftp_get_addrport(data_start, data_limit,
310 CLIENT_STRING, sizeof(CLIENT_STRING)-1,
315 IP_VS_DBG(7, "PORT %u.%u.%u.%u:%d detected\n",
316 NIPQUAD(to.ip), ntohs(port));
318 /* Passive mode off */
322 * Now update or create a connection entry for it
324 IP_VS_DBG(7, "protocol %s %u.%u.%u.%u:%d %u.%u.%u.%u:%d\n",
325 ip_vs_proto_name(iph->protocol),
326 NIPQUAD(to.ip), ntohs(port), NIPQUAD(cp->vaddr.ip), 0);
328 n_cp = ip_vs_conn_in_get(AF_INET, iph->protocol,
330 &cp->vaddr, htons(ntohs(cp->vport)-1));
332 n_cp = ip_vs_conn_new(AF_INET, IPPROTO_TCP,
334 &cp->vaddr, htons(ntohs(cp->vport)-1),
335 &cp->daddr, htons(ntohs(cp->dport)-1),
341 /* add its controller */
342 ip_vs_control_add(n_cp, cp);
346 * Move tunnel to listen state
348 ip_vs_tcp_conn_listen(n_cp);
349 ip_vs_conn_put(n_cp);
355 static struct ip_vs_app ip_vs_ftp = {
357 .type = IP_VS_APP_TYPE_FTP,
358 .protocol = IPPROTO_TCP,
359 .module = THIS_MODULE,
360 .incs_list = LIST_HEAD_INIT(ip_vs_ftp.incs_list),
361 .init_conn = ip_vs_ftp_init_conn,
362 .done_conn = ip_vs_ftp_done_conn,
365 .pkt_out = ip_vs_ftp_out,
366 .pkt_in = ip_vs_ftp_in,
371 * ip_vs_ftp initialization
373 static int __init ip_vs_ftp_init(void)
376 struct ip_vs_app *app = &ip_vs_ftp;
378 ret = register_ip_vs_app(app);
382 for (i=0; i<IP_VS_APP_MAX_PORTS; i++) {
385 ret = register_ip_vs_app_inc(app, app->protocol, ports[i]);
388 IP_VS_INFO("%s: loaded support on port[%d] = %d\n",
389 app->name, i, ports[i]);
393 unregister_ip_vs_app(app);
402 static void __exit ip_vs_ftp_exit(void)
404 unregister_ip_vs_app(&ip_vs_ftp);
408 module_init(ip_vs_ftp_init);
409 module_exit(ip_vs_ftp_exit);
410 MODULE_LICENSE("GPL");