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 #define KMSG_COMPONENT "IPVS"
26 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
28 #include <linux/module.h>
29 #include <linux/moduleparam.h>
30 #include <linux/kernel.h>
31 #include <linux/skbuff.h>
34 #include <linux/netfilter.h>
35 #include <net/netfilter/nf_conntrack.h>
36 #include <net/netfilter/nf_conntrack_expect.h>
37 #include <net/netfilter/nf_nat.h>
38 #include <net/netfilter/nf_nat_helper.h>
39 #include <linux/gfp.h>
40 #include <net/protocol.h>
42 #include <asm/unaligned.h>
44 #include <net/ip_vs.h>
47 #define SERVER_STRING "227 "
48 #define CLIENT_STRING "PORT"
52 * List of ports (up to IP_VS_APP_MAX_PORTS) to be handled by helper
53 * First port is set to the default port.
55 static unsigned int ports_count = 1;
56 static unsigned short ports[IP_VS_APP_MAX_PORTS] = {21, 0};
57 module_param_array(ports, ushort, &ports_count, 0444);
58 MODULE_PARM_DESC(ports, "Ports to monitor for FTP control commands");
62 static int ip_vs_ftp_pasv;
66 ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
68 /* We use connection tracking for the command connection */
69 cp->flags |= IP_VS_CONN_F_NFCT;
75 ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
82 * Get <addr,port> from the string "xxx.xxx.xxx.xxx,ppp,ppp", started
83 * with the "pattern", ignoring before "skip" and terminated with
84 * the "term" character.
85 * <addr,port> is in network order.
87 static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
88 const char *pattern, size_t plen,
90 __be32 *addr, __be16 *port,
91 char **start, char **end)
97 if (data_limit - data < plen) {
98 /* check if there is partial match */
99 if (strncasecmp(data, pattern, data_limit - data) == 0)
105 if (strncasecmp(data, pattern, plen) != 0) {
118 } else if (*s != skip) {
124 for (data = s; ; data++) {
125 if (data == data_limit)
132 memset(p, 0, sizeof(p));
133 for (data = s; ; data++) {
137 if (c >= '0' && c <= '9') {
138 p[i] = p[i]*10 + c - '0';
139 } else if (c == ',' && i < 5) {
142 /* unexpected character */
151 *addr = get_unaligned((__be32 *) p);
152 *port = get_unaligned((__be16 *) (p + 4));
157 * Look at outgoing ftp packets to catch the response to a PASV command
158 * from the server (inside-to-outside).
159 * When we see one, we build a connection entry with the client address,
160 * client port 0 (unknown at the moment), the server address and the
161 * server port. Mark the current connection entry as a control channel
162 * of the new entry. All this work is just to make the data connection
163 * can be scheduled to the right server later.
165 * The outgoing packet should be something like
166 * "227 Entering Passive Mode (xxx,xxx,xxx,xxx,ppp,ppp)".
167 * xxx,xxx,xxx,xxx is the server address, ppp,ppp is the server port number.
169 static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
170 struct sk_buff *skb, int *diff)
174 char *data, *data_limit;
176 union nf_inet_addr from;
178 struct ip_vs_conn *n_cp;
179 char buf[24]; /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
180 unsigned int buf_len;
182 enum ip_conntrack_info ctinfo;
187 #ifdef CONFIG_IP_VS_IPV6
188 /* This application helper doesn't work with IPv6 yet,
189 * so turn this into a no-op for IPv6 packets
191 if (cp->af == AF_INET6)
195 /* Only useful for established sessions */
196 if (cp->state != IP_VS_TCP_S_ESTABLISHED)
199 /* Linear packets are much easier to deal with. */
200 if (!skb_make_writable(skb, skb->len))
203 if (cp->app_data == &ip_vs_ftp_pasv) {
205 th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
206 data = (char *)th + (th->doff << 2);
207 data_limit = skb_tail_pointer(skb);
209 if (ip_vs_ftp_get_addrport(data, data_limit,
211 sizeof(SERVER_STRING)-1,
217 IP_VS_DBG(7, "PASV response (%pI4:%d) -> %pI4:%d detected\n",
218 &from.ip, ntohs(port), &cp->caddr.ip, 0);
221 * Now update or create an connection entry for it
224 struct ip_vs_conn_param p;
225 ip_vs_conn_fill_param(cp->ipvs, AF_INET,
226 iph->protocol, &from, port,
228 n_cp = ip_vs_conn_out_get(&p);
231 struct ip_vs_conn_param p;
232 ip_vs_conn_fill_param(cp->ipvs,
233 AF_INET, IPPROTO_TCP, &cp->caddr,
234 0, &cp->vaddr, port, &p);
235 /* As above, this is ipv4 only */
236 n_cp = ip_vs_conn_new(&p, AF_INET, &from, port,
237 IP_VS_CONN_F_NO_CPORT |
239 cp->dest, skb->mark);
243 /* add its controller */
244 ip_vs_control_add(n_cp, cp);
248 * Replace the old passive address with the new one
250 from.ip = n_cp->vaddr.ip;
252 snprintf(buf, sizeof(buf), "%u,%u,%u,%u,%u,%u",
253 ((unsigned char *)&from.ip)[0],
254 ((unsigned char *)&from.ip)[1],
255 ((unsigned char *)&from.ip)[2],
256 ((unsigned char *)&from.ip)[3],
260 buf_len = strlen(buf);
262 ct = nf_ct_get(skb, &ctinfo);
263 if (ct && !nf_ct_is_untracked(ct) && nfct_nat(ct)) {
264 /* If mangling fails this function will return 0
265 * which will cause the packet to be dropped.
266 * Mangling can only fail under memory pressure,
267 * hopefully it will succeed on the retransmitted
271 ret = nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
273 start-data, end-start,
277 ip_vs_nfct_expect_related(skb, ct, n_cp,
279 if (skb->ip_summed == CHECKSUM_COMPLETE)
280 skb->ip_summed = CHECKSUM_UNNECESSARY;
281 /* csum is updated */
287 * Not setting 'diff' is intentional, otherwise the sequence
288 * would be adjusted twice.
292 ip_vs_tcp_conn_listen(n_cp);
293 ip_vs_conn_put(n_cp);
301 * Look at incoming ftp packets to catch the PASV/PORT command
302 * (outside-to-inside).
304 * The incoming packet having the PORT command should be something like
305 * "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
306 * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
307 * In this case, we create a connection entry using the client address and
308 * port, so that the active ftp data connection from the server can reach
311 static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
312 struct sk_buff *skb, int *diff)
316 char *data, *data_start, *data_limit;
318 union nf_inet_addr to;
320 struct ip_vs_conn *n_cp;
322 /* no diff required for incoming packets */
325 #ifdef CONFIG_IP_VS_IPV6
326 /* This application helper doesn't work with IPv6 yet,
327 * so turn this into a no-op for IPv6 packets
329 if (cp->af == AF_INET6)
333 /* Only useful for established sessions */
334 if (cp->state != IP_VS_TCP_S_ESTABLISHED)
337 /* Linear packets are much easier to deal with. */
338 if (!skb_make_writable(skb, skb->len))
342 * Detecting whether it is passive
345 th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
347 /* Since there may be OPTIONS in the TCP packet and the HLEN is
348 the length of the header in 32-bit multiples, it is accurate
349 to calculate data address by th+HLEN*4 */
350 data = data_start = (char *)th + (th->doff << 2);
351 data_limit = skb_tail_pointer(skb);
353 while (data <= data_limit - 6) {
354 if (strncasecmp(data, "PASV\r\n", 6) == 0) {
355 /* Passive mode on */
356 IP_VS_DBG(7, "got PASV at %td of %td\n",
358 data_limit - data_start);
359 cp->app_data = &ip_vs_ftp_pasv;
366 * To support virtual FTP server, the scenerio is as follows:
367 * FTP client ----> Load Balancer ----> FTP server
368 * First detect the port number in the application data,
369 * then create a new connection entry for the coming data
372 if (ip_vs_ftp_get_addrport(data_start, data_limit,
373 CLIENT_STRING, sizeof(CLIENT_STRING)-1,
374 ' ', '\r', &to.ip, &port,
378 IP_VS_DBG(7, "PORT %pI4:%d detected\n", &to.ip, ntohs(port));
380 /* Passive mode off */
384 * Now update or create a connection entry for it
386 IP_VS_DBG(7, "protocol %s %pI4:%d %pI4:%d\n",
387 ip_vs_proto_name(iph->protocol),
388 &to.ip, ntohs(port), &cp->vaddr.ip, 0);
391 struct ip_vs_conn_param p;
392 ip_vs_conn_fill_param(cp->ipvs, AF_INET,
393 iph->protocol, &to, port, &cp->vaddr,
394 htons(ntohs(cp->vport)-1), &p);
395 n_cp = ip_vs_conn_in_get(&p);
397 /* This is ipv4 only */
398 n_cp = ip_vs_conn_new(&p, AF_INET, &cp->daddr,
399 htons(ntohs(cp->dport)-1),
400 IP_VS_CONN_F_NFCT, cp->dest,
405 /* add its controller */
406 ip_vs_control_add(n_cp, cp);
411 * Move tunnel to listen state
413 ip_vs_tcp_conn_listen(n_cp);
414 ip_vs_conn_put(n_cp);
420 static struct ip_vs_app ip_vs_ftp = {
422 .type = IP_VS_APP_TYPE_FTP,
423 .protocol = IPPROTO_TCP,
424 .module = THIS_MODULE,
425 .incs_list = LIST_HEAD_INIT(ip_vs_ftp.incs_list),
426 .init_conn = ip_vs_ftp_init_conn,
427 .done_conn = ip_vs_ftp_done_conn,
430 .pkt_out = ip_vs_ftp_out,
431 .pkt_in = ip_vs_ftp_in,
435 * per netns ip_vs_ftp initialization
437 static int __net_init __ip_vs_ftp_init(struct net *net)
440 struct ip_vs_app *app;
441 struct netns_ipvs *ipvs = net_ipvs(net);
446 app = register_ip_vs_app(ipvs, &ip_vs_ftp);
450 for (i = 0; i < ports_count; i++) {
453 ret = register_ip_vs_app_inc(ipvs, app, app->protocol, ports[i]);
456 pr_info("%s: loaded support on port[%d] = %d\n",
457 app->name, i, ports[i]);
462 unregister_ip_vs_app(ipvs, &ip_vs_ftp);
468 static void __ip_vs_ftp_exit(struct net *net)
470 struct netns_ipvs *ipvs = net_ipvs(net);
475 unregister_ip_vs_app(ipvs, &ip_vs_ftp);
478 static struct pernet_operations ip_vs_ftp_ops = {
479 .init = __ip_vs_ftp_init,
480 .exit = __ip_vs_ftp_exit,
483 static int __init ip_vs_ftp_init(void)
487 rv = register_pernet_subsys(&ip_vs_ftp_ops);
488 /* rcu_barrier() is called by netns on error */
495 static void __exit ip_vs_ftp_exit(void)
497 unregister_pernet_subsys(&ip_vs_ftp_ops);
498 /* rcu_barrier() is called by netns */
502 module_init(ip_vs_ftp_init);
503 module_exit(ip_vs_ftp_exit);
504 MODULE_LICENSE("GPL");