a64fa15790e53f8ad0eda7c53b73be8bd849f2aa
[sfrench/cifs-2.6.git] / net / netfilter / ipvs / ip_vs_ftp.c
1 /*
2  * ip_vs_ftp.c: IPVS ftp application module
3  *
4  * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
5  *
6  * Changes:
7  *
8  *
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.
13  *
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.
16  *
17  *              IP_MASQ_FTP ftp masquerading module
18  *
19  * Version:     @(#)ip_masq_ftp.c 0.04   02/05/96
20  *
21  * Author:      Wouter Gadeyne
22  *
23  */
24
25 #define KMSG_COMPONENT "IPVS"
26 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
27
28 #include <linux/module.h>
29 #include <linux/moduleparam.h>
30 #include <linux/kernel.h>
31 #include <linux/skbuff.h>
32 #include <linux/in.h>
33 #include <linux/ip.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>
41 #include <net/tcp.h>
42 #include <asm/unaligned.h>
43
44 #include <net/ip_vs.h>
45
46
47 #define SERVER_STRING "227 "
48 #define CLIENT_STRING "PORT"
49
50
51 /*
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.
54  */
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");
59
60
61 /*      Dummy variable */
62 static int ip_vs_ftp_pasv;
63
64
65 static int
66 ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
67 {
68         /* We use connection tracking for the command connection */
69         cp->flags |= IP_VS_CONN_F_NFCT;
70         return 0;
71 }
72
73
74 static int
75 ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
76 {
77         return 0;
78 }
79
80
81 /*
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.
86  */
87 static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
88                                   const char *pattern, size_t plen,
89                                   char skip, char term,
90                                   __be32 *addr, __be16 *port,
91                                   char **start, char **end)
92 {
93         char *s, c;
94         unsigned char p[6];
95         int i = 0;
96
97         if (data_limit - data < plen) {
98                 /* check if there is partial match */
99                 if (strnicmp(data, pattern, data_limit - data) == 0)
100                         return -1;
101                 else
102                         return 0;
103         }
104
105         if (strnicmp(data, pattern, plen) != 0) {
106                 return 0;
107         }
108         s = data + plen;
109         if (skip) {
110                 int found = 0;
111
112                 for (;; s++) {
113                         if (s == data_limit)
114                                 return -1;
115                         if (!found) {
116                                 if (*s == skip)
117                                         found = 1;
118                         } else if (*s != skip) {
119                                 break;
120                         }
121                 }
122         }
123
124         for (data = s; ; data++) {
125                 if (data == data_limit)
126                         return -1;
127                 if (*data == term)
128                         break;
129         }
130         *end = data;
131
132         memset(p, 0, sizeof(p));
133         for (data = s; ; data++) {
134                 c = *data;
135                 if (c == term)
136                         break;
137                 if (c >= '0' && c <= '9') {
138                         p[i] = p[i]*10 + c - '0';
139                 } else if (c == ',' && i < 5) {
140                         i++;
141                 } else {
142                         /* unexpected character */
143                         return -1;
144                 }
145         }
146
147         if (i != 5)
148                 return -1;
149
150         *start = s;
151         *addr = get_unaligned((__be32 *) p);
152         *port = get_unaligned((__be16 *) (p + 4));
153         return 1;
154 }
155
156 /*
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.
164  *
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.
168  */
169 static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
170                          struct sk_buff *skb, int *diff)
171 {
172         struct iphdr *iph;
173         struct tcphdr *th;
174         char *data, *data_limit;
175         char *start, *end;
176         union nf_inet_addr from;
177         __be16 port;
178         struct ip_vs_conn *n_cp;
179         char buf[24];           /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
180         unsigned int buf_len;
181         int ret = 0;
182         enum ip_conntrack_info ctinfo;
183         struct nf_conn *ct;
184         struct net *net;
185
186 #ifdef CONFIG_IP_VS_IPV6
187         /* This application helper doesn't work with IPv6 yet,
188          * so turn this into a no-op for IPv6 packets
189          */
190         if (cp->af == AF_INET6)
191                 return 1;
192 #endif
193
194         *diff = 0;
195
196         /* Only useful for established sessions */
197         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
198                 return 1;
199
200         /* Linear packets are much easier to deal with. */
201         if (!skb_make_writable(skb, skb->len))
202                 return 0;
203
204         if (cp->app_data == &ip_vs_ftp_pasv) {
205                 iph = ip_hdr(skb);
206                 th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
207                 data = (char *)th + (th->doff << 2);
208                 data_limit = skb_tail_pointer(skb);
209
210                 if (ip_vs_ftp_get_addrport(data, data_limit,
211                                            SERVER_STRING,
212                                            sizeof(SERVER_STRING)-1,
213                                            '(', ')',
214                                            &from.ip, &port,
215                                            &start, &end) != 1)
216                         return 1;
217
218                 IP_VS_DBG(7, "PASV response (%pI4:%d) -> %pI4:%d detected\n",
219                           &from.ip, ntohs(port), &cp->caddr.ip, 0);
220
221                 /*
222                  * Now update or create an connection entry for it
223                  */
224                 {
225                         struct ip_vs_conn_param p;
226                         ip_vs_conn_fill_param(ip_vs_conn_net(cp), AF_INET,
227                                               iph->protocol, &from, port,
228                                               &cp->caddr, 0, &p);
229                         n_cp = ip_vs_conn_out_get(&p);
230                 }
231                 if (!n_cp) {
232                         struct ip_vs_conn_param p;
233                         ip_vs_conn_fill_param(ip_vs_conn_net(cp),
234                                               AF_INET, IPPROTO_TCP, &cp->caddr,
235                                               0, &cp->vaddr, port, &p);
236                         /* As above, this is ipv4 only */
237                         n_cp = ip_vs_conn_new(&p, AF_INET, &from, port,
238                                               IP_VS_CONN_F_NO_CPORT |
239                                               IP_VS_CONN_F_NFCT,
240                                               cp->dest, skb->mark);
241                         if (!n_cp)
242                                 return 0;
243
244                         /* add its controller */
245                         ip_vs_control_add(n_cp, cp);
246                 }
247
248                 /*
249                  * Replace the old passive address with the new one
250                  */
251                 from.ip = n_cp->vaddr.ip;
252                 port = n_cp->vport;
253                 snprintf(buf, sizeof(buf), "%u,%u,%u,%u,%u,%u",
254                          ((unsigned char *)&from.ip)[0],
255                          ((unsigned char *)&from.ip)[1],
256                          ((unsigned char *)&from.ip)[2],
257                          ((unsigned char *)&from.ip)[3],
258                          ntohs(port) >> 8,
259                          ntohs(port) & 0xFF);
260
261                 buf_len = strlen(buf);
262
263                 ct = nf_ct_get(skb, &ctinfo);
264                 if (ct && !nf_ct_is_untracked(ct) && nfct_nat(ct)) {
265                         /* If mangling fails this function will return 0
266                          * which will cause the packet to be dropped.
267                          * Mangling can only fail under memory pressure,
268                          * hopefully it will succeed on the retransmitted
269                          * packet.
270                          */
271                         rcu_read_lock();
272                         ret = nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
273                                                        iph->ihl * 4,
274                                                        start-data, end-start,
275                                                        buf, buf_len);
276                         rcu_read_unlock();
277                         if (ret) {
278                                 ip_vs_nfct_expect_related(skb, ct, n_cp,
279                                                           IPPROTO_TCP, 0, 0);
280                                 if (skb->ip_summed == CHECKSUM_COMPLETE)
281                                         skb->ip_summed = CHECKSUM_UNNECESSARY;
282                                 /* csum is updated */
283                                 ret = 1;
284                         }
285                 }
286
287                 /*
288                  * Not setting 'diff' is intentional, otherwise the sequence
289                  * would be adjusted twice.
290                  */
291
292                 net = skb_net(skb);
293                 cp->app_data = NULL;
294                 ip_vs_tcp_conn_listen(net, n_cp);
295                 ip_vs_conn_put(n_cp);
296                 return ret;
297         }
298         return 1;
299 }
300
301
302 /*
303  * Look at incoming ftp packets to catch the PASV/PORT command
304  * (outside-to-inside).
305  *
306  * The incoming packet having the PORT command should be something like
307  *      "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
308  * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
309  * In this case, we create a connection entry using the client address and
310  * port, so that the active ftp data connection from the server can reach
311  * the client.
312  */
313 static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
314                         struct sk_buff *skb, int *diff)
315 {
316         struct iphdr *iph;
317         struct tcphdr *th;
318         char *data, *data_start, *data_limit;
319         char *start, *end;
320         union nf_inet_addr to;
321         __be16 port;
322         struct ip_vs_conn *n_cp;
323         struct net *net;
324
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
328          */
329         if (cp->af == AF_INET6)
330                 return 1;
331 #endif
332
333         /* no diff required for incoming packets */
334         *diff = 0;
335
336         /* Only useful for established sessions */
337         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
338                 return 1;
339
340         /* Linear packets are much easier to deal with. */
341         if (!skb_make_writable(skb, skb->len))
342                 return 0;
343
344         /*
345          * Detecting whether it is passive
346          */
347         iph = ip_hdr(skb);
348         th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
349
350         /* Since there may be OPTIONS in the TCP packet and the HLEN is
351            the length of the header in 32-bit multiples, it is accurate
352            to calculate data address by th+HLEN*4 */
353         data = data_start = (char *)th + (th->doff << 2);
354         data_limit = skb_tail_pointer(skb);
355
356         while (data <= data_limit - 6) {
357                 if (strnicmp(data, "PASV\r\n", 6) == 0) {
358                         /* Passive mode on */
359                         IP_VS_DBG(7, "got PASV at %td of %td\n",
360                                   data - data_start,
361                                   data_limit - data_start);
362                         cp->app_data = &ip_vs_ftp_pasv;
363                         return 1;
364                 }
365                 data++;
366         }
367
368         /*
369          * To support virtual FTP server, the scenerio is as follows:
370          *       FTP client ----> Load Balancer ----> FTP server
371          * First detect the port number in the application data,
372          * then create a new connection entry for the coming data
373          * connection.
374          */
375         if (ip_vs_ftp_get_addrport(data_start, data_limit,
376                                    CLIENT_STRING, sizeof(CLIENT_STRING)-1,
377                                    ' ', '\r', &to.ip, &port,
378                                    &start, &end) != 1)
379                 return 1;
380
381         IP_VS_DBG(7, "PORT %pI4:%d detected\n", &to.ip, ntohs(port));
382
383         /* Passive mode off */
384         cp->app_data = NULL;
385
386         /*
387          * Now update or create a connection entry for it
388          */
389         IP_VS_DBG(7, "protocol %s %pI4:%d %pI4:%d\n",
390                   ip_vs_proto_name(iph->protocol),
391                   &to.ip, ntohs(port), &cp->vaddr.ip, 0);
392
393         {
394                 struct ip_vs_conn_param p;
395                 ip_vs_conn_fill_param(ip_vs_conn_net(cp), AF_INET,
396                                       iph->protocol, &to, port, &cp->vaddr,
397                                       htons(ntohs(cp->vport)-1), &p);
398                 n_cp = ip_vs_conn_in_get(&p);
399                 if (!n_cp) {
400                         /* This is ipv4 only */
401                         n_cp = ip_vs_conn_new(&p, AF_INET, &cp->daddr,
402                                               htons(ntohs(cp->dport)-1),
403                                               IP_VS_CONN_F_NFCT, cp->dest,
404                                               skb->mark);
405                         if (!n_cp)
406                                 return 0;
407
408                         /* add its controller */
409                         ip_vs_control_add(n_cp, cp);
410                 }
411         }
412
413         /*
414          *      Move tunnel to listen state
415          */
416         net = skb_net(skb);
417         ip_vs_tcp_conn_listen(net, n_cp);
418         ip_vs_conn_put(n_cp);
419
420         return 1;
421 }
422
423
424 static struct ip_vs_app ip_vs_ftp = {
425         .name =         "ftp",
426         .type =         IP_VS_APP_TYPE_FTP,
427         .protocol =     IPPROTO_TCP,
428         .module =       THIS_MODULE,
429         .incs_list =    LIST_HEAD_INIT(ip_vs_ftp.incs_list),
430         .init_conn =    ip_vs_ftp_init_conn,
431         .done_conn =    ip_vs_ftp_done_conn,
432         .bind_conn =    NULL,
433         .unbind_conn =  NULL,
434         .pkt_out =      ip_vs_ftp_out,
435         .pkt_in =       ip_vs_ftp_in,
436 };
437
438 /*
439  *      per netns ip_vs_ftp initialization
440  */
441 static int __net_init __ip_vs_ftp_init(struct net *net)
442 {
443         int i, ret;
444         struct ip_vs_app *app;
445         struct netns_ipvs *ipvs = net_ipvs(net);
446
447         if (!ipvs)
448                 return -ENOENT;
449
450         app = register_ip_vs_app(net, &ip_vs_ftp);
451         if (IS_ERR(app))
452                 return PTR_ERR(app);
453
454         for (i = 0; i < ports_count; i++) {
455                 if (!ports[i])
456                         continue;
457                 ret = register_ip_vs_app_inc(net, app, app->protocol, ports[i]);
458                 if (ret)
459                         goto err_unreg;
460                 pr_info("%s: loaded support on port[%d] = %d\n",
461                         app->name, i, ports[i]);
462         }
463         return 0;
464
465 err_unreg:
466         unregister_ip_vs_app(net, &ip_vs_ftp);
467         return ret;
468 }
469 /*
470  *      netns exit
471  */
472 static void __ip_vs_ftp_exit(struct net *net)
473 {
474         unregister_ip_vs_app(net, &ip_vs_ftp);
475 }
476
477 static struct pernet_operations ip_vs_ftp_ops = {
478         .init = __ip_vs_ftp_init,
479         .exit = __ip_vs_ftp_exit,
480 };
481
482 static int __init ip_vs_ftp_init(void)
483 {
484         int rv;
485
486         rv = register_pernet_subsys(&ip_vs_ftp_ops);
487         /* rcu_barrier() is called by netns on error */
488         return rv;
489 }
490
491 /*
492  *      ip_vs_ftp finish.
493  */
494 static void __exit ip_vs_ftp_exit(void)
495 {
496         unregister_pernet_subsys(&ip_vs_ftp_ops);
497         /* rcu_barrier() is called by netns */
498 }
499
500
501 module_init(ip_vs_ftp_init);
502 module_exit(ip_vs_ftp_exit);
503 MODULE_LICENSE("GPL");