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 #include <linux/module.h>
26 #include <linux/moduleparam.h>
27 #include <linux/kernel.h>
28 #include <linux/skbuff.h>
29 #include <linux/in.h>
30 #include <linux/ip.h>
31 #include <linux/netfilter.h>
32 #include <net/protocol.h>
33 #include <net/tcp.h>
34 #include <asm/unaligned.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 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");
50
51
52 /* Dummy variable */
53 static int ip_vs_ftp_pasv;
54
55
56 static int
ip_vs_ftp_init_conn(struct ip_vs_app * app,struct ip_vs_conn * cp)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
ip_vs_ftp_done_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)
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 */
ip_vs_ftp_get_addrport(char * data,char * data_limit,const char * pattern,size_t plen,char term,__be32 * addr,__be16 * port,char ** start,char ** end)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)
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 = get_unaligned((__be32 *)p);
118 *port = get_unaligned((__be16 *)(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 */
ip_vs_ftp_out(struct ip_vs_app * app,struct ip_vs_conn * cp,struct sk_buff * skb,int * diff)136 static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
137 struct sk_buff *skb, int *diff)
138 {
139 struct iphdr *iph;
140 struct tcphdr *th;
141 char *data, *data_limit;
142 char *start, *end;
143 union nf_inet_addr from;
144 __be16 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 #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
153 */
154 if (cp->af == AF_INET6)
155 return 1;
156 #endif
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 (!skb_make_writable(skb, skb->len))
166 return 0;
167
168 if (cp->app_data == &ip_vs_ftp_pasv) {
169 iph = ip_hdr(skb);
170 th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
171 data = (char *)th + (th->doff << 2);
172 data_limit = skb_tail_pointer(skb);
173
174 if (ip_vs_ftp_get_addrport(data, data_limit,
175 SERVER_STRING,
176 sizeof(SERVER_STRING)-1, ')',
177 &from.ip, &port,
178 &start, &end) != 1)
179 return 1;
180
181 IP_VS_DBG(7, "PASV response (%pI4:%d) -> %pI4:%d detected\n",
182 &from.ip, ntohs(port), &cp->caddr.ip, 0);
183
184 /*
185 * Now update or create an connection entry for it
186 */
187 n_cp = ip_vs_conn_out_get(AF_INET, iph->protocol, &from, port,
188 &cp->caddr, 0);
189 if (!n_cp) {
190 n_cp = ip_vs_conn_new(AF_INET, IPPROTO_TCP,
191 &cp->caddr, 0,
192 &cp->vaddr, port,
193 &from, port,
194 IP_VS_CONN_F_NO_CPORT,
195 cp->dest);
196 if (!n_cp)
197 return 0;
198
199 /* add its controller */
200 ip_vs_control_add(n_cp, cp);
201 }
202
203 /*
204 * Replace the old passive address with the new one
205 */
206 from.ip = n_cp->vaddr.ip;
207 port = n_cp->vport;
208 sprintf(buf, "%d,%d,%d,%d,%d,%d", NIPQUAD(from.ip),
209 (ntohs(port)>>8)&255, ntohs(port)&255);
210 buf_len = strlen(buf);
211
212 /*
213 * Calculate required delta-offset to keep TCP happy
214 */
215 *diff = buf_len - (end-start);
216
217 if (*diff == 0) {
218 /* simply replace it with new passive address */
219 memcpy(start, buf, buf_len);
220 ret = 1;
221 } else {
222 ret = !ip_vs_skb_replace(skb, GFP_ATOMIC, start,
223 end-start, buf, buf_len);
224 }
225
226 cp->app_data = NULL;
227 ip_vs_tcp_conn_listen(n_cp);
228 ip_vs_conn_put(n_cp);
229 return ret;
230 }
231 return 1;
232 }
233
234
235 /*
236 * Look at incoming ftp packets to catch the PASV/PORT command
237 * (outside-to-inside).
238 *
239 * The incoming packet having the PORT command should be something like
240 * "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
241 * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
242 * In this case, we create a connection entry using the client address and
243 * port, so that the active ftp data connection from the server can reach
244 * the client.
245 */
ip_vs_ftp_in(struct ip_vs_app * app,struct ip_vs_conn * cp,struct sk_buff * skb,int * diff)246 static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
247 struct sk_buff *skb, int *diff)
248 {
249 struct iphdr *iph;
250 struct tcphdr *th;
251 char *data, *data_start, *data_limit;
252 char *start, *end;
253 union nf_inet_addr to;
254 __be16 port;
255 struct ip_vs_conn *n_cp;
256
257 #ifdef CONFIG_IP_VS_IPV6
258 /* This application helper doesn't work with IPv6 yet,
259 * so turn this into a no-op for IPv6 packets
260 */
261 if (cp->af == AF_INET6)
262 return 1;
263 #endif
264
265 /* no diff required for incoming packets */
266 *diff = 0;
267
268 /* Only useful for established sessions */
269 if (cp->state != IP_VS_TCP_S_ESTABLISHED)
270 return 1;
271
272 /* Linear packets are much easier to deal with. */
273 if (!skb_make_writable(skb, skb->len))
274 return 0;
275
276 /*
277 * Detecting whether it is passive
278 */
279 iph = ip_hdr(skb);
280 th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
281
282 /* Since there may be OPTIONS in the TCP packet and the HLEN is
283 the length of the header in 32-bit multiples, it is accurate
284 to calculate data address by th+HLEN*4 */
285 data = data_start = (char *)th + (th->doff << 2);
286 data_limit = skb_tail_pointer(skb);
287
288 while (data <= data_limit - 6) {
289 if (strnicmp(data, "PASV\r\n", 6) == 0) {
290 /* Passive mode on */
291 IP_VS_DBG(7, "got PASV at %td of %td\n",
292 data - data_start,
293 data_limit - data_start);
294 cp->app_data = &ip_vs_ftp_pasv;
295 return 1;
296 }
297 data++;
298 }
299
300 /*
301 * To support virtual FTP server, the scenerio is as follows:
302 * FTP client ----> Load Balancer ----> FTP server
303 * First detect the port number in the application data,
304 * then create a new connection entry for the coming data
305 * connection.
306 */
307 if (ip_vs_ftp_get_addrport(data_start, data_limit,
308 CLIENT_STRING, sizeof(CLIENT_STRING)-1,
309 '\r', &to.ip, &port,
310 &start, &end) != 1)
311 return 1;
312
313 IP_VS_DBG(7, "PORT %pI4:%d detected\n", &to.ip, ntohs(port));
314
315 /* Passive mode off */
316 cp->app_data = NULL;
317
318 /*
319 * Now update or create a connection entry for it
320 */
321 IP_VS_DBG(7, "protocol %s %pI4:%d %pI4:%d\n",
322 ip_vs_proto_name(iph->protocol),
323 &to.ip, ntohs(port), &cp->vaddr.ip, 0);
324
325 n_cp = ip_vs_conn_in_get(AF_INET, iph->protocol,
326 &to, port,
327 &cp->vaddr, htons(ntohs(cp->vport)-1));
328 if (!n_cp) {
329 n_cp = ip_vs_conn_new(AF_INET, IPPROTO_TCP,
330 &to, port,
331 &cp->vaddr, htons(ntohs(cp->vport)-1),
332 &cp->daddr, htons(ntohs(cp->dport)-1),
333 0,
334 cp->dest);
335 if (!n_cp)
336 return 0;
337
338 /* add its controller */
339 ip_vs_control_add(n_cp, cp);
340 }
341
342 /*
343 * Move tunnel to listen state
344 */
345 ip_vs_tcp_conn_listen(n_cp);
346 ip_vs_conn_put(n_cp);
347
348 return 1;
349 }
350
351
352 static struct ip_vs_app ip_vs_ftp = {
353 .name = "ftp",
354 .type = IP_VS_APP_TYPE_FTP,
355 .protocol = IPPROTO_TCP,
356 .module = THIS_MODULE,
357 .incs_list = LIST_HEAD_INIT(ip_vs_ftp.incs_list),
358 .init_conn = ip_vs_ftp_init_conn,
359 .done_conn = ip_vs_ftp_done_conn,
360 .bind_conn = NULL,
361 .unbind_conn = NULL,
362 .pkt_out = ip_vs_ftp_out,
363 .pkt_in = ip_vs_ftp_in,
364 };
365
366
367 /*
368 * ip_vs_ftp initialization
369 */
ip_vs_ftp_init(void)370 static int __init ip_vs_ftp_init(void)
371 {
372 int i, ret;
373 struct ip_vs_app *app = &ip_vs_ftp;
374
375 ret = register_ip_vs_app(app);
376 if (ret)
377 return ret;
378
379 for (i=0; i<IP_VS_APP_MAX_PORTS; i++) {
380 if (!ports[i])
381 continue;
382 ret = register_ip_vs_app_inc(app, app->protocol, ports[i]);
383 if (ret)
384 break;
385 IP_VS_INFO("%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 */
ip_vs_ftp_exit(void)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");
408