1/*
2 * ip_vs_ftp.c: IPVS ftp application module
3 *
4 * Version:	$Id: ip_vs_ftp.c,v 1.1.1.1 2007/08/03 18:53:51 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#include <asm/unaligned.h>
36
37#include <net/ip_vs.h>
38
39
40#define SERVER_STRING "227 Entering Passive Mode ("
41#define CLIENT_STRING "PORT "
42
43
44/*
45 * List of ports (up to IP_VS_APP_MAX_PORTS) to be handled by helper
46 * First port is set to the default port.
47 */
48static unsigned short ports[IP_VS_APP_MAX_PORTS] = {21, 0};
49module_param_array(ports, ushort, NULL, 0);
50MODULE_PARM_DESC(ports, "Ports to monitor for FTP control commands");
51
52
53/*	Dummy variable */
54static int ip_vs_ftp_pasv;
55
56
57static int
58ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
59{
60	return 0;
61}
62
63
64static int
65ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
66{
67	return 0;
68}
69
70
71static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
72				  const char *pattern, size_t plen, char term,
73				  __be32 *addr, __be16 *port,
74				  char **start, char **end)
75{
76	unsigned char p[6];
77	int i = 0;
78
79	if (data_limit - data < plen) {
80		/* check if there is partial match */
81		if (strnicmp(data, pattern, data_limit - data) == 0)
82			return -1;
83		else
84			return 0;
85	}
86
87	if (strnicmp(data, pattern, plen) != 0) {
88		return 0;
89	}
90	*start = data + plen;
91
92	for (data = *start; *data != term; data++) {
93		if (data == data_limit)
94			return -1;
95	}
96	*end = data;
97
98	memset(p, 0, sizeof(p));
99	for (data = *start; data != *end; data++) {
100		if (*data >= '0' && *data <= '9') {
101			p[i] = p[i]*10 + *data - '0';
102		} else if (*data == ',' && i < 5) {
103			i++;
104		} else {
105			/* unexpected character */
106			return -1;
107		}
108	}
109
110	if (i != 5)
111		return -1;
112
113	*addr = get_unaligned((__be32 *)p);
114	*port = get_unaligned((__be16 *)(p + 4));
115	return 1;
116}
117
118
119static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
120			 struct sk_buff **pskb, int *diff)
121{
122	struct iphdr *iph;
123	struct tcphdr *th;
124	char *data, *data_limit;
125	char *start, *end;
126	__be32 from;
127	__be16 port;
128	struct ip_vs_conn *n_cp;
129	char buf[24];
130	unsigned buf_len;
131	int ret;
132
133	*diff = 0;
134
135	/* Only useful for established sessions */
136	if (cp->state != IP_VS_TCP_S_ESTABLISHED)
137		return 1;
138
139	/* Linear packets are much easier to deal with. */
140	if (!ip_vs_make_skb_writable(pskb, (*pskb)->len))
141		return 0;
142
143	if (cp->app_data == &ip_vs_ftp_pasv) {
144		iph = ip_hdr(*pskb);
145		th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
146		data = (char *)th + (th->doff << 2);
147		data_limit = skb_tail_pointer(*pskb);
148
149		if (ip_vs_ftp_get_addrport(data, data_limit,
150					   SERVER_STRING,
151					   sizeof(SERVER_STRING)-1, ')',
152					   &from, &port,
153					   &start, &end) != 1)
154			return 1;
155
156		IP_VS_DBG(7, "PASV response (%u.%u.%u.%u:%d) -> "
157			  "%u.%u.%u.%u:%d detected\n",
158			  NIPQUAD(from), ntohs(port), NIPQUAD(cp->caddr), 0);
159
160		/*
161		 * Now update or create an connection entry for it
162		 */
163		n_cp = ip_vs_conn_out_get(iph->protocol, from, port,
164					  cp->caddr, 0);
165		if (!n_cp) {
166			n_cp = ip_vs_conn_new(IPPROTO_TCP,
167					      cp->caddr, 0,
168					      cp->vaddr, port,
169					      from, port,
170					      IP_VS_CONN_F_NO_CPORT,
171					      cp->dest);
172			if (!n_cp)
173				return 0;
174
175			/* add its controller */
176			ip_vs_control_add(n_cp, cp);
177		}
178
179		/*
180		 * Replace the old passive address with the new one
181		 */
182		from = n_cp->vaddr;
183		port = n_cp->vport;
184		sprintf(buf,"%d,%d,%d,%d,%d,%d", NIPQUAD(from),
185			(ntohs(port)>>8)&255, ntohs(port)&255);
186		buf_len = strlen(buf);
187
188		/*
189		 * Calculate required delta-offset to keep TCP happy
190		 */
191		*diff = buf_len - (end-start);
192
193		if (*diff == 0) {
194			/* simply replace it with new passive address */
195			memcpy(start, buf, buf_len);
196			ret = 1;
197		} else {
198			ret = !ip_vs_skb_replace(*pskb, GFP_ATOMIC, start,
199					  end-start, buf, buf_len);
200		}
201
202		cp->app_data = NULL;
203		ip_vs_tcp_conn_listen(n_cp);
204		ip_vs_conn_put(n_cp);
205		return ret;
206	}
207	return 1;
208}
209
210
211static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
212			struct sk_buff **pskb, int *diff)
213{
214	struct iphdr *iph;
215	struct tcphdr *th;
216	char *data, *data_start, *data_limit;
217	char *start, *end;
218	__be32 to;
219	__be16 port;
220	struct ip_vs_conn *n_cp;
221
222	/* no diff required for incoming packets */
223	*diff = 0;
224
225	/* Only useful for established sessions */
226	if (cp->state != IP_VS_TCP_S_ESTABLISHED)
227		return 1;
228
229	/* Linear packets are much easier to deal with. */
230	if (!ip_vs_make_skb_writable(pskb, (*pskb)->len))
231		return 0;
232
233	/*
234	 * Detecting whether it is passive
235	 */
236	iph = ip_hdr(*pskb);
237	th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
238
239	/* Since there may be OPTIONS in the TCP packet and the HLEN is
240	   the length of the header in 32-bit multiples, it is accurate
241	   to calculate data address by th+HLEN*4 */
242	data = data_start = (char *)th + (th->doff << 2);
243	data_limit = skb_tail_pointer(*pskb);
244
245	while (data <= data_limit - 6) {
246		if (strnicmp(data, "PASV\r\n", 6) == 0) {
247			/* Passive mode on */
248			IP_VS_DBG(7, "got PASV at %td of %td\n",
249				  data - data_start,
250				  data_limit - data_start);
251			cp->app_data = &ip_vs_ftp_pasv;
252			return 1;
253		}
254		data++;
255	}
256
257	/*
258	 * To support virtual FTP server, the scenerio is as follows:
259	 *       FTP client ----> Load Balancer ----> FTP server
260	 * First detect the port number in the application data,
261	 * then create a new connection entry for the coming data
262	 * connection.
263	 */
264	if (ip_vs_ftp_get_addrport(data_start, data_limit,
265				   CLIENT_STRING, sizeof(CLIENT_STRING)-1,
266				   '\r', &to, &port,
267				   &start, &end) != 1)
268		return 1;
269
270	IP_VS_DBG(7, "PORT %u.%u.%u.%u:%d detected\n",
271		  NIPQUAD(to), ntohs(port));
272
273	/* Passive mode off */
274	cp->app_data = NULL;
275
276	/*
277	 * Now update or create a connection entry for it
278	 */
279	IP_VS_DBG(7, "protocol %s %u.%u.%u.%u:%d %u.%u.%u.%u:%d\n",
280		  ip_vs_proto_name(iph->protocol),
281		  NIPQUAD(to), ntohs(port), NIPQUAD(cp->vaddr), 0);
282
283	n_cp = ip_vs_conn_in_get(iph->protocol,
284				 to, port,
285				 cp->vaddr, htons(ntohs(cp->vport)-1));
286	if (!n_cp) {
287		n_cp = ip_vs_conn_new(IPPROTO_TCP,
288				      to, port,
289				      cp->vaddr, htons(ntohs(cp->vport)-1),
290				      cp->daddr, htons(ntohs(cp->dport)-1),
291				      0,
292				      cp->dest);
293		if (!n_cp)
294			return 0;
295
296		/* add its controller */
297		ip_vs_control_add(n_cp, cp);
298	}
299
300	/*
301	 *	Move tunnel to listen state
302	 */
303	ip_vs_tcp_conn_listen(n_cp);
304	ip_vs_conn_put(n_cp);
305
306	return 1;
307}
308
309
310static struct ip_vs_app ip_vs_ftp = {
311	.name =		"ftp",
312	.type =		IP_VS_APP_TYPE_FTP,
313	.protocol =	IPPROTO_TCP,
314	.module =	THIS_MODULE,
315	.incs_list =	LIST_HEAD_INIT(ip_vs_ftp.incs_list),
316	.init_conn =	ip_vs_ftp_init_conn,
317	.done_conn =	ip_vs_ftp_done_conn,
318	.bind_conn =	NULL,
319	.unbind_conn =	NULL,
320	.pkt_out =	ip_vs_ftp_out,
321	.pkt_in =	ip_vs_ftp_in,
322};
323
324
325/*
326 *	ip_vs_ftp initialization
327 */
328static int __init ip_vs_ftp_init(void)
329{
330	int i, ret;
331	struct ip_vs_app *app = &ip_vs_ftp;
332
333	ret = register_ip_vs_app(app);
334	if (ret)
335		return ret;
336
337	for (i=0; i<IP_VS_APP_MAX_PORTS; i++) {
338		if (!ports[i])
339			continue;
340		ret = register_ip_vs_app_inc(app, app->protocol, ports[i]);
341		if (ret)
342			break;
343		IP_VS_INFO("%s: loaded support on port[%d] = %d\n",
344			   app->name, i, ports[i]);
345	}
346
347	if (ret)
348		unregister_ip_vs_app(app);
349
350	return ret;
351}
352
353
354/*
355 *	ip_vs_ftp finish.
356 */
357static void __exit ip_vs_ftp_exit(void)
358{
359	unregister_ip_vs_app(&ip_vs_ftp);
360}
361
362
363module_init(ip_vs_ftp_init);
364module_exit(ip_vs_ftp_exit);
365MODULE_LICENSE("GPL");
366