Free Electrons

Embedded Linux Experts

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
/*
 * ip_vs_ftp.c: IPVS ftp application module
 *
 * Authors:	Wensong Zhang <wensong@linuxvirtualserver.org>
 *
 * Changes:
 *
 *
 *	This program is free software; you can redistribute it and/or
 *	modify it under the terms of the GNU General Public License
 *	as published by the Free Software Foundation; either version
 *	2 of the License, or (at your option) any later version.
 *
 * Most code here is taken from ip_masq_ftp.c in kernel 2.2. The difference
 * is that ip_vs_ftp module handles the reverse direction to ip_masq_ftp.
 *
 *		IP_MASQ_FTP ftp masquerading module
 *
 * Version:	@(#)ip_masq_ftp.c 0.04   02/05/96
 *
 * Author:	Wouter Gadeyne
 *
 */

#define KMSG_COMPONENT "IPVS"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/netfilter.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_helper.h>
#include <linux/gfp.h>
#include <net/protocol.h>
#include <net/tcp.h>
#include <asm/unaligned.h>

#include <net/ip_vs.h>


#define SERVER_STRING "227 "
#define CLIENT_STRING "PORT"


/*
 * List of ports (up to IP_VS_APP_MAX_PORTS) to be handled by helper
 * First port is set to the default port.
 */
static unsigned int ports_count = 1;
static unsigned short ports[IP_VS_APP_MAX_PORTS] = {21, 0};
module_param_array(ports, ushort, &ports_count, 0444);
MODULE_PARM_DESC(ports, "Ports to monitor for FTP control commands");


/*	Dummy variable */
static int ip_vs_ftp_pasv;


static int
ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
{
	/* We use connection tracking for the command connection */
	cp->flags |= IP_VS_CONN_F_NFCT;
	return 0;
}


static int
ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
{
	return 0;
}


/*
 * Get <addr,port> from the string "xxx.xxx.xxx.xxx,ppp,ppp", started
 * with the "pattern", ignoring before "skip" and terminated with
 * the "term" character.
 * <addr,port> is in network order.
 */
static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
				  const char *pattern, size_t plen,
				  char skip, char term,
				  __be32 *addr, __be16 *port,
				  char **start, char **end)
{
	char *s, c;
	unsigned char p[6];
	int i = 0;

	if (data_limit - data < plen) {
		/* check if there is partial match */
		if (strnicmp(data, pattern, data_limit - data) == 0)
			return -1;
		else
			return 0;
	}

	if (strnicmp(data, pattern, plen) != 0) {
		return 0;
	}
	s = data + plen;
	if (skip) {
		int found = 0;

		for (;; s++) {
			if (s == data_limit)
				return -1;
			if (!found) {
				if (*s == skip)
					found = 1;
			} else if (*s != skip) {
				break;
			}
		}
	}

	for (data = s; ; data++) {
		if (data == data_limit)
			return -1;
		if (*data == term)
			break;
	}
	*end = data;

	memset(p, 0, sizeof(p));
	for (data = s; ; data++) {
		c = *data;
		if (c == term)
			break;
		if (c >= '0' && c <= '9') {
			p[i] = p[i]*10 + c - '0';
		} else if (c == ',' && i < 5) {
			i++;
		} else {
			/* unexpected character */
			return -1;
		}
	}

	if (i != 5)
		return -1;

	*start = s;
	*addr = get_unaligned((__be32 *) p);
	*port = get_unaligned((__be16 *) (p + 4));
	return 1;
}

/*
 * Look at outgoing ftp packets to catch the response to a PASV command
 * from the server (inside-to-outside).
 * When we see one, we build a connection entry with the client address,
 * client port 0 (unknown at the moment), the server address and the
 * server port.  Mark the current connection entry as a control channel
 * of the new entry. All this work is just to make the data connection
 * can be scheduled to the right server later.
 *
 * The outgoing packet should be something like
 *   "227 Entering Passive Mode (xxx,xxx,xxx,xxx,ppp,ppp)".
 * xxx,xxx,xxx,xxx is the server address, ppp,ppp is the server port number.
 */
static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
			 struct sk_buff *skb, int *diff)
{
	struct iphdr *iph;
	struct tcphdr *th;
	char *data, *data_limit;
	char *start, *end;
	union nf_inet_addr from;
	__be16 port;
	struct ip_vs_conn *n_cp;
	char buf[24];		/* xxx.xxx.xxx.xxx,ppp,ppp\000 */
	unsigned int buf_len;
	int ret = 0;
	enum ip_conntrack_info ctinfo;
	struct nf_conn *ct;
	struct net *net;

	*diff = 0;

#ifdef CONFIG_IP_VS_IPV6
	/* This application helper doesn't work with IPv6 yet,
	 * so turn this into a no-op for IPv6 packets
	 */
	if (cp->af == AF_INET6)
		return 1;
#endif

	/* Only useful for established sessions */
	if (cp->state != IP_VS_TCP_S_ESTABLISHED)
		return 1;

	/* Linear packets are much easier to deal with. */
	if (!skb_make_writable(skb, skb->len))
		return 0;

	if (cp->app_data == &ip_vs_ftp_pasv) {
		iph = ip_hdr(skb);
		th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
		data = (char *)th + (th->doff << 2);
		data_limit = skb_tail_pointer(skb);

		if (ip_vs_ftp_get_addrport(data, data_limit,
					   SERVER_STRING,
					   sizeof(SERVER_STRING)-1,
					   '(', ')',
					   &from.ip, &port,
					   &start, &end) != 1)
			return 1;

		IP_VS_DBG(7, "PASV response (%pI4:%d) -> %pI4:%d detected\n",
			  &from.ip, ntohs(port), &cp->caddr.ip, 0);

		/*
		 * Now update or create an connection entry for it
		 */
		{
			struct ip_vs_conn_param p;
			ip_vs_conn_fill_param(ip_vs_conn_net(cp), AF_INET,
					      iph->protocol, &from, port,
					      &cp->caddr, 0, &p);
			n_cp = ip_vs_conn_out_get(&p);
		}
		if (!n_cp) {
			struct ip_vs_conn_param p;
			ip_vs_conn_fill_param(ip_vs_conn_net(cp),
					      AF_INET, IPPROTO_TCP, &cp->caddr,
					      0, &cp->vaddr, port, &p);
			n_cp = ip_vs_conn_new(&p, &from, port,
					      IP_VS_CONN_F_NO_CPORT |
					      IP_VS_CONN_F_NFCT,
					      cp->dest, skb->mark);
			if (!n_cp)
				return 0;

			/* add its controller */
			ip_vs_control_add(n_cp, cp);
		}

		/*
		 * Replace the old passive address with the new one
		 */
		from.ip = n_cp->vaddr.ip;
		port = n_cp->vport;
		snprintf(buf, sizeof(buf), "%u,%u,%u,%u,%u,%u",
			 ((unsigned char *)&from.ip)[0],
			 ((unsigned char *)&from.ip)[1],
			 ((unsigned char *)&from.ip)[2],
			 ((unsigned char *)&from.ip)[3],
			 ntohs(port) >> 8,
			 ntohs(port) & 0xFF);

		buf_len = strlen(buf);

		ct = nf_ct_get(skb, &ctinfo);
		if (ct && !nf_ct_is_untracked(ct) && nfct_nat(ct)) {
			/* If mangling fails this function will return 0
			 * which will cause the packet to be dropped.
			 * Mangling can only fail under memory pressure,
			 * hopefully it will succeed on the retransmitted
			 * packet.
			 */
			rcu_read_lock();
			ret = nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
						       iph->ihl * 4,
						       start-data, end-start,
						       buf, buf_len);
			rcu_read_unlock();
			if (ret) {
				ip_vs_nfct_expect_related(skb, ct, n_cp,
							  IPPROTO_TCP, 0, 0);
				if (skb->ip_summed == CHECKSUM_COMPLETE)
					skb->ip_summed = CHECKSUM_UNNECESSARY;
				/* csum is updated */
				ret = 1;
			}
		}

		/*
		 * Not setting 'diff' is intentional, otherwise the sequence
		 * would be adjusted twice.
		 */

		net = skb_net(skb);
		cp->app_data = NULL;
		ip_vs_tcp_conn_listen(net, n_cp);
		ip_vs_conn_put(n_cp);
		return ret;
	}
	return 1;
}


/*
 * Look at incoming ftp packets to catch the PASV/PORT command
 * (outside-to-inside).
 *
 * The incoming packet having the PORT command should be something like
 *      "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
 * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
 * In this case, we create a connection entry using the client address and
 * port, so that the active ftp data connection from the server can reach
 * the client.
 */
static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
			struct sk_buff *skb, int *diff)
{
	struct iphdr *iph;
	struct tcphdr *th;
	char *data, *data_start, *data_limit;
	char *start, *end;
	union nf_inet_addr to;
	__be16 port;
	struct ip_vs_conn *n_cp;
	struct net *net;

	/* no diff required for incoming packets */
	*diff = 0;

#ifdef CONFIG_IP_VS_IPV6
	/* This application helper doesn't work with IPv6 yet,
	 * so turn this into a no-op for IPv6 packets
	 */
	if (cp->af == AF_INET6)
		return 1;
#endif

	/* Only useful for established sessions */
	if (cp->state != IP_VS_TCP_S_ESTABLISHED)
		return 1;

	/* Linear packets are much easier to deal with. */
	if (!skb_make_writable(skb, skb->len))
		return 0;

	/*
	 * Detecting whether it is passive
	 */
	iph = ip_hdr(skb);
	th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);

	/* Since there may be OPTIONS in the TCP packet and the HLEN is
	   the length of the header in 32-bit multiples, it is accurate
	   to calculate data address by th+HLEN*4 */
	data = data_start = (char *)th + (th->doff << 2);
	data_limit = skb_tail_pointer(skb);

	while (data <= data_limit - 6) {
		if (strnicmp(data, "PASV\r\n", 6) == 0) {
			/* Passive mode on */
			IP_VS_DBG(7, "got PASV at %td of %td\n",
				  data - data_start,
				  data_limit - data_start);
			cp->app_data = &ip_vs_ftp_pasv;
			return 1;
		}
		data++;
	}

	/*
	 * To support virtual FTP server, the scenerio is as follows:
	 *       FTP client ----> Load Balancer ----> FTP server
	 * First detect the port number in the application data,
	 * then create a new connection entry for the coming data
	 * connection.
	 */
	if (ip_vs_ftp_get_addrport(data_start, data_limit,
				   CLIENT_STRING, sizeof(CLIENT_STRING)-1,
				   ' ', '\r', &to.ip, &port,
				   &start, &end) != 1)
		return 1;

	IP_VS_DBG(7, "PORT %pI4:%d detected\n", &to.ip, ntohs(port));

	/* Passive mode off */
	cp->app_data = NULL;

	/*
	 * Now update or create a connection entry for it
	 */
	IP_VS_DBG(7, "protocol %s %pI4:%d %pI4:%d\n",
		  ip_vs_proto_name(iph->protocol),
		  &to.ip, ntohs(port), &cp->vaddr.ip, 0);

	{
		struct ip_vs_conn_param p;
		ip_vs_conn_fill_param(ip_vs_conn_net(cp), AF_INET,
				      iph->protocol, &to, port, &cp->vaddr,
				      htons(ntohs(cp->vport)-1), &p);
		n_cp = ip_vs_conn_in_get(&p);
		if (!n_cp) {
			n_cp = ip_vs_conn_new(&p, &cp->daddr,
					      htons(ntohs(cp->dport)-1),
					      IP_VS_CONN_F_NFCT, cp->dest,
					      skb->mark);
			if (!n_cp)
				return 0;

			/* add its controller */
			ip_vs_control_add(n_cp, cp);
		}
	}

	/*
	 *	Move tunnel to listen state
	 */
	net = skb_net(skb);
	ip_vs_tcp_conn_listen(net, n_cp);
	ip_vs_conn_put(n_cp);

	return 1;
}


static struct ip_vs_app ip_vs_ftp = {
	.name =		"ftp",
	.type =		IP_VS_APP_TYPE_FTP,
	.protocol =	IPPROTO_TCP,
	.module =	THIS_MODULE,
	.incs_list =	LIST_HEAD_INIT(ip_vs_ftp.incs_list),
	.init_conn =	ip_vs_ftp_init_conn,
	.done_conn =	ip_vs_ftp_done_conn,
	.bind_conn =	NULL,
	.unbind_conn =	NULL,
	.pkt_out =	ip_vs_ftp_out,
	.pkt_in =	ip_vs_ftp_in,
};

/*
 *	per netns ip_vs_ftp initialization
 */
static int __net_init __ip_vs_ftp_init(struct net *net)
{
	int i, ret;
	struct ip_vs_app *app;
	struct netns_ipvs *ipvs = net_ipvs(net);

	if (!ipvs)
		return -ENOENT;

	app = register_ip_vs_app(net, &ip_vs_ftp);
	if (IS_ERR(app))
		return PTR_ERR(app);

	for (i = 0; i < ports_count; i++) {
		if (!ports[i])
			continue;
		ret = register_ip_vs_app_inc(net, app, app->protocol, ports[i]);
		if (ret)
			goto err_unreg;
		pr_info("%s: loaded support on port[%d] = %d\n",
			app->name, i, ports[i]);
	}
	return 0;

err_unreg:
	unregister_ip_vs_app(net, &ip_vs_ftp);
	return ret;
}
/*
 *	netns exit
 */
static void __ip_vs_ftp_exit(struct net *net)
{
	unregister_ip_vs_app(net, &ip_vs_ftp);
}

static struct pernet_operations ip_vs_ftp_ops = {
	.init = __ip_vs_ftp_init,
	.exit = __ip_vs_ftp_exit,
};

static int __init ip_vs_ftp_init(void)
{
	int rv;

	rv = register_pernet_subsys(&ip_vs_ftp_ops);
	/* rcu_barrier() is called by netns on error */
	return rv;
}

/*
 *	ip_vs_ftp finish.
 */
static void __exit ip_vs_ftp_exit(void)
{
	unregister_pernet_subsys(&ip_vs_ftp_ops);
	/* rcu_barrier() is called by netns */
}


module_init(ip_vs_ftp_init);
module_exit(ip_vs_ftp_exit);
MODULE_LICENSE("GPL");