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 Entering Passive Mode ("
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 short ports[IP_VS_APP_MAX_PORTS] = {21, 0};
56 module_param_array(ports, ushort, NULL, 0);
57 MODULE_PARM_DESC(ports, "Ports to monitor for FTP control commands");
61 static int ip_vs_ftp_pasv;
65 ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
67 /* We use connection tracking for the command connection */
68 cp->flags |= IP_VS_CONN_F_NFCT;
74 ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
81 * Get <addr,port> from the string "xxx.xxx.xxx.xxx,ppp,ppp", started
82 * with the "pattern" and terminated with the "term" character.
83 * <addr,port> is in network order.
85 static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
86 const char *pattern, size_t plen, char term,
87 __be32 *addr, __be16 *port,
88 char **start, char **end)
93 if (data_limit - data < plen) {
94 /* check if there is partial match */
95 if (strnicmp(data, pattern, data_limit - data) == 0)
101 if (strnicmp(data, pattern, plen) != 0) {
104 *start = data + plen;
106 for (data = *start; *data != term; data++) {
107 if (data == data_limit)
112 memset(p, 0, sizeof(p));
113 for (data = *start; data != *end; data++) {
114 if (*data >= '0' && *data <= '9') {
115 p[i] = p[i]*10 + *data - '0';
116 } else if (*data == ',' && i < 5) {
119 /* unexpected character */
127 *addr = get_unaligned((__be32 *)p);
128 *port = get_unaligned((__be16 *)(p + 4));
133 * Look at outgoing ftp packets to catch the response to a PASV command
134 * from the server (inside-to-outside).
135 * When we see one, we build a connection entry with the client address,
136 * client port 0 (unknown at the moment), the server address and the
137 * server port. Mark the current connection entry as a control channel
138 * of the new entry. All this work is just to make the data connection
139 * can be scheduled to the right server later.
141 * The outgoing packet should be something like
142 * "227 Entering Passive Mode (xxx,xxx,xxx,xxx,ppp,ppp)".
143 * xxx,xxx,xxx,xxx is the server address, ppp,ppp is the server port number.
145 static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
146 struct sk_buff *skb, int *diff)
150 char *data, *data_limit;
152 union nf_inet_addr from;
154 struct ip_vs_conn *n_cp;
155 char buf[24]; /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
158 enum ip_conntrack_info ctinfo;
161 #ifdef CONFIG_IP_VS_IPV6
162 /* This application helper doesn't work with IPv6 yet,
163 * so turn this into a no-op for IPv6 packets
165 if (cp->af == AF_INET6)
171 /* Only useful for established sessions */
172 if (cp->state != IP_VS_TCP_S_ESTABLISHED)
175 /* Linear packets are much easier to deal with. */
176 if (!skb_make_writable(skb, skb->len))
179 if (cp->app_data == &ip_vs_ftp_pasv) {
181 th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
182 data = (char *)th + (th->doff << 2);
183 data_limit = skb_tail_pointer(skb);
185 if (ip_vs_ftp_get_addrport(data, data_limit,
187 sizeof(SERVER_STRING)-1, ')',
192 IP_VS_DBG(7, "PASV response (%pI4:%d) -> %pI4:%d detected\n",
193 &from.ip, ntohs(port), &cp->caddr.ip, 0);
196 * Now update or create an connection entry for it
198 n_cp = ip_vs_conn_out_get(AF_INET, iph->protocol, &from, port,
201 n_cp = ip_vs_conn_new(AF_INET, IPPROTO_TCP,
205 IP_VS_CONN_F_NO_CPORT |
211 /* add its controller */
212 ip_vs_control_add(n_cp, cp);
216 * Replace the old passive address with the new one
218 from.ip = n_cp->vaddr.ip;
220 snprintf(buf, sizeof(buf), "%u,%u,%u,%u,%u,%u",
221 ((unsigned char *)&from.ip)[0],
222 ((unsigned char *)&from.ip)[1],
223 ((unsigned char *)&from.ip)[2],
224 ((unsigned char *)&from.ip)[3],
228 buf_len = strlen(buf);
230 ct = nf_ct_get(skb, &ctinfo);
231 if (ct && !nf_ct_is_untracked(ct) && nfct_nat(ct)) {
232 /* If mangling fails this function will return 0
233 * which will cause the packet to be dropped.
234 * Mangling can only fail under memory pressure,
235 * hopefully it will succeed on the retransmitted
238 ret = nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
239 start-data, end-start,
242 ip_vs_nfct_expect_related(skb, ct, n_cp,
247 * Not setting 'diff' is intentional, otherwise the sequence
248 * would be adjusted twice.
252 ip_vs_tcp_conn_listen(n_cp);
253 ip_vs_conn_put(n_cp);
261 * Look at incoming ftp packets to catch the PASV/PORT command
262 * (outside-to-inside).
264 * The incoming packet having the PORT command should be something like
265 * "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
266 * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
267 * In this case, we create a connection entry using the client address and
268 * port, so that the active ftp data connection from the server can reach
271 static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
272 struct sk_buff *skb, int *diff)
276 char *data, *data_start, *data_limit;
278 union nf_inet_addr to;
280 struct ip_vs_conn *n_cp;
282 #ifdef CONFIG_IP_VS_IPV6
283 /* This application helper doesn't work with IPv6 yet,
284 * so turn this into a no-op for IPv6 packets
286 if (cp->af == AF_INET6)
290 /* no diff required for incoming packets */
293 /* Only useful for established sessions */
294 if (cp->state != IP_VS_TCP_S_ESTABLISHED)
297 /* Linear packets are much easier to deal with. */
298 if (!skb_make_writable(skb, skb->len))
302 * Detecting whether it is passive
305 th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
307 /* Since there may be OPTIONS in the TCP packet and the HLEN is
308 the length of the header in 32-bit multiples, it is accurate
309 to calculate data address by th+HLEN*4 */
310 data = data_start = (char *)th + (th->doff << 2);
311 data_limit = skb_tail_pointer(skb);
313 while (data <= data_limit - 6) {
314 if (strnicmp(data, "PASV\r\n", 6) == 0) {
315 /* Passive mode on */
316 IP_VS_DBG(7, "got PASV at %td of %td\n",
318 data_limit - data_start);
319 cp->app_data = &ip_vs_ftp_pasv;
326 * To support virtual FTP server, the scenerio is as follows:
327 * FTP client ----> Load Balancer ----> FTP server
328 * First detect the port number in the application data,
329 * then create a new connection entry for the coming data
332 if (ip_vs_ftp_get_addrport(data_start, data_limit,
333 CLIENT_STRING, sizeof(CLIENT_STRING)-1,
338 IP_VS_DBG(7, "PORT %pI4:%d detected\n", &to.ip, ntohs(port));
340 /* Passive mode off */
344 * Now update or create a connection entry for it
346 IP_VS_DBG(7, "protocol %s %pI4:%d %pI4:%d\n",
347 ip_vs_proto_name(iph->protocol),
348 &to.ip, ntohs(port), &cp->vaddr.ip, 0);
350 n_cp = ip_vs_conn_in_get(AF_INET, iph->protocol,
352 &cp->vaddr, htons(ntohs(cp->vport)-1));
354 n_cp = ip_vs_conn_new(AF_INET, IPPROTO_TCP,
356 &cp->vaddr, htons(ntohs(cp->vport)-1),
357 &cp->daddr, htons(ntohs(cp->dport)-1),
363 /* add its controller */
364 ip_vs_control_add(n_cp, cp);
368 * Move tunnel to listen state
370 ip_vs_tcp_conn_listen(n_cp);
371 ip_vs_conn_put(n_cp);
377 static struct ip_vs_app ip_vs_ftp = {
379 .type = IP_VS_APP_TYPE_FTP,
380 .protocol = IPPROTO_TCP,
381 .module = THIS_MODULE,
382 .incs_list = LIST_HEAD_INIT(ip_vs_ftp.incs_list),
383 .init_conn = ip_vs_ftp_init_conn,
384 .done_conn = ip_vs_ftp_done_conn,
387 .pkt_out = ip_vs_ftp_out,
388 .pkt_in = ip_vs_ftp_in,
393 * ip_vs_ftp initialization
395 static int __init ip_vs_ftp_init(void)
398 struct ip_vs_app *app = &ip_vs_ftp;
400 ret = register_ip_vs_app(app);
404 for (i=0; i<IP_VS_APP_MAX_PORTS; i++) {
407 ret = register_ip_vs_app_inc(app, app->protocol, ports[i]);
410 pr_info("%s: loaded support on port[%d] = %d\n",
411 app->name, i, ports[i]);
415 unregister_ip_vs_app(app);
424 static void __exit ip_vs_ftp_exit(void)
426 unregister_ip_vs_app(&ip_vs_ftp);
430 module_init(ip_vs_ftp_init);
431 module_exit(ip_vs_ftp_exit);
432 MODULE_LICENSE("GPL");