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gerrit-public.fairphone.software / kernel / msm-4.9 / 55a733247d6d2883d9bb77825fafac3dfca13fc2 / . / net / ipv4 / netfilter / nf_nat_ftp.c
blob: 751b598017555e9e2a1faefbec43cc67be3fae6f [file] [log] [blame]
Jozsef Kadlecsik55a73322006-12-02 22:07:44 -0800[diff] [blame^]1/* FTP extension for TCP NAT alteration. */
2
3/* (C) 1999-2001 Paul `Rusty' Russell
4 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 */
10
11#include <linux/module.h>
12#include <linux/moduleparam.h>
13#include <linux/ip.h>
14#include <linux/tcp.h>
15#include <linux/netfilter_ipv4.h>
16#include <net/netfilter/nf_nat.h>
17#include <net/netfilter/nf_nat_helper.h>
18#include <net/netfilter/nf_nat_rule.h>
19#include <net/netfilter/nf_conntrack_helper.h>
20#include <net/netfilter/nf_conntrack_expect.h>
21#include <linux/netfilter/nf_conntrack_ftp.h>
22
23MODULE_LICENSE("GPL");
24MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
25MODULE_DESCRIPTION("ftp NAT helper");
26MODULE_ALIAS("ip_nat_ftp");
27
28#if 0
29#define DEBUGP printk
30#else
31#define DEBUGP(format, args...)
32#endif
33
34/* FIXME: Time out? --RR */
35
36static int
37mangle_rfc959_packet(struct sk_buff **pskb,
38 __be32 newip,
39 u_int16_t port,
40 unsigned int matchoff,
41 unsigned int matchlen,
42 struct nf_conn *ct,
43 enum ip_conntrack_info ctinfo,
44 u32 *seq)
45{
46 char buffer[sizeof("nnn,nnn,nnn,nnn,nnn,nnn")];
47
48 sprintf(buffer, "%u,%u,%u,%u,%u,%u",
49 NIPQUAD(newip), port>>8, port&0xFF);
50
51 DEBUGP("calling nf_nat_mangle_tcp_packet\n");
52
53 *seq += strlen(buffer) - matchlen;
54 return nf_nat_mangle_tcp_packet(pskb, ct, ctinfo, matchoff,
55 matchlen, buffer, strlen(buffer));
56}
57
58/* |1|132.235.1.2|6275| */
59static int
60mangle_eprt_packet(struct sk_buff **pskb,
61 __be32 newip,
62 u_int16_t port,
63 unsigned int matchoff,
64 unsigned int matchlen,
65 struct nf_conn *ct,
66 enum ip_conntrack_info ctinfo,
67 u32 *seq)
68{
69 char buffer[sizeof("|1|255.255.255.255|65535|")];
70
71 sprintf(buffer, "|1|%u.%u.%u.%u|%u|", NIPQUAD(newip), port);
72
73 DEBUGP("calling nf_nat_mangle_tcp_packet\n");
74
75 *seq += strlen(buffer) - matchlen;
76 return nf_nat_mangle_tcp_packet(pskb, ct, ctinfo, matchoff,
77 matchlen, buffer, strlen(buffer));
78}
79
80/* |1|132.235.1.2|6275| */
81static int
82mangle_epsv_packet(struct sk_buff **pskb,
83 __be32 newip,
84 u_int16_t port,
85 unsigned int matchoff,
86 unsigned int matchlen,
87 struct nf_conn *ct,
88 enum ip_conntrack_info ctinfo,
89 u32 *seq)
90{
91 char buffer[sizeof("|||65535|")];
92
93 sprintf(buffer, "|||%u|", port);
94
95 DEBUGP("calling nf_nat_mangle_tcp_packet\n");
96
97 *seq += strlen(buffer) - matchlen;
98 return nf_nat_mangle_tcp_packet(pskb, ct, ctinfo, matchoff,
99 matchlen, buffer, strlen(buffer));
100}
101
102static int (*mangle[])(struct sk_buff **, __be32, u_int16_t,
103 unsigned int, unsigned int, struct nf_conn *,
104 enum ip_conntrack_info, u32 *seq)
105= {
106 [NF_CT_FTP_PORT] = mangle_rfc959_packet,
107 [NF_CT_FTP_PASV] = mangle_rfc959_packet,
108 [NF_CT_FTP_EPRT] = mangle_eprt_packet,
109 [NF_CT_FTP_EPSV] = mangle_epsv_packet
110};
111
112/* So, this packet has hit the connection tracking matching code.
113 Mangle it, and change the expectation to match the new version. */
114static unsigned int nf_nat_ftp(struct sk_buff **pskb,
115 enum ip_conntrack_info ctinfo,
116 enum nf_ct_ftp_type type,
117 unsigned int matchoff,
118 unsigned int matchlen,
119 struct nf_conntrack_expect *exp,
120 u32 *seq)
121{
122 __be32 newip;
123 u_int16_t port;
124 int dir = CTINFO2DIR(ctinfo);
125 struct nf_conn *ct = exp->master;
126
127 DEBUGP("FTP_NAT: type %i, off %u len %u\n", type, matchoff, matchlen);
128
129 /* Connection will come from wherever this packet goes, hence !dir */
130 newip = ct->tuplehash[!dir].tuple.dst.u3.ip;
131 exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
132 exp->dir = !dir;
133
134 /* When you see the packet, we need to NAT it the same as the
135 * this one. */
136 exp->expectfn = nf_nat_follow_master;
137
138 /* Try to get same port: if not, try to change it. */
139 for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
140 exp->tuple.dst.u.tcp.port = htons(port);
141 if (nf_conntrack_expect_related(exp) == 0)
142 break;
143 }
144
145 if (port == 0)
146 return NF_DROP;
147
148 if (!mangle[type](pskb, newip, port, matchoff, matchlen, ct, ctinfo,
149 seq)) {
150 nf_conntrack_unexpect_related(exp);
151 return NF_DROP;
152 }
153 return NF_ACCEPT;
154}
155
156static void __exit nf_nat_ftp_fini(void)
157{
158 rcu_assign_pointer(nf_nat_ftp_hook, NULL);
159 synchronize_rcu();
160}
161
162static int __init nf_nat_ftp_init(void)
163{
164 BUG_ON(rcu_dereference(nf_nat_ftp_hook));
165 rcu_assign_pointer(nf_nat_ftp_hook, nf_nat_ftp);
166 return 0;
167}
168
169/* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */
170static int warn_set(const char *val, struct kernel_param *kp)
171{
172 printk(KERN_INFO KBUILD_MODNAME
173 ": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
174 return 0;
175}
176module_param_call(ports, warn_set, NULL, NULL, 0);
177
178module_init(nf_nat_ftp_init);
179module_exit(nf_nat_ftp_fini);