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Commit | Line | Data |
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55a73324 JK |
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 | ||
23 | MODULE_LICENSE("GPL"); | |
24 | MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>"); | |
25 | MODULE_DESCRIPTION("ftp NAT helper"); | |
26 | MODULE_ALIAS("ip_nat_ftp"); | |
27 | ||
55a73324 JK |
28 | /* FIXME: Time out? --RR */ |
29 | ||
c299bd53 JP |
30 | static int nf_nat_ftp_fmt_cmd(enum nf_ct_ftp_type type, |
31 | char *buffer, size_t buflen, | |
32 | __be32 addr, u16 port) | |
55a73324 | 33 | { |
c299bd53 JP |
34 | switch (type) { |
35 | case NF_CT_FTP_PORT: | |
36 | case NF_CT_FTP_PASV: | |
37 | return snprintf(buffer, buflen, "%u,%u,%u,%u,%u,%u", | |
38 | ((unsigned char *)&addr)[0], | |
39 | ((unsigned char *)&addr)[1], | |
40 | ((unsigned char *)&addr)[2], | |
41 | ((unsigned char *)&addr)[3], | |
42 | port >> 8, | |
43 | port & 0xFF); | |
44 | case NF_CT_FTP_EPRT: | |
45 | return snprintf(buffer, buflen, "|1|%pI4|%u|", &addr, port); | |
46 | case NF_CT_FTP_EPSV: | |
47 | return snprintf(buffer, buflen, "|||%u|", port); | |
48 | } | |
55a73324 | 49 | |
c299bd53 | 50 | return 0; |
55a73324 JK |
51 | } |
52 | ||
55a73324 JK |
53 | /* So, this packet has hit the connection tracking matching code. |
54 | Mangle it, and change the expectation to match the new version. */ | |
3db05fea | 55 | static unsigned int nf_nat_ftp(struct sk_buff *skb, |
55a73324 JK |
56 | enum ip_conntrack_info ctinfo, |
57 | enum nf_ct_ftp_type type, | |
58 | unsigned int matchoff, | |
59 | unsigned int matchlen, | |
25b86e05 | 60 | struct nf_conntrack_expect *exp) |
55a73324 JK |
61 | { |
62 | __be32 newip; | |
63 | u_int16_t port; | |
64 | int dir = CTINFO2DIR(ctinfo); | |
65 | struct nf_conn *ct = exp->master; | |
c299bd53 JP |
66 | char buffer[sizeof("|1|255.255.255.255|65535|")]; |
67 | unsigned int buflen; | |
55a73324 | 68 | |
0d53778e | 69 | pr_debug("FTP_NAT: type %i, off %u len %u\n", type, matchoff, matchlen); |
55a73324 JK |
70 | |
71 | /* Connection will come from wherever this packet goes, hence !dir */ | |
72 | newip = ct->tuplehash[!dir].tuple.dst.u3.ip; | |
73 | exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port; | |
74 | exp->dir = !dir; | |
75 | ||
76 | /* When you see the packet, we need to NAT it the same as the | |
77 | * this one. */ | |
78 | exp->expectfn = nf_nat_follow_master; | |
79 | ||
80 | /* Try to get same port: if not, try to change it. */ | |
81 | for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) { | |
5b92b61f PNA |
82 | int ret; |
83 | ||
55a73324 | 84 | exp->tuple.dst.u.tcp.port = htons(port); |
5b92b61f PNA |
85 | ret = nf_ct_expect_related(exp); |
86 | if (ret == 0) | |
87 | break; | |
88 | else if (ret != -EBUSY) { | |
89 | port = 0; | |
55a73324 | 90 | break; |
5b92b61f | 91 | } |
55a73324 JK |
92 | } |
93 | ||
94 | if (port == 0) | |
95 | return NF_DROP; | |
96 | ||
c299bd53 JP |
97 | buflen = nf_nat_ftp_fmt_cmd(type, buffer, sizeof(buffer), newip, port); |
98 | if (!buflen) | |
99 | goto out; | |
100 | ||
101 | pr_debug("calling nf_nat_mangle_tcp_packet\n"); | |
102 | ||
103 | if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, matchoff, | |
104 | matchlen, buffer, buflen)) | |
105 | goto out; | |
106 | ||
55a73324 | 107 | return NF_ACCEPT; |
c299bd53 JP |
108 | |
109 | out: | |
110 | nf_ct_unexpect_related(exp); | |
111 | return NF_DROP; | |
55a73324 JK |
112 | } |
113 | ||
114 | static void __exit nf_nat_ftp_fini(void) | |
115 | { | |
116 | rcu_assign_pointer(nf_nat_ftp_hook, NULL); | |
117 | synchronize_rcu(); | |
118 | } | |
119 | ||
120 | static int __init nf_nat_ftp_init(void) | |
121 | { | |
d1332e0a | 122 | BUG_ON(nf_nat_ftp_hook != NULL); |
55a73324 JK |
123 | rcu_assign_pointer(nf_nat_ftp_hook, nf_nat_ftp); |
124 | return 0; | |
125 | } | |
126 | ||
127 | /* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */ | |
128 | static int warn_set(const char *val, struct kernel_param *kp) | |
129 | { | |
130 | printk(KERN_INFO KBUILD_MODNAME | |
131 | ": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n"); | |
132 | return 0; | |
133 | } | |
134 | module_param_call(ports, warn_set, NULL, NULL, 0); | |
135 | ||
136 | module_init(nf_nat_ftp_init); | |
137 | module_exit(nf_nat_ftp_fini); |