1 /* FTP extension for TCP NAT alteration. */
3 /* (C) 1999-2001 Paul `Rusty' Russell
4 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
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.
11 #include <linux/module.h>
12 #include <linux/moduleparam.h>
13 #include <linux/inet.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_conntrack_helper.h>
19 #include <net/netfilter/nf_conntrack_expect.h>
20 #include <linux/netfilter/nf_conntrack_ftp.h>
22 MODULE_LICENSE("GPL");
23 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
24 MODULE_DESCRIPTION("ftp NAT helper");
25 MODULE_ALIAS("ip_nat_ftp");
27 /* FIXME: Time out? --RR */
29 static int nf_nat_ftp_fmt_cmd(struct nf_conn
*ct
, enum nf_ct_ftp_type type
,
30 char *buffer
, size_t buflen
,
31 union nf_inet_addr
*addr
, u16 port
)
36 return snprintf(buffer
, buflen
, "%u,%u,%u,%u,%u,%u",
37 ((unsigned char *)&addr
->ip
)[0],
38 ((unsigned char *)&addr
->ip
)[1],
39 ((unsigned char *)&addr
->ip
)[2],
40 ((unsigned char *)&addr
->ip
)[3],
44 if (nf_ct_l3num(ct
) == NFPROTO_IPV4
)
45 return snprintf(buffer
, buflen
, "|1|%pI4|%u|",
48 return snprintf(buffer
, buflen
, "|2|%pI6|%u|",
51 return snprintf(buffer
, buflen
, "|||%u|", port
);
57 /* So, this packet has hit the connection tracking matching code.
58 Mangle it, and change the expectation to match the new version. */
59 static unsigned int nf_nat_ftp(struct sk_buff
*skb
,
60 enum ip_conntrack_info ctinfo
,
61 enum nf_ct_ftp_type type
,
63 unsigned int matchoff
,
64 unsigned int matchlen
,
65 struct nf_conntrack_expect
*exp
)
67 union nf_inet_addr newaddr
;
69 int dir
= CTINFO2DIR(ctinfo
);
70 struct nf_conn
*ct
= exp
->master
;
71 char buffer
[sizeof("|1||65535|") + INET6_ADDRSTRLEN
];
74 pr_debug("FTP_NAT: type %i, off %u len %u\n", type
, matchoff
, matchlen
);
76 /* Connection will come from wherever this packet goes, hence !dir */
77 newaddr
= ct
->tuplehash
[!dir
].tuple
.dst
.u3
;
78 exp
->saved_proto
.tcp
.port
= exp
->tuple
.dst
.u
.tcp
.port
;
81 /* When you see the packet, we need to NAT it the same as the
83 exp
->expectfn
= nf_nat_follow_master
;
85 /* Try to get same port: if not, try to change it. */
86 for (port
= ntohs(exp
->saved_proto
.tcp
.port
); port
!= 0; port
++) {
89 exp
->tuple
.dst
.u
.tcp
.port
= htons(port
);
90 ret
= nf_ct_expect_related(exp
);
93 else if (ret
!= -EBUSY
) {
100 nf_ct_helper_log(skb
, ct
, "all ports in use");
104 buflen
= nf_nat_ftp_fmt_cmd(ct
, type
, buffer
, sizeof(buffer
),
109 pr_debug("calling nf_nat_mangle_tcp_packet\n");
111 if (!nf_nat_mangle_tcp_packet(skb
, ct
, ctinfo
, protoff
, matchoff
,
112 matchlen
, buffer
, buflen
))
118 nf_ct_helper_log(skb
, ct
, "cannot mangle packet");
119 nf_ct_unexpect_related(exp
);
123 static void __exit
nf_nat_ftp_fini(void)
125 RCU_INIT_POINTER(nf_nat_ftp_hook
, NULL
);
129 static int __init
nf_nat_ftp_init(void)
131 BUG_ON(nf_nat_ftp_hook
!= NULL
);
132 RCU_INIT_POINTER(nf_nat_ftp_hook
, nf_nat_ftp
);
136 /* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */
137 static int warn_set(const char *val
, struct kernel_param
*kp
)
139 printk(KERN_INFO KBUILD_MODNAME
140 ": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
143 module_param_call(ports
, warn_set
, NULL
, NULL
, 0);
145 module_init(nf_nat_ftp_init
);
146 module_exit(nf_nat_ftp_fini
);
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