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/* FTP extension for TCP NAT alteration. */
/* (C) 1999-2001 Paul `Rusty' Russell
* (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/netfilter_ipv4.h>
#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_helper.h>
#include <net/netfilter/nf_nat_rule.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <linux/netfilter/nf_conntrack_ftp.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
MODULE_DESCRIPTION("ftp NAT helper");
MODULE_ALIAS("ip_nat_ftp");
/* FIXME: Time out? --RR */
static int
mangle_rfc959_packet(struct sk_buff *skb,
__be32 newip,
u_int16_t port,
unsigned int matchoff,
unsigned int matchlen,
struct nf_conn *ct,
enum ip_conntrack_info ctinfo)
{
char buffer[sizeof("nnn,nnn,nnn,nnn,nnn,nnn")];
sprintf(buffer, "%u,%u,%u,%u,%u,%u",
NIPQUAD(newip), port>>8, port&0xFF);
pr_debug("calling nf_nat_mangle_tcp_packet\n");
return nf_nat_mangle_tcp_packet(skb, ct, ctinfo, matchoff,
matchlen, buffer, strlen(buffer));
}
/* |1|132.235.1.2|6275| */
static int
mangle_eprt_packet(struct sk_buff *skb,
__be32 newip,
u_int16_t port,
unsigned int matchoff,
unsigned int matchlen,
struct nf_conn *ct,
enum ip_conntrack_info ctinfo)
{
char buffer[sizeof("|1|255.255.255.255|65535|")];
sprintf(buffer, "|1|%u.%u.%u.%u|%u|", NIPQUAD(newip), port);
pr_debug("calling nf_nat_mangle_tcp_packet\n");
return nf_nat_mangle_tcp_packet(skb, ct, ctinfo, matchoff,
matchlen, buffer, strlen(buffer));
}
/* |1|132.235.1.2|6275| */
static int
mangle_epsv_packet(struct sk_buff *skb,
__be32 newip,
u_int16_t port,
unsigned int matchoff,
unsigned int matchlen,
struct nf_conn *ct,
enum ip_conntrack_info ctinfo)
{
char buffer[sizeof("|||65535|")];
sprintf(buffer, "|||%u|", port);
pr_debug("calling nf_nat_mangle_tcp_packet\n");
return nf_nat_mangle_tcp_packet(skb, ct, ctinfo, matchoff,
matchlen, buffer, strlen(buffer));
}
static int (*mangle[])(struct sk_buff *, __be32, u_int16_t,
unsigned int, unsigned int, struct nf_conn *,
enum ip_conntrack_info)
= {
[NF_CT_FTP_PORT] = mangle_rfc959_packet,
[NF_CT_FTP_PASV] = mangle_rfc959_packet,
[NF_CT_FTP_EPRT] = mangle_eprt_packet,
[NF_CT_FTP_EPSV] = mangle_epsv_packet
};
/* So, this packet has hit the connection tracking matching code.
Mangle it, and change the expectation to match the new version. */
static unsigned int nf_nat_ftp(struct sk_buff *skb,
enum ip_conntrack_info ctinfo,
enum nf_ct_ftp_type type,
unsigned int matchoff,
unsigned int matchlen,
struct nf_conntrack_expect *exp)
{
__be32 newip;
u_int16_t port;
int dir = CTINFO2DIR(ctinfo);
struct nf_conn *ct = exp->master;
pr_debug("FTP_NAT: type %i, off %u len %u\n", type, matchoff, matchlen);
/* Connection will come from wherever this packet goes, hence !dir */
newip = ct->tuplehash[!dir].tuple.dst.u3.ip;
exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
exp->dir = !dir;
/* When you see the packet, we need to NAT it the same as the
* this one. */
exp->expectfn = nf_nat_follow_master;
/* Try to get same port: if not, try to change it. */
for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
exp->tuple.dst.u.tcp.port = htons(port);
if (nf_ct_expect_related(exp) == 0)
break;
}
if (port == 0)
return NF_DROP;
if (!mangle[type](skb, newip, port, matchoff, matchlen, ct, ctinfo)) {
nf_ct_unexpect_related(exp);
return NF_DROP;
}
return NF_ACCEPT;
}
static void __exit nf_nat_ftp_fini(void)
{
rcu_assign_pointer(nf_nat_ftp_hook, NULL);
synchronize_rcu();
}
static int __init nf_nat_ftp_init(void)
{
BUG_ON(nf_nat_ftp_hook != NULL);
rcu_assign_pointer(nf_nat_ftp_hook, nf_nat_ftp);
return 0;
}
/* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */
static int warn_set(const char *val, struct kernel_param *kp)
{
printk(KERN_INFO KBUILD_MODNAME
": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
return 0;
}
module_param_call(ports, warn_set, NULL, NULL, 0);
module_init(nf_nat_ftp_init);
module_exit(nf_nat_ftp_fini);
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