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- /* FTP extension for TCP NAT alteration. */
- /* (C) 1999-2001 Paul `Rusty' Russell
- * (C) 2002-2004 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/netfilter_ipv4.h>
- #include <linux/ip.h>
- #include <linux/tcp.h>
- #include <linux/moduleparam.h>
- #include <net/tcp.h>
- #include <linux/netfilter_ipv4/ip_nat.h>
- #include <linux/netfilter_ipv4/ip_nat_helper.h>
- #include <linux/netfilter_ipv4/ip_nat_rule.h>
- #include <linux/netfilter_ipv4/ip_conntrack_ftp.h>
- #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
- MODULE_LICENSE("GPL");
- MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
- MODULE_DESCRIPTION("ftp NAT helper");
- #if 0
- #define DEBUGP printk
- #else
- #define DEBUGP(format, args...)
- #endif
- /* FIXME: Time out? --RR */
- static int
- mangle_rfc959_packet(struct sk_buff **pskb,
- __be32 newip,
- u_int16_t port,
- unsigned int matchoff,
- unsigned int matchlen,
- struct ip_conntrack *ct,
- enum ip_conntrack_info ctinfo,
- u32 *seq)
- {
- char buffer[sizeof("nnn,nnn,nnn,nnn,nnn,nnn")];
- sprintf(buffer, "%u,%u,%u,%u,%u,%u",
- NIPQUAD(newip), port>>8, port&0xFF);
- DEBUGP("calling ip_nat_mangle_tcp_packet\n");
- *seq += strlen(buffer) - matchlen;
- return ip_nat_mangle_tcp_packet(pskb, ct, ctinfo, matchoff,
- matchlen, buffer, strlen(buffer));
- }
- /* |1|132.235.1.2|6275| */
- static int
- mangle_eprt_packet(struct sk_buff **pskb,
- __be32 newip,
- u_int16_t port,
- unsigned int matchoff,
- unsigned int matchlen,
- struct ip_conntrack *ct,
- enum ip_conntrack_info ctinfo,
- u32 *seq)
- {
- char buffer[sizeof("|1|255.255.255.255|65535|")];
- sprintf(buffer, "|1|%u.%u.%u.%u|%u|", NIPQUAD(newip), port);
- DEBUGP("calling ip_nat_mangle_tcp_packet\n");
- *seq += strlen(buffer) - matchlen;
- return ip_nat_mangle_tcp_packet(pskb, ct, ctinfo, matchoff,
- matchlen, buffer, strlen(buffer));
- }
- /* |1|132.235.1.2|6275| */
- static int
- mangle_epsv_packet(struct sk_buff **pskb,
- __be32 newip,
- u_int16_t port,
- unsigned int matchoff,
- unsigned int matchlen,
- struct ip_conntrack *ct,
- enum ip_conntrack_info ctinfo,
- u32 *seq)
- {
- char buffer[sizeof("|||65535|")];
- sprintf(buffer, "|||%u|", port);
- DEBUGP("calling ip_nat_mangle_tcp_packet\n");
- *seq += strlen(buffer) - matchlen;
- return ip_nat_mangle_tcp_packet(pskb, ct, ctinfo, matchoff,
- matchlen, buffer, strlen(buffer));
- }
- static int (*mangle[])(struct sk_buff **, __be32, u_int16_t,
- unsigned int,
- unsigned int,
- struct ip_conntrack *,
- enum ip_conntrack_info,
- u32 *seq)
- = { [IP_CT_FTP_PORT] = mangle_rfc959_packet,
- [IP_CT_FTP_PASV] = mangle_rfc959_packet,
- [IP_CT_FTP_EPRT] = mangle_eprt_packet,
- [IP_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 ip_nat_ftp(struct sk_buff **pskb,
- enum ip_conntrack_info ctinfo,
- enum ip_ct_ftp_type type,
- unsigned int matchoff,
- unsigned int matchlen,
- struct ip_conntrack_expect *exp,
- u32 *seq)
- {
- __be32 newip;
- u_int16_t port;
- int dir = CTINFO2DIR(ctinfo);
- struct ip_conntrack *ct = exp->master;
- DEBUGP("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.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 = ip_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 (ip_conntrack_expect_related(exp) == 0)
- break;
- }
- if (port == 0)
- return NF_DROP;
- if (!mangle[type](pskb, newip, port, matchoff, matchlen, ct, ctinfo,
- seq)) {
- ip_conntrack_unexpect_related(exp);
- return NF_DROP;
- }
- return NF_ACCEPT;
- }
- static void __exit ip_nat_ftp_fini(void)
- {
- rcu_assign_pointer(ip_nat_ftp_hook, NULL);
- synchronize_rcu();
- }
- static int __init ip_nat_ftp_init(void)
- {
- BUG_ON(rcu_dereference(ip_nat_ftp_hook));
- rcu_assign_pointer(ip_nat_ftp_hook, ip_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(ip_nat_ftp_init);
- module_exit(ip_nat_ftp_fini);
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