| /* 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); |