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@@ -0,0 +1,179 @@
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+/* FTP extension for TCP NAT alteration. */
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+
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+/* (C) 1999-2001 Paul `Rusty' Russell
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+ * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
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+ *
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+ * This program is free software; you can redistribute it and/or modify
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+ * it under the terms of the GNU General Public License version 2 as
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+ * published by the Free Software Foundation.
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+ */
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+
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+#include <linux/module.h>
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+#include <linux/moduleparam.h>
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+#include <linux/ip.h>
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+#include <linux/tcp.h>
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+#include <linux/netfilter_ipv4.h>
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+#include <net/netfilter/nf_nat.h>
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+#include <net/netfilter/nf_nat_helper.h>
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+#include <net/netfilter/nf_nat_rule.h>
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+#include <net/netfilter/nf_conntrack_helper.h>
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+#include <net/netfilter/nf_conntrack_expect.h>
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+#include <linux/netfilter/nf_conntrack_ftp.h>
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+
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+MODULE_LICENSE("GPL");
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+MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
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+MODULE_DESCRIPTION("ftp NAT helper");
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+MODULE_ALIAS("ip_nat_ftp");
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+
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+#if 0
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+#define DEBUGP printk
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+#else
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+#define DEBUGP(format, args...)
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+#endif
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+
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+/* FIXME: Time out? --RR */
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+
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+static int
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+mangle_rfc959_packet(struct sk_buff **pskb,
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+ __be32 newip,
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+ u_int16_t port,
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+ unsigned int matchoff,
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+ unsigned int matchlen,
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+ struct nf_conn *ct,
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+ enum ip_conntrack_info ctinfo,
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+ u32 *seq)
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+{
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+ char buffer[sizeof("nnn,nnn,nnn,nnn,nnn,nnn")];
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+
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+ sprintf(buffer, "%u,%u,%u,%u,%u,%u",
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+ NIPQUAD(newip), port>>8, port&0xFF);
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+
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+ DEBUGP("calling nf_nat_mangle_tcp_packet\n");
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+
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+ *seq += strlen(buffer) - matchlen;
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+ return nf_nat_mangle_tcp_packet(pskb, ct, ctinfo, matchoff,
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+ matchlen, buffer, strlen(buffer));
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+}
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+
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+/* |1|132.235.1.2|6275| */
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+static int
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+mangle_eprt_packet(struct sk_buff **pskb,
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+ __be32 newip,
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+ u_int16_t port,
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+ unsigned int matchoff,
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+ unsigned int matchlen,
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+ struct nf_conn *ct,
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+ enum ip_conntrack_info ctinfo,
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+ u32 *seq)
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+{
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+ char buffer[sizeof("|1|255.255.255.255|65535|")];
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+
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+ sprintf(buffer, "|1|%u.%u.%u.%u|%u|", NIPQUAD(newip), port);
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+
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+ DEBUGP("calling nf_nat_mangle_tcp_packet\n");
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+
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+ *seq += strlen(buffer) - matchlen;
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+ return nf_nat_mangle_tcp_packet(pskb, ct, ctinfo, matchoff,
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+ matchlen, buffer, strlen(buffer));
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+}
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+
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+/* |1|132.235.1.2|6275| */
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+static int
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+mangle_epsv_packet(struct sk_buff **pskb,
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+ __be32 newip,
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+ u_int16_t port,
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+ unsigned int matchoff,
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+ unsigned int matchlen,
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+ struct nf_conn *ct,
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+ enum ip_conntrack_info ctinfo,
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+ u32 *seq)
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+{
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+ char buffer[sizeof("|||65535|")];
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+
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+ sprintf(buffer, "|||%u|", port);
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+
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+ DEBUGP("calling nf_nat_mangle_tcp_packet\n");
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+
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+ *seq += strlen(buffer) - matchlen;
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+ return nf_nat_mangle_tcp_packet(pskb, ct, ctinfo, matchoff,
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+ matchlen, buffer, strlen(buffer));
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+}
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+
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+static int (*mangle[])(struct sk_buff **, __be32, u_int16_t,
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+ unsigned int, unsigned int, struct nf_conn *,
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+ enum ip_conntrack_info, u32 *seq)
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+= {
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+ [NF_CT_FTP_PORT] = mangle_rfc959_packet,
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+ [NF_CT_FTP_PASV] = mangle_rfc959_packet,
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+ [NF_CT_FTP_EPRT] = mangle_eprt_packet,
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+ [NF_CT_FTP_EPSV] = mangle_epsv_packet
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+};
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+
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+/* So, this packet has hit the connection tracking matching code.
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+ Mangle it, and change the expectation to match the new version. */
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+static unsigned int nf_nat_ftp(struct sk_buff **pskb,
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+ enum ip_conntrack_info ctinfo,
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+ enum nf_ct_ftp_type type,
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+ unsigned int matchoff,
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+ unsigned int matchlen,
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+ struct nf_conntrack_expect *exp,
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+ u32 *seq)
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+{
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+ __be32 newip;
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+ u_int16_t port;
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+ int dir = CTINFO2DIR(ctinfo);
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+ struct nf_conn *ct = exp->master;
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+
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+ DEBUGP("FTP_NAT: type %i, off %u len %u\n", type, matchoff, matchlen);
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+
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+ /* Connection will come from wherever this packet goes, hence !dir */
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+ newip = ct->tuplehash[!dir].tuple.dst.u3.ip;
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+ exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
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+ exp->dir = !dir;
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+
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+ /* When you see the packet, we need to NAT it the same as the
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+ * this one. */
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+ exp->expectfn = nf_nat_follow_master;
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+
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+ /* Try to get same port: if not, try to change it. */
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+ for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
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+ exp->tuple.dst.u.tcp.port = htons(port);
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+ if (nf_conntrack_expect_related(exp) == 0)
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+ break;
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+ }
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+
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+ if (port == 0)
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+ return NF_DROP;
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+
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+ if (!mangle[type](pskb, newip, port, matchoff, matchlen, ct, ctinfo,
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+ seq)) {
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+ nf_conntrack_unexpect_related(exp);
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+ return NF_DROP;
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+ }
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+ return NF_ACCEPT;
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+}
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+
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+static void __exit nf_nat_ftp_fini(void)
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+{
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+ rcu_assign_pointer(nf_nat_ftp_hook, NULL);
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+ synchronize_rcu();
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+}
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+
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+static int __init nf_nat_ftp_init(void)
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+{
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+ BUG_ON(rcu_dereference(nf_nat_ftp_hook));
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+ rcu_assign_pointer(nf_nat_ftp_hook, nf_nat_ftp);
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+ return 0;
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+}
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+
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+/* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */
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+static int warn_set(const char *val, struct kernel_param *kp)
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+{
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+ printk(KERN_INFO KBUILD_MODNAME
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+ ": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
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+ return 0;
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+}
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+module_param_call(ports, warn_set, NULL, NULL, 0);
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+
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+module_init(nf_nat_ftp_init);
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+module_exit(nf_nat_ftp_fini);
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Jozsef Kadlecsik