[NETFILTER]: Add nf_conntrack subsystem.

The existing connection tracking subsystem in netfilter can only
handle ipv4.  There were basically two choices present to add
connection tracking support for ipv6.  We could either duplicate all
of the ipv4 connection tracking code into an ipv6 counterpart, or (the
choice taken by these patches) we could design a generic layer that
could handle both ipv4 and ipv6 and thus requiring only one sub-protocol
(TCP, UDP, etc.) connection tracking helper module to be written.

In fact nf_conntrack is capable of working with any layer 3
protocol.

The existing ipv4 specific conntrack code could also not deal
with the pecularities of doing connection tracking on ipv6,
which is also cured here.  For example, these issues include:

1) ICMPv6 handling, which is used for neighbour discovery in
   ipv6 thus some messages such as these should not participate
   in connection tracking since effectively they are like ARP
   messages

2) fragmentation must be handled differently in ipv6, because
   the simplistic "defrag, connection track and NAT, refrag"
   (which the existing ipv4 connection tracking does) approach simply
   isn't feasible in ipv6

3) ipv6 extension header parsing must occur at the correct spots
   before and after connection tracking decisions, and there were
   no provisions for this in the existing connection tracking
   design

4) ipv6 has no need for stateful NAT

The ipv4 specific conntrack layer is kept around, until all of
the ipv4 specific conntrack helpers are ported over to nf_conntrack
and it is feature complete.  Once that occurs, the old conntrack
stuff will get placed into the feature-removal-schedule and we will
fully kill it off 6 months later.

Signed-off-by: Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp>
Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>

1 files changed, 571 insertions, 0 deletions

diff --git a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
new file mode 100644
index 0000000000000..8202c1c0afada
--- /dev/null
+++ b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
@@ -0,0 +1,571 @@
+/* (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.
+ *
+ * 16 Dec 2003: Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
+ *	- move L3 protocol dependent part to this file.
+ * 23 Mar 2004: Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
+ *	- add get_features() to support various size of conntrack
+ *	  structures.
+ *
+ * Derived from net/ipv4/netfilter/ip_conntrack_standalone.c
+ */
+
+#include <linux/config.h>
+#include <linux/types.h>
+#include <linux/ip.h>
+#include <linux/netfilter.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/icmp.h>
+#include <linux/sysctl.h>
+#include <net/ip.h>
+
+#include <linux/netfilter_ipv4.h>
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_helper.h>
+#include <net/netfilter/nf_conntrack_protocol.h>
+#include <net/netfilter/nf_conntrack_l3proto.h>
+#include <net/netfilter/nf_conntrack_core.h>
+#include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
+
+#if 0
+#define DEBUGP printk
+#else
+#define DEBUGP(format, args...)
+#endif
+
+DECLARE_PER_CPU(struct nf_conntrack_stat, nf_conntrack_stat);
+
+static int ipv4_pkt_to_tuple(const struct sk_buff *skb, unsigned int nhoff,
+			     struct nf_conntrack_tuple *tuple)
+{
+	u_int32_t _addrs[2], *ap;
+	ap = skb_header_pointer(skb, nhoff + offsetof(struct iphdr, saddr),
+				sizeof(u_int32_t) * 2, _addrs);
+	if (ap == NULL)
+		return 0;
+
+	tuple->src.u3.ip = ap[0];
+	tuple->dst.u3.ip = ap[1];
+
+	return 1;
+}
+
+static int ipv4_invert_tuple(struct nf_conntrack_tuple *tuple,
+			   const struct nf_conntrack_tuple *orig)
+{
+	tuple->src.u3.ip = orig->dst.u3.ip;
+	tuple->dst.u3.ip = orig->src.u3.ip;
+
+	return 1;
+}
+
+static int ipv4_print_tuple(struct seq_file *s,
+			    const struct nf_conntrack_tuple *tuple)
+{
+	return seq_printf(s, "src=%u.%u.%u.%u dst=%u.%u.%u.%u ",
+		          NIPQUAD(tuple->src.u3.ip),
+			  NIPQUAD(tuple->dst.u3.ip));
+}
+
+static int ipv4_print_conntrack(struct seq_file *s,
+				const struct nf_conn *conntrack)
+{
+	return 0;
+}
+
+/* Returns new sk_buff, or NULL */
+static struct sk_buff *
+nf_ct_ipv4_gather_frags(struct sk_buff *skb, u_int32_t user)
+{
+	skb_orphan(skb);
+
+        local_bh_disable();
+        skb = ip_defrag(skb, user);
+        local_bh_enable();
+
+        if (skb)
+		ip_send_check(skb->nh.iph);
+
+        return skb;
+}
+
+static int
+ipv4_prepare(struct sk_buff **pskb, unsigned int hooknum, unsigned int *dataoff,
+	     u_int8_t *protonum)
+{
+	/* Never happen */
+	if ((*pskb)->nh.iph->frag_off & htons(IP_OFFSET)) {
+		if (net_ratelimit()) {
+			printk(KERN_ERR "ipv4_prepare: Frag of proto %u (hook=%u)\n",
+			(*pskb)->nh.iph->protocol, hooknum);
+		}
+		return -NF_DROP;
+	}
+
+	*dataoff = (*pskb)->nh.raw - (*pskb)->data + (*pskb)->nh.iph->ihl*4;
+	*protonum = (*pskb)->nh.iph->protocol;
+
+	return NF_ACCEPT;
+}
+
+int nat_module_is_loaded = 0;
+static u_int32_t ipv4_get_features(const struct nf_conntrack_tuple *tuple)
+{
+	if (nat_module_is_loaded)
+		return NF_CT_F_NAT;
+
+	return NF_CT_F_BASIC;
+}
+
+static unsigned int ipv4_confirm(unsigned int hooknum,
+				 struct sk_buff **pskb,
+				 const struct net_device *in,
+				 const struct net_device *out,
+				 int (*okfn)(struct sk_buff *))
+{
+	/* We've seen it coming out the other side: confirm it */
+	return nf_conntrack_confirm(pskb);
+}
+
+static unsigned int ipv4_conntrack_help(unsigned int hooknum,
+				      struct sk_buff **pskb,
+				      const struct net_device *in,
+				      const struct net_device *out,
+				      int (*okfn)(struct sk_buff *))
+{
+	struct nf_conn *ct;
+	enum ip_conntrack_info ctinfo;
+
+	/* This is where we call the helper: as the packet goes out. */
+	ct = nf_ct_get(*pskb, &ctinfo);
+	if (ct && ct->helper) {
+		unsigned int ret;
+		ret = ct->helper->help(pskb,
+				       (*pskb)->nh.raw - (*pskb)->data
+						       + (*pskb)->nh.iph->ihl*4,
+				       ct, ctinfo);
+		if (ret != NF_ACCEPT)
+			return ret;
+	}
+	return NF_ACCEPT;
+}
+
+static unsigned int ipv4_conntrack_defrag(unsigned int hooknum,
+					  struct sk_buff **pskb,
+					  const struct net_device *in,
+					  const struct net_device *out,
+					  int (*okfn)(struct sk_buff *))
+{
+#if !defined(CONFIG_IP_NF_NAT) && !defined(CONFIG_IP_NF_NAT_MODULE)
+	/* Previously seen (loopback)?  Ignore.  Do this before
+	   fragment check. */
+	if ((*pskb)->nfct)
+		return NF_ACCEPT;
+#endif
+
+	/* Gather fragments. */
+	if ((*pskb)->nh.iph->frag_off & htons(IP_MF|IP_OFFSET)) {
+		*pskb = nf_ct_ipv4_gather_frags(*pskb,
+						hooknum == NF_IP_PRE_ROUTING ?
+						IP_DEFRAG_CONNTRACK_IN :
+						IP_DEFRAG_CONNTRACK_OUT);
+		if (!*pskb)
+			return NF_STOLEN;
+	}
+	return NF_ACCEPT;
+}
+
+static unsigned int ipv4_refrag(unsigned int hooknum,
+				struct sk_buff **pskb,
+				const struct net_device *in,
+				const struct net_device *out,
+				int (*okfn)(struct sk_buff *))
+{
+	struct rtable *rt = (struct rtable *)(*pskb)->dst;
+
+	/* We've seen it coming out the other side: confirm */
+	if (ipv4_confirm(hooknum, pskb, in, out, okfn) != NF_ACCEPT)
+		return NF_DROP;
+
+	/* Local packets are never produced too large for their
+	   interface.  We degfragment them at LOCAL_OUT, however,
+	   so we have to refragment them here. */
+	if ((*pskb)->len > dst_mtu(&rt->u.dst) &&
+	    !skb_shinfo(*pskb)->tso_size) {
+		/* No hook can be after us, so this should be OK. */
+		ip_fragment(*pskb, okfn);
+		return NF_STOLEN;
+	}
+	return NF_ACCEPT;
+}
+
+static unsigned int ipv4_conntrack_in(unsigned int hooknum,
+				      struct sk_buff **pskb,
+				      const struct net_device *in,
+				      const struct net_device *out,
+				      int (*okfn)(struct sk_buff *))
+{
+	return nf_conntrack_in(PF_INET, hooknum, pskb);
+}
+
+static unsigned int ipv4_conntrack_local(unsigned int hooknum,
+				         struct sk_buff **pskb,
+				         const struct net_device *in,
+				         const struct net_device *out,
+				         int (*okfn)(struct sk_buff *))
+{
+	/* root is playing with raw sockets. */
+	if ((*pskb)->len < sizeof(struct iphdr)
+	    || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr)) {
+		if (net_ratelimit())
+			printk("ipt_hook: happy cracking.\n");
+		return NF_ACCEPT;
+	}
+	return nf_conntrack_in(PF_INET, hooknum, pskb);
+}
+
+/* Connection tracking may drop packets, but never alters them, so
+   make it the first hook. */
+static struct nf_hook_ops ipv4_conntrack_defrag_ops = {
+	.hook		= ipv4_conntrack_defrag,
+	.owner		= THIS_MODULE,
+	.pf		= PF_INET,
+	.hooknum	= NF_IP_PRE_ROUTING,
+	.priority	= NF_IP_PRI_CONNTRACK_DEFRAG,
+};
+
+static struct nf_hook_ops ipv4_conntrack_in_ops = {
+	.hook		= ipv4_conntrack_in,
+	.owner		= THIS_MODULE,
+	.pf		= PF_INET,
+	.hooknum	= NF_IP_PRE_ROUTING,
+	.priority	= NF_IP_PRI_CONNTRACK,
+};
+
+static struct nf_hook_ops ipv4_conntrack_defrag_local_out_ops = {
+	.hook           = ipv4_conntrack_defrag,
+	.owner          = THIS_MODULE,
+	.pf             = PF_INET,
+	.hooknum        = NF_IP_LOCAL_OUT,
+	.priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
+};
+
+static struct nf_hook_ops ipv4_conntrack_local_out_ops = {
+	.hook		= ipv4_conntrack_local,
+	.owner		= THIS_MODULE,
+	.pf		= PF_INET,
+	.hooknum	= NF_IP_LOCAL_OUT,
+	.priority	= NF_IP_PRI_CONNTRACK,
+};
+
+/* helpers */
+static struct nf_hook_ops ipv4_conntrack_helper_out_ops = {
+	.hook		= ipv4_conntrack_help,
+	.owner		= THIS_MODULE,
+	.pf		= PF_INET,
+	.hooknum	= NF_IP_POST_ROUTING,
+	.priority	= NF_IP_PRI_CONNTRACK_HELPER,
+};
+
+static struct nf_hook_ops ipv4_conntrack_helper_in_ops = {
+	.hook		= ipv4_conntrack_help,
+	.owner		= THIS_MODULE,
+	.pf		= PF_INET,
+	.hooknum	= NF_IP_LOCAL_IN,
+	.priority	= NF_IP_PRI_CONNTRACK_HELPER,
+};
+
+
+/* Refragmenter; last chance. */
+static struct nf_hook_ops ipv4_conntrack_out_ops = {
+	.hook		= ipv4_refrag,
+	.owner		= THIS_MODULE,
+	.pf		= PF_INET,
+	.hooknum	= NF_IP_POST_ROUTING,
+	.priority	= NF_IP_PRI_CONNTRACK_CONFIRM,
+};
+
+static struct nf_hook_ops ipv4_conntrack_local_in_ops = {
+	.hook		= ipv4_confirm,
+	.owner		= THIS_MODULE,
+	.pf		= PF_INET,
+	.hooknum	= NF_IP_LOCAL_IN,
+	.priority	= NF_IP_PRI_CONNTRACK_CONFIRM,
+};
+
+#ifdef CONFIG_SYSCTL
+/* From nf_conntrack_proto_icmp.c */
+extern unsigned long nf_ct_icmp_timeout;
+static struct ctl_table_header *nf_ct_ipv4_sysctl_header;
+
+static ctl_table nf_ct_sysctl_table[] = {
+	{
+		.ctl_name	= NET_NF_CONNTRACK_ICMP_TIMEOUT,
+		.procname	= "nf_conntrack_icmp_timeout",
+		.data		= &nf_ct_icmp_timeout,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec_jiffies,
+	},
+        { .ctl_name = 0 }
+};
+
+static ctl_table nf_ct_netfilter_table[] = {
+	{
+		.ctl_name       = NET_NETFILTER,
+		.procname       = "netfilter",
+		.mode           = 0555,
+		.child          = nf_ct_sysctl_table,
+	},
+	{ .ctl_name = 0 }
+};
+
+static ctl_table nf_ct_net_table[] = {
+	{
+		.ctl_name       = CTL_NET,
+		.procname       = "net",
+		.mode           = 0555,
+		.child          = nf_ct_netfilter_table,
+	},
+	{ .ctl_name = 0 }
+};
+#endif
+
+/* Fast function for those who don't want to parse /proc (and I don't
+   blame them). */
+/* Reversing the socket's dst/src point of view gives us the reply
+   mapping. */
+static int
+getorigdst(struct sock *sk, int optval, void __user *user, int *len)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	struct nf_conntrack_tuple_hash *h;
+	struct nf_conntrack_tuple tuple;
+	
+	NF_CT_TUPLE_U_BLANK(&tuple);
+	tuple.src.u3.ip = inet->rcv_saddr;
+	tuple.src.u.tcp.port = inet->sport;
+	tuple.dst.u3.ip = inet->daddr;
+	tuple.dst.u.tcp.port = inet->dport;
+	tuple.src.l3num = PF_INET;
+	tuple.dst.protonum = IPPROTO_TCP;
+
+	/* We only do TCP at the moment: is there a better way? */
+	if (strcmp(sk->sk_prot->name, "TCP")) {
+		DEBUGP("SO_ORIGINAL_DST: Not a TCP socket\n");
+		return -ENOPROTOOPT;
+	}
+
+	if ((unsigned int) *len < sizeof(struct sockaddr_in)) {
+		DEBUGP("SO_ORIGINAL_DST: len %u not %u\n",
+		       *len, sizeof(struct sockaddr_in));
+		return -EINVAL;
+	}
+
+	h = nf_conntrack_find_get(&tuple, NULL);
+	if (h) {
+		struct sockaddr_in sin;
+		struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);
+
+		sin.sin_family = AF_INET;
+		sin.sin_port = ct->tuplehash[IP_CT_DIR_ORIGINAL]
+			.tuple.dst.u.tcp.port;
+		sin.sin_addr.s_addr = ct->tuplehash[IP_CT_DIR_ORIGINAL]
+			.tuple.dst.u3.ip;
+
+		DEBUGP("SO_ORIGINAL_DST: %u.%u.%u.%u %u\n",
+		       NIPQUAD(sin.sin_addr.s_addr), ntohs(sin.sin_port));
+		nf_ct_put(ct);
+		if (copy_to_user(user, &sin, sizeof(sin)) != 0)
+			return -EFAULT;
+		else
+			return 0;
+	}
+	DEBUGP("SO_ORIGINAL_DST: Can't find %u.%u.%u.%u/%u-%u.%u.%u.%u/%u.\n",
+	       NIPQUAD(tuple.src.u3.ip), ntohs(tuple.src.u.tcp.port),
+	       NIPQUAD(tuple.dst.u3.ip), ntohs(tuple.dst.u.tcp.port));
+	return -ENOENT;
+}
+
+static struct nf_sockopt_ops so_getorigdst = {
+	.pf		= PF_INET,
+	.get_optmin	= SO_ORIGINAL_DST,
+	.get_optmax	= SO_ORIGINAL_DST+1,
+	.get		= &getorigdst,
+};
+
+struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv4 = {
+	.l3proto	 = PF_INET,
+	.name		 = "ipv4",
+	.pkt_to_tuple	 = ipv4_pkt_to_tuple,
+	.invert_tuple	 = ipv4_invert_tuple,
+	.print_tuple	 = ipv4_print_tuple,
+	.print_conntrack = ipv4_print_conntrack,
+	.prepare	 = ipv4_prepare,
+	.get_features	 = ipv4_get_features,
+	.me		 = THIS_MODULE,
+};
+
+extern struct nf_conntrack_protocol nf_conntrack_protocol_tcp4;
+extern struct nf_conntrack_protocol nf_conntrack_protocol_udp4;
+extern struct nf_conntrack_protocol nf_conntrack_protocol_icmp;
+static int init_or_cleanup(int init)
+{
+	int ret = 0;
+
+	if (!init) goto cleanup;
+
+	ret = nf_register_sockopt(&so_getorigdst);
+	if (ret < 0) {
+		printk(KERN_ERR "Unable to register netfilter socket option\n");
+		goto cleanup_nothing;
+	}
+
+	ret = nf_conntrack_protocol_register(&nf_conntrack_protocol_tcp4);
+	if (ret < 0) {
+		printk("nf_conntrack_ipv4: can't register tcp.\n");
+		goto cleanup_sockopt;
+	}
+
+	ret = nf_conntrack_protocol_register(&nf_conntrack_protocol_udp4);
+	if (ret < 0) {
+		printk("nf_conntrack_ipv4: can't register udp.\n");
+		goto cleanup_tcp;
+	}
+
+	ret = nf_conntrack_protocol_register(&nf_conntrack_protocol_icmp);
+	if (ret < 0) {
+		printk("nf_conntrack_ipv4: can't register icmp.\n");
+		goto cleanup_udp;
+	}
+
+	ret = nf_conntrack_l3proto_register(&nf_conntrack_l3proto_ipv4);
+	if (ret < 0) {
+		printk("nf_conntrack_ipv4: can't register ipv4\n");
+		goto cleanup_icmp;
+	}
+
+	ret = nf_register_hook(&ipv4_conntrack_defrag_ops);
+	if (ret < 0) {
+		printk("nf_conntrack_ipv4: can't register pre-routing defrag hook.\n");
+		goto cleanup_ipv4;
+	}
+	ret = nf_register_hook(&ipv4_conntrack_defrag_local_out_ops);
+	if (ret < 0) {
+		printk("nf_conntrack_ipv4: can't register local_out defrag hook.\n");
+		goto cleanup_defragops;
+	}
+
+	ret = nf_register_hook(&ipv4_conntrack_in_ops);
+	if (ret < 0) {
+		printk("nf_conntrack_ipv4: can't register pre-routing hook.\n");
+		goto cleanup_defraglocalops;
+	}
+
+	ret = nf_register_hook(&ipv4_conntrack_local_out_ops);
+	if (ret < 0) {
+		printk("nf_conntrack_ipv4: can't register local out hook.\n");
+		goto cleanup_inops;
+	}
+
+	ret = nf_register_hook(&ipv4_conntrack_helper_in_ops);
+	if (ret < 0) {
+		printk("nf_conntrack_ipv4: can't register local helper hook.\n");
+		goto cleanup_inandlocalops;
+	}
+
+	ret = nf_register_hook(&ipv4_conntrack_helper_out_ops);
+	if (ret < 0) {
+		printk("nf_conntrack_ipv4: can't register postrouting helper hook.\n");
+		goto cleanup_helperinops;
+	}
+
+	ret = nf_register_hook(&ipv4_conntrack_out_ops);
+	if (ret < 0) {
+		printk("nf_conntrack_ipv4: can't register post-routing hook.\n");
+		goto cleanup_helperoutops;
+	}
+
+	ret = nf_register_hook(&ipv4_conntrack_local_in_ops);
+	if (ret < 0) {
+		printk("nf_conntrack_ipv4: can't register local in hook.\n");
+		goto cleanup_inoutandlocalops;
+	}
+
+#ifdef CONFIG_SYSCTL
+	nf_ct_ipv4_sysctl_header = register_sysctl_table(nf_ct_net_table, 0);
+	if (nf_ct_ipv4_sysctl_header == NULL) {
+		printk("nf_conntrack: can't register to sysctl.\n");
+		ret = -ENOMEM;
+		goto cleanup_localinops;
+	}
+#endif
+
+	/* For use by REJECT target */
+	ip_ct_attach = __nf_conntrack_attach;
+
+	return ret;
+
+ cleanup:
+	synchronize_net();
+	ip_ct_attach = NULL;
+#ifdef CONFIG_SYSCTL
+ 	unregister_sysctl_table(nf_ct_ipv4_sysctl_header);
+ cleanup_localinops:
+#endif
+	nf_unregister_hook(&ipv4_conntrack_local_in_ops);
+ cleanup_inoutandlocalops:
+	nf_unregister_hook(&ipv4_conntrack_out_ops);
+ cleanup_helperoutops:
+	nf_unregister_hook(&ipv4_conntrack_helper_out_ops);
+ cleanup_helperinops:
+	nf_unregister_hook(&ipv4_conntrack_helper_in_ops);
+ cleanup_inandlocalops:
+	nf_unregister_hook(&ipv4_conntrack_local_out_ops);
+ cleanup_inops:
+	nf_unregister_hook(&ipv4_conntrack_in_ops);
+ cleanup_defraglocalops:
+	nf_unregister_hook(&ipv4_conntrack_defrag_local_out_ops);
+ cleanup_defragops:
+	nf_unregister_hook(&ipv4_conntrack_defrag_ops);
+ cleanup_ipv4:
+	nf_conntrack_l3proto_unregister(&nf_conntrack_l3proto_ipv4);
+ cleanup_icmp:
+	nf_conntrack_protocol_unregister(&nf_conntrack_protocol_icmp);
+ cleanup_udp:
+	nf_conntrack_protocol_unregister(&nf_conntrack_protocol_udp4);
+ cleanup_tcp:
+	nf_conntrack_protocol_unregister(&nf_conntrack_protocol_tcp4);
+ cleanup_sockopt:
+	nf_unregister_sockopt(&so_getorigdst);
+ cleanup_nothing:
+	return ret;
+}
+
+MODULE_LICENSE("GPL");
+
+static int __init init(void)
+{
+	need_nf_conntrack();
+	return init_or_cleanup(1);
+}
+
+static void __exit fini(void)
+{
+	init_or_cleanup(0);
+}
+
+module_init(init);
+module_exit(fini);
+
+void need_ip_conntrack(void)
+{
+}
+
+EXPORT_SYMBOL(need_ip_conntrack);
+EXPORT_SYMBOL(nf_ct_ipv4_gather_frags);