[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, 301 insertions, 0 deletions

diff --git a/net/ipv4/netfilter/nf_conntrack_proto_icmp.c b/net/ipv4/netfilter/nf_conntrack_proto_icmp.c
new file mode 100644
index 0000000000000..7ddb5c08f7b8a
--- /dev/null
+++ b/net/ipv4/netfilter/nf_conntrack_proto_icmp.c
@@ -0,0 +1,301 @@
+/* (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>
+ *	- enable working with Layer 3 protocol independent connection tracking.
+ *
+ * Derived from net/ipv4/netfilter/ip_conntrack_proto_icmp.c
+ */
+
+#include <linux/types.h>
+#include <linux/sched.h>
+#include <linux/timer.h>
+#include <linux/netfilter.h>
+#include <linux/in.h>
+#include <linux/icmp.h>
+#include <linux/seq_file.h>
+#include <net/ip.h>
+#include <net/checksum.h>
+#include <linux/netfilter_ipv4.h>
+#include <net/netfilter/nf_conntrack_tuple.h>
+#include <net/netfilter/nf_conntrack_protocol.h>
+#include <net/netfilter/nf_conntrack_core.h>
+
+unsigned long nf_ct_icmp_timeout = 30*HZ;
+
+#if 0
+#define DEBUGP printk
+#else
+#define DEBUGP(format, args...)
+#endif
+
+static int icmp_pkt_to_tuple(const struct sk_buff *skb,
+			     unsigned int dataoff,
+			     struct nf_conntrack_tuple *tuple)
+{
+	struct icmphdr _hdr, *hp;
+
+	hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
+	if (hp == NULL)
+		return 0;
+
+	tuple->dst.u.icmp.type = hp->type;
+	tuple->src.u.icmp.id = hp->un.echo.id;
+	tuple->dst.u.icmp.code = hp->code;
+
+	return 1;
+}
+
+static int icmp_invert_tuple(struct nf_conntrack_tuple *tuple,
+			     const struct nf_conntrack_tuple *orig)
+{
+	/* Add 1; spaces filled with 0. */
+	static u_int8_t invmap[]
+		= { [ICMP_ECHO] = ICMP_ECHOREPLY + 1,
+		    [ICMP_ECHOREPLY] = ICMP_ECHO + 1,
+		    [ICMP_TIMESTAMP] = ICMP_TIMESTAMPREPLY + 1,
+		    [ICMP_TIMESTAMPREPLY] = ICMP_TIMESTAMP + 1,
+		    [ICMP_INFO_REQUEST] = ICMP_INFO_REPLY + 1,
+		    [ICMP_INFO_REPLY] = ICMP_INFO_REQUEST + 1,
+		    [ICMP_ADDRESS] = ICMP_ADDRESSREPLY + 1,
+		    [ICMP_ADDRESSREPLY] = ICMP_ADDRESS + 1};
+
+	if (orig->dst.u.icmp.type >= sizeof(invmap)
+	    || !invmap[orig->dst.u.icmp.type])
+		return 0;
+
+	tuple->src.u.icmp.id = orig->src.u.icmp.id;
+	tuple->dst.u.icmp.type = invmap[orig->dst.u.icmp.type] - 1;
+	tuple->dst.u.icmp.code = orig->dst.u.icmp.code;
+	return 1;
+}
+
+/* Print out the per-protocol part of the tuple. */
+static int icmp_print_tuple(struct seq_file *s,
+			    const struct nf_conntrack_tuple *tuple)
+{
+	return seq_printf(s, "type=%u code=%u id=%u ",
+			  tuple->dst.u.icmp.type,
+			  tuple->dst.u.icmp.code,
+			  ntohs(tuple->src.u.icmp.id));
+}
+
+/* Print out the private part of the conntrack. */
+static int icmp_print_conntrack(struct seq_file *s,
+				const struct nf_conn *conntrack)
+{
+	return 0;
+}
+
+/* Returns verdict for packet, or -1 for invalid. */
+static int icmp_packet(struct nf_conn *ct,
+		       const struct sk_buff *skb,
+		       unsigned int dataoff,
+		       enum ip_conntrack_info ctinfo,
+		       int pf,
+		       unsigned int hooknum)
+{
+	/* Try to delete connection immediately after all replies:
+           won't actually vanish as we still have skb, and del_timer
+           means this will only run once even if count hits zero twice
+           (theoretically possible with SMP) */
+	if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY) {
+		if (atomic_dec_and_test(&ct->proto.icmp.count)
+		    && del_timer(&ct->timeout))
+			ct->timeout.function((unsigned long)ct);
+	} else {
+		atomic_inc(&ct->proto.icmp.count);
+		nf_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE, skb);
+		nf_ct_refresh_acct(ct, ctinfo, skb, nf_ct_icmp_timeout);
+	}
+
+	return NF_ACCEPT;
+}
+
+/* Called when a new connection for this protocol found. */
+static int icmp_new(struct nf_conn *conntrack,
+		    const struct sk_buff *skb, unsigned int dataoff)
+{
+	static u_int8_t valid_new[]
+		= { [ICMP_ECHO] = 1,
+		    [ICMP_TIMESTAMP] = 1,
+		    [ICMP_INFO_REQUEST] = 1,
+		    [ICMP_ADDRESS] = 1 };
+
+	if (conntrack->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new)
+	    || !valid_new[conntrack->tuplehash[0].tuple.dst.u.icmp.type]) {
+		/* Can't create a new ICMP `conn' with this. */
+		DEBUGP("icmp: can't create new conn with type %u\n",
+		       conntrack->tuplehash[0].tuple.dst.u.icmp.type);
+		NF_CT_DUMP_TUPLE(&conntrack->tuplehash[0].tuple);
+		return 0;
+	}
+	atomic_set(&conntrack->proto.icmp.count, 0);
+	return 1;
+}
+
+extern struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv4;
+/* Returns conntrack if it dealt with ICMP, and filled in skb fields */
+static int
+icmp_error_message(struct sk_buff *skb,
+                 enum ip_conntrack_info *ctinfo,
+                 unsigned int hooknum)
+{
+	struct nf_conntrack_tuple innertuple, origtuple;
+	struct {
+		struct icmphdr icmp;
+		struct iphdr ip;
+	} _in, *inside;
+	struct nf_conntrack_protocol *innerproto;
+	struct nf_conntrack_tuple_hash *h;
+	int dataoff;
+
+	NF_CT_ASSERT(skb->nfct == NULL);
+
+	/* Not enough header? */
+	inside = skb_header_pointer(skb, skb->nh.iph->ihl*4, sizeof(_in), &_in);
+	if (inside == NULL)
+		return -NF_ACCEPT;
+
+	/* Ignore ICMP's containing fragments (shouldn't happen) */
+	if (inside->ip.frag_off & htons(IP_OFFSET)) {
+		DEBUGP("icmp_error_message: fragment of proto %u\n",
+		       inside->ip.protocol);
+		return -NF_ACCEPT;
+	}
+
+	innerproto = nf_ct_find_proto(PF_INET, inside->ip.protocol);
+	dataoff = skb->nh.iph->ihl*4 + sizeof(inside->icmp);
+	/* Are they talking about one of our connections? */
+	if (!nf_ct_get_tuple(skb, dataoff, dataoff + inside->ip.ihl*4, PF_INET,
+			     inside->ip.protocol, &origtuple,
+			     &nf_conntrack_l3proto_ipv4, innerproto)) {
+		DEBUGP("icmp_error_message: ! get_tuple p=%u",
+		       inside->ip.protocol);
+		return -NF_ACCEPT;
+	}
+
+        /* Ordinarily, we'd expect the inverted tupleproto, but it's
+           been preserved inside the ICMP. */
+        if (!nf_ct_invert_tuple(&innertuple, &origtuple,
+				&nf_conntrack_l3proto_ipv4, innerproto)) {
+		DEBUGP("icmp_error_message: no match\n");
+		return -NF_ACCEPT;
+	}
+
+	*ctinfo = IP_CT_RELATED;
+
+	h = nf_conntrack_find_get(&innertuple, NULL);
+	if (!h) {
+		/* Locally generated ICMPs will match inverted if they
+		   haven't been SNAT'ed yet */
+		/* FIXME: NAT code has to handle half-done double NAT --RR */
+		if (hooknum == NF_IP_LOCAL_OUT)
+			h = nf_conntrack_find_get(&origtuple, NULL);
+
+		if (!h) {
+			DEBUGP("icmp_error_message: no match\n");
+			return -NF_ACCEPT;
+		}
+
+		/* Reverse direction from that found */
+		if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
+			*ctinfo += IP_CT_IS_REPLY;
+	} else {
+		if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
+			*ctinfo += IP_CT_IS_REPLY;
+	}
+
+        /* Update skb to refer to this connection */
+        skb->nfct = &nf_ct_tuplehash_to_ctrack(h)->ct_general;
+        skb->nfctinfo = *ctinfo;
+        return -NF_ACCEPT;
+}
+
+/* Small and modified version of icmp_rcv */
+static int
+icmp_error(struct sk_buff *skb, unsigned int dataoff,
+	   enum ip_conntrack_info *ctinfo, int pf, unsigned int hooknum)
+{
+	struct icmphdr _ih, *icmph;
+
+	/* Not enough header? */
+	icmph = skb_header_pointer(skb, skb->nh.iph->ihl*4, sizeof(_ih), &_ih);
+	if (icmph == NULL) {
+		if (LOG_INVALID(IPPROTO_ICMP))
+			nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
+				      "nf_ct_icmp: short packet ");
+		return -NF_ACCEPT;
+	}
+
+	/* See ip_conntrack_proto_tcp.c */
+	if (hooknum != NF_IP_PRE_ROUTING)
+		goto checksum_skipped;
+
+	switch (skb->ip_summed) {
+	case CHECKSUM_HW:
+		if (!(u16)csum_fold(skb->csum))
+			break;
+		if (LOG_INVALID(IPPROTO_ICMP))
+			nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
+				      "nf_ct_icmp: bad HW ICMP checksum ");
+		return -NF_ACCEPT;
+	case CHECKSUM_NONE:
+		if ((u16)csum_fold(skb_checksum(skb, 0, skb->len, 0))) {
+			if (LOG_INVALID(IPPROTO_ICMP))
+				nf_log_packet(PF_INET, 0, skb, NULL, NULL,
+					      NULL,
+					      "nf_ct_icmp: bad ICMP checksum ");
+			return -NF_ACCEPT;
+		}
+	default:
+		break;
+	}
+
+checksum_skipped:
+	/*
+	 *	18 is the highest 'known' ICMP type. Anything else is a mystery
+	 *
+	 *	RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
+	 *		  discarded.
+	 */
+	if (icmph->type > NR_ICMP_TYPES) {
+		if (LOG_INVALID(IPPROTO_ICMP))
+			nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
+				      "nf_ct_icmp: invalid ICMP type ");
+		return -NF_ACCEPT;
+	}
+
+	/* Need to track icmp error message? */
+	if (icmph->type != ICMP_DEST_UNREACH
+	    && icmph->type != ICMP_SOURCE_QUENCH
+	    && icmph->type != ICMP_TIME_EXCEEDED
+	    && icmph->type != ICMP_PARAMETERPROB
+	    && icmph->type != ICMP_REDIRECT)
+		return NF_ACCEPT;
+
+	return icmp_error_message(skb, ctinfo, hooknum);
+}
+
+struct nf_conntrack_protocol nf_conntrack_protocol_icmp =
+{
+	.list			= { NULL, NULL },
+	.l3proto		= PF_INET,
+	.proto			= IPPROTO_ICMP,
+	.name			= "icmp",
+	.pkt_to_tuple		= icmp_pkt_to_tuple,
+	.invert_tuple		= icmp_invert_tuple,
+	.print_tuple		= icmp_print_tuple,
+	.print_conntrack	= icmp_print_conntrack,
+	.packet			= icmp_packet,
+	.new			= icmp_new,
+	.error			= icmp_error,
+	.destroy		= NULL,
+	.me			= NULL
+};
+
+EXPORT_SYMBOL(nf_conntrack_protocol_icmp);