[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, 216 insertions, 0 deletions

diff --git a/net/netfilter/nf_conntrack_proto_udp.c b/net/netfilter/nf_conntrack_proto_udp.c
new file mode 100644
index 0000000000000..3cae7ce420dd8
--- /dev/null
+++ b/net/netfilter/nf_conntrack_proto_udp.c
@@ -0,0 +1,216 @@
+/* (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_udp.c
+ */
+
+#include <linux/types.h>
+#include <linux/sched.h>
+#include <linux/timer.h>
+#include <linux/module.h>
+#include <linux/netfilter.h>
+#include <linux/udp.h>
+#include <linux/seq_file.h>
+#include <linux/skbuff.h>
+#include <linux/ipv6.h>
+#include <net/ip6_checksum.h>
+#include <net/checksum.h>
+#include <linux/netfilter.h>
+#include <linux/netfilter_ipv4.h>
+#include <linux/netfilter_ipv6.h>
+#include <net/netfilter/nf_conntrack_protocol.h>
+
+unsigned long nf_ct_udp_timeout = 30*HZ;
+unsigned long nf_ct_udp_timeout_stream = 180*HZ;
+
+static int udp_pkt_to_tuple(const struct sk_buff *skb,
+			     unsigned int dataoff,
+			     struct nf_conntrack_tuple *tuple)
+{
+	struct udphdr _hdr, *hp;
+
+	/* Actually only need first 8 bytes. */
+	hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
+	if (hp == NULL)
+		return 0;
+
+	tuple->src.u.udp.port = hp->source;
+	tuple->dst.u.udp.port = hp->dest;
+
+	return 1;
+}
+
+static int udp_invert_tuple(struct nf_conntrack_tuple *tuple,
+			    const struct nf_conntrack_tuple *orig)
+{
+	tuple->src.u.udp.port = orig->dst.u.udp.port;
+	tuple->dst.u.udp.port = orig->src.u.udp.port;
+	return 1;
+}
+
+/* Print out the per-protocol part of the tuple. */
+static int udp_print_tuple(struct seq_file *s,
+			   const struct nf_conntrack_tuple *tuple)
+{
+	return seq_printf(s, "sport=%hu dport=%hu ",
+			  ntohs(tuple->src.u.udp.port),
+			  ntohs(tuple->dst.u.udp.port));
+}
+
+/* Print out the private part of the conntrack. */
+static int udp_print_conntrack(struct seq_file *s,
+			       const struct nf_conn *conntrack)
+{
+	return 0;
+}
+
+/* Returns verdict for packet, and may modify conntracktype */
+static int udp_packet(struct nf_conn *conntrack,
+		      const struct sk_buff *skb,
+		      unsigned int dataoff,
+		      enum ip_conntrack_info ctinfo,
+		      int pf,
+		      unsigned int hooknum)
+{
+	/* If we've seen traffic both ways, this is some kind of UDP
+	   stream.  Extend timeout. */
+	if (test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)) {
+		nf_ct_refresh_acct(conntrack, ctinfo, skb,
+				   nf_ct_udp_timeout_stream);
+		/* Also, more likely to be important, and not a probe */
+		if (!test_and_set_bit(IPS_ASSURED_BIT, &conntrack->status))
+			nf_conntrack_event_cache(IPCT_STATUS, skb);
+	} else
+		nf_ct_refresh_acct(conntrack, ctinfo, skb, nf_ct_udp_timeout);
+
+	return NF_ACCEPT;
+}
+
+/* Called when a new connection for this protocol found. */
+static int udp_new(struct nf_conn *conntrack, const struct sk_buff *skb,
+		   unsigned int dataoff)
+{
+	return 1;
+}
+
+static int udp_error(struct sk_buff *skb, unsigned int dataoff,
+		     enum ip_conntrack_info *ctinfo,
+		     int pf,
+		     unsigned int hooknum,
+		     int (*csum)(const struct sk_buff *, unsigned int))
+{
+	unsigned int udplen = skb->len - dataoff;
+	struct udphdr _hdr, *hdr;
+
+	/* Header is too small? */
+	hdr = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
+	if (hdr == NULL) {
+		if (LOG_INVALID(IPPROTO_UDP))
+			nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
+				      "nf_ct_udp: short packet ");
+		return -NF_ACCEPT;
+	}
+
+	/* Truncated/malformed packets */
+	if (ntohs(hdr->len) > udplen || ntohs(hdr->len) < sizeof(*hdr)) {
+		if (LOG_INVALID(IPPROTO_UDP))
+			nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
+				"nf_ct_udp: truncated/malformed packet ");
+		return -NF_ACCEPT;
+	}
+
+	/* Packet with no checksum */
+	if (!hdr->check)
+		return NF_ACCEPT;
+
+	/* Checksum invalid? Ignore.
+	 * We skip checking packets on the outgoing path
+	 * because the semantic of CHECKSUM_HW is different there
+	 * and moreover root might send raw packets.
+	 * FIXME: Source route IP option packets --RR */
+	if (((pf == PF_INET && hooknum == NF_IP_PRE_ROUTING) ||
+	     (pf == PF_INET6 && hooknum == NF_IP6_PRE_ROUTING))
+	    && skb->ip_summed != CHECKSUM_UNNECESSARY
+	    && csum(skb, dataoff)) {
+		if (LOG_INVALID(IPPROTO_UDP))
+			nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
+				"nf_ct_udp: bad UDP checksum ");
+		return -NF_ACCEPT;
+	}
+
+	return NF_ACCEPT;
+}
+
+static int csum4(const struct sk_buff *skb, unsigned int dataoff)
+{
+	return csum_tcpudp_magic(skb->nh.iph->saddr, skb->nh.iph->daddr,
+				 skb->len - dataoff, IPPROTO_UDP,
+				 skb->ip_summed == CHECKSUM_HW ? skb->csum
+				 : skb_checksum(skb, dataoff,
+						skb->len - dataoff, 0));
+}
+
+static int csum6(const struct sk_buff *skb, unsigned int dataoff)
+{
+	return csum_ipv6_magic(&skb->nh.ipv6h->saddr, &skb->nh.ipv6h->daddr,
+			       skb->len - dataoff, IPPROTO_UDP,
+			       skb->ip_summed == CHECKSUM_HW ? skb->csum
+			       : skb_checksum(skb, dataoff, skb->len - dataoff,
+					      0));
+}
+
+static int udp_error4(struct sk_buff *skb,
+		      unsigned int dataoff,
+		      enum ip_conntrack_info *ctinfo,
+		      int pf,
+		      unsigned int hooknum)
+{
+	return udp_error(skb, dataoff, ctinfo, pf, hooknum, csum4);
+}
+
+static int udp_error6(struct sk_buff *skb,
+		      unsigned int dataoff,
+		      enum ip_conntrack_info *ctinfo,
+		      int pf,
+		      unsigned int hooknum)
+{
+	return udp_error(skb, dataoff, ctinfo, pf, hooknum, csum6);
+}
+
+struct nf_conntrack_protocol nf_conntrack_protocol_udp4 =
+{
+	.l3proto		= PF_INET,
+	.proto			= IPPROTO_UDP,
+	.name			= "udp",
+	.pkt_to_tuple		= udp_pkt_to_tuple,
+	.invert_tuple		= udp_invert_tuple,
+	.print_tuple		= udp_print_tuple,
+	.print_conntrack	= udp_print_conntrack,
+	.packet			= udp_packet,
+	.new			= udp_new,
+	.error			= udp_error4,
+};
+
+struct nf_conntrack_protocol nf_conntrack_protocol_udp6 =
+{
+	.l3proto		= PF_INET6,
+	.proto			= IPPROTO_UDP,
+	.name			= "udp",
+	.pkt_to_tuple		= udp_pkt_to_tuple,
+	.invert_tuple		= udp_invert_tuple,
+	.print_tuple		= udp_print_tuple,
+	.print_conntrack	= udp_print_conntrack,
+	.packet			= udp_packet,
+	.new			= udp_new,
+	.error			= udp_error6,
+};
+
+EXPORT_SYMBOL(nf_conntrack_protocol_udp4);
+EXPORT_SYMBOL(nf_conntrack_protocol_udp6);