[NETFILTER]: Add new iptables "connbytes" match

This patch ads a new "connbytes" match that utilizes the CONFIG_NF_CT_ACCT
per-connection byte and packet counters.  Using it you can do things like
packet classification on average packet size within a connection.
Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netfilter_ipv4/ipt_connbytes.h

+#ifndef _IPT_CONNBYTES_H
+#define _IPT_CONNBYTES_H
+
+enum ipt_connbytes_what {
+	IPT_CONNBYTES_WHAT_PKTS,
+	IPT_CONNBYTES_WHAT_BYTES,
+	IPT_CONNBYTES_WHAT_AVGPKT,
+};
+
+enum ipt_connbytes_direction {
+	IPT_CONNBYTES_DIR_ORIGINAL,
+	IPT_CONNBYTES_DIR_REPLY,
+	IPT_CONNBYTES_DIR_BOTH,
+};
+
+struct ipt_connbytes_info
+{
+	struct {
+		aligned_u64 from;	/* count to be matched */
+		aligned_u64 to;		/* count to be matched */
+	} count;
+	u_int8_t what;		/* ipt_connbytes_what */
+	u_int8_t direction;	/* ipt_connbytes_direction */
+};
+#endif

net/ipv4/netfilter/Kconfig

@@ -386,6 +386,16 @@ config IP_NF_MATCH_CONNMARK
 	  <file:Documentation/modules.txt>.  The module will be called
 	  ipt_connmark.o.  If unsure, say `N'.
 
+config IP_NF_MATCH_CONNBYTES
+	tristate  'Connection byte/packet counter match support'
+	depends on IP_NF_CT_ACCT && IP_NF_IPTABLES
+	help
+	  This option adds a `connbytes' match, which allows you to match the
+	  number of bytes and/or packets for each direction within a connection.
+
+	  If you want to compile it as a module, say M here and read
+	  <file:Documentation/modules.txt>.  If unsure, say `N'.
+
 config IP_NF_MATCH_HASHLIMIT
 	tristate  'hashlimit match support'
 	depends on IP_NF_IPTABLES
@@ -723,6 +733,5 @@ config IP_NF_CONNTRACK_NETLINK
         help
           This option enables support for a netlink-based userspace interface
 
-
 endmenu
 

net/ipv4/netfilter/Makefile

@@ -59,6 +59,7 @@ obj-$(CONFIG_IP_NF_MATCH_TTL) += ipt_ttl.o
 obj-$(CONFIG_IP_NF_MATCH_STATE) += ipt_state.o
 obj-$(CONFIG_IP_NF_MATCH_CONNMARK) += ipt_connmark.o
 obj-$(CONFIG_IP_NF_MATCH_CONNTRACK) += ipt_conntrack.o
+obj-$(CONFIG_IP_NF_MATCH_CONNBYTES) += ipt_connbytes.o
 obj-$(CONFIG_IP_NF_MATCH_TCPMSS) += ipt_tcpmss.o
 obj-$(CONFIG_IP_NF_MATCH_REALM) += ipt_realm.o
 obj-$(CONFIG_IP_NF_MATCH_ADDRTYPE) += ipt_addrtype.o

net/ipv4/netfilter/ipt_connbytes.c

+/* Kernel module to match connection tracking byte counter.
+ * GPL (C) 2002 Martin Devera (devik@cdi.cz).
+ *
+ * 2004-07-20 Harald Welte <laforge@netfilter.org>
+ * 	- reimplemented to use per-connection accounting counters
+ * 	- add functionality to match number of packets
+ * 	- add functionality to match average packet size
+ * 	- add support to match directions seperately
+ *
+ */
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/netfilter_ipv4/ip_conntrack.h>
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter_ipv4/ipt_connbytes.h>
+
+#include <asm/div64.h>
+#include <asm/bitops.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
+MODULE_DESCRIPTION("iptables match for matching number of pkts/bytes per connection");
+
+/* 64bit divisor, dividend and result. dynamic precision */
+static u_int64_t div64_64(u_int64_t divisor, u_int64_t dividend)
+{
+	u_int64_t result = divisor;
+
+	if (dividend > 0xffffffff) {
+		int first_bit = find_first_bit((unsigned long *) &dividend, sizeof(dividend));
+		/* calculate number of bits to shift. shift exactly enough
+		 * bits to make dividend fit in 32bits. */
+		int num_shift = (64 - 32 - first_bit);
+		/* first bit has to be < 32, since dividend was > 0xffffffff */
+		result = result >> num_shift;
+		dividend = dividend >> num_shift;
+	}
+
+	do_div(divisor, dividend);
+
+	return divisor;
+}
+
+static int
+match(const struct sk_buff *skb,
+      const struct net_device *in,
+      const struct net_device *out,
+      const void *matchinfo,
+      int offset,
+      int *hotdrop)
+{
+	const struct ipt_connbytes_info *sinfo = matchinfo;
+	enum ip_conntrack_info ctinfo;
+	struct ip_conntrack *ct;
+	u_int64_t what = 0;	/* initialize to make gcc happy */
+
+	if (!(ct = ip_conntrack_get((struct sk_buff *)skb, &ctinfo)))
+		return 0; /* no match */
+
+	switch (sinfo->what) {
+	case IPT_CONNBYTES_WHAT_PKTS:
+		switch (sinfo->direction) {
+		case IPT_CONNBYTES_DIR_ORIGINAL:
+			what = ct->counters[IP_CT_DIR_ORIGINAL].packets;
+			break;
+		case IPT_CONNBYTES_DIR_REPLY:
+			what = ct->counters[IP_CT_DIR_REPLY].packets;
+			break;
+		case IPT_CONNBYTES_DIR_BOTH:
+			what = ct->counters[IP_CT_DIR_ORIGINAL].packets;
+			what += ct->counters[IP_CT_DIR_REPLY].packets;
+			break;
+		}
+		break;
+	case IPT_CONNBYTES_WHAT_BYTES:
+		switch (sinfo->direction) {
+		case IPT_CONNBYTES_DIR_ORIGINAL:
+			what = ct->counters[IP_CT_DIR_ORIGINAL].bytes;
+			break;
+		case IPT_CONNBYTES_DIR_REPLY:
+			what = ct->counters[IP_CT_DIR_REPLY].bytes;
+			break;
+		case IPT_CONNBYTES_DIR_BOTH:
+			what = ct->counters[IP_CT_DIR_ORIGINAL].bytes;
+			what += ct->counters[IP_CT_DIR_REPLY].bytes;
+			break;
+		}
+		break;
+	case IPT_CONNBYTES_WHAT_AVGPKT:
+		switch (sinfo->direction) {
+		case IPT_CONNBYTES_DIR_ORIGINAL:
+			what = div64_64(ct->counters[IP_CT_DIR_ORIGINAL].bytes,
+					ct->counters[IP_CT_DIR_ORIGINAL].packets);
+			break;
+		case IPT_CONNBYTES_DIR_REPLY:
+			what = div64_64(ct->counters[IP_CT_DIR_REPLY].bytes,
+					ct->counters[IP_CT_DIR_REPLY].packets);
+			break;
+		case IPT_CONNBYTES_DIR_BOTH:
+			{
+				u_int64_t bytes;
+				u_int64_t pkts;
+				bytes = ct->counters[IP_CT_DIR_ORIGINAL].bytes +
+					ct->counters[IP_CT_DIR_REPLY].bytes;
+				pkts = ct->counters[IP_CT_DIR_ORIGINAL].packets+
+					ct->counters[IP_CT_DIR_REPLY].packets;
+
+				/* FIXME_THEORETICAL: what to do if sum
+				 * overflows ? */
+
+				what = div64_64(bytes, pkts);
+			}
+			break;
+		}
+		break;
+	}
+
+	if (sinfo->count.to)
+		return (what <= sinfo->count.to && what >= sinfo->count.from);
+	else
+		return (what >= sinfo->count.from);
+}
+
+static int check(const char *tablename,
+		 const struct ipt_ip *ip,
+		 void *matchinfo,
+		 unsigned int matchsize,
+		 unsigned int hook_mask)
+{
+	const struct ipt_connbytes_info *sinfo = matchinfo;
+
+	if (matchsize != IPT_ALIGN(sizeof(struct ipt_connbytes_info)))
+		return 0;
+
+	if (sinfo->what != IPT_CONNBYTES_WHAT_PKTS &&
+	    sinfo->what != IPT_CONNBYTES_WHAT_BYTES &&
+	    sinfo->what != IPT_CONNBYTES_WHAT_AVGPKT)
+		return 0;
+
+	if (sinfo->direction != IPT_CONNBYTES_DIR_ORIGINAL &&
+	    sinfo->direction != IPT_CONNBYTES_DIR_REPLY &&
+	    sinfo->direction != IPT_CONNBYTES_DIR_BOTH)
+		return 0;
+
+	return 1;
+}
+
+static struct ipt_match state_match = {
+	.name		= "connbytes",
+	.match		= &match,
+	.checkentry	= &check,
+	.me		= THIS_MODULE
+};
+
+static int __init init(void)
+{
+	return ipt_register_match(&state_match);
+}
+
+static void __exit fini(void)
+{
+	ipt_unregister_match(&state_match);
+}
+
+module_init(init);
+module_exit(fini);