[NETFILTER]: x_tables: add connlimit match (370786f9) · Commits · 戴 / test

include/linux/netfilter/xt_connlimit.h

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		#ifndef _XT_CONNLIMIT_H
		#define _XT_CONNLIMIT_H

		struct xt_connlimit_data;

		struct xt_connlimit_info {
		union {
		u_int32_t v4_mask;
		u_int32_t v6_mask[4];
		};
		unsigned int limit, inverse;

		/* this needs to be at the end */
		struct xt_connlimit_data *data __attribute__((aligned(8)));
		};

		#endif /* _XT_CONNLIMIT_H */

net/netfilter/Kconfig

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		@@ -423,6 +423,13 @@ config NETFILTER_XT_MATCH_CONNBYTES
		If you want to compile it as a module, say M here and read
		<file:Documentation/kbuild/modules.txt>. If unsure, say `N'.

		config NETFILTER_XT_MATCH_CONNLIMIT
		tristate '"connlimit" match support"'
		depends on NETFILTER_XTABLES
		---help---
		This match allows you to match against the number of parallel
		connections to a server per client IP address (or address block).

		config NETFILTER_XT_MATCH_CONNMARK
		tristate '"connmark" connection mark match support'
		depends on NETFILTER_XTABLES

net/netfilter/Makefile

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		@@ -52,6 +52,7 @@ obj-$(CONFIG_NETFILTER_XT_TARGET_CONNSECMARK) += xt_CONNSECMARK.o
		# matches
		obj-$(CONFIG_NETFILTER_XT_MATCH_COMMENT) += xt_comment.o
		obj-$(CONFIG_NETFILTER_XT_MATCH_CONNBYTES) += xt_connbytes.o
		obj-$(CONFIG_NETFILTER_XT_MATCH_CONNLIMIT) += xt_connlimit.o
		obj-$(CONFIG_NETFILTER_XT_MATCH_CONNMARK) += xt_connmark.o
		obj-$(CONFIG_NETFILTER_XT_MATCH_CONNTRACK) += xt_conntrack.o
		obj-$(CONFIG_NETFILTER_XT_MATCH_DCCP) += xt_dccp.o

net/netfilter/xt_connlimit.c

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		/*
		* netfilter module to limit the number of parallel tcp
		* connections per IP address.
		* (c) 2000 Gerd Knorr <kraxel@bytesex.org>
		* Nov 2002: Martin Bene <martin.bene@icomedias.com>:
		* only ignore TIME_WAIT or gone connections
		* Copyright © Jan Engelhardt <jengelh@gmx.de>, 2007
		*
		* based on ...
		*
		* Kernel module to match connection tracking information.
		* GPL (C) 1999 Rusty Russell (rusty@rustcorp.com.au).
		*/
		#include <linux/in.h>
		#include <linux/in6.h>
		#include <linux/ip.h>
		#include <linux/ipv6.h>
		#include <linux/jhash.h>
		#include <linux/list.h>
		#include <linux/module.h>
		#include <linux/random.h>
		#include <linux/skbuff.h>
		#include <linux/spinlock.h>
		#include <linux/netfilter/nf_conntrack_tcp.h>
		#include <linux/netfilter/x_tables.h>
		#include <linux/netfilter/xt_connlimit.h>
		#include <net/netfilter/nf_conntrack.h>
		#include <net/netfilter/nf_conntrack_core.h>
		#include <net/netfilter/nf_conntrack_tuple.h>

		/* we will save the tuples of all connections we care about */
		struct xt_connlimit_conn {
		struct list_head list;
		struct nf_conntrack_tuple tuple;
		};

		struct xt_connlimit_data {
		struct list_head iphash[256];
		spinlock_t lock;
		};

		static u_int32_t connlimit_rnd;
		static bool connlimit_rnd_inited;

		static inline unsigned int connlimit_iphash(u_int32_t addr)
		{
		if (unlikely(!connlimit_rnd_inited)) {
		get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd));
		connlimit_rnd_inited = true;
		}
		return jhash_1word(addr, connlimit_rnd) & 0xFF;
		}

		static inline unsigned int
		connlimit_iphash6(const union nf_conntrack_address *addr,
		const union nf_conntrack_address *mask)
		{
		union nf_conntrack_address res;
		unsigned int i;

		if (unlikely(!connlimit_rnd_inited)) {
		get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd));
		connlimit_rnd_inited = true;
		}

		for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i)
		res.ip6[i] = addr->ip6[i] & mask->ip6[i];

		return jhash2(res.ip6, ARRAY_SIZE(res.ip6), connlimit_rnd) & 0xFF;
		}

		static inline bool already_closed(const struct nf_conn *conn)
		{
		u_int16_t proto = conn->tuplehash[0].tuple.dst.protonum;

		if (proto == IPPROTO_TCP)
		return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT;
		else
		return 0;
		}

		static inline unsigned int
		same_source_net(const union nf_conntrack_address *addr,
		const union nf_conntrack_address *mask,
		const union nf_conntrack_address *u3, unsigned int family)
		{
		if (family == AF_INET) {
		return (addr->ip & mask->ip) == (u3->ip & mask->ip);
		} else {
		union nf_conntrack_address lh, rh;
		unsigned int i;

		for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) {
		lh.ip6[i] = addr->ip6[i] & mask->ip6[i];
		rh.ip6[i] = u3->ip6[i] & mask->ip6[i];
		}

		return memcmp(&lh.ip6, &rh.ip6, sizeof(lh.ip6)) == 0;
		}
		}

		static int count_them(struct xt_connlimit_data *data,
		const struct nf_conntrack_tuple *tuple,
		const union nf_conntrack_address *addr,
		const union nf_conntrack_address *mask,
		const struct xt_match *match)
		{
		struct nf_conntrack_tuple_hash *found;
		struct xt_connlimit_conn *conn;
		struct xt_connlimit_conn *tmp;
		struct nf_conn *found_ct;
		struct list_head *hash;
		bool addit = true;
		int matches = 0;


		if (match->family == AF_INET6)
		hash = &data->iphash[connlimit_iphash6(addr, mask)];
		else
		hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)];

		read_lock_bh(&nf_conntrack_lock);

		/* check the saved connections */
		list_for_each_entry_safe(conn, tmp, hash, list) {
		found = __nf_conntrack_find(&conn->tuple, NULL);
		found_ct = NULL;

		if (found != NULL)
		found_ct = nf_ct_tuplehash_to_ctrack(found);

		if (found_ct != NULL &&
		nf_ct_tuple_equal(&conn->tuple, tuple) &&
		!already_closed(found_ct))
		/*
		* Just to be sure we have it only once in the list.
		* We should not see tuples twice unless someone hooks
		* this into a table without "-p tcp --syn".
		*/
		addit = false;

		if (found == NULL) {
		/* this one is gone */
		list_del(&conn->list);
		kfree(conn);
		continue;
		}

		if (already_closed(found_ct)) {
		/*
		* we do not care about connections which are
		* closed already -> ditch it
		*/
		list_del(&conn->list);
		kfree(conn);
		continue;
		}

		if (same_source_net(addr, mask, &conn->tuple.src.u3,
		match->family))
		/* same source network -> be counted! */
		++matches;
		}

		read_unlock_bh(&nf_conntrack_lock);

		if (addit) {
		/* save the new connection in our list */
		conn = kzalloc(sizeof(*conn), GFP_ATOMIC);
		if (conn == NULL)
		return -ENOMEM;
		conn->tuple = *tuple;
		list_add(&conn->list, hash);
		++matches;
		}

		return matches;
		}

		static bool connlimit_match(const struct sk_buff *skb,
		const struct net_device *in,
		const struct net_device *out,
		const struct xt_match *match,
		const void *matchinfo, int offset,
		unsigned int protoff, bool *hotdrop)
		{
		const struct xt_connlimit_info *info = matchinfo;
		union nf_conntrack_address addr, mask;
		struct nf_conntrack_tuple tuple;
		const struct nf_conntrack_tuple *tuple_ptr = &tuple;
		enum ip_conntrack_info ctinfo;
		const struct nf_conn *ct;
		int connections;

		ct = nf_ct_get(skb, &ctinfo);
		if (ct != NULL)
		tuple_ptr = &ct->tuplehash[0].tuple;
		else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb),
		match->family, &tuple))
		goto hotdrop;

		if (match->family == AF_INET6) {
		const struct ipv6hdr *iph = ipv6_hdr(skb);
		memcpy(&addr.ip6, &iph->saddr, sizeof(iph->saddr));
		memcpy(&mask.ip6, info->v6_mask, sizeof(info->v6_mask));
		} else {
		const struct iphdr *iph = ip_hdr(skb);
		addr.ip = iph->saddr;
		mask.ip = info->v4_mask;
		}

		spin_lock_bh(&info->data->lock);
		connections = count_them(info->data, tuple_ptr, &addr, &mask, match);
		spin_unlock_bh(&info->data->lock);

		if (connections < 0) {
		/* kmalloc failed, drop it entirely */
		*hotdrop = true;
		return false;
		}

		return (connections > info->limit) ^ info->inverse;

		hotdrop:
		*hotdrop = true;
		return false;
		}

		static bool connlimit_check(const char tablename, const void ip,
		const struct xt_match match, void matchinfo,
		unsigned int hook_mask)
		{
		struct xt_connlimit_info *info = matchinfo;
		unsigned int i;

		if (nf_ct_l3proto_try_module_get(match->family) < 0) {
		printk(KERN_WARNING "cannot load conntrack support for "
		"address family %u\n", match->family);
		return false;
		}

		/* init private data */
		info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL);
		if (info->data == NULL) {
		nf_ct_l3proto_module_put(match->family);
		return false;
		}

		spin_lock_init(&info->data->lock);
		for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i)
		INIT_LIST_HEAD(&info->data->iphash[i]);

		return true;
		}

		static void connlimit_destroy(const struct xt_match match, void matchinfo)
		{
		struct xt_connlimit_info *info = matchinfo;
		struct xt_connlimit_conn *conn;
		struct xt_connlimit_conn *tmp;
		struct list_head *hash = info->data->iphash;
		unsigned int i;

		nf_ct_l3proto_module_put(match->family);

		for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) {
		list_for_each_entry_safe(conn, tmp, &hash[i], list) {
		list_del(&conn->list);
		kfree(conn);
		}
		}

		kfree(info->data);
		}

		static struct xt_match connlimit_reg[] __read_mostly = {
		{
		.name = "connlimit",
		.family = AF_INET,
		.checkentry = connlimit_check,
		.match = connlimit_match,
		.matchsize = sizeof(struct xt_connlimit_info),
		.destroy = connlimit_destroy,
		.me = THIS_MODULE,
		},
		{
		.name = "connlimit",
		.family = AF_INET6,
		.checkentry = connlimit_check,
		.match = connlimit_match,
		.matchsize = sizeof(struct xt_connlimit_info),
		.destroy = connlimit_destroy,
		.me = THIS_MODULE,
		},
		};

		static int __init xt_connlimit_init(void)
		{
		return xt_register_matches(connlimit_reg, ARRAY_SIZE(connlimit_reg));
		}

		static void __exit xt_connlimit_exit(void)
		{
		xt_unregister_matches(connlimit_reg, ARRAY_SIZE(connlimit_reg));
		}

		module_init(xt_connlimit_init);
		module_exit(xt_connlimit_exit);
		MODULE_AUTHOR("Jan Engelhardt <jengelh@gmx.de>");
		MODULE_DESCRIPTION("netfilter xt_connlimit match module");
		MODULE_LICENSE("GPL");
		MODULE_ALIAS("ipt_connlimit");
		MODULE_ALIAS("ip6t_connlimit");

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