net/netfilter/xt_connlimit.c - linux - Git at Google

 /*
  * 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(__be32 addr)
 {
 	if (unlikely(!connlimit_rnd_inited)) {
 		get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd));
 		connlimit_rnd_inited = true;
 	}
 	return jhash_1word((__force __u32)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((u32 *)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");
	/*
	* 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(__be32 addr)
	{
	if (unlikely(!connlimit_rnd_inited)) {
	get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd));
	connlimit_rnd_inited = true;
	}
	return jhash_1word((__force __u32)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((u32 *)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");