[NETFILTER]: x_tables: add connlimit match
ipt_connlimit has been sitting in POM-NG for a long time.
Here is a new shiny xt_connlimit with:
* xtables'ified
* will request the layer3 module
(previously it hotdropped every packet when it was not loaded)
* fixed: there was a deadlock in case of an OOM condition
* support for any layer4 protocol (e.g. UDP/SCTP)
* using jhash, as suggested by Eric Dumazet
* ipv6 support
Signed-off-by: Jan Engelhardt <jengelh@gmx.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/netfilter/xt_connlimit.c b/net/netfilter/xt_connlimit.c
new file mode 100644
index 0000000..3335dd5
--- /dev/null
+++ b/net/netfilter/xt_connlimit.c
@@ -0,0 +1,313 @@
+/*
+ * 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");