[NETFILTER]: x_tables: add connlimit match
authorJan Engelhardt <jengelh@gmx.de>
Sun, 15 Jul 2007 03:47:26 +0000 (20:47 -0700)
committerDavid S. Miller <davem@davemloft.net>
Sun, 15 Jul 2007 03:47:26 +0000 (20:47 -0700)
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>
include/linux/netfilter/xt_connlimit.h [new file with mode: 0644]
net/netfilter/Kconfig
net/netfilter/Makefile
net/netfilter/xt_connlimit.c [new file with mode: 0644]

diff --git a/include/linux/netfilter/xt_connlimit.h b/include/linux/netfilter/xt_connlimit.h
new file mode 100644 (file)
index 0000000..90ae8b4
--- /dev/null
@@ -0,0 +1,17 @@
+#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 */
index df5e8dab871d535acfb7eff9ae05ee71304c026f..9415b9a5dba67e2dbdf6354ac678788103101e9c 100644 (file)
@@ -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
index 58b4245a1723b52c81b1738b4a605cf88552c077..3e4a16aeb04e7ee6d7e5fd941d10e7e76d1178b5 100644 (file)
@@ -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
diff --git a/net/netfilter/xt_connlimit.c b/net/netfilter/xt_connlimit.c
new file mode 100644 (file)
index 0000000..3335dd5
--- /dev/null
@@ -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");