netfilter: connlimit: split xt_connlimit into front and backend
This allows to reuse xt_connlimit infrastructure from nf_tables.
The upcoming nf_tables frontend can just pass in an nftables register
as input key, this allows limiting by any nft-supported key, including
concatenations.
For xt_connlimit, pass in the zone and the ip/ipv6 address.
With help from Yi-Hung Wei.
Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Yi-Hung Wei <yihung.wei@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/net/netfilter/nf_conncount.c b/net/netfilter/nf_conncount.c
new file mode 100644
index 0000000..a955182
--- /dev/null
+++ b/net/netfilter/nf_conncount.c
@@ -0,0 +1,373 @@
+/*
+ * count the number of connections matching an arbitrary key.
+ *
+ * (C) 2017 Red Hat GmbH
+ * Author: Florian Westphal <fw@strlen.de>
+ *
+ * split from xt_connlimit.c:
+ * (c) 2000 Gerd Knorr <kraxel@bytesex.org>
+ * Nov 2002: Martin Bene <martin.bene@icomedias.com>:
+ * only ignore TIME_WAIT or gone connections
+ * (C) CC Computer Consultants GmbH, 2007
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/in.h>
+#include <linux/in6.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+#include <linux/jhash.h>
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <linux/rbtree.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 <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_count.h>
+#include <net/netfilter/nf_conntrack_core.h>
+#include <net/netfilter/nf_conntrack_tuple.h>
+#include <net/netfilter/nf_conntrack_zones.h>
+
+#define CONNCOUNT_SLOTS 256U
+
+#ifdef CONFIG_LOCKDEP
+#define CONNCOUNT_LOCK_SLOTS 8U
+#else
+#define CONNCOUNT_LOCK_SLOTS 256U
+#endif
+
+#define CONNCOUNT_GC_MAX_NODES 8
+#define MAX_KEYLEN 5
+
+/* we will save the tuples of all connections we care about */
+struct nf_conncount_tuple {
+ struct hlist_node node;
+ struct nf_conntrack_tuple tuple;
+};
+
+struct nf_conncount_rb {
+ struct rb_node node;
+ struct hlist_head hhead; /* connections/hosts in same subnet */
+ u32 key[MAX_KEYLEN];
+};
+
+static spinlock_t nf_conncount_locks[CONNCOUNT_LOCK_SLOTS] __cacheline_aligned_in_smp;
+
+struct nf_conncount_data {
+ unsigned int keylen;
+ struct rb_root root[CONNCOUNT_SLOTS];
+};
+
+static u_int32_t conncount_rnd __read_mostly;
+static struct kmem_cache *conncount_rb_cachep __read_mostly;
+static struct kmem_cache *conncount_conn_cachep __read_mostly;
+
+static inline bool already_closed(const struct nf_conn *conn)
+{
+ if (nf_ct_protonum(conn) == IPPROTO_TCP)
+ return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT ||
+ conn->proto.tcp.state == TCP_CONNTRACK_CLOSE;
+ else
+ return 0;
+}
+
+static int key_diff(const u32 *a, const u32 *b, unsigned int klen)
+{
+ return memcmp(a, b, klen * sizeof(u32));
+}
+
+static bool add_hlist(struct hlist_head *head,
+ const struct nf_conntrack_tuple *tuple)
+{
+ struct nf_conncount_tuple *conn;
+
+ conn = kmem_cache_alloc(conncount_conn_cachep, GFP_ATOMIC);
+ if (conn == NULL)
+ return false;
+ conn->tuple = *tuple;
+ hlist_add_head(&conn->node, head);
+ return true;
+}
+
+static unsigned int check_hlist(struct net *net,
+ struct hlist_head *head,
+ const struct nf_conntrack_tuple *tuple,
+ const struct nf_conntrack_zone *zone,
+ bool *addit)
+{
+ const struct nf_conntrack_tuple_hash *found;
+ struct nf_conncount_tuple *conn;
+ struct hlist_node *n;
+ struct nf_conn *found_ct;
+ unsigned int length = 0;
+
+ *addit = true;
+
+ /* check the saved connections */
+ hlist_for_each_entry_safe(conn, n, head, node) {
+ found = nf_conntrack_find_get(net, zone, &conn->tuple);
+ if (found == NULL) {
+ hlist_del(&conn->node);
+ kmem_cache_free(conncount_conn_cachep, conn);
+ continue;
+ }
+
+ found_ct = nf_ct_tuplehash_to_ctrack(found);
+
+ if (nf_ct_tuple_equal(&conn->tuple, tuple)) {
+ /*
+ * 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;
+ } else if (already_closed(found_ct)) {
+ /*
+ * we do not care about connections which are
+ * closed already -> ditch it
+ */
+ nf_ct_put(found_ct);
+ hlist_del(&conn->node);
+ kmem_cache_free(conncount_conn_cachep, conn);
+ continue;
+ }
+
+ nf_ct_put(found_ct);
+ length++;
+ }
+
+ return length;
+}
+
+static void tree_nodes_free(struct rb_root *root,
+ struct nf_conncount_rb *gc_nodes[],
+ unsigned int gc_count)
+{
+ struct nf_conncount_rb *rbconn;
+
+ while (gc_count) {
+ rbconn = gc_nodes[--gc_count];
+ rb_erase(&rbconn->node, root);
+ kmem_cache_free(conncount_rb_cachep, rbconn);
+ }
+}
+
+static unsigned int
+count_tree(struct net *net, struct rb_root *root,
+ const u32 *key, u8 keylen,
+ u8 family,
+ const struct nf_conntrack_tuple *tuple,
+ const struct nf_conntrack_zone *zone)
+{
+ struct nf_conncount_rb *gc_nodes[CONNCOUNT_GC_MAX_NODES];
+ struct rb_node **rbnode, *parent;
+ struct nf_conncount_rb *rbconn;
+ struct nf_conncount_tuple *conn;
+ unsigned int gc_count;
+ bool no_gc = false;
+
+ restart:
+ gc_count = 0;
+ parent = NULL;
+ rbnode = &(root->rb_node);
+ while (*rbnode) {
+ int diff;
+ bool addit;
+
+ rbconn = rb_entry(*rbnode, struct nf_conncount_rb, node);
+
+ parent = *rbnode;
+ diff = key_diff(key, rbconn->key, keylen);
+ if (diff < 0) {
+ rbnode = &((*rbnode)->rb_left);
+ } else if (diff > 0) {
+ rbnode = &((*rbnode)->rb_right);
+ } else {
+ /* same source network -> be counted! */
+ unsigned int count;
+ count = check_hlist(net, &rbconn->hhead, tuple, zone, &addit);
+
+ tree_nodes_free(root, gc_nodes, gc_count);
+ if (!addit)
+ return count;
+
+ if (!add_hlist(&rbconn->hhead, tuple))
+ return 0; /* hotdrop */
+
+ return count + 1;
+ }
+
+ if (no_gc || gc_count >= ARRAY_SIZE(gc_nodes))
+ continue;
+
+ /* only used for GC on hhead, retval and 'addit' ignored */
+ check_hlist(net, &rbconn->hhead, tuple, zone, &addit);
+ if (hlist_empty(&rbconn->hhead))
+ gc_nodes[gc_count++] = rbconn;
+ }
+
+ if (gc_count) {
+ no_gc = true;
+ tree_nodes_free(root, gc_nodes, gc_count);
+ /* tree_node_free before new allocation permits
+ * allocator to re-use newly free'd object.
+ *
+ * This is a rare event; in most cases we will find
+ * existing node to re-use. (or gc_count is 0).
+ */
+ goto restart;
+ }
+
+ /* no match, need to insert new node */
+ rbconn = kmem_cache_alloc(conncount_rb_cachep, GFP_ATOMIC);
+ if (rbconn == NULL)
+ return 0;
+
+ conn = kmem_cache_alloc(conncount_conn_cachep, GFP_ATOMIC);
+ if (conn == NULL) {
+ kmem_cache_free(conncount_rb_cachep, rbconn);
+ return 0;
+ }
+
+ conn->tuple = *tuple;
+ memcpy(rbconn->key, key, sizeof(u32) * keylen);
+
+ INIT_HLIST_HEAD(&rbconn->hhead);
+ hlist_add_head(&conn->node, &rbconn->hhead);
+
+ rb_link_node(&rbconn->node, parent, rbnode);
+ rb_insert_color(&rbconn->node, root);
+ return 1;
+}
+
+unsigned int nf_conncount_count(struct net *net,
+ struct nf_conncount_data *data,
+ const u32 *key,
+ unsigned int family,
+ const struct nf_conntrack_tuple *tuple,
+ const struct nf_conntrack_zone *zone)
+{
+ struct rb_root *root;
+ int count;
+ u32 hash;
+
+ hash = jhash2(key, data->keylen, conncount_rnd) % CONNCOUNT_SLOTS;
+ root = &data->root[hash];
+
+ spin_lock_bh(&nf_conncount_locks[hash % CONNCOUNT_LOCK_SLOTS]);
+
+ count = count_tree(net, root, key, data->keylen, family, tuple, zone);
+
+ spin_unlock_bh(&nf_conncount_locks[hash % CONNCOUNT_LOCK_SLOTS]);
+
+ return count;
+}
+EXPORT_SYMBOL_GPL(nf_conncount_count);
+
+struct nf_conncount_data *nf_conncount_init(struct net *net, unsigned int family,
+ unsigned int keylen)
+{
+ struct nf_conncount_data *data;
+ int ret, i;
+
+ if (keylen % sizeof(u32) ||
+ keylen / sizeof(u32) > MAX_KEYLEN ||
+ keylen == 0)
+ return ERR_PTR(-EINVAL);
+
+ net_get_random_once(&conncount_rnd, sizeof(conncount_rnd));
+
+ data = kmalloc(sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return ERR_PTR(-ENOMEM);
+
+ ret = nf_ct_netns_get(net, family);
+ if (ret < 0) {
+ kfree(data);
+ return ERR_PTR(ret);
+ }
+
+ for (i = 0; i < ARRAY_SIZE(data->root); ++i)
+ data->root[i] = RB_ROOT;
+
+ data->keylen = keylen / sizeof(u32);
+
+ return data;
+}
+EXPORT_SYMBOL_GPL(nf_conncount_init);
+
+static void destroy_tree(struct rb_root *r)
+{
+ struct nf_conncount_tuple *conn;
+ struct nf_conncount_rb *rbconn;
+ struct hlist_node *n;
+ struct rb_node *node;
+
+ while ((node = rb_first(r)) != NULL) {
+ rbconn = rb_entry(node, struct nf_conncount_rb, node);
+
+ rb_erase(node, r);
+
+ hlist_for_each_entry_safe(conn, n, &rbconn->hhead, node)
+ kmem_cache_free(conncount_conn_cachep, conn);
+
+ kmem_cache_free(conncount_rb_cachep, rbconn);
+ }
+}
+
+void nf_conncount_destroy(struct net *net, unsigned int family,
+ struct nf_conncount_data *data)
+{
+ unsigned int i;
+
+ nf_ct_netns_put(net, family);
+
+ for (i = 0; i < ARRAY_SIZE(data->root); ++i)
+ destroy_tree(&data->root[i]);
+
+ kfree(data);
+}
+EXPORT_SYMBOL_GPL(nf_conncount_destroy);
+
+static int __init nf_conncount_modinit(void)
+{
+ int i;
+
+ BUILD_BUG_ON(CONNCOUNT_LOCK_SLOTS > CONNCOUNT_SLOTS);
+ BUILD_BUG_ON((CONNCOUNT_SLOTS % CONNCOUNT_LOCK_SLOTS) != 0);
+
+ for (i = 0; i < CONNCOUNT_LOCK_SLOTS; ++i)
+ spin_lock_init(&nf_conncount_locks[i]);
+
+ conncount_conn_cachep = kmem_cache_create("nf_conncount_tuple",
+ sizeof(struct nf_conncount_tuple),
+ 0, 0, NULL);
+ if (!conncount_conn_cachep)
+ return -ENOMEM;
+
+ conncount_rb_cachep = kmem_cache_create("nf_conncount_rb",
+ sizeof(struct nf_conncount_rb),
+ 0, 0, NULL);
+ if (!conncount_rb_cachep) {
+ kmem_cache_destroy(conncount_conn_cachep);
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+static void __exit nf_conncount_modexit(void)
+{
+ kmem_cache_destroy(conncount_conn_cachep);
+ kmem_cache_destroy(conncount_rb_cachep);
+}
+
+module_init(nf_conncount_modinit);
+module_exit(nf_conncount_modexit);
+MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
+MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
+MODULE_DESCRIPTION("netfilter: count number of connections matching a key");
+MODULE_LICENSE("GPL");
