--- /dev/null
+/*
+ * 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
+ * (C) CC Computer Consultants GmbH, 2007
+ *
+ * based on ...
+ *
+ * Kernel module to match connection tracking information.
+ * GPL (C) 1999 Rusty Russell (rusty@rustcorp.com.au).
+ */
+#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 <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>
+#include <net/netfilter/nf_conntrack_zones.h>
+
+#define CONNLIMIT_SLOTS 256U
+
+#ifdef CONFIG_LOCKDEP
+#define CONNLIMIT_LOCK_SLOTS 8U
+#else
+#define CONNLIMIT_LOCK_SLOTS 256U
+#endif
+
+#define CONNLIMIT_GC_MAX_NODES 8
+
+/* we will save the tuples of all connections we care about */
+struct xt_connlimit_conn {
+ struct hlist_node node;
+ struct nf_conntrack_tuple tuple;
+ union nf_inet_addr addr;
+};
+
+struct xt_connlimit_rb {
+ struct rb_node node;
+ struct hlist_head hhead; /* connections/hosts in same subnet */
+ union nf_inet_addr addr; /* search key */
+};
+
+static spinlock_t xt_connlimit_locks[CONNLIMIT_LOCK_SLOTS] __cacheline_aligned_in_smp;
+
+struct xt_connlimit_data {
+ struct rb_root climit_root4[CONNLIMIT_SLOTS];
+ struct rb_root climit_root6[CONNLIMIT_SLOTS];
+};
+
+static u_int32_t connlimit_rnd __read_mostly;
+static struct kmem_cache *connlimit_rb_cachep __read_mostly;
+static struct kmem_cache *connlimit_conn_cachep __read_mostly;
+
+static inline unsigned int connlimit_iphash(__be32 addr)
+{
+ return jhash_1word((__force __u32)addr,
+ connlimit_rnd) % CONNLIMIT_SLOTS;
+}
+
+static inline unsigned int
+connlimit_iphash6(const union nf_inet_addr *addr,
+ const union nf_inet_addr *mask)
+{
+ union nf_inet_addr res;
+ unsigned int i;
+
+ 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) % CONNLIMIT_SLOTS;
+}
+
+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
+same_source_net(const union nf_inet_addr *addr,
+ const union nf_inet_addr *mask,
+ const union nf_inet_addr *u3, u_int8_t family)
+{
+ if (family == NFPROTO_IPV4) {
+ return ntohl(addr->ip & mask->ip) -
+ ntohl(u3->ip & mask->ip);
+ } else {
+ union nf_inet_addr 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));
+ }
+}
+
+static bool add_hlist(struct hlist_head *head,
+ const struct nf_conntrack_tuple *tuple,
+ const union nf_inet_addr *addr)
+{
+ struct xt_connlimit_conn *conn;
+
+ conn = kmem_cache_alloc(connlimit_conn_cachep, GFP_ATOMIC);
+ if (conn == NULL)
+ return false;
+ conn->tuple = *tuple;
+ conn->addr = *addr;
+ 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,
+ u16 zone,
+ bool *addit)
+{
+ const struct nf_conntrack_tuple_hash *found;
+ struct xt_connlimit_conn *conn;
+ struct hlist_node *n;
+ struct nf_conn *found_ct;
+ unsigned int length = 0;
+
+ *addit = true;
+ rcu_read_lock();
+
+ /* 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(connlimit_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(connlimit_conn_cachep, conn);
+ continue;
+ }
+
+ nf_ct_put(found_ct);
+ length++;
+ }
+
+ rcu_read_unlock();
+
+ return length;
+}
+
+static void tree_nodes_free(struct rb_root *root,
+ struct xt_connlimit_rb *gc_nodes[],
+ unsigned int gc_count)
+{
+ struct xt_connlimit_rb *rbconn;
+
+ while (gc_count) {
+ rbconn = gc_nodes[--gc_count];
+ rb_erase(&rbconn->node, root);
+ kmem_cache_free(connlimit_rb_cachep, rbconn);
+ }
+}
+
+static unsigned int
+count_tree(struct net *net, struct rb_root *root,
+ const struct nf_conntrack_tuple *tuple,
+ const union nf_inet_addr *addr, const union nf_inet_addr *mask,
+ u8 family, u16 zone)
+{
+ struct xt_connlimit_rb *gc_nodes[CONNLIMIT_GC_MAX_NODES];
+ struct rb_node **rbnode, *parent;
+ struct xt_connlimit_rb *rbconn;
+ struct xt_connlimit_conn *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 = container_of(*rbnode, struct xt_connlimit_rb, node);
+
+ parent = *rbnode;
+ diff = same_source_net(addr, mask, &rbconn->addr, family);
+ 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, addr))
+ 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(connlimit_rb_cachep, GFP_ATOMIC);
+ if (rbconn == NULL)
+ return 0;
+
+ conn = kmem_cache_alloc(connlimit_conn_cachep, GFP_ATOMIC);
+ if (conn == NULL) {
+ kmem_cache_free(connlimit_rb_cachep, rbconn);
+ return 0;
+ }
+
+ conn->tuple = *tuple;
+ conn->addr = *addr;
+ rbconn->addr = *addr;
+
+ 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;
+}
+
+static int count_them(struct net *net,
+ struct xt_connlimit_data *data,
+ const struct nf_conntrack_tuple *tuple,
+ const union nf_inet_addr *addr,
+ const union nf_inet_addr *mask,
+ u_int8_t family, u16 zone)
+{
+ struct rb_root *root;
+ int count;
+ u32 hash;
+
+ if (family == NFPROTO_IPV6) {
+ hash = connlimit_iphash6(addr, mask);
+ root = &data->climit_root6[hash];
+ } else {
+ hash = connlimit_iphash(addr->ip & mask->ip);
+ root = &data->climit_root4[hash];
+ }
+
+ spin_lock_bh(&xt_connlimit_locks[hash % CONNLIMIT_LOCK_SLOTS]);
+
+ count = count_tree(net, root, tuple, addr, mask, family, zone);
+
+ spin_unlock_bh(&xt_connlimit_locks[hash % CONNLIMIT_LOCK_SLOTS]);
+
+ return count;
+}
+
+static bool
+connlimit_mt(const struct sk_buff *skb, struct xt_action_param *par)
+{
+ struct net *net = dev_net(par->in ? par->in : par->out);
+ const struct xt_connlimit_info *info = par->matchinfo;
+ union nf_inet_addr addr;
+ struct nf_conntrack_tuple tuple;
+ const struct nf_conntrack_tuple *tuple_ptr = &tuple;
+ enum ip_conntrack_info ctinfo;
+ const struct nf_conn *ct;
+ unsigned int connections;
+ u16 zone = NF_CT_DEFAULT_ZONE;
+
+ ct = nf_ct_get(skb, &ctinfo);
+ if (ct != NULL) {
+ tuple_ptr = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
+ zone = nf_ct_zone(ct);
+ } else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb),
+ par->family, &tuple)) {
+ goto hotdrop;
+ }
+
+ if (par->family == NFPROTO_IPV6) {
+ const struct ipv6hdr *iph = ipv6_hdr(skb);
+ memcpy(&addr.ip6, (info->flags & XT_CONNLIMIT_DADDR) ?
+ &iph->daddr : &iph->saddr, sizeof(addr.ip6));
+ } else {
+ const struct iphdr *iph = ip_hdr(skb);
+ addr.ip = (info->flags & XT_CONNLIMIT_DADDR) ?
+ iph->daddr : iph->saddr;
+ }
+
+ connections = count_them(net, info->data, tuple_ptr, &addr,
+ &info->mask, par->family, zone);
+ if (connections == 0)
+ /* kmalloc failed, drop it entirely */
+ goto hotdrop;
+
+ return (connections > info->limit) ^
+ !!(info->flags & XT_CONNLIMIT_INVERT);
+
+ hotdrop:
+ par->hotdrop = true;
+ return false;
+}
+
+static int connlimit_mt_check(const struct xt_mtchk_param *par)
+{
+ struct xt_connlimit_info *info = par->matchinfo;
+ unsigned int i;
+ int ret;
+
+ if (unlikely(!connlimit_rnd)) {
+ u_int32_t rand;
+
+ do {
+ get_random_bytes(&rand, sizeof(rand));
+ } while (!rand);
+ cmpxchg(&connlimit_rnd, 0, rand);
+ }
+ ret = nf_ct_l3proto_try_module_get(par->family);
+ if (ret < 0) {
+ pr_info("cannot load conntrack support for "
+ "address family %u\n", par->family);
+ return ret;
+ }
+
+ /* init private data */
+ info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL);
+ if (info->data == NULL) {
+ nf_ct_l3proto_module_put(par->family);
+ return -ENOMEM;
+ }
+
+ for (i = 0; i < ARRAY_SIZE(info->data->climit_root4); ++i)
+ info->data->climit_root4[i] = RB_ROOT;
+ for (i = 0; i < ARRAY_SIZE(info->data->climit_root6); ++i)
+ info->data->climit_root6[i] = RB_ROOT;
+
+ return 0;
+}
+
+static void destroy_tree(struct rb_root *r)
+{
+ struct xt_connlimit_conn *conn;
+ struct xt_connlimit_rb *rbconn;
+ struct hlist_node *n;
+ struct rb_node *node;
+
+ while ((node = rb_first(r)) != NULL) {
+ rbconn = container_of(node, struct xt_connlimit_rb, node);
+
+ rb_erase(node, r);
+
+ hlist_for_each_entry_safe(conn, n, &rbconn->hhead, node)
+ kmem_cache_free(connlimit_conn_cachep, conn);
+
+ kmem_cache_free(connlimit_rb_cachep, rbconn);
+ }
+}
+
+static void connlimit_mt_destroy(const struct xt_mtdtor_param *par)
+{
+ const struct xt_connlimit_info *info = par->matchinfo;
+ unsigned int i;
+
+ nf_ct_l3proto_module_put(par->family);
+
+ for (i = 0; i < ARRAY_SIZE(info->data->climit_root4); ++i)
+ destroy_tree(&info->data->climit_root4[i]);
+ for (i = 0; i < ARRAY_SIZE(info->data->climit_root6); ++i)
+ destroy_tree(&info->data->climit_root6[i]);
+
+ kfree(info->data);
+}
+
+static struct xt_match connlimit_mt_reg __read_mostly = {
+ .name = "connlimit",
+ .revision = 1,
+ .family = NFPROTO_UNSPEC,
+ .checkentry = connlimit_mt_check,
+ .match = connlimit_mt,
+ .matchsize = sizeof(struct xt_connlimit_info),
+ .destroy = connlimit_mt_destroy,
+ .me = THIS_MODULE,
+};
+
+static int __init connlimit_mt_init(void)
+{
+ int ret, i;
+
+ BUILD_BUG_ON(CONNLIMIT_LOCK_SLOTS > CONNLIMIT_SLOTS);
+ BUILD_BUG_ON((CONNLIMIT_SLOTS % CONNLIMIT_LOCK_SLOTS) != 0);
+
+ for (i = 0; i < CONNLIMIT_LOCK_SLOTS; ++i)
+ spin_lock_init(&xt_connlimit_locks[i]);
+
+ connlimit_conn_cachep = kmem_cache_create("xt_connlimit_conn",
+ sizeof(struct xt_connlimit_conn),
+ 0, 0, NULL);
+ if (!connlimit_conn_cachep)
+ return -ENOMEM;
+
+ connlimit_rb_cachep = kmem_cache_create("xt_connlimit_rb",
+ sizeof(struct xt_connlimit_rb),
+ 0, 0, NULL);
+ if (!connlimit_rb_cachep) {
+ kmem_cache_destroy(connlimit_conn_cachep);
+ return -ENOMEM;
+ }
+ ret = xt_register_match(&connlimit_mt_reg);
+ if (ret != 0) {
+ kmem_cache_destroy(connlimit_conn_cachep);
+ kmem_cache_destroy(connlimit_rb_cachep);
+ }
+ return ret;
+}
+
+static void __exit connlimit_mt_exit(void)
+{
+ xt_unregister_match(&connlimit_mt_reg);
+ kmem_cache_destroy(connlimit_conn_cachep);
+ kmem_cache_destroy(connlimit_rb_cachep);
+}
+
+module_init(connlimit_mt_init);
+module_exit(connlimit_mt_exit);
+MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
+MODULE_DESCRIPTION("Xtables: Number of connections matching");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("ipt_connlimit");
+MODULE_ALIAS("ip6t_connlimit");
Code Review / kvmfornfv.git / blobdiff