![Daniel Borkmann](/assets/img/avatar_default.png)
This patch replaces the zone id which is pushed down into functions with the actual zone object. It's a bigger one-time change, but needed for later on extending zones with a direction parameter, and thus decoupling this additional information from all call-sites. No functional changes in this patch. The default zone becomes a global const object, namely nf_ct_zone_dflt and will be returned directly in various cases, one being, when there's f.e. no zoning support. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
489 lines
12 KiB
C
489 lines
12 KiB
C
/*
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* netfilter module to limit the number of parallel tcp
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* connections per IP address.
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* (c) 2000 Gerd Knorr <kraxel@bytesex.org>
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* Nov 2002: Martin Bene <martin.bene@icomedias.com>:
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* only ignore TIME_WAIT or gone connections
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* (C) CC Computer Consultants GmbH, 2007
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*
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* based on ...
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*
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* Kernel module to match connection tracking information.
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* GPL (C) 1999 Rusty Russell (rusty@rustcorp.com.au).
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/in.h>
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#include <linux/in6.h>
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#include <linux/ip.h>
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#include <linux/ipv6.h>
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#include <linux/jhash.h>
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#include <linux/slab.h>
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#include <linux/list.h>
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#include <linux/rbtree.h>
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#include <linux/module.h>
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#include <linux/random.h>
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#include <linux/skbuff.h>
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#include <linux/spinlock.h>
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#include <linux/netfilter/nf_conntrack_tcp.h>
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#include <linux/netfilter/x_tables.h>
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#include <linux/netfilter/xt_connlimit.h>
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#include <net/netfilter/nf_conntrack.h>
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#include <net/netfilter/nf_conntrack_core.h>
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#include <net/netfilter/nf_conntrack_tuple.h>
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#include <net/netfilter/nf_conntrack_zones.h>
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#define CONNLIMIT_SLOTS 256U
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#ifdef CONFIG_LOCKDEP
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#define CONNLIMIT_LOCK_SLOTS 8U
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#else
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#define CONNLIMIT_LOCK_SLOTS 256U
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#endif
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#define CONNLIMIT_GC_MAX_NODES 8
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/* we will save the tuples of all connections we care about */
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struct xt_connlimit_conn {
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struct hlist_node node;
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struct nf_conntrack_tuple tuple;
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union nf_inet_addr addr;
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};
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struct xt_connlimit_rb {
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struct rb_node node;
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struct hlist_head hhead; /* connections/hosts in same subnet */
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union nf_inet_addr addr; /* search key */
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};
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static spinlock_t xt_connlimit_locks[CONNLIMIT_LOCK_SLOTS] __cacheline_aligned_in_smp;
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struct xt_connlimit_data {
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struct rb_root climit_root4[CONNLIMIT_SLOTS];
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struct rb_root climit_root6[CONNLIMIT_SLOTS];
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};
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static u_int32_t connlimit_rnd __read_mostly;
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static struct kmem_cache *connlimit_rb_cachep __read_mostly;
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static struct kmem_cache *connlimit_conn_cachep __read_mostly;
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static inline unsigned int connlimit_iphash(__be32 addr)
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{
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return jhash_1word((__force __u32)addr,
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connlimit_rnd) % CONNLIMIT_SLOTS;
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}
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static inline unsigned int
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connlimit_iphash6(const union nf_inet_addr *addr,
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const union nf_inet_addr *mask)
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{
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union nf_inet_addr res;
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unsigned int i;
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for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i)
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res.ip6[i] = addr->ip6[i] & mask->ip6[i];
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return jhash2((u32 *)res.ip6, ARRAY_SIZE(res.ip6),
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connlimit_rnd) % CONNLIMIT_SLOTS;
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}
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static inline bool already_closed(const struct nf_conn *conn)
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{
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if (nf_ct_protonum(conn) == IPPROTO_TCP)
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return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT ||
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conn->proto.tcp.state == TCP_CONNTRACK_CLOSE;
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else
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return 0;
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}
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static int
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same_source_net(const union nf_inet_addr *addr,
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const union nf_inet_addr *mask,
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const union nf_inet_addr *u3, u_int8_t family)
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{
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if (family == NFPROTO_IPV4) {
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return ntohl(addr->ip & mask->ip) -
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ntohl(u3->ip & mask->ip);
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} else {
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union nf_inet_addr lh, rh;
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unsigned int i;
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for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) {
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lh.ip6[i] = addr->ip6[i] & mask->ip6[i];
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rh.ip6[i] = u3->ip6[i] & mask->ip6[i];
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}
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return memcmp(&lh.ip6, &rh.ip6, sizeof(lh.ip6));
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}
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}
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static bool add_hlist(struct hlist_head *head,
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const struct nf_conntrack_tuple *tuple,
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const union nf_inet_addr *addr)
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{
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struct xt_connlimit_conn *conn;
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conn = kmem_cache_alloc(connlimit_conn_cachep, GFP_ATOMIC);
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if (conn == NULL)
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return false;
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conn->tuple = *tuple;
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conn->addr = *addr;
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hlist_add_head(&conn->node, head);
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return true;
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}
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static unsigned int check_hlist(struct net *net,
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struct hlist_head *head,
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const struct nf_conntrack_tuple *tuple,
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const struct nf_conntrack_zone *zone,
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bool *addit)
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{
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const struct nf_conntrack_tuple_hash *found;
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struct xt_connlimit_conn *conn;
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struct hlist_node *n;
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struct nf_conn *found_ct;
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unsigned int length = 0;
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*addit = true;
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rcu_read_lock();
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/* check the saved connections */
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hlist_for_each_entry_safe(conn, n, head, node) {
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found = nf_conntrack_find_get(net, zone, &conn->tuple);
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if (found == NULL) {
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hlist_del(&conn->node);
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kmem_cache_free(connlimit_conn_cachep, conn);
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continue;
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}
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found_ct = nf_ct_tuplehash_to_ctrack(found);
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if (nf_ct_tuple_equal(&conn->tuple, tuple)) {
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/*
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* Just to be sure we have it only once in the list.
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* We should not see tuples twice unless someone hooks
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* this into a table without "-p tcp --syn".
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*/
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*addit = false;
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} else if (already_closed(found_ct)) {
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/*
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* we do not care about connections which are
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* closed already -> ditch it
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*/
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nf_ct_put(found_ct);
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hlist_del(&conn->node);
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kmem_cache_free(connlimit_conn_cachep, conn);
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continue;
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}
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nf_ct_put(found_ct);
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length++;
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}
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rcu_read_unlock();
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return length;
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}
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static void tree_nodes_free(struct rb_root *root,
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struct xt_connlimit_rb *gc_nodes[],
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unsigned int gc_count)
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{
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struct xt_connlimit_rb *rbconn;
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while (gc_count) {
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rbconn = gc_nodes[--gc_count];
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rb_erase(&rbconn->node, root);
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kmem_cache_free(connlimit_rb_cachep, rbconn);
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}
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}
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static unsigned int
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count_tree(struct net *net, struct rb_root *root,
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const struct nf_conntrack_tuple *tuple,
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const union nf_inet_addr *addr, const union nf_inet_addr *mask,
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u8 family, const struct nf_conntrack_zone *zone)
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{
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struct xt_connlimit_rb *gc_nodes[CONNLIMIT_GC_MAX_NODES];
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struct rb_node **rbnode, *parent;
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struct xt_connlimit_rb *rbconn;
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struct xt_connlimit_conn *conn;
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unsigned int gc_count;
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bool no_gc = false;
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restart:
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gc_count = 0;
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parent = NULL;
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rbnode = &(root->rb_node);
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while (*rbnode) {
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int diff;
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bool addit;
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rbconn = container_of(*rbnode, struct xt_connlimit_rb, node);
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parent = *rbnode;
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diff = same_source_net(addr, mask, &rbconn->addr, family);
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if (diff < 0) {
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rbnode = &((*rbnode)->rb_left);
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} else if (diff > 0) {
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rbnode = &((*rbnode)->rb_right);
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} else {
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/* same source network -> be counted! */
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unsigned int count;
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count = check_hlist(net, &rbconn->hhead, tuple, zone, &addit);
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tree_nodes_free(root, gc_nodes, gc_count);
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if (!addit)
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return count;
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if (!add_hlist(&rbconn->hhead, tuple, addr))
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return 0; /* hotdrop */
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return count + 1;
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}
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if (no_gc || gc_count >= ARRAY_SIZE(gc_nodes))
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continue;
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/* only used for GC on hhead, retval and 'addit' ignored */
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check_hlist(net, &rbconn->hhead, tuple, zone, &addit);
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if (hlist_empty(&rbconn->hhead))
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gc_nodes[gc_count++] = rbconn;
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}
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if (gc_count) {
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no_gc = true;
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tree_nodes_free(root, gc_nodes, gc_count);
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/* tree_node_free before new allocation permits
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* allocator to re-use newly free'd object.
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*
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* This is a rare event; in most cases we will find
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* existing node to re-use. (or gc_count is 0).
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*/
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goto restart;
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}
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/* no match, need to insert new node */
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rbconn = kmem_cache_alloc(connlimit_rb_cachep, GFP_ATOMIC);
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if (rbconn == NULL)
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return 0;
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conn = kmem_cache_alloc(connlimit_conn_cachep, GFP_ATOMIC);
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if (conn == NULL) {
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kmem_cache_free(connlimit_rb_cachep, rbconn);
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return 0;
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}
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conn->tuple = *tuple;
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conn->addr = *addr;
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rbconn->addr = *addr;
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INIT_HLIST_HEAD(&rbconn->hhead);
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hlist_add_head(&conn->node, &rbconn->hhead);
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rb_link_node(&rbconn->node, parent, rbnode);
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rb_insert_color(&rbconn->node, root);
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return 1;
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}
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static int count_them(struct net *net,
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struct xt_connlimit_data *data,
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const struct nf_conntrack_tuple *tuple,
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const union nf_inet_addr *addr,
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const union nf_inet_addr *mask,
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u_int8_t family,
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const struct nf_conntrack_zone *zone)
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{
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struct rb_root *root;
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int count;
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u32 hash;
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if (family == NFPROTO_IPV6) {
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hash = connlimit_iphash6(addr, mask);
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root = &data->climit_root6[hash];
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} else {
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hash = connlimit_iphash(addr->ip & mask->ip);
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root = &data->climit_root4[hash];
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}
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spin_lock_bh(&xt_connlimit_locks[hash % CONNLIMIT_LOCK_SLOTS]);
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count = count_tree(net, root, tuple, addr, mask, family, zone);
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spin_unlock_bh(&xt_connlimit_locks[hash % CONNLIMIT_LOCK_SLOTS]);
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return count;
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}
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static bool
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connlimit_mt(const struct sk_buff *skb, struct xt_action_param *par)
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{
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struct net *net = dev_net(par->in ? par->in : par->out);
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const struct xt_connlimit_info *info = par->matchinfo;
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union nf_inet_addr addr;
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struct nf_conntrack_tuple tuple;
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const struct nf_conntrack_tuple *tuple_ptr = &tuple;
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const struct nf_conntrack_zone *zone = &nf_ct_zone_dflt;
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enum ip_conntrack_info ctinfo;
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const struct nf_conn *ct;
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unsigned int connections;
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ct = nf_ct_get(skb, &ctinfo);
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if (ct != NULL) {
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tuple_ptr = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
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zone = nf_ct_zone(ct);
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} else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb),
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par->family, &tuple)) {
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goto hotdrop;
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}
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if (par->family == NFPROTO_IPV6) {
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const struct ipv6hdr *iph = ipv6_hdr(skb);
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memcpy(&addr.ip6, (info->flags & XT_CONNLIMIT_DADDR) ?
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&iph->daddr : &iph->saddr, sizeof(addr.ip6));
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} else {
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const struct iphdr *iph = ip_hdr(skb);
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addr.ip = (info->flags & XT_CONNLIMIT_DADDR) ?
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iph->daddr : iph->saddr;
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}
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connections = count_them(net, info->data, tuple_ptr, &addr,
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&info->mask, par->family, zone);
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if (connections == 0)
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/* kmalloc failed, drop it entirely */
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goto hotdrop;
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return (connections > info->limit) ^
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!!(info->flags & XT_CONNLIMIT_INVERT);
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hotdrop:
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par->hotdrop = true;
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return false;
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}
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static int connlimit_mt_check(const struct xt_mtchk_param *par)
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{
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struct xt_connlimit_info *info = par->matchinfo;
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unsigned int i;
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int ret;
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if (unlikely(!connlimit_rnd)) {
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u_int32_t rand;
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do {
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get_random_bytes(&rand, sizeof(rand));
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} while (!rand);
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cmpxchg(&connlimit_rnd, 0, rand);
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}
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ret = nf_ct_l3proto_try_module_get(par->family);
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if (ret < 0) {
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pr_info("cannot load conntrack support for "
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"address family %u\n", par->family);
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return ret;
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}
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/* init private data */
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info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL);
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if (info->data == NULL) {
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nf_ct_l3proto_module_put(par->family);
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return -ENOMEM;
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}
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for (i = 0; i < ARRAY_SIZE(info->data->climit_root4); ++i)
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info->data->climit_root4[i] = RB_ROOT;
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for (i = 0; i < ARRAY_SIZE(info->data->climit_root6); ++i)
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info->data->climit_root6[i] = RB_ROOT;
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return 0;
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}
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static void destroy_tree(struct rb_root *r)
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{
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struct xt_connlimit_conn *conn;
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struct xt_connlimit_rb *rbconn;
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struct hlist_node *n;
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struct rb_node *node;
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while ((node = rb_first(r)) != NULL) {
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rbconn = container_of(node, struct xt_connlimit_rb, node);
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rb_erase(node, r);
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hlist_for_each_entry_safe(conn, n, &rbconn->hhead, node)
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kmem_cache_free(connlimit_conn_cachep, conn);
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kmem_cache_free(connlimit_rb_cachep, rbconn);
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}
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}
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static void connlimit_mt_destroy(const struct xt_mtdtor_param *par)
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{
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const struct xt_connlimit_info *info = par->matchinfo;
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unsigned int i;
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nf_ct_l3proto_module_put(par->family);
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for (i = 0; i < ARRAY_SIZE(info->data->climit_root4); ++i)
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destroy_tree(&info->data->climit_root4[i]);
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for (i = 0; i < ARRAY_SIZE(info->data->climit_root6); ++i)
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destroy_tree(&info->data->climit_root6[i]);
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kfree(info->data);
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}
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static struct xt_match connlimit_mt_reg __read_mostly = {
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.name = "connlimit",
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.revision = 1,
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.family = NFPROTO_UNSPEC,
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.checkentry = connlimit_mt_check,
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.match = connlimit_mt,
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.matchsize = sizeof(struct xt_connlimit_info),
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.destroy = connlimit_mt_destroy,
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.me = THIS_MODULE,
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};
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static int __init connlimit_mt_init(void)
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{
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int ret, i;
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BUILD_BUG_ON(CONNLIMIT_LOCK_SLOTS > CONNLIMIT_SLOTS);
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BUILD_BUG_ON((CONNLIMIT_SLOTS % CONNLIMIT_LOCK_SLOTS) != 0);
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for (i = 0; i < CONNLIMIT_LOCK_SLOTS; ++i)
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spin_lock_init(&xt_connlimit_locks[i]);
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connlimit_conn_cachep = kmem_cache_create("xt_connlimit_conn",
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sizeof(struct xt_connlimit_conn),
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0, 0, NULL);
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if (!connlimit_conn_cachep)
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return -ENOMEM;
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connlimit_rb_cachep = kmem_cache_create("xt_connlimit_rb",
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sizeof(struct xt_connlimit_rb),
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0, 0, NULL);
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if (!connlimit_rb_cachep) {
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kmem_cache_destroy(connlimit_conn_cachep);
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return -ENOMEM;
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}
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ret = xt_register_match(&connlimit_mt_reg);
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if (ret != 0) {
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kmem_cache_destroy(connlimit_conn_cachep);
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kmem_cache_destroy(connlimit_rb_cachep);
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}
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return ret;
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}
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static void __exit connlimit_mt_exit(void)
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{
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xt_unregister_match(&connlimit_mt_reg);
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kmem_cache_destroy(connlimit_conn_cachep);
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kmem_cache_destroy(connlimit_rb_cachep);
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}
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module_init(connlimit_mt_init);
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module_exit(connlimit_mt_exit);
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MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
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MODULE_DESCRIPTION("Xtables: Number of connections matching");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("ipt_connlimit");
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MODULE_ALIAS("ip6t_connlimit");
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