2 * netfilter module to limit the number of parallel tcp
3 * connections per IP address.
4 * (c) 2000 Gerd Knorr <kraxel@bytesex.org>
5 * Nov 2002: Martin Bene <martin.bene@icomedias.com>:
6 * only ignore TIME_WAIT or gone connections
7 * (C) CC Computer Consultants GmbH, 2007
11 * Kernel module to match connection tracking information.
12 * GPL (C) 1999 Rusty Russell (rusty@rustcorp.com.au).
14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
16 #include <linux/in6.h>
18 #include <linux/ipv6.h>
19 #include <linux/jhash.h>
20 #include <linux/slab.h>
21 #include <linux/list.h>
22 #include <linux/module.h>
23 #include <linux/random.h>
24 #include <linux/skbuff.h>
25 #include <linux/spinlock.h>
26 #include <linux/netfilter/nf_conntrack_tcp.h>
27 #include <linux/netfilter/x_tables.h>
28 #include <linux/netfilter/xt_connlimit.h>
29 #include <net/netfilter/nf_conntrack.h>
30 #include <net/netfilter/nf_conntrack_core.h>
31 #include <net/netfilter/nf_conntrack_tuple.h>
32 #include <net/netfilter/nf_conntrack_zones.h>
34 /* we will save the tuples of all connections we care about */
35 struct xt_connlimit_conn
{
36 struct hlist_node node
;
37 struct nf_conntrack_tuple tuple
;
38 union nf_inet_addr addr
;
41 struct xt_connlimit_data
{
42 struct hlist_head iphash
[256];
46 static u_int32_t connlimit_rnd __read_mostly
;
48 static inline unsigned int connlimit_iphash(__be32 addr
)
50 return jhash_1word((__force __u32
)addr
, connlimit_rnd
) & 0xFF;
53 static inline unsigned int
54 connlimit_iphash6(const union nf_inet_addr
*addr
,
55 const union nf_inet_addr
*mask
)
57 union nf_inet_addr res
;
60 for (i
= 0; i
< ARRAY_SIZE(addr
->ip6
); ++i
)
61 res
.ip6
[i
] = addr
->ip6
[i
] & mask
->ip6
[i
];
63 return jhash2((u32
*)res
.ip6
, ARRAY_SIZE(res
.ip6
), connlimit_rnd
) & 0xFF;
66 static inline bool already_closed(const struct nf_conn
*conn
)
68 if (nf_ct_protonum(conn
) == IPPROTO_TCP
)
69 return conn
->proto
.tcp
.state
== TCP_CONNTRACK_TIME_WAIT
||
70 conn
->proto
.tcp
.state
== TCP_CONNTRACK_CLOSE
;
75 static inline unsigned int
76 same_source_net(const union nf_inet_addr
*addr
,
77 const union nf_inet_addr
*mask
,
78 const union nf_inet_addr
*u3
, u_int8_t family
)
80 if (family
== NFPROTO_IPV4
) {
81 return (addr
->ip
& mask
->ip
) == (u3
->ip
& mask
->ip
);
83 union nf_inet_addr lh
, rh
;
86 for (i
= 0; i
< ARRAY_SIZE(addr
->ip6
); ++i
) {
87 lh
.ip6
[i
] = addr
->ip6
[i
] & mask
->ip6
[i
];
88 rh
.ip6
[i
] = u3
->ip6
[i
] & mask
->ip6
[i
];
91 return memcmp(&lh
.ip6
, &rh
.ip6
, sizeof(lh
.ip6
)) == 0;
95 static int count_them(struct net
*net
,
96 struct xt_connlimit_data
*data
,
97 const struct nf_conntrack_tuple
*tuple
,
98 const union nf_inet_addr
*addr
,
99 const union nf_inet_addr
*mask
,
102 const struct nf_conntrack_tuple_hash
*found
;
103 struct xt_connlimit_conn
*conn
;
104 struct hlist_node
*pos
, *n
;
105 struct nf_conn
*found_ct
;
106 struct hlist_head
*hash
;
110 if (family
== NFPROTO_IPV6
)
111 hash
= &data
->iphash
[connlimit_iphash6(addr
, mask
)];
113 hash
= &data
->iphash
[connlimit_iphash(addr
->ip
& mask
->ip
)];
117 /* check the saved connections */
118 hlist_for_each_entry_safe(conn
, pos
, n
, hash
, node
) {
119 found
= nf_conntrack_find_get(net
, NF_CT_DEFAULT_ZONE
,
124 found_ct
= nf_ct_tuplehash_to_ctrack(found
);
126 if (found_ct
!= NULL
&&
127 nf_ct_tuple_equal(&conn
->tuple
, tuple
) &&
128 !already_closed(found_ct
))
130 * Just to be sure we have it only once in the list.
131 * We should not see tuples twice unless someone hooks
132 * this into a table without "-p tcp --syn".
137 /* this one is gone */
138 hlist_del(&conn
->node
);
143 if (already_closed(found_ct
)) {
145 * we do not care about connections which are
146 * closed already -> ditch it
149 hlist_del(&conn
->node
);
154 if (same_source_net(addr
, mask
, &conn
->addr
, family
))
155 /* same source network -> be counted! */
163 /* save the new connection in our list */
164 conn
= kmalloc(sizeof(*conn
), GFP_ATOMIC
);
167 conn
->tuple
= *tuple
;
169 hlist_add_head(&conn
->node
, hash
);
177 connlimit_mt(const struct sk_buff
*skb
, struct xt_action_param
*par
)
179 struct net
*net
= dev_net(par
->in
? par
->in
: par
->out
);
180 const struct xt_connlimit_info
*info
= par
->matchinfo
;
181 union nf_inet_addr addr
;
182 struct nf_conntrack_tuple tuple
;
183 const struct nf_conntrack_tuple
*tuple_ptr
= &tuple
;
184 enum ip_conntrack_info ctinfo
;
185 const struct nf_conn
*ct
;
188 ct
= nf_ct_get(skb
, &ctinfo
);
190 tuple_ptr
= &ct
->tuplehash
[IP_CT_DIR_ORIGINAL
].tuple
;
191 else if (!nf_ct_get_tuplepr(skb
, skb_network_offset(skb
),
192 par
->family
, &tuple
))
195 if (par
->family
== NFPROTO_IPV6
) {
196 const struct ipv6hdr
*iph
= ipv6_hdr(skb
);
197 memcpy(&addr
.ip6
, (info
->flags
& XT_CONNLIMIT_DADDR
) ?
198 &iph
->daddr
: &iph
->saddr
, sizeof(addr
.ip6
));
200 const struct iphdr
*iph
= ip_hdr(skb
);
201 addr
.ip
= (info
->flags
& XT_CONNLIMIT_DADDR
) ?
202 iph
->daddr
: iph
->saddr
;
205 spin_lock_bh(&info
->data
->lock
);
206 connections
= count_them(net
, info
->data
, tuple_ptr
, &addr
,
207 &info
->mask
, par
->family
);
208 spin_unlock_bh(&info
->data
->lock
);
211 /* kmalloc failed, drop it entirely */
214 return (connections
> info
->limit
) ^
215 !!(info
->flags
& XT_CONNLIMIT_INVERT
);
222 static int connlimit_mt_check(const struct xt_mtchk_param
*par
)
224 struct xt_connlimit_info
*info
= par
->matchinfo
;
228 if (unlikely(!connlimit_rnd
)) {
232 get_random_bytes(&rand
, sizeof(rand
));
234 cmpxchg(&connlimit_rnd
, 0, rand
);
236 ret
= nf_ct_l3proto_try_module_get(par
->family
);
238 pr_info("cannot load conntrack support for "
239 "address family %u\n", par
->family
);
243 /* init private data */
244 info
->data
= kmalloc(sizeof(struct xt_connlimit_data
), GFP_KERNEL
);
245 if (info
->data
== NULL
) {
246 nf_ct_l3proto_module_put(par
->family
);
250 spin_lock_init(&info
->data
->lock
);
251 for (i
= 0; i
< ARRAY_SIZE(info
->data
->iphash
); ++i
)
252 INIT_HLIST_HEAD(&info
->data
->iphash
[i
]);
257 static void connlimit_mt_destroy(const struct xt_mtdtor_param
*par
)
259 const struct xt_connlimit_info
*info
= par
->matchinfo
;
260 struct xt_connlimit_conn
*conn
;
261 struct hlist_node
*pos
, *n
;
262 struct hlist_head
*hash
= info
->data
->iphash
;
265 nf_ct_l3proto_module_put(par
->family
);
267 for (i
= 0; i
< ARRAY_SIZE(info
->data
->iphash
); ++i
) {
268 hlist_for_each_entry_safe(conn
, pos
, n
, &hash
[i
], node
) {
269 hlist_del(&conn
->node
);
277 static struct xt_match connlimit_mt_reg __read_mostly
= {
280 .family
= NFPROTO_UNSPEC
,
281 .checkentry
= connlimit_mt_check
,
282 .match
= connlimit_mt
,
283 .matchsize
= sizeof(struct xt_connlimit_info
),
284 .destroy
= connlimit_mt_destroy
,
288 static int __init
connlimit_mt_init(void)
290 return xt_register_match(&connlimit_mt_reg
);
293 static void __exit
connlimit_mt_exit(void)
295 xt_unregister_match(&connlimit_mt_reg
);
298 module_init(connlimit_mt_init
);
299 module_exit(connlimit_mt_exit
);
300 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
301 MODULE_DESCRIPTION("Xtables: Number of connections matching");
302 MODULE_LICENSE("GPL");
303 MODULE_ALIAS("ipt_connlimit");
304 MODULE_ALIAS("ip6t_connlimit");