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
8 * Contact: <jengelh@computergmbh.de>
12 * Kernel module to match connection tracking information.
13 * GPL (C) 1999 Rusty Russell (rusty@rustcorp.com.au).
16 #include <linux/in6.h>
18 #include <linux/ipv6.h>
19 #include <linux/jhash.h>
20 #include <linux/list.h>
21 #include <linux/module.h>
22 #include <linux/random.h>
23 #include <linux/skbuff.h>
24 #include <linux/spinlock.h>
25 #include <linux/netfilter/nf_conntrack_tcp.h>
26 #include <linux/netfilter/x_tables.h>
27 #include <linux/netfilter/xt_connlimit.h>
28 #include <net/netfilter/nf_conntrack.h>
29 #include <net/netfilter/nf_conntrack_core.h>
30 #include <net/netfilter/nf_conntrack_tuple.h>
32 /* we will save the tuples of all connections we care about */
33 struct xt_connlimit_conn
{
34 struct list_head list
;
35 struct nf_conntrack_tuple tuple
;
38 struct xt_connlimit_data
{
39 struct list_head iphash
[256];
43 static u_int32_t connlimit_rnd
;
44 static bool connlimit_rnd_inited
;
46 static inline unsigned int connlimit_iphash(__be32 addr
)
48 if (unlikely(!connlimit_rnd_inited
)) {
49 get_random_bytes(&connlimit_rnd
, sizeof(connlimit_rnd
));
50 connlimit_rnd_inited
= true;
52 return jhash_1word((__force __u32
)addr
, connlimit_rnd
) & 0xFF;
55 static inline unsigned int
56 connlimit_iphash6(const union nf_inet_addr
*addr
,
57 const union nf_inet_addr
*mask
)
59 union nf_inet_addr res
;
62 if (unlikely(!connlimit_rnd_inited
)) {
63 get_random_bytes(&connlimit_rnd
, sizeof(connlimit_rnd
));
64 connlimit_rnd_inited
= true;
67 for (i
= 0; i
< ARRAY_SIZE(addr
->ip6
); ++i
)
68 res
.ip6
[i
] = addr
->ip6
[i
] & mask
->ip6
[i
];
70 return jhash2((u32
*)res
.ip6
, ARRAY_SIZE(res
.ip6
), connlimit_rnd
) & 0xFF;
73 static inline bool already_closed(const struct nf_conn
*conn
)
75 if (nf_ct_protonum(conn
) == IPPROTO_TCP
)
76 return conn
->proto
.tcp
.state
== TCP_CONNTRACK_TIME_WAIT
||
77 conn
->proto
.tcp
.state
== TCP_CONNTRACK_CLOSE
;
82 static inline unsigned int
83 same_source_net(const union nf_inet_addr
*addr
,
84 const union nf_inet_addr
*mask
,
85 const union nf_inet_addr
*u3
, u_int8_t family
)
87 if (family
== NFPROTO_IPV4
) {
88 return (addr
->ip
& mask
->ip
) == (u3
->ip
& mask
->ip
);
90 union nf_inet_addr lh
, rh
;
93 for (i
= 0; i
< ARRAY_SIZE(addr
->ip6
); ++i
) {
94 lh
.ip6
[i
] = addr
->ip6
[i
] & mask
->ip6
[i
];
95 rh
.ip6
[i
] = u3
->ip6
[i
] & mask
->ip6
[i
];
98 return memcmp(&lh
.ip6
, &rh
.ip6
, sizeof(lh
.ip6
)) == 0;
102 static int count_them(struct xt_connlimit_data
*data
,
103 const struct nf_conntrack_tuple
*tuple
,
104 const union nf_inet_addr
*addr
,
105 const union nf_inet_addr
*mask
,
106 const struct xt_match
*match
)
108 const struct nf_conntrack_tuple_hash
*found
;
109 struct xt_connlimit_conn
*conn
;
110 struct xt_connlimit_conn
*tmp
;
111 struct nf_conn
*found_ct
;
112 struct list_head
*hash
;
117 if (match
->family
== NFPROTO_IPV6
)
118 hash
= &data
->iphash
[connlimit_iphash6(addr
, mask
)];
120 hash
= &data
->iphash
[connlimit_iphash(addr
->ip
& mask
->ip
)];
124 /* check the saved connections */
125 list_for_each_entry_safe(conn
, tmp
, hash
, list
) {
126 found
= nf_conntrack_find_get(&init_net
, &conn
->tuple
);
130 found_ct
= nf_ct_tuplehash_to_ctrack(found
);
132 if (found_ct
!= NULL
&&
133 nf_ct_tuple_equal(&conn
->tuple
, tuple
) &&
134 !already_closed(found_ct
))
136 * Just to be sure we have it only once in the list.
137 * We should not see tuples twice unless someone hooks
138 * this into a table without "-p tcp --syn".
143 /* this one is gone */
144 list_del(&conn
->list
);
149 if (already_closed(found_ct
)) {
151 * we do not care about connections which are
152 * closed already -> ditch it
155 list_del(&conn
->list
);
160 if (same_source_net(addr
, mask
, &conn
->tuple
.src
.u3
,
162 /* same source network -> be counted! */
170 /* save the new connection in our list */
171 conn
= kzalloc(sizeof(*conn
), GFP_ATOMIC
);
174 conn
->tuple
= *tuple
;
175 list_add(&conn
->list
, hash
);
183 connlimit_mt(const struct sk_buff
*skb
, const struct xt_match_param
*par
)
185 const struct xt_connlimit_info
*info
= par
->matchinfo
;
186 union nf_inet_addr addr
;
187 struct nf_conntrack_tuple tuple
;
188 const struct nf_conntrack_tuple
*tuple_ptr
= &tuple
;
189 enum ip_conntrack_info ctinfo
;
190 const struct nf_conn
*ct
;
193 ct
= nf_ct_get(skb
, &ctinfo
);
195 tuple_ptr
= &ct
->tuplehash
[0].tuple
;
196 else if (!nf_ct_get_tuplepr(skb
, skb_network_offset(skb
),
197 par
->family
, &tuple
))
200 if (par
->family
== NFPROTO_IPV6
) {
201 const struct ipv6hdr
*iph
= ipv6_hdr(skb
);
202 memcpy(&addr
.ip6
, &iph
->saddr
, sizeof(iph
->saddr
));
204 const struct iphdr
*iph
= ip_hdr(skb
);
205 addr
.ip
= iph
->saddr
;
208 spin_lock_bh(&info
->data
->lock
);
209 connections
= count_them(info
->data
, tuple_ptr
, &addr
,
210 &info
->mask
, par
->match
);
211 spin_unlock_bh(&info
->data
->lock
);
213 if (connections
< 0) {
214 /* kmalloc failed, drop it entirely */
215 *par
->hotdrop
= true;
219 return (connections
> info
->limit
) ^ info
->inverse
;
222 *par
->hotdrop
= true;
226 static bool connlimit_mt_check(const struct xt_mtchk_param
*par
)
228 struct xt_connlimit_info
*info
= par
->matchinfo
;
231 if (nf_ct_l3proto_try_module_get(par
->family
) < 0) {
232 printk(KERN_WARNING
"cannot load conntrack support for "
233 "address family %u\n", par
->family
);
237 /* init private data */
238 info
->data
= kmalloc(sizeof(struct xt_connlimit_data
), GFP_KERNEL
);
239 if (info
->data
== NULL
) {
240 nf_ct_l3proto_module_put(par
->family
);
244 spin_lock_init(&info
->data
->lock
);
245 for (i
= 0; i
< ARRAY_SIZE(info
->data
->iphash
); ++i
)
246 INIT_LIST_HEAD(&info
->data
->iphash
[i
]);
251 static void connlimit_mt_destroy(const struct xt_mtdtor_param
*par
)
253 const struct xt_connlimit_info
*info
= par
->matchinfo
;
254 struct xt_connlimit_conn
*conn
;
255 struct xt_connlimit_conn
*tmp
;
256 struct list_head
*hash
= info
->data
->iphash
;
259 nf_ct_l3proto_module_put(par
->family
);
261 for (i
= 0; i
< ARRAY_SIZE(info
->data
->iphash
); ++i
) {
262 list_for_each_entry_safe(conn
, tmp
, &hash
[i
], list
) {
263 list_del(&conn
->list
);
271 static struct xt_match connlimit_mt_reg __read_mostly
= {
274 .family
= NFPROTO_UNSPEC
,
275 .checkentry
= connlimit_mt_check
,
276 .match
= connlimit_mt
,
277 .matchsize
= sizeof(struct xt_connlimit_info
),
278 .destroy
= connlimit_mt_destroy
,
282 static int __init
connlimit_mt_init(void)
284 return xt_register_match(&connlimit_mt_reg
);
287 static void __exit
connlimit_mt_exit(void)
289 xt_unregister_match(&connlimit_mt_reg
);
292 module_init(connlimit_mt_init
);
293 module_exit(connlimit_mt_exit
);
294 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
295 MODULE_DESCRIPTION("Xtables: Number of connections matching");
296 MODULE_LICENSE("GPL");
297 MODULE_ALIAS("ipt_connlimit");
298 MODULE_ALIAS("ip6t_connlimit");