[NETFILTER]: x_tables: add connlimit match
ipt_connlimit has been sitting in POM-NG for a long time. Here is a new shiny xt_connlimit with: * xtables'ified * will request the layer3 module (previously it hotdropped every packet when it was not loaded) * fixed: there was a deadlock in case of an OOM condition * support for any layer4 protocol (e.g. UDP/SCTP) * using jhash, as suggested by Eric Dumazet * ipv6 support Signed-off-by: Jan Engelhardt <jengelh@gmx.de> Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jan Engelhardt
David S. Miller
parent
a887c1c148
commit
370786f9cf
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@ -0,0 +1,17 @@
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#ifndef _XT_CONNLIMIT_H
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#define _XT_CONNLIMIT_H
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struct xt_connlimit_data;
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struct xt_connlimit_info {
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union {
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u_int32_t v4_mask;
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u_int32_t v6_mask[4];
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};
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unsigned int limit, inverse;
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/* this needs to be at the end */
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struct xt_connlimit_data *data __attribute__((aligned(8)));
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};
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#endif /* _XT_CONNLIMIT_H */
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@ -423,6 +423,13 @@ config NETFILTER_XT_MATCH_CONNBYTES
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If you want to compile it as a module, say M here and read
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<file:Documentation/kbuild/modules.txt>. If unsure, say `N'.
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config NETFILTER_XT_MATCH_CONNLIMIT
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tristate '"connlimit" match support"'
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depends on NETFILTER_XTABLES
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---help---
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This match allows you to match against the number of parallel
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connections to a server per client IP address (or address block).
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config NETFILTER_XT_MATCH_CONNMARK
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tristate '"connmark" connection mark match support'
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depends on NETFILTER_XTABLES
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@ -52,6 +52,7 @@ obj-$(CONFIG_NETFILTER_XT_TARGET_CONNSECMARK) += xt_CONNSECMARK.o
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# matches
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obj-$(CONFIG_NETFILTER_XT_MATCH_COMMENT) += xt_comment.o
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obj-$(CONFIG_NETFILTER_XT_MATCH_CONNBYTES) += xt_connbytes.o
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obj-$(CONFIG_NETFILTER_XT_MATCH_CONNLIMIT) += xt_connlimit.o
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obj-$(CONFIG_NETFILTER_XT_MATCH_CONNMARK) += xt_connmark.o
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obj-$(CONFIG_NETFILTER_XT_MATCH_CONNTRACK) += xt_conntrack.o
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obj-$(CONFIG_NETFILTER_XT_MATCH_DCCP) += xt_dccp.o
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@ -0,0 +1,313 @@
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/*
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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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* Copyright © Jan Engelhardt <jengelh@gmx.de>, 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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#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/list.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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/* we will save the tuples of all connections we care about */
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struct xt_connlimit_conn {
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struct list_head list;
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struct nf_conntrack_tuple tuple;
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};
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struct xt_connlimit_data {
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struct list_head iphash[256];
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spinlock_t lock;
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};
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static u_int32_t connlimit_rnd;
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static bool connlimit_rnd_inited;
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static inline unsigned int connlimit_iphash(u_int32_t addr)
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{
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if (unlikely(!connlimit_rnd_inited)) {
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get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd));
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connlimit_rnd_inited = true;
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}
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return jhash_1word(addr, connlimit_rnd) & 0xFF;
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}
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static inline unsigned int
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connlimit_iphash6(const union nf_conntrack_address *addr,
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const union nf_conntrack_address *mask)
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{
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union nf_conntrack_address res;
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unsigned int i;
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if (unlikely(!connlimit_rnd_inited)) {
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get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd));
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connlimit_rnd_inited = true;
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}
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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(res.ip6, ARRAY_SIZE(res.ip6), connlimit_rnd) & 0xFF;
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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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u_int16_t proto = conn->tuplehash[0].tuple.dst.protonum;
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if (proto == IPPROTO_TCP)
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return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT;
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else
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return 0;
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}
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static inline unsigned int
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same_source_net(const union nf_conntrack_address *addr,
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const union nf_conntrack_address *mask,
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const union nf_conntrack_address *u3, unsigned int family)
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{
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if (family == AF_INET) {
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return (addr->ip & mask->ip) == (u3->ip & mask->ip);
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} else {
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union nf_conntrack_address 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)) == 0;
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}
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}
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static int count_them(struct xt_connlimit_data *data,
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const struct nf_conntrack_tuple *tuple,
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const union nf_conntrack_address *addr,
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const union nf_conntrack_address *mask,
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const struct xt_match *match)
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{
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struct nf_conntrack_tuple_hash *found;
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struct xt_connlimit_conn *conn;
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struct xt_connlimit_conn *tmp;
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struct nf_conn *found_ct;
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struct list_head *hash;
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bool addit = true;
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int matches = 0;
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if (match->family == AF_INET6)
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hash = &data->iphash[connlimit_iphash6(addr, mask)];
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else
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hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)];
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read_lock_bh(&nf_conntrack_lock);
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/* check the saved connections */
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list_for_each_entry_safe(conn, tmp, hash, list) {
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found = __nf_conntrack_find(&conn->tuple, NULL);
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found_ct = NULL;
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if (found != NULL)
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found_ct = nf_ct_tuplehash_to_ctrack(found);
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if (found_ct != NULL &&
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nf_ct_tuple_equal(&conn->tuple, tuple) &&
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!already_closed(found_ct))
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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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if (found == NULL) {
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/* this one is gone */
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list_del(&conn->list);
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kfree(conn);
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continue;
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}
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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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list_del(&conn->list);
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kfree(conn);
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continue;
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}
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if (same_source_net(addr, mask, &conn->tuple.src.u3,
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match->family))
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/* same source network -> be counted! */
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++matches;
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}
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read_unlock_bh(&nf_conntrack_lock);
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if (addit) {
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/* save the new connection in our list */
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conn = kzalloc(sizeof(*conn), GFP_ATOMIC);
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if (conn == NULL)
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return -ENOMEM;
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conn->tuple = *tuple;
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list_add(&conn->list, hash);
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++matches;
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}
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return matches;
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}
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static bool connlimit_match(const struct sk_buff *skb,
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const struct net_device *in,
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const struct net_device *out,
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const struct xt_match *match,
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const void *matchinfo, int offset,
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unsigned int protoff, bool *hotdrop)
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{
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const struct xt_connlimit_info *info = matchinfo;
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union nf_conntrack_address addr, mask;
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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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enum ip_conntrack_info ctinfo;
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const struct nf_conn *ct;
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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[0].tuple;
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else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb),
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match->family, &tuple))
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goto hotdrop;
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if (match->family == AF_INET6) {
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const struct ipv6hdr *iph = ipv6_hdr(skb);
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memcpy(&addr.ip6, &iph->saddr, sizeof(iph->saddr));
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memcpy(&mask.ip6, info->v6_mask, sizeof(info->v6_mask));
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} else {
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const struct iphdr *iph = ip_hdr(skb);
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addr.ip = iph->saddr;
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mask.ip = info->v4_mask;
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}
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spin_lock_bh(&info->data->lock);
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connections = count_them(info->data, tuple_ptr, &addr, &mask, match);
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spin_unlock_bh(&info->data->lock);
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if (connections < 0) {
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/* kmalloc failed, drop it entirely */
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*hotdrop = true;
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return false;
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}
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return (connections > info->limit) ^ info->inverse;
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hotdrop:
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*hotdrop = true;
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return false;
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}
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static bool connlimit_check(const char *tablename, const void *ip,
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const struct xt_match *match, void *matchinfo,
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unsigned int hook_mask)
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{
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struct xt_connlimit_info *info = matchinfo;
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unsigned int i;
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if (nf_ct_l3proto_try_module_get(match->family) < 0) {
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printk(KERN_WARNING "cannot load conntrack support for "
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"address family %u\n", match->family);
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return false;
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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(match->family);
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return false;
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}
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spin_lock_init(&info->data->lock);
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for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i)
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INIT_LIST_HEAD(&info->data->iphash[i]);
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return true;
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}
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static void connlimit_destroy(const struct xt_match *match, void *matchinfo)
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{
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struct xt_connlimit_info *info = matchinfo;
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struct xt_connlimit_conn *conn;
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struct xt_connlimit_conn *tmp;
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struct list_head *hash = info->data->iphash;
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unsigned int i;
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nf_ct_l3proto_module_put(match->family);
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for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) {
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list_for_each_entry_safe(conn, tmp, &hash[i], list) {
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list_del(&conn->list);
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kfree(conn);
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}
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}
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kfree(info->data);
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}
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static struct xt_match connlimit_reg[] __read_mostly = {
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{
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.name = "connlimit",
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.family = AF_INET,
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.checkentry = connlimit_check,
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.match = connlimit_match,
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.matchsize = sizeof(struct xt_connlimit_info),
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.destroy = connlimit_destroy,
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.me = THIS_MODULE,
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},
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{
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.name = "connlimit",
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.family = AF_INET6,
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.checkentry = connlimit_check,
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.match = connlimit_match,
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.matchsize = sizeof(struct xt_connlimit_info),
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.destroy = connlimit_destroy,
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.me = THIS_MODULE,
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},
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};
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static int __init xt_connlimit_init(void)
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{
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return xt_register_matches(connlimit_reg, ARRAY_SIZE(connlimit_reg));
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}
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static void __exit xt_connlimit_exit(void)
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{
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xt_unregister_matches(connlimit_reg, ARRAY_SIZE(connlimit_reg));
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}
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module_init(xt_connlimit_init);
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module_exit(xt_connlimit_exit);
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MODULE_AUTHOR("Jan Engelhardt <jengelh@gmx.de>");
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MODULE_DESCRIPTION("netfilter xt_connlimit match module");
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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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