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1 /*
2  * (C) 2008-2009 Pablo Neira Ayuso <pablo@netfilter.org>
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License version 2 as
6  * published by the Free Software Foundation.
7  */
8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9 #include <linux/module.h>
10 #include <linux/skbuff.h>
11 #include <linux/jhash.h>
12 #include <linux/ip.h>
13 #include <net/ipv6.h>
14 
15 #include <linux/netfilter/x_tables.h>
16 #include <net/netfilter/nf_conntrack.h>
17 #include <linux/netfilter/xt_cluster.h>
18 
nf_ct_orig_ipv4_src(const struct nf_conn * ct)19 static inline u32 nf_ct_orig_ipv4_src(const struct nf_conn *ct)
20 {
21 	return (__force u32)ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
22 }
23 
nf_ct_orig_ipv6_src(const struct nf_conn * ct)24 static inline const u32 *nf_ct_orig_ipv6_src(const struct nf_conn *ct)
25 {
26 	return (__force u32 *)ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip6;
27 }
28 
29 static inline u_int32_t
xt_cluster_hash_ipv4(u_int32_t ip,const struct xt_cluster_match_info * info)30 xt_cluster_hash_ipv4(u_int32_t ip, const struct xt_cluster_match_info *info)
31 {
32 	return jhash_1word(ip, info->hash_seed);
33 }
34 
35 static inline u_int32_t
xt_cluster_hash_ipv6(const void * ip,const struct xt_cluster_match_info * info)36 xt_cluster_hash_ipv6(const void *ip, const struct xt_cluster_match_info *info)
37 {
38 	return jhash2(ip, NF_CT_TUPLE_L3SIZE / sizeof(__u32), info->hash_seed);
39 }
40 
41 static inline u_int32_t
xt_cluster_hash(const struct nf_conn * ct,const struct xt_cluster_match_info * info)42 xt_cluster_hash(const struct nf_conn *ct,
43 		const struct xt_cluster_match_info *info)
44 {
45 	u_int32_t hash = 0;
46 
47 	switch(nf_ct_l3num(ct)) {
48 	case AF_INET:
49 		hash = xt_cluster_hash_ipv4(nf_ct_orig_ipv4_src(ct), info);
50 		break;
51 	case AF_INET6:
52 		hash = xt_cluster_hash_ipv6(nf_ct_orig_ipv6_src(ct), info);
53 		break;
54 	default:
55 		WARN_ON(1);
56 		break;
57 	}
58 
59 	return reciprocal_scale(hash, info->total_nodes);
60 }
61 
62 static inline bool
xt_cluster_ipv6_is_multicast(const struct in6_addr * addr)63 xt_cluster_ipv6_is_multicast(const struct in6_addr *addr)
64 {
65 	__be32 st = addr->s6_addr32[0];
66 	return ((st & htonl(0xFF000000)) == htonl(0xFF000000));
67 }
68 
69 static inline bool
xt_cluster_is_multicast_addr(const struct sk_buff * skb,u_int8_t family)70 xt_cluster_is_multicast_addr(const struct sk_buff *skb, u_int8_t family)
71 {
72 	bool is_multicast = false;
73 
74 	switch(family) {
75 	case NFPROTO_IPV4:
76 		is_multicast = ipv4_is_multicast(ip_hdr(skb)->daddr);
77 		break;
78 	case NFPROTO_IPV6:
79 		is_multicast =
80 			xt_cluster_ipv6_is_multicast(&ipv6_hdr(skb)->daddr);
81 		break;
82 	default:
83 		WARN_ON(1);
84 		break;
85 	}
86 	return is_multicast;
87 }
88 
89 static bool
xt_cluster_mt(const struct sk_buff * skb,struct xt_action_param * par)90 xt_cluster_mt(const struct sk_buff *skb, struct xt_action_param *par)
91 {
92 	struct sk_buff *pskb = (struct sk_buff *)skb;
93 	const struct xt_cluster_match_info *info = par->matchinfo;
94 	const struct nf_conn *ct;
95 	enum ip_conntrack_info ctinfo;
96 	unsigned long hash;
97 
98 	/* This match assumes that all nodes see the same packets. This can be
99 	 * achieved if the switch that connects the cluster nodes support some
100 	 * sort of 'port mirroring'. However, if your switch does not support
101 	 * this, your cluster nodes can reply ARP request using a multicast MAC
102 	 * address. Thus, your switch will flood the same packets to the
103 	 * cluster nodes with the same multicast MAC address. Using a multicast
104 	 * link address is a RFC 1812 (section 3.3.2) violation, but this works
105 	 * fine in practise.
106 	 *
107 	 * Unfortunately, if you use the multicast MAC address, the link layer
108 	 * sets skbuff's pkt_type to PACKET_MULTICAST, which is not accepted
109 	 * by TCP and others for packets coming to this node. For that reason,
110 	 * this match mangles skbuff's pkt_type if it detects a packet
111 	 * addressed to a unicast address but using PACKET_MULTICAST. Yes, I
112 	 * know, matches should not alter packets, but we are doing this here
113 	 * because we would need to add a PKTTYPE target for this sole purpose.
114 	 */
115 	if (!xt_cluster_is_multicast_addr(skb, par->family) &&
116 	    skb->pkt_type == PACKET_MULTICAST) {
117 	    	pskb->pkt_type = PACKET_HOST;
118 	}
119 
120 	ct = nf_ct_get(skb, &ctinfo);
121 	if (ct == NULL)
122 		return false;
123 
124 	if (nf_ct_is_untracked(ct))
125 		return false;
126 
127 	if (ct->master)
128 		hash = xt_cluster_hash(ct->master, info);
129 	else
130 		hash = xt_cluster_hash(ct, info);
131 
132 	return !!((1 << hash) & info->node_mask) ^
133 	       !!(info->flags & XT_CLUSTER_F_INV);
134 }
135 
xt_cluster_mt_checkentry(const struct xt_mtchk_param * par)136 static int xt_cluster_mt_checkentry(const struct xt_mtchk_param *par)
137 {
138 	struct xt_cluster_match_info *info = par->matchinfo;
139 
140 	if (info->total_nodes > XT_CLUSTER_NODES_MAX) {
141 		pr_info("you have exceeded the maximum "
142 			"number of cluster nodes (%u > %u)\n",
143 			info->total_nodes, XT_CLUSTER_NODES_MAX);
144 		return -EINVAL;
145 	}
146 	if (info->node_mask >= (1ULL << info->total_nodes)) {
147 		pr_info("this node mask cannot be "
148 			"higher than the total number of nodes\n");
149 		return -EDOM;
150 	}
151 	return 0;
152 }
153 
154 static struct xt_match xt_cluster_match __read_mostly = {
155 	.name		= "cluster",
156 	.family		= NFPROTO_UNSPEC,
157 	.match		= xt_cluster_mt,
158 	.checkentry	= xt_cluster_mt_checkentry,
159 	.matchsize	= sizeof(struct xt_cluster_match_info),
160 	.me		= THIS_MODULE,
161 };
162 
xt_cluster_mt_init(void)163 static int __init xt_cluster_mt_init(void)
164 {
165 	return xt_register_match(&xt_cluster_match);
166 }
167 
xt_cluster_mt_fini(void)168 static void __exit xt_cluster_mt_fini(void)
169 {
170 	xt_unregister_match(&xt_cluster_match);
171 }
172 
173 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
174 MODULE_LICENSE("GPL");
175 MODULE_DESCRIPTION("Xtables: hash-based cluster match");
176 MODULE_ALIAS("ipt_cluster");
177 MODULE_ALIAS("ip6t_cluster");
178 module_init(xt_cluster_mt_init);
179 module_exit(xt_cluster_mt_fini);
180