1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * (C) 2008-2009 Pablo Neira Ayuso <pablo@netfilter.org>
4 */
5 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
6 #include <linux/module.h>
7 #include <linux/skbuff.h>
8 #include <linux/jhash.h>
9 #include <linux/ip.h>
10 #include <net/ipv6.h>
11
12 #include <linux/netfilter/x_tables.h>
13 #include <net/netfilter/nf_conntrack.h>
14 #include <linux/netfilter/xt_cluster.h>
15
16 static inline u32 nf_ct_orig_ipv4_src(const struct nf_conn *ct)
17 {
18 return (__force u32)ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
19 }
20
21 static inline const u32 *nf_ct_orig_ipv6_src(const struct nf_conn *ct)
22 {
23 return (__force u32 *)ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip6;
24 }
25
26 static inline u_int32_t
27 xt_cluster_hash_ipv4(u_int32_t ip, const struct xt_cluster_match_info *info)
28 {
29 return jhash_1word(ip, info->hash_seed);
30 }
31
32 static inline u_int32_t
33 xt_cluster_hash_ipv6(const void *ip, const struct xt_cluster_match_info *info)
34 {
35 return jhash2(ip, NF_CT_TUPLE_L3SIZE / sizeof(__u32), info->hash_seed);
36 }
37
38 static inline u_int32_t
39 xt_cluster_hash(const struct nf_conn *ct,
40 const struct xt_cluster_match_info *info)
41 {
42 u_int32_t hash = 0;
43
44 switch(nf_ct_l3num(ct)) {
45 case AF_INET:
46 hash = xt_cluster_hash_ipv4(nf_ct_orig_ipv4_src(ct), info);
47 break;
48 case AF_INET6:
49 hash = xt_cluster_hash_ipv6(nf_ct_orig_ipv6_src(ct), info);
50 break;
51 default:
52 WARN_ON(1);
53 break;
54 }
55
56 return reciprocal_scale(hash, info->total_nodes);
57 }
58
59 static inline bool
60 xt_cluster_is_multicast_addr(const struct sk_buff *skb, u_int8_t family)
61 {
62 bool is_multicast = false;
63
64 switch(family) {
65 case NFPROTO_IPV4:
66 is_multicast = ipv4_is_multicast(ip_hdr(skb)->daddr);
67 break;
68 case NFPROTO_IPV6:
69 is_multicast = ipv6_addr_is_multicast(&ipv6_hdr(skb)->daddr);
70 break;
71 default:
72 WARN_ON(1);
73 break;
74 }
75 return is_multicast;
76 }
77
78 static bool
79 xt_cluster_mt(const struct sk_buff *skb, struct xt_action_param *par)
80 {
81 struct sk_buff *pskb = (struct sk_buff *)skb;
82 const struct xt_cluster_match_info *info = par->matchinfo;
83 const struct nf_conn *ct;
84 enum ip_conntrack_info ctinfo;
85 unsigned long hash;
86
87 /* This match assumes that all nodes see the same packets. This can be
88 * achieved if the switch that connects the cluster nodes support some
89 * sort of 'port mirroring'. However, if your switch does not support
90 * this, your cluster nodes can reply ARP request using a multicast MAC
91 * address. Thus, your switch will flood the same packets to the
92 * cluster nodes with the same multicast MAC address. Using a multicast
93 * link address is a RFC 1812 (section 3.3.2) violation, but this works
94 * fine in practise.
95 *
96 * Unfortunately, if you use the multicast MAC address, the link layer
97 * sets skbuff's pkt_type to PACKET_MULTICAST, which is not accepted
98 * by TCP and others for packets coming to this node. For that reason,
99 * this match mangles skbuff's pkt_type if it detects a packet
100 * addressed to a unicast address but using PACKET_MULTICAST. Yes, I
101 * know, matches should not alter packets, but we are doing this here
102 * because we would need to add a PKTTYPE target for this sole purpose.
103 */
104 if (!xt_cluster_is_multicast_addr(skb, xt_family(par)) &&
105 skb->pkt_type == PACKET_MULTICAST) {
106 pskb->pkt_type = PACKET_HOST;
107 }
108
109 ct = nf_ct_get(skb, &ctinfo);
110 if (ct == NULL)
111 return false;
112
113 if (ct->master)
114 hash = xt_cluster_hash(ct->master, info);
115 else
116 hash = xt_cluster_hash(ct, info);
117
118 return !!((1 << hash) & info->node_mask) ^
119 !!(info->flags & XT_CLUSTER_F_INV);
120 }
121
122 static int xt_cluster_mt_checkentry(const struct xt_mtchk_param *par)
123 {
124 struct xt_cluster_match_info *info = par->matchinfo;
125 int ret;
126
127 if (info->total_nodes > XT_CLUSTER_NODES_MAX) {
128 pr_info_ratelimited("you have exceeded the maximum number of cluster nodes (%u > %u)\n",
129 info->total_nodes, XT_CLUSTER_NODES_MAX);
130 return -EINVAL;
131 }
132 if (info->node_mask >= (1ULL << info->total_nodes)) {
133 pr_info_ratelimited("node mask cannot exceed total number of nodes\n");
134 return -EDOM;
135 }
136
137 ret = nf_ct_netns_get(par->net, par->family);
138 if (ret < 0)
139 pr_info_ratelimited("cannot load conntrack support for proto=%u\n",
140 par->family);
141 return ret;
142 }
143
144 static void xt_cluster_mt_destroy(const struct xt_mtdtor_param *par)
145 {
146 nf_ct_netns_put(par->net, par->family);
147 }
148
149 static struct xt_match xt_cluster_match __read_mostly = {
150 .name = "cluster",
151 .family = NFPROTO_UNSPEC,
152 .match = xt_cluster_mt,
153 .checkentry = xt_cluster_mt_checkentry,
154 .matchsize = sizeof(struct xt_cluster_match_info),
155 .destroy = xt_cluster_mt_destroy,
156 .me = THIS_MODULE,
157 };
158
159 static int __init xt_cluster_mt_init(void)
160 {
161 return xt_register_match(&xt_cluster_match);
162 }
163
164 static void __exit xt_cluster_mt_fini(void)
165 {
166 xt_unregister_match(&xt_cluster_match);
167 }
168
169 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
170 MODULE_LICENSE("GPL");
171 MODULE_DESCRIPTION("Xtables: hash-based cluster match");
172 MODULE_ALIAS("ipt_cluster");
173 MODULE_ALIAS("ip6t_cluster");
174 module_init(xt_cluster_mt_init);
175 module_exit(xt_cluster_mt_fini);
176
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