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
16static 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
21static 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
26static inline u_int32_t
27xt_cluster_hash_ipv4(u_int32_t ip, const struct xt_cluster_match_info *info)
28{
29 return jhash_1word(a: ip, initval: info->hash_seed);
30}
31
32static inline u_int32_t
33xt_cluster_hash_ipv6(const void *ip, const struct xt_cluster_match_info *info)
34{
35 return jhash2(k: ip, NF_CT_TUPLE_L3SIZE / sizeof(__u32), initval: info->hash_seed);
36}
37
38static inline u_int32_t
39xt_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(ip: nf_ct_orig_ipv4_src(ct), info);
47 break;
48 case AF_INET6:
49 hash = xt_cluster_hash_ipv6(ip: nf_ct_orig_ipv6_src(ct), info);
50 break;
51 default:
52 WARN_ON(1);
53 break;
54 }
55
56 return reciprocal_scale(val: hash, ep_ro: info->total_nodes);
57}
58
59static inline bool
60xt_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(addr: ip_hdr(skb)->daddr);
67 break;
68 case NFPROTO_IPV6:
69 is_multicast = ipv6_addr_is_multicast(addr: &ipv6_hdr(skb)->daddr);
70 break;
71 default:
72 WARN_ON(1);
73 break;
74 }
75 return is_multicast;
76}
77
78static bool
79xt_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, family: xt_family(par)) &&
105 skb->pkt_type == PACKET_MULTICAST) {
106 pskb->pkt_type = PACKET_HOST;
107 }
108
109 ct = nf_ct_get(skb, ctinfo: &ctinfo);
110 if (ct == NULL)
111 return false;
112
113 if (ct->master)
114 hash = xt_cluster_hash(ct: 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
122static 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(net: par->net, nfproto: 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
144static void xt_cluster_mt_destroy(const struct xt_mtdtor_param *par)
145{
146 nf_ct_netns_put(net: par->net, nfproto: par->family);
147}
148
149static struct xt_match xt_cluster_match[] __read_mostly = {
150 {
151 .name = "cluster",
152 .family = NFPROTO_IPV4,
153 .match = xt_cluster_mt,
154 .checkentry = xt_cluster_mt_checkentry,
155 .matchsize = sizeof(struct xt_cluster_match_info),
156 .destroy = xt_cluster_mt_destroy,
157 .me = THIS_MODULE,
158 },
159#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
160 {
161 .name = "cluster",
162 .family = NFPROTO_IPV6,
163 .match = xt_cluster_mt,
164 .checkentry = xt_cluster_mt_checkentry,
165 .matchsize = sizeof(struct xt_cluster_match_info),
166 .destroy = xt_cluster_mt_destroy,
167 .me = THIS_MODULE,
168 },
169#endif
170};
171
172static int __init xt_cluster_mt_init(void)
173{
174 return xt_register_matches(match: xt_cluster_match, ARRAY_SIZE(xt_cluster_match));
175}
176
177static void __exit xt_cluster_mt_fini(void)
178{
179 xt_unregister_matches(match: xt_cluster_match, ARRAY_SIZE(xt_cluster_match));
180}
181
182MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
183MODULE_LICENSE("GPL");
184MODULE_DESCRIPTION("Xtables: hash-based cluster match");
185MODULE_ALIAS("ipt_cluster");
186MODULE_ALIAS("ip6t_cluster");
187module_init(xt_cluster_mt_init);
188module_exit(xt_cluster_mt_fini);
189

source code of linux/net/netfilter/xt_cluster.c