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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 | |
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 | |
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 |
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 |
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 |
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 | return (((u64)hash * info->total_nodes) >> 32); |
59 | } |
60 | |
61 | static inline bool |
62 | xt_cluster_ipv6_is_multicast(const struct in6_addr *addr) |
63 | { |
64 | __be32 st = addr->s6_addr32[0]; |
65 | return ((st & htonl(0xFF000000)) == htonl(0xFF000000)); |
66 | } |
67 | |
68 | static inline bool |
69 | xt_cluster_is_multicast_addr(const struct sk_buff *skb, u_int8_t family) |
70 | { |
71 | bool is_multicast = false; |
72 | |
73 | switch(family) { |
74 | case NFPROTO_IPV4: |
75 | is_multicast = ipv4_is_multicast(ip_hdr(skb)->daddr); |
76 | break; |
77 | case NFPROTO_IPV6: |
78 | is_multicast = |
79 | xt_cluster_ipv6_is_multicast(&ipv6_hdr(skb)->daddr); |
80 | break; |
81 | default: |
82 | WARN_ON(1); |
83 | break; |
84 | } |
85 | return is_multicast; |
86 | } |
87 | |
88 | static bool |
89 | xt_cluster_mt(const struct sk_buff *skb, struct xt_action_param *par) |
90 | { |
91 | struct sk_buff *pskb = (struct sk_buff *)skb; |
92 | const struct xt_cluster_match_info *info = par->matchinfo; |
93 | const struct nf_conn *ct; |
94 | enum ip_conntrack_info ctinfo; |
95 | unsigned long hash; |
96 | |
97 | /* This match assumes that all nodes see the same packets. This can be |
98 | * achieved if the switch that connects the cluster nodes support some |
99 | * sort of 'port mirroring'. However, if your switch does not support |
100 | * this, your cluster nodes can reply ARP request using a multicast MAC |
101 | * address. Thus, your switch will flood the same packets to the |
102 | * cluster nodes with the same multicast MAC address. Using a multicast |
103 | * link address is a RFC 1812 (section 3.3.2) violation, but this works |
104 | * fine in practise. |
105 | * |
106 | * Unfortunately, if you use the multicast MAC address, the link layer |
107 | * sets skbuff's pkt_type to PACKET_MULTICAST, which is not accepted |
108 | * by TCP and others for packets coming to this node. For that reason, |
109 | * this match mangles skbuff's pkt_type if it detects a packet |
110 | * addressed to a unicast address but using PACKET_MULTICAST. Yes, I |
111 | * know, matches should not alter packets, but we are doing this here |
112 | * because we would need to add a PKTTYPE target for this sole purpose. |
113 | */ |
114 | if (!xt_cluster_is_multicast_addr(skb, par->family) && |
115 | skb->pkt_type == PACKET_MULTICAST) { |
116 | pskb->pkt_type = PACKET_HOST; |
117 | } |
118 | |
119 | ct = nf_ct_get(skb, &ctinfo); |
120 | if (ct == NULL) |
121 | return false; |
122 | |
123 | if (nf_ct_is_untracked(ct)) |
124 | return false; |
125 | |
126 | if (ct->master) |
127 | hash = xt_cluster_hash(ct->master, info); |
128 | else |
129 | hash = xt_cluster_hash(ct, info); |
130 | |
131 | return !!((1 << hash) & info->node_mask) ^ |
132 | !!(info->flags & XT_CLUSTER_F_INV); |
133 | } |
134 | |
135 | static int xt_cluster_mt_checkentry(const struct xt_mtchk_param *par) |
136 | { |
137 | struct xt_cluster_match_info *info = par->matchinfo; |
138 | |
139 | if (info->total_nodes > XT_CLUSTER_NODES_MAX) { |
140 | pr_info("you have exceeded the maximum " |
141 | "number of cluster nodes (%u > %u)\n", |
142 | info->total_nodes, XT_CLUSTER_NODES_MAX); |
143 | return -EINVAL; |
144 | } |
145 | if (info->node_mask >= (1ULL << info->total_nodes)) { |
146 | pr_info("this node mask cannot be " |
147 | "higher than the total number of nodes\n"); |
148 | return -EDOM; |
149 | } |
150 | return 0; |
151 | } |
152 | |
153 | static struct xt_match xt_cluster_match __read_mostly = { |
154 | .name = "cluster", |
155 | .family = NFPROTO_UNSPEC, |
156 | .match = xt_cluster_mt, |
157 | .checkentry = xt_cluster_mt_checkentry, |
158 | .matchsize = sizeof(struct xt_cluster_match_info), |
159 | .me = THIS_MODULE, |
160 | }; |
161 | |
162 | static int __init xt_cluster_mt_init(void) |
163 | { |
164 | return xt_register_match(&xt_cluster_match); |
165 | } |
166 | |
167 | static void __exit xt_cluster_mt_fini(void) |
168 | { |
169 | xt_unregister_match(&xt_cluster_match); |
170 | } |
171 | |
172 | MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>"); |
173 | MODULE_LICENSE("GPL"); |
174 | MODULE_DESCRIPTION("Xtables: hash-based cluster match"); |
175 | MODULE_ALIAS("ipt_cluster"); |
176 | MODULE_ALIAS("ip6t_cluster"); |
177 | module_init(xt_cluster_mt_init); |
178 | module_exit(xt_cluster_mt_fini); |
179 |
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