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 59 return reciprocal_scale(hash, info->total_nodes); 60 } 61 62 static inline bool 63 xt_cluster_is_multicast_addr(const struct sk_buff *skb, u_int8_t family) 64 { 65 bool is_multicast = false; 66 67 switch(family) { 68 case NFPROTO_IPV4: 69 is_multicast = ipv4_is_multicast(ip_hdr(skb)->daddr); 70 break; 71 case NFPROTO_IPV6: 72 is_multicast = ipv6_addr_is_multicast(&ipv6_hdr(skb)->daddr); 73 break; 74 default: 75 WARN_ON(1); 76 break; 77 } 78 return is_multicast; 79 } 80 81 static bool 82 xt_cluster_mt(const struct sk_buff *skb, struct xt_action_param *par) 83 { 84 struct sk_buff *pskb = (struct sk_buff *)skb; 85 const struct xt_cluster_match_info *info = par->matchinfo; 86 const struct nf_conn *ct; 87 enum ip_conntrack_info ctinfo; 88 unsigned long hash; 89 90 /* This match assumes that all nodes see the same packets. This can be 91 * achieved if the switch that connects the cluster nodes support some 92 * sort of 'port mirroring'. However, if your switch does not support 93 * this, your cluster nodes can reply ARP request using a multicast MAC 94 * address. Thus, your switch will flood the same packets to the 95 * cluster nodes with the same multicast MAC address. Using a multicast 96 * link address is a RFC 1812 (section 3.3.2) violation, but this works 97 * fine in practise. 98 * 99 * Unfortunately, if you use the multicast MAC address, the link layer 100 * sets skbuff's pkt_type to PACKET_MULTICAST, which is not accepted 101 * by TCP and others for packets coming to this node. For that reason, 102 * this match mangles skbuff's pkt_type if it detects a packet 103 * addressed to a unicast address but using PACKET_MULTICAST. Yes, I 104 * know, matches should not alter packets, but we are doing this here 105 * because we would need to add a PKTTYPE target for this sole purpose. 106 */ 107 if (!xt_cluster_is_multicast_addr(skb, xt_family(par)) && 108 skb->pkt_type == PACKET_MULTICAST) { 109 pskb->pkt_type = PACKET_HOST; 110 } 111 112 ct = nf_ct_get(skb, &ctinfo); 113 if (ct == NULL) 114 return false; 115 116 if (ct->master) 117 hash = xt_cluster_hash(ct->master, info); 118 else 119 hash = xt_cluster_hash(ct, info); 120 121 return !!((1 << hash) & info->node_mask) ^ 122 !!(info->flags & XT_CLUSTER_F_INV); 123 } 124 125 static int xt_cluster_mt_checkentry(const struct xt_mtchk_param *par) 126 { 127 struct xt_cluster_match_info *info = par->matchinfo; 128 int ret; 129 130 if (info->total_nodes > XT_CLUSTER_NODES_MAX) { 131 pr_info_ratelimited("you have exceeded the maximum number of cluster nodes (%u > %u)\n", 132 info->total_nodes, XT_CLUSTER_NODES_MAX); 133 return -EINVAL; 134 } 135 if (info->node_mask >= (1ULL << info->total_nodes)) { 136 pr_info_ratelimited("node mask cannot exceed total number of nodes\n"); 137 return -EDOM; 138 } 139 140 ret = nf_ct_netns_get(par->net, par->family); 141 if (ret < 0) 142 pr_info_ratelimited("cannot load conntrack support for proto=%u\n", 143 par->family); 144 return ret; 145 } 146 147 static void xt_cluster_mt_destroy(const struct xt_mtdtor_param *par) 148 { 149 nf_ct_netns_put(par->net, par->family); 150 } 151 152 static struct xt_match xt_cluster_match __read_mostly = { 153 .name = "cluster", 154 .family = NFPROTO_UNSPEC, 155 .match = xt_cluster_mt, 156 .checkentry = xt_cluster_mt_checkentry, 157 .matchsize = sizeof(struct xt_cluster_match_info), 158 .destroy = xt_cluster_mt_destroy, 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