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_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 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 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 } 135 136 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 }; 162 163 static int __init xt_cluster_mt_init(void) 164 { 165 return xt_register_match(&xt_cluster_match); 166 } 167 168 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