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 19static 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 24static 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 29static inline u_int32_t 30xt_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 35static inline u_int32_t 36xt_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 41static inline u_int32_t 42xt_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 61static inline bool 62xt_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 68static inline bool 69xt_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 88static bool 89xt_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 135static 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 153static 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 162static int __init xt_cluster_mt_init(void) 163{ 164 return xt_register_match(&xt_cluster_match); 165} 166 167static void __exit xt_cluster_mt_fini(void) 168{ 169 xt_unregister_match(&xt_cluster_match); 170} 171 172MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>"); 173MODULE_LICENSE("GPL"); 174MODULE_DESCRIPTION("Xtables: hash-based cluster match"); 175MODULE_ALIAS("ipt_cluster"); 176MODULE_ALIAS("ip6t_cluster"); 177module_init(xt_cluster_mt_init); 178module_exit(xt_cluster_mt_fini); 179