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 16 static 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 21 static 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 26 static inline u_int32_t 27 xt_cluster_hash_ipv4(u_int32_t ip, const struct xt_cluster_match_info *info) 28 { 29 return jhash_1word(ip, info->hash_seed); 30 } 31 32 static inline u_int32_t 33 xt_cluster_hash_ipv6(const void *ip, const struct xt_cluster_match_info *info) 34 { 35 return jhash2(ip, NF_CT_TUPLE_L3SIZE / sizeof(__u32), info->hash_seed); 36 } 37 38 static inline u_int32_t 39 xt_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(nf_ct_orig_ipv4_src(ct), info); 47 break; 48 case AF_INET6: 49 hash = xt_cluster_hash_ipv6(nf_ct_orig_ipv6_src(ct), info); 50 break; 51 default: 52 WARN_ON(1); 53 break; 54 } 55 56 return reciprocal_scale(hash, info->total_nodes); 57 } 58 59 static inline bool 60 xt_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(ip_hdr(skb)->daddr); 67 break; 68 case NFPROTO_IPV6: 69 is_multicast = ipv6_addr_is_multicast(&ipv6_hdr(skb)->daddr); 70 break; 71 default: 72 WARN_ON(1); 73 break; 74 } 75 return is_multicast; 76 } 77 78 static bool 79 xt_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, xt_family(par)) && 105 skb->pkt_type == PACKET_MULTICAST) { 106 pskb->pkt_type = PACKET_HOST; 107 } 108 109 ct = nf_ct_get(skb, &ctinfo); 110 if (ct == NULL) 111 return false; 112 113 if (ct->master) 114 hash = xt_cluster_hash(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 } 121 122 static 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(par->net, 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 } 143 144 static void xt_cluster_mt_destroy(const struct xt_mtdtor_param *par) 145 { 146 nf_ct_netns_put(par->net, par->family); 147 } 148 149 static struct xt_match xt_cluster_match __read_mostly = { 150 .name = "cluster", 151 .family = NFPROTO_UNSPEC, 152 .match = xt_cluster_mt, 153 .checkentry = xt_cluster_mt_checkentry, 154 .matchsize = sizeof(struct xt_cluster_match_info), 155 .destroy = xt_cluster_mt_destroy, 156 .me = THIS_MODULE, 157 }; 158 159 static int __init xt_cluster_mt_init(void) 160 { 161 return xt_register_match(&xt_cluster_match); 162 } 163 164 static void __exit xt_cluster_mt_fini(void) 165 { 166 xt_unregister_match(&xt_cluster_match); 167 } 168 169 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>"); 170 MODULE_LICENSE("GPL"); 171 MODULE_DESCRIPTION("Xtables: hash-based cluster match"); 172 MODULE_ALIAS("ipt_cluster"); 173 MODULE_ALIAS("ip6t_cluster"); 174 module_init(xt_cluster_mt_init); 175 module_exit(xt_cluster_mt_fini); 176