// SPDX-License-Identifier: GPL-2.0-only
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/*
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* (C) 2008-2009 Pablo Neira Ayuso <pablo@netfilter.org>
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/jhash.h>
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#include <linux/ip.h>
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#include <net/ipv6.h>
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#include <linux/netfilter/x_tables.h>
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#include <net/netfilter/nf_conntrack.h>
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#include <linux/netfilter/xt_cluster.h>
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static inline u32 nf_ct_orig_ipv4_src(const struct nf_conn *ct)
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{
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return (__force u32)ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
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}
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static inline const u32 *nf_ct_orig_ipv6_src(const struct nf_conn *ct)
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{
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return (__force u32 *)ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip6;
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}
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static inline u_int32_t
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xt_cluster_hash_ipv4(u_int32_t ip, const struct xt_cluster_match_info *info)
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{
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return jhash_1word(ip, info->hash_seed);
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}
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static inline u_int32_t
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xt_cluster_hash_ipv6(const void *ip, const struct xt_cluster_match_info *info)
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{
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return jhash2(ip, NF_CT_TUPLE_L3SIZE / sizeof(__u32), info->hash_seed);
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}
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static inline u_int32_t
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xt_cluster_hash(const struct nf_conn *ct,
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const struct xt_cluster_match_info *info)
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{
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u_int32_t hash = 0;
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switch(nf_ct_l3num(ct)) {
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case AF_INET:
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hash = xt_cluster_hash_ipv4(nf_ct_orig_ipv4_src(ct), info);
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break;
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case AF_INET6:
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hash = xt_cluster_hash_ipv6(nf_ct_orig_ipv6_src(ct), info);
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break;
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default:
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WARN_ON(1);
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break;
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}
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return reciprocal_scale(hash, info->total_nodes);
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}
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static inline bool
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xt_cluster_is_multicast_addr(const struct sk_buff *skb, u_int8_t family)
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{
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bool is_multicast = false;
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switch(family) {
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case NFPROTO_IPV4:
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is_multicast = ipv4_is_multicast(ip_hdr(skb)->daddr);
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break;
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case NFPROTO_IPV6:
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is_multicast = ipv6_addr_is_multicast(&ipv6_hdr(skb)->daddr);
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break;
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default:
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WARN_ON(1);
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break;
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}
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return is_multicast;
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}
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static bool
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xt_cluster_mt(const struct sk_buff *skb, struct xt_action_param *par)
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{
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struct sk_buff *pskb = (struct sk_buff *)skb;
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const struct xt_cluster_match_info *info = par->matchinfo;
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const struct nf_conn *ct;
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enum ip_conntrack_info ctinfo;
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unsigned long hash;
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/* This match assumes that all nodes see the same packets. This can be
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* achieved if the switch that connects the cluster nodes support some
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* sort of 'port mirroring'. However, if your switch does not support
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* this, your cluster nodes can reply ARP request using a multicast MAC
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* address. Thus, your switch will flood the same packets to the
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* cluster nodes with the same multicast MAC address. Using a multicast
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* link address is a RFC 1812 (section 3.3.2) violation, but this works
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* fine in practise.
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*
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* Unfortunately, if you use the multicast MAC address, the link layer
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* sets skbuff's pkt_type to PACKET_MULTICAST, which is not accepted
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* by TCP and others for packets coming to this node. For that reason,
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* this match mangles skbuff's pkt_type if it detects a packet
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* addressed to a unicast address but using PACKET_MULTICAST. Yes, I
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* know, matches should not alter packets, but we are doing this here
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* because we would need to add a PKTTYPE target for this sole purpose.
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*/
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if (!xt_cluster_is_multicast_addr(skb, xt_family(par)) &&
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skb->pkt_type == PACKET_MULTICAST) {
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pskb->pkt_type = PACKET_HOST;
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}
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ct = nf_ct_get(skb, &ctinfo);
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if (ct == NULL)
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return false;
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if (ct->master)
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hash = xt_cluster_hash(ct->master, info);
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else
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hash = xt_cluster_hash(ct, info);
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return !!((1 << hash) & info->node_mask) ^
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!!(info->flags & XT_CLUSTER_F_INV);
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}
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static int xt_cluster_mt_checkentry(const struct xt_mtchk_param *par)
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{
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struct xt_cluster_match_info *info = par->matchinfo;
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int ret;
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if (info->total_nodes > XT_CLUSTER_NODES_MAX) {
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pr_info_ratelimited("you have exceeded the maximum number of cluster nodes (%u > %u)\n",
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info->total_nodes, XT_CLUSTER_NODES_MAX);
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return -EINVAL;
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}
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if (info->node_mask >= (1ULL << info->total_nodes)) {
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pr_info_ratelimited("node mask cannot exceed total number of nodes\n");
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return -EDOM;
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}
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ret = nf_ct_netns_get(par->net, par->family);
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if (ret < 0)
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pr_info_ratelimited("cannot load conntrack support for proto=%u\n",
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par->family);
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return ret;
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}
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static void xt_cluster_mt_destroy(const struct xt_mtdtor_param *par)
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{
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nf_ct_netns_put(par->net, par->family);
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}
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static struct xt_match xt_cluster_match __read_mostly = {
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.name = "cluster",
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.family = NFPROTO_UNSPEC,
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.match = xt_cluster_mt,
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.checkentry = xt_cluster_mt_checkentry,
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.matchsize = sizeof(struct xt_cluster_match_info),
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.destroy = xt_cluster_mt_destroy,
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.me = THIS_MODULE,
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};
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static int __init xt_cluster_mt_init(void)
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{
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return xt_register_match(&xt_cluster_match);
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}
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static void __exit xt_cluster_mt_fini(void)
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{
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xt_unregister_match(&xt_cluster_match);
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}
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MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("Xtables: hash-based cluster match");
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MODULE_ALIAS("ipt_cluster");
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MODULE_ALIAS("ip6t_cluster");
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module_init(xt_cluster_mt_init);
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module_exit(xt_cluster_mt_fini);
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