1 /* 2 * netfilter module to limit the number of parallel tcp 3 * connections per IP address. 4 * (c) 2000 Gerd Knorr <kraxel@bytesex.org> 5 * Nov 2002: Martin Bene <martin.bene@icomedias.com>: 6 * only ignore TIME_WAIT or gone connections 7 * (C) CC Computer Consultants GmbH, 2007 8 * 9 * based on ... 10 * 11 * Kernel module to match connection tracking information. 12 * GPL (C) 1999 Rusty Russell (rusty@rustcorp.com.au). 13 */ 14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 15 16 #include <linux/ip.h> 17 #include <linux/ipv6.h> 18 #include <linux/module.h> 19 #include <linux/skbuff.h> 20 #include <linux/netfilter/x_tables.h> 21 #include <linux/netfilter/xt_connlimit.h> 22 23 #include <net/netfilter/nf_conntrack.h> 24 #include <net/netfilter/nf_conntrack_core.h> 25 #include <net/netfilter/nf_conntrack_tuple.h> 26 #include <net/netfilter/nf_conntrack_zones.h> 27 #include <net/netfilter/nf_conntrack_count.h> 28 29 static bool 30 connlimit_mt(const struct sk_buff *skb, struct xt_action_param *par) 31 { 32 struct net *net = xt_net(par); 33 const struct xt_connlimit_info *info = par->matchinfo; 34 struct nf_conntrack_tuple tuple; 35 const struct nf_conntrack_tuple *tuple_ptr = &tuple; 36 const struct nf_conntrack_zone *zone = &nf_ct_zone_dflt; 37 enum ip_conntrack_info ctinfo; 38 const struct nf_conn *ct; 39 unsigned int connections; 40 u32 key[5]; 41 42 ct = nf_ct_get(skb, &ctinfo); 43 if (ct != NULL) { 44 tuple_ptr = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple; 45 zone = nf_ct_zone(ct); 46 } else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb), 47 xt_family(par), net, &tuple)) { 48 goto hotdrop; 49 } 50 51 if (xt_family(par) == NFPROTO_IPV6) { 52 const struct ipv6hdr *iph = ipv6_hdr(skb); 53 union nf_inet_addr addr; 54 unsigned int i; 55 56 memcpy(&addr.ip6, (info->flags & XT_CONNLIMIT_DADDR) ? 57 &iph->daddr : &iph->saddr, sizeof(addr.ip6)); 58 59 for (i = 0; i < ARRAY_SIZE(addr.ip6); ++i) 60 addr.ip6[i] &= info->mask.ip6[i]; 61 memcpy(key, &addr, sizeof(addr.ip6)); 62 key[4] = zone->id; 63 } else { 64 const struct iphdr *iph = ip_hdr(skb); 65 66 key[0] = (info->flags & XT_CONNLIMIT_DADDR) ? 67 (__force __u32)iph->daddr : (__force __u32)iph->saddr; 68 key[0] &= (__force __u32)info->mask.ip; 69 key[1] = zone->id; 70 } 71 72 connections = nf_conncount_count(net, info->data, key, tuple_ptr, 73 zone); 74 if (connections == 0) 75 /* kmalloc failed, drop it entirely */ 76 goto hotdrop; 77 78 return (connections > info->limit) ^ !!(info->flags & XT_CONNLIMIT_INVERT); 79 80 hotdrop: 81 par->hotdrop = true; 82 return false; 83 } 84 85 static int connlimit_mt_check(const struct xt_mtchk_param *par) 86 { 87 struct xt_connlimit_info *info = par->matchinfo; 88 unsigned int keylen; 89 int ret; 90 91 keylen = sizeof(u32); 92 if (par->family == NFPROTO_IPV6) 93 keylen += sizeof(struct in6_addr); 94 else 95 keylen += sizeof(struct in_addr); 96 97 ret = nf_ct_netns_get(par->net, par->family); 98 if (ret < 0) { 99 pr_info_ratelimited("cannot load conntrack support for proto=%u\n", 100 par->family); 101 return ret; 102 } 103 104 /* init private data */ 105 info->data = nf_conncount_init(par->net, keylen); 106 if (IS_ERR(info->data)) 107 nf_ct_netns_put(par->net, par->family); 108 109 return PTR_ERR_OR_ZERO(info->data); 110 } 111 112 static void connlimit_mt_destroy(const struct xt_mtdtor_param *par) 113 { 114 const struct xt_connlimit_info *info = par->matchinfo; 115 116 nf_conncount_destroy(par->net, info->data); 117 nf_ct_netns_put(par->net, par->family); 118 } 119 120 static struct xt_match connlimit_mt_reg[] __read_mostly = { 121 { 122 .name = "connlimit", 123 .revision = 1, 124 .family = NFPROTO_IPV4, 125 .checkentry = connlimit_mt_check, 126 .match = connlimit_mt, 127 .matchsize = sizeof(struct xt_connlimit_info), 128 .usersize = offsetof(struct xt_connlimit_info, data), 129 .destroy = connlimit_mt_destroy, 130 .me = THIS_MODULE, 131 }, 132 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES) 133 { 134 .name = "connlimit", 135 .revision = 1, 136 .family = NFPROTO_IPV6, 137 .checkentry = connlimit_mt_check, 138 .match = connlimit_mt, 139 .matchsize = sizeof(struct xt_connlimit_info), 140 .usersize = offsetof(struct xt_connlimit_info, data), 141 .destroy = connlimit_mt_destroy, 142 .me = THIS_MODULE, 143 }, 144 #endif 145 }; 146 147 static int __init connlimit_mt_init(void) 148 { 149 return xt_register_matches(connlimit_mt_reg, ARRAY_SIZE(connlimit_mt_reg)); 150 } 151 152 static void __exit connlimit_mt_exit(void) 153 { 154 xt_unregister_matches(connlimit_mt_reg, ARRAY_SIZE(connlimit_mt_reg)); 155 } 156 157 module_init(connlimit_mt_init); 158 module_exit(connlimit_mt_exit); 159 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>"); 160 MODULE_DESCRIPTION("Xtables: Number of connections matching"); 161 MODULE_LICENSE("GPL"); 162 MODULE_ALIAS("ipt_connlimit"); 163 MODULE_ALIAS("ip6t_connlimit"); 164