1 /* 2 * This is a module which is used for rejecting packets. 3 */ 4 5 /* (C) 1999-2001 Paul `Rusty' Russell 6 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org> 7 * 8 * This program is free software; you can redistribute it and/or modify 9 * it under the terms of the GNU General Public License version 2 as 10 * published by the Free Software Foundation. 11 */ 12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 13 #include <linux/module.h> 14 #include <linux/skbuff.h> 15 #include <linux/slab.h> 16 #include <linux/ip.h> 17 #include <linux/udp.h> 18 #include <linux/icmp.h> 19 #include <net/icmp.h> 20 #include <linux/netfilter/x_tables.h> 21 #include <linux/netfilter_ipv4/ip_tables.h> 22 #include <linux/netfilter_ipv4/ipt_REJECT.h> 23 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER) 24 #include <linux/netfilter_bridge.h> 25 #endif 26 27 #include <net/netfilter/ipv4/nf_reject.h> 28 29 MODULE_LICENSE("GPL"); 30 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>"); 31 MODULE_DESCRIPTION("Xtables: packet \"rejection\" target for IPv4"); 32 33 static unsigned int 34 reject_tg(struct sk_buff *skb, const struct xt_action_param *par) 35 { 36 const struct ipt_reject_info *reject = par->targinfo; 37 int hook = par->hooknum; 38 39 switch (reject->with) { 40 case IPT_ICMP_NET_UNREACHABLE: 41 nf_send_unreach(skb, ICMP_NET_UNREACH, hook); 42 break; 43 case IPT_ICMP_HOST_UNREACHABLE: 44 nf_send_unreach(skb, ICMP_HOST_UNREACH, hook); 45 break; 46 case IPT_ICMP_PROT_UNREACHABLE: 47 nf_send_unreach(skb, ICMP_PROT_UNREACH, hook); 48 break; 49 case IPT_ICMP_PORT_UNREACHABLE: 50 nf_send_unreach(skb, ICMP_PORT_UNREACH, hook); 51 break; 52 case IPT_ICMP_NET_PROHIBITED: 53 nf_send_unreach(skb, ICMP_NET_ANO, hook); 54 break; 55 case IPT_ICMP_HOST_PROHIBITED: 56 nf_send_unreach(skb, ICMP_HOST_ANO, hook); 57 break; 58 case IPT_ICMP_ADMIN_PROHIBITED: 59 nf_send_unreach(skb, ICMP_PKT_FILTERED, hook); 60 break; 61 case IPT_TCP_RESET: 62 nf_send_reset(skb, hook); 63 case IPT_ICMP_ECHOREPLY: 64 /* Doesn't happen. */ 65 break; 66 } 67 68 return NF_DROP; 69 } 70 71 static int reject_tg_check(const struct xt_tgchk_param *par) 72 { 73 const struct ipt_reject_info *rejinfo = par->targinfo; 74 const struct ipt_entry *e = par->entryinfo; 75 76 if (rejinfo->with == IPT_ICMP_ECHOREPLY) { 77 pr_info("ECHOREPLY no longer supported.\n"); 78 return -EINVAL; 79 } else if (rejinfo->with == IPT_TCP_RESET) { 80 /* Must specify that it's a TCP packet */ 81 if (e->ip.proto != IPPROTO_TCP || 82 (e->ip.invflags & XT_INV_PROTO)) { 83 pr_info("TCP_RESET invalid for non-tcp\n"); 84 return -EINVAL; 85 } 86 } 87 return 0; 88 } 89 90 static struct xt_target reject_tg_reg __read_mostly = { 91 .name = "REJECT", 92 .family = NFPROTO_IPV4, 93 .target = reject_tg, 94 .targetsize = sizeof(struct ipt_reject_info), 95 .table = "filter", 96 .hooks = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD) | 97 (1 << NF_INET_LOCAL_OUT), 98 .checkentry = reject_tg_check, 99 .me = THIS_MODULE, 100 }; 101 102 static int __init reject_tg_init(void) 103 { 104 return xt_register_target(&reject_tg_reg); 105 } 106 107 static void __exit reject_tg_exit(void) 108 { 109 xt_unregister_target(&reject_tg_reg); 110 } 111 112 module_init(reject_tg_init); 113 module_exit(reject_tg_exit); 114