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 29MODULE_LICENSE("GPL"); 30MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>"); 31MODULE_DESCRIPTION("Xtables: packet \"rejection\" target for IPv4"); 32 33static unsigned int 34reject_tg(struct sk_buff *skb, const struct xt_action_param *par) 35{ 36 const struct ipt_reject_info *reject = par->targinfo; 37 38 switch (reject->with) { 39 case IPT_ICMP_NET_UNREACHABLE: 40 nf_send_unreach(skb, ICMP_NET_UNREACH); 41 break; 42 case IPT_ICMP_HOST_UNREACHABLE: 43 nf_send_unreach(skb, ICMP_HOST_UNREACH); 44 break; 45 case IPT_ICMP_PROT_UNREACHABLE: 46 nf_send_unreach(skb, ICMP_PROT_UNREACH); 47 break; 48 case IPT_ICMP_PORT_UNREACHABLE: 49 nf_send_unreach(skb, ICMP_PORT_UNREACH); 50 break; 51 case IPT_ICMP_NET_PROHIBITED: 52 nf_send_unreach(skb, ICMP_NET_ANO); 53 break; 54 case IPT_ICMP_HOST_PROHIBITED: 55 nf_send_unreach(skb, ICMP_HOST_ANO); 56 break; 57 case IPT_ICMP_ADMIN_PROHIBITED: 58 nf_send_unreach(skb, ICMP_PKT_FILTERED); 59 break; 60 case IPT_TCP_RESET: 61 nf_send_reset(skb, par->hooknum); 62 case IPT_ICMP_ECHOREPLY: 63 /* Doesn't happen. */ 64 break; 65 } 66 67 return NF_DROP; 68} 69 70static int reject_tg_check(const struct xt_tgchk_param *par) 71{ 72 const struct ipt_reject_info *rejinfo = par->targinfo; 73 const struct ipt_entry *e = par->entryinfo; 74 75 if (rejinfo->with == IPT_ICMP_ECHOREPLY) { 76 pr_info("ECHOREPLY no longer supported.\n"); 77 return -EINVAL; 78 } else if (rejinfo->with == IPT_TCP_RESET) { 79 /* Must specify that it's a TCP packet */ 80 if (e->ip.proto != IPPROTO_TCP || 81 (e->ip.invflags & XT_INV_PROTO)) { 82 pr_info("TCP_RESET invalid for non-tcp\n"); 83 return -EINVAL; 84 } 85 } 86 return 0; 87} 88 89static struct xt_target reject_tg_reg __read_mostly = { 90 .name = "REJECT", 91 .family = NFPROTO_IPV4, 92 .target = reject_tg, 93 .targetsize = sizeof(struct ipt_reject_info), 94 .table = "filter", 95 .hooks = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD) | 96 (1 << NF_INET_LOCAL_OUT), 97 .checkentry = reject_tg_check, 98 .me = THIS_MODULE, 99}; 100 101static int __init reject_tg_init(void) 102{ 103 return xt_register_target(&reject_tg_reg); 104} 105 106static void __exit reject_tg_exit(void) 107{ 108 xt_unregister_target(&reject_tg_reg); 109} 110 111module_init(reject_tg_init); 112module_exit(reject_tg_exit); 113