1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * This is a module which is used for rejecting packets. 4 */ 5 6 /* (C) 1999-2001 Paul `Rusty' Russell 7 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org> 8 */ 9 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 10 #include <linux/module.h> 11 #include <linux/skbuff.h> 12 #include <linux/slab.h> 13 #include <linux/ip.h> 14 #include <linux/udp.h> 15 #include <linux/icmp.h> 16 #include <net/icmp.h> 17 #include <linux/netfilter/x_tables.h> 18 #include <linux/netfilter_ipv4/ip_tables.h> 19 #include <linux/netfilter_ipv4/ipt_REJECT.h> 20 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER) 21 #include <linux/netfilter_bridge.h> 22 #endif 23 24 #include <net/netfilter/ipv4/nf_reject.h> 25 26 MODULE_LICENSE("GPL"); 27 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>"); 28 MODULE_DESCRIPTION("Xtables: packet \"rejection\" target for IPv4"); 29 30 static unsigned int 31 reject_tg(struct sk_buff *skb, const struct xt_action_param *par) 32 { 33 const struct ipt_reject_info *reject = par->targinfo; 34 int hook = xt_hooknum(par); 35 36 switch (reject->with) { 37 case IPT_ICMP_NET_UNREACHABLE: 38 nf_send_unreach(skb, ICMP_NET_UNREACH, hook); 39 break; 40 case IPT_ICMP_HOST_UNREACHABLE: 41 nf_send_unreach(skb, ICMP_HOST_UNREACH, hook); 42 break; 43 case IPT_ICMP_PROT_UNREACHABLE: 44 nf_send_unreach(skb, ICMP_PROT_UNREACH, hook); 45 break; 46 case IPT_ICMP_PORT_UNREACHABLE: 47 nf_send_unreach(skb, ICMP_PORT_UNREACH, hook); 48 break; 49 case IPT_ICMP_NET_PROHIBITED: 50 nf_send_unreach(skb, ICMP_NET_ANO, hook); 51 break; 52 case IPT_ICMP_HOST_PROHIBITED: 53 nf_send_unreach(skb, ICMP_HOST_ANO, hook); 54 break; 55 case IPT_ICMP_ADMIN_PROHIBITED: 56 nf_send_unreach(skb, ICMP_PKT_FILTERED, hook); 57 break; 58 case IPT_TCP_RESET: 59 nf_send_reset(xt_net(par), skb, hook); 60 case IPT_ICMP_ECHOREPLY: 61 /* Doesn't happen. */ 62 break; 63 } 64 65 return NF_DROP; 66 } 67 68 static int reject_tg_check(const struct xt_tgchk_param *par) 69 { 70 const struct ipt_reject_info *rejinfo = par->targinfo; 71 const struct ipt_entry *e = par->entryinfo; 72 73 if (rejinfo->with == IPT_ICMP_ECHOREPLY) { 74 pr_info_ratelimited("ECHOREPLY no longer supported.\n"); 75 return -EINVAL; 76 } else if (rejinfo->with == IPT_TCP_RESET) { 77 /* Must specify that it's a TCP packet */ 78 if (e->ip.proto != IPPROTO_TCP || 79 (e->ip.invflags & XT_INV_PROTO)) { 80 pr_info_ratelimited("TCP_RESET invalid for non-tcp\n"); 81 return -EINVAL; 82 } 83 } 84 return 0; 85 } 86 87 static struct xt_target reject_tg_reg __read_mostly = { 88 .name = "REJECT", 89 .family = NFPROTO_IPV4, 90 .target = reject_tg, 91 .targetsize = sizeof(struct ipt_reject_info), 92 .table = "filter", 93 .hooks = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD) | 94 (1 << NF_INET_LOCAL_OUT), 95 .checkentry = reject_tg_check, 96 .me = THIS_MODULE, 97 }; 98 99 static int __init reject_tg_init(void) 100 { 101 return xt_register_target(&reject_tg_reg); 102 } 103 104 static void __exit reject_tg_exit(void) 105 { 106 xt_unregister_target(&reject_tg_reg); 107 } 108 109 module_init(reject_tg_init); 110 module_exit(reject_tg_exit); 111