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), par->state->sk, skb, hook); 60 break; 61 case IPT_ICMP_ECHOREPLY: 62 /* Doesn't happen. */ 63 break; 64 } 65 66 return NF_DROP; 67 } 68 69 static int reject_tg_check(const struct xt_tgchk_param *par) 70 { 71 const struct ipt_reject_info *rejinfo = par->targinfo; 72 const struct ipt_entry *e = par->entryinfo; 73 74 if (rejinfo->with == IPT_ICMP_ECHOREPLY) { 75 pr_info_ratelimited("ECHOREPLY no longer supported.\n"); 76 return -EINVAL; 77 } else if (rejinfo->with == IPT_TCP_RESET) { 78 /* Must specify that it's a TCP packet */ 79 if (e->ip.proto != IPPROTO_TCP || 80 (e->ip.invflags & XT_INV_PROTO)) { 81 pr_info_ratelimited("TCP_RESET invalid for non-tcp\n"); 82 return -EINVAL; 83 } 84 } 85 return 0; 86 } 87 88 static struct xt_target reject_tg_reg __read_mostly = { 89 .name = "REJECT", 90 .family = NFPROTO_IPV4, 91 .target = reject_tg, 92 .targetsize = sizeof(struct ipt_reject_info), 93 .table = "filter", 94 .hooks = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD) | 95 (1 << NF_INET_LOCAL_OUT), 96 .checkentry = reject_tg_check, 97 .me = THIS_MODULE, 98 }; 99 100 static int __init reject_tg_init(void) 101 { 102 return xt_register_target(&reject_tg_reg); 103 } 104 105 static void __exit reject_tg_exit(void) 106 { 107 xt_unregister_target(&reject_tg_reg); 108 } 109 110 module_init(reject_tg_init); 111 module_exit(reject_tg_exit); 112