1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * IP tables module for matching the value of the TTL 4 * (C) 2000,2001 by Harald Welte <laforge@netfilter.org> 5 * 6 * Hop Limit matching module 7 * (C) 2001-2002 Maciej Soltysiak <solt@dns.toxicfilms.tv> 8 */ 9 10 #include <linux/ip.h> 11 #include <linux/ipv6.h> 12 #include <linux/module.h> 13 #include <linux/skbuff.h> 14 15 #include <linux/netfilter/x_tables.h> 16 #include <linux/netfilter_ipv4/ipt_ttl.h> 17 #include <linux/netfilter_ipv6/ip6t_hl.h> 18 19 MODULE_AUTHOR("Maciej Soltysiak <solt@dns.toxicfilms.tv>"); 20 MODULE_DESCRIPTION("Xtables: Hoplimit/TTL field match"); 21 MODULE_LICENSE("GPL"); 22 MODULE_ALIAS("ipt_ttl"); 23 MODULE_ALIAS("ip6t_hl"); 24 25 static bool ttl_mt(const struct sk_buff *skb, struct xt_action_param *par) 26 { 27 const struct ipt_ttl_info *info = par->matchinfo; 28 const u8 ttl = ip_hdr(skb)->ttl; 29 30 switch (info->mode) { 31 case IPT_TTL_EQ: 32 return ttl == info->ttl; 33 case IPT_TTL_NE: 34 return ttl != info->ttl; 35 case IPT_TTL_LT: 36 return ttl < info->ttl; 37 case IPT_TTL_GT: 38 return ttl > info->ttl; 39 } 40 41 return false; 42 } 43 44 static bool hl_mt6(const struct sk_buff *skb, struct xt_action_param *par) 45 { 46 const struct ip6t_hl_info *info = par->matchinfo; 47 const struct ipv6hdr *ip6h = ipv6_hdr(skb); 48 49 switch (info->mode) { 50 case IP6T_HL_EQ: 51 return ip6h->hop_limit == info->hop_limit; 52 case IP6T_HL_NE: 53 return ip6h->hop_limit != info->hop_limit; 54 case IP6T_HL_LT: 55 return ip6h->hop_limit < info->hop_limit; 56 case IP6T_HL_GT: 57 return ip6h->hop_limit > info->hop_limit; 58 } 59 60 return false; 61 } 62 63 static struct xt_match hl_mt_reg[] __read_mostly = { 64 { 65 .name = "ttl", 66 .revision = 0, 67 .family = NFPROTO_IPV4, 68 .match = ttl_mt, 69 .matchsize = sizeof(struct ipt_ttl_info), 70 .me = THIS_MODULE, 71 }, 72 { 73 .name = "hl", 74 .revision = 0, 75 .family = NFPROTO_IPV6, 76 .match = hl_mt6, 77 .matchsize = sizeof(struct ip6t_hl_info), 78 .me = THIS_MODULE, 79 }, 80 }; 81 82 static int __init hl_mt_init(void) 83 { 84 return xt_register_matches(hl_mt_reg, ARRAY_SIZE(hl_mt_reg)); 85 } 86 87 static void __exit hl_mt_exit(void) 88 { 89 xt_unregister_matches(hl_mt_reg, ARRAY_SIZE(hl_mt_reg)); 90 } 91 92 module_init(hl_mt_init); 93 module_exit(hl_mt_exit); 94