1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Xtables module for matching the value of the IPv4/IPv6 and TCP ECN bits 4 * 5 * (C) 2002 by Harald Welte <laforge@gnumonks.org> 6 * (C) 2011 Patrick McHardy <kaber@trash.net> 7 */ 8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 9 #include <linux/in.h> 10 #include <linux/ip.h> 11 #include <net/ip.h> 12 #include <linux/module.h> 13 #include <linux/skbuff.h> 14 #include <linux/tcp.h> 15 16 #include <linux/netfilter/x_tables.h> 17 #include <linux/netfilter/xt_ecn.h> 18 #include <linux/netfilter_ipv4/ip_tables.h> 19 #include <linux/netfilter_ipv6/ip6_tables.h> 20 21 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); 22 MODULE_DESCRIPTION("Xtables: Explicit Congestion Notification (ECN) flag match"); 23 MODULE_LICENSE("GPL"); 24 MODULE_ALIAS("ipt_ecn"); 25 MODULE_ALIAS("ip6t_ecn"); 26 27 static bool match_tcp(const struct sk_buff *skb, struct xt_action_param *par) 28 { 29 const struct xt_ecn_info *einfo = par->matchinfo; 30 struct tcphdr _tcph; 31 const struct tcphdr *th; 32 33 /* In practice, TCP match does this, so can't fail. But let's 34 * be good citizens. 35 */ 36 th = skb_header_pointer(skb, par->thoff, sizeof(_tcph), &_tcph); 37 if (th == NULL) 38 return false; 39 40 if (einfo->operation & XT_ECN_OP_MATCH_ECE) { 41 if (einfo->invert & XT_ECN_OP_MATCH_ECE) { 42 if (th->ece == 1) 43 return false; 44 } else { 45 if (th->ece == 0) 46 return false; 47 } 48 } 49 50 if (einfo->operation & XT_ECN_OP_MATCH_CWR) { 51 if (einfo->invert & XT_ECN_OP_MATCH_CWR) { 52 if (th->cwr == 1) 53 return false; 54 } else { 55 if (th->cwr == 0) 56 return false; 57 } 58 } 59 60 return true; 61 } 62 63 static inline bool match_ip(const struct sk_buff *skb, 64 const struct xt_ecn_info *einfo) 65 { 66 return ((ip_hdr(skb)->tos & XT_ECN_IP_MASK) == einfo->ip_ect) ^ 67 !!(einfo->invert & XT_ECN_OP_MATCH_IP); 68 } 69 70 static bool ecn_mt4(const struct sk_buff *skb, struct xt_action_param *par) 71 { 72 const struct xt_ecn_info *info = par->matchinfo; 73 74 if (info->operation & XT_ECN_OP_MATCH_IP && !match_ip(skb, info)) 75 return false; 76 77 if (info->operation & (XT_ECN_OP_MATCH_ECE | XT_ECN_OP_MATCH_CWR) && 78 !match_tcp(skb, par)) 79 return false; 80 81 return true; 82 } 83 84 static int ecn_mt_check4(const struct xt_mtchk_param *par) 85 { 86 const struct xt_ecn_info *info = par->matchinfo; 87 const struct ipt_ip *ip = par->entryinfo; 88 89 if (info->operation & XT_ECN_OP_MATCH_MASK) 90 return -EINVAL; 91 92 if (info->invert & XT_ECN_OP_MATCH_MASK) 93 return -EINVAL; 94 95 if (info->operation & (XT_ECN_OP_MATCH_ECE | XT_ECN_OP_MATCH_CWR) && 96 (ip->proto != IPPROTO_TCP || ip->invflags & IPT_INV_PROTO)) { 97 pr_info_ratelimited("cannot match TCP bits for non-tcp packets\n"); 98 return -EINVAL; 99 } 100 101 return 0; 102 } 103 104 static inline bool match_ipv6(const struct sk_buff *skb, 105 const struct xt_ecn_info *einfo) 106 { 107 return (((ipv6_hdr(skb)->flow_lbl[0] >> 4) & XT_ECN_IP_MASK) == 108 einfo->ip_ect) ^ 109 !!(einfo->invert & XT_ECN_OP_MATCH_IP); 110 } 111 112 static bool ecn_mt6(const struct sk_buff *skb, struct xt_action_param *par) 113 { 114 const struct xt_ecn_info *info = par->matchinfo; 115 116 if (info->operation & XT_ECN_OP_MATCH_IP && !match_ipv6(skb, info)) 117 return false; 118 119 if (info->operation & (XT_ECN_OP_MATCH_ECE | XT_ECN_OP_MATCH_CWR) && 120 !match_tcp(skb, par)) 121 return false; 122 123 return true; 124 } 125 126 static int ecn_mt_check6(const struct xt_mtchk_param *par) 127 { 128 const struct xt_ecn_info *info = par->matchinfo; 129 const struct ip6t_ip6 *ip = par->entryinfo; 130 131 if (info->operation & XT_ECN_OP_MATCH_MASK) 132 return -EINVAL; 133 134 if (info->invert & XT_ECN_OP_MATCH_MASK) 135 return -EINVAL; 136 137 if (info->operation & (XT_ECN_OP_MATCH_ECE | XT_ECN_OP_MATCH_CWR) && 138 (ip->proto != IPPROTO_TCP || ip->invflags & IP6T_INV_PROTO)) { 139 pr_info_ratelimited("cannot match TCP bits for non-tcp packets\n"); 140 return -EINVAL; 141 } 142 143 return 0; 144 } 145 146 static struct xt_match ecn_mt_reg[] __read_mostly = { 147 { 148 .name = "ecn", 149 .family = NFPROTO_IPV4, 150 .match = ecn_mt4, 151 .matchsize = sizeof(struct xt_ecn_info), 152 .checkentry = ecn_mt_check4, 153 .me = THIS_MODULE, 154 }, 155 { 156 .name = "ecn", 157 .family = NFPROTO_IPV6, 158 .match = ecn_mt6, 159 .matchsize = sizeof(struct xt_ecn_info), 160 .checkentry = ecn_mt_check6, 161 .me = THIS_MODULE, 162 }, 163 }; 164 165 static int __init ecn_mt_init(void) 166 { 167 return xt_register_matches(ecn_mt_reg, ARRAY_SIZE(ecn_mt_reg)); 168 } 169 170 static void __exit ecn_mt_exit(void) 171 { 172 xt_unregister_matches(ecn_mt_reg, ARRAY_SIZE(ecn_mt_reg)); 173 } 174 175 module_init(ecn_mt_init); 176 module_exit(ecn_mt_exit); 177