1 /* IP tables module for matching the value of the IPv4 and TCP ECN bits
3 * (C) 2002 by Harald Welte <laforge@gnumonks.org>
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License version 2 as
7 * published by the Free Software Foundation.
9 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13 #include <linux/module.h>
14 #include <linux/skbuff.h>
15 #include <linux/tcp.h>
17 #include <linux/netfilter/x_tables.h>
18 #include <linux/netfilter_ipv4/ip_tables.h>
19 #include <linux/netfilter_ipv4/ipt_ecn.h>
21 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
22 MODULE_DESCRIPTION("Xtables: Explicit Congestion Notification (ECN) flag match for IPv4");
23 MODULE_LICENSE("GPL");
25 static inline bool match_ip(const struct sk_buff *skb,
26 const struct ipt_ecn_info *einfo)
28 return ((ip_hdr(skb)->tos & IPT_ECN_IP_MASK) == einfo->ip_ect) ^
29 !!(einfo->invert & IPT_ECN_OP_MATCH_IP);
32 static inline bool match_tcp(const struct sk_buff *skb,
33 const struct ipt_ecn_info *einfo,
37 const struct tcphdr *th;
39 /* In practice, TCP match does this, so can't fail. But let's
42 th = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_tcph), &_tcph);
48 if (einfo->operation & IPT_ECN_OP_MATCH_ECE) {
49 if (einfo->invert & IPT_ECN_OP_MATCH_ECE) {
58 if (einfo->operation & IPT_ECN_OP_MATCH_CWR) {
59 if (einfo->invert & IPT_ECN_OP_MATCH_CWR) {
71 static bool ecn_mt(const struct sk_buff *skb, struct xt_action_param *par)
73 const struct ipt_ecn_info *info = par->matchinfo;
75 if (info->operation & IPT_ECN_OP_MATCH_IP)
76 if (!match_ip(skb, info))
79 if (info->operation & (IPT_ECN_OP_MATCH_ECE|IPT_ECN_OP_MATCH_CWR)) {
80 if (!match_tcp(skb, info, &par->hotdrop))
87 static int ecn_mt_check(const struct xt_mtchk_param *par)
89 const struct ipt_ecn_info *info = par->matchinfo;
90 const struct ipt_ip *ip = par->entryinfo;
92 if (info->operation & IPT_ECN_OP_MATCH_MASK)
95 if (info->invert & IPT_ECN_OP_MATCH_MASK)
98 if (info->operation & (IPT_ECN_OP_MATCH_ECE|IPT_ECN_OP_MATCH_CWR) &&
99 (ip->proto != IPPROTO_TCP || ip->invflags & IPT_INV_PROTO)) {
100 pr_info("cannot match TCP bits in rule for non-tcp packets\n");
107 static struct xt_match ecn_mt_reg __read_mostly = {
109 .family = NFPROTO_IPV4,
111 .matchsize = sizeof(struct ipt_ecn_info),
112 .checkentry = ecn_mt_check,
116 static int __init ecn_mt_init(void)
118 return xt_register_match(&ecn_mt_reg);
121 static void __exit ecn_mt_exit(void)
123 xt_unregister_match(&ecn_mt_reg);
126 module_init(ecn_mt_init);
127 module_exit(ecn_mt_exit);