1/* IP tables module for matching the value of the IPv4 and TCP ECN bits
2 *
3 * ipt_ecn.c,v 1.3 2002/05/29 15:09:00 laforge Exp
4 *
5 * (C) 2002 by Harald Welte <laforge@gnumonks.org>
6 *
7 * This software is distributed under the terms GNU GPL v2
8 */
9
10#include <linux/module.h>
11#include <linux/skbuff.h>
12#include <linux/tcp.h>
13
14#include <linux/netfilter_ipv4/ip_tables.h>
15#include <linux/netfilter_ipv4/ipt_ecn.h>
16
17MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
18MODULE_DESCRIPTION("IP tables ECN matching module");
19MODULE_LICENSE("GPL");
20
21static inline int match_ip(const struct sk_buff *skb,
22			   const struct iphdr *iph,
23			   const struct ipt_ecn_info *einfo)
24{
25	return ((iph->tos&IPT_ECN_IP_MASK) == einfo->ip_ect);
26}
27
28static inline int match_tcp(const struct sk_buff *skb,
29			    const struct iphdr *iph,
30			    const struct ipt_ecn_info *einfo)
31{
32	struct tcphdr *tcph = (void *)iph + iph->ihl*4;
33
34	if (einfo->operation & IPT_ECN_OP_MATCH_ECE) {
35		if (einfo->invert & IPT_ECN_OP_MATCH_ECE) {
36			if (tcph->ece == 1)
37				return 0;
38		} else {
39			if (tcph->ece == 0)
40				return 0;
41		}
42	}
43
44	if (einfo->operation & IPT_ECN_OP_MATCH_CWR) {
45		if (einfo->invert & IPT_ECN_OP_MATCH_CWR) {
46			if (tcph->cwr == 1)
47				return 0;
48		} else {
49			if (tcph->cwr == 0)
50				return 0;
51		}
52	}
53
54	return 1;
55}
56
57static int match(const struct sk_buff *skb, const struct net_device *in,
58		 const struct net_device *out, const void *matchinfo,
59		 int offset, const void *hdr, u_int16_t datalen,
60		 int *hotdrop)
61{
62	const struct ipt_ecn_info *info = matchinfo;
63	const struct iphdr *iph = skb->nh.iph;
64
65	if (info->operation & IPT_ECN_OP_MATCH_IP)
66		if (!match_ip(skb, iph, info))
67			return 0;
68
69	if (info->operation & (IPT_ECN_OP_MATCH_ECE|IPT_ECN_OP_MATCH_CWR)) {
70		if (iph->protocol != IPPROTO_TCP)
71			return 0;
72		if (!match_tcp(skb, iph, info))
73			return 0;
74	}
75
76	return 1;
77}
78
79static int checkentry(const char *tablename, const struct ipt_ip *ip,
80		      void *matchinfo, unsigned int matchsize,
81		      unsigned int hook_mask)
82{
83	const struct ipt_ecn_info *info = matchinfo;
84
85	if (matchsize != IPT_ALIGN(sizeof(struct ipt_ecn_info)))
86		return 0;
87
88	if (info->operation & IPT_ECN_OP_MATCH_MASK)
89		return 0;
90
91	if (info->invert & IPT_ECN_OP_MATCH_MASK)
92		return 0;
93
94	if (info->operation & (IPT_ECN_OP_MATCH_ECE|IPT_ECN_OP_MATCH_CWR)
95	    && ip->proto != IPPROTO_TCP) {
96		printk(KERN_WARNING "ipt_ecn: can't match TCP bits in rule for"
97		       " non-tcp packets\n");
98		return 0;
99	}
100
101	return 1;
102}
103
104static struct ipt_match ecn_match = { { NULL, NULL }, "ecn", &match,
105		&checkentry, NULL, THIS_MODULE };
106
107static int __init init(void)
108{
109	return ipt_register_match(&ecn_match);
110}
111
112static void __exit fini(void)
113{
114	ipt_unregister_match(&ecn_match);
115}
116
117module_init(init);
118module_exit(fini);
119