1 /* iptables module for the IPv4 and TCP ECN bits, Version 1.5
3 * (C) 2002 by Harald Welte <laforge@netfilter.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 * ipt_ECN.c,v 1.5 2002/08/18 19:36:51 laforge Exp
12 #include <linux/module.h>
13 #include <linux/skbuff.h>
15 #include <linux/tcp.h>
16 #include <net/checksum.h>
18 #include <linux/netfilter_ipv4/ip_tables.h>
19 #include <linux/netfilter_ipv4/ipt_ECN.h>
21 MODULE_LICENSE("GPL");
22 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
23 MODULE_DESCRIPTION("iptables ECN modification module");
25 /* set ECT codepoint from IP header.
26 * return 0 if there was an error. */
28 set_ect_ip(struct sk_buff **pskb, const struct ipt_ECN_info *einfo)
30 if (((*pskb)->nh.iph->tos & IPT_ECN_IP_MASK)
31 != (einfo->ip_ect & IPT_ECN_IP_MASK)) {
34 if (!skb_make_writable(pskb, sizeof(struct iphdr)))
37 diffs[0] = htons((*pskb)->nh.iph->tos) ^ 0xFFFF;
38 (*pskb)->nh.iph->tos &= ~IPT_ECN_IP_MASK;
39 (*pskb)->nh.iph->tos |= (einfo->ip_ect & IPT_ECN_IP_MASK);
40 diffs[1] = htons((*pskb)->nh.iph->tos);
41 (*pskb)->nh.iph->check
42 = csum_fold(csum_partial((char *)diffs,
44 (*pskb)->nh.iph->check
50 /* Return 0 if there was an error. */
52 set_ect_tcp(struct sk_buff **pskb, const struct ipt_ECN_info *einfo, int inward)
54 struct tcphdr _tcph, *tcph;
57 /* Not enought header? */
58 tcph = skb_header_pointer(*pskb, (*pskb)->nh.iph->ihl*4,
59 sizeof(_tcph), &_tcph);
63 if ((!(einfo->operation & IPT_ECN_OP_SET_ECE) ||
64 tcph->ece == einfo->proto.tcp.ece) &&
65 ((!(einfo->operation & IPT_ECN_OP_SET_CWR) ||
66 tcph->cwr == einfo->proto.tcp.cwr)))
69 if (!skb_make_writable(pskb, (*pskb)->nh.iph->ihl*4+sizeof(*tcph)))
71 tcph = (void *)(*pskb)->nh.iph + (*pskb)->nh.iph->ihl*4;
73 if ((*pskb)->ip_summed == CHECKSUM_HW &&
74 skb_checksum_help(*pskb, inward))
77 diffs[0] = ((u_int16_t *)tcph)[6];
78 if (einfo->operation & IPT_ECN_OP_SET_ECE)
79 tcph->ece = einfo->proto.tcp.ece;
80 if (einfo->operation & IPT_ECN_OP_SET_CWR)
81 tcph->cwr = einfo->proto.tcp.cwr;
82 diffs[1] = ((u_int16_t *)tcph)[6];
83 diffs[0] = diffs[0] ^ 0xFFFF;
85 if ((*pskb)->ip_summed != CHECKSUM_UNNECESSARY)
86 tcph->check = csum_fold(csum_partial((char *)diffs,
93 target(struct sk_buff **pskb,
94 const struct net_device *in,
95 const struct net_device *out,
97 const struct xt_target *target,
101 const struct ipt_ECN_info *einfo = targinfo;
103 if (einfo->operation & IPT_ECN_OP_SET_IP)
104 if (!set_ect_ip(pskb, einfo))
107 if (einfo->operation & (IPT_ECN_OP_SET_ECE | IPT_ECN_OP_SET_CWR)
108 && (*pskb)->nh.iph->protocol == IPPROTO_TCP)
109 if (!set_ect_tcp(pskb, einfo, (out == NULL)))
116 checkentry(const char *tablename,
118 const struct xt_target *target,
120 unsigned int targinfosize,
121 unsigned int hook_mask)
123 const struct ipt_ECN_info *einfo = (struct ipt_ECN_info *)targinfo;
124 const struct ipt_entry *e = e_void;
126 if (einfo->operation & IPT_ECN_OP_MASK) {
127 printk(KERN_WARNING "ECN: unsupported ECN operation %x\n",
131 if (einfo->ip_ect & ~IPT_ECN_IP_MASK) {
132 printk(KERN_WARNING "ECN: new ECT codepoint %x out of mask\n",
136 if ((einfo->operation & (IPT_ECN_OP_SET_ECE|IPT_ECN_OP_SET_CWR))
137 && (e->ip.proto != IPPROTO_TCP || (e->ip.invflags & IPT_INV_PROTO))) {
138 printk(KERN_WARNING "ECN: cannot use TCP operations on a "
145 static struct ipt_target ipt_ecn_reg = {
148 .targetsize = sizeof(struct ipt_ECN_info),
150 .checkentry = checkentry,
154 static int __init ipt_ecn_init(void)
156 return ipt_register_target(&ipt_ecn_reg);
159 static void __exit ipt_ecn_fini(void)
161 ipt_unregister_target(&ipt_ecn_reg);
164 module_init(ipt_ecn_init);
165 module_exit(ipt_ecn_fini);