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_ip_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
46 (*pskb)->nfcache |= NFC_ALTERED;
51 /* Return 0 if there was an error. */
53 set_ect_tcp(struct sk_buff **pskb, const struct ipt_ECN_info *einfo, int inward)
55 struct tcphdr _tcph, *th;
58 /* Not enought header? */
59 th = skb_header_pointer(*pskb, (*pskb)->nh.iph->ihl*4,
60 sizeof(_tcph), &_tcph);
64 diffs[0] = ((u_int16_t *)th)[6];
65 if (einfo->operation & IPT_ECN_OP_SET_ECE)
66 th->ece = einfo->proto.tcp.ece;
68 if (einfo->operation & IPT_ECN_OP_SET_CWR)
69 th->cwr = einfo->proto.tcp.cwr;
70 diffs[1] = ((u_int16_t *)&th)[6];
72 /* Only mangle if it's changed. */
73 if (diffs[0] != diffs[1]) {
74 diffs[0] = diffs[0] ^ 0xFFFF;
75 if (!skb_ip_make_writable(pskb,
76 (*pskb)->nh.iph->ihl*4+sizeof(_tcph)))
80 memcpy(&_tcph, th, sizeof(_tcph));
82 if ((*pskb)->ip_summed != CHECKSUM_HW)
83 _tcph.check = csum_fold(csum_partial((char *)diffs,
86 memcpy((*pskb)->data + (*pskb)->nh.iph->ihl*4,
87 &_tcph, sizeof(_tcph));
88 if ((*pskb)->ip_summed == CHECKSUM_HW)
89 if (skb_checksum_help(*pskb, inward))
91 (*pskb)->nfcache |= NFC_ALTERED;
97 target(struct sk_buff **pskb,
98 const struct net_device *in,
99 const struct net_device *out,
100 unsigned int hooknum,
101 const void *targinfo,
104 const struct ipt_ECN_info *einfo = targinfo;
106 if (einfo->operation & IPT_ECN_OP_SET_IP)
107 if (!set_ect_ip(pskb, einfo))
110 if (einfo->operation & (IPT_ECN_OP_SET_ECE | IPT_ECN_OP_SET_CWR)
111 && (*pskb)->nh.iph->protocol == IPPROTO_TCP)
112 if (!set_ect_tcp(pskb, einfo, (out == NULL)))
119 checkentry(const char *tablename,
120 const struct ipt_entry *e,
122 unsigned int targinfosize,
123 unsigned int hook_mask)
125 const struct ipt_ECN_info *einfo = (struct ipt_ECN_info *)targinfo;
127 if (targinfosize != IPT_ALIGN(sizeof(struct ipt_ECN_info))) {
128 printk(KERN_WARNING "ECN: targinfosize %u != %Zu\n",
130 IPT_ALIGN(sizeof(struct ipt_ECN_info)));
134 if (strcmp(tablename, "mangle") != 0) {
135 printk(KERN_WARNING "ECN: can only be called from \"mangle\" table, not \"%s\"\n", tablename);
139 if (einfo->operation & IPT_ECN_OP_MASK) {
140 printk(KERN_WARNING "ECN: unsupported ECN operation %x\n",
144 if (einfo->ip_ect & ~IPT_ECN_IP_MASK) {
145 printk(KERN_WARNING "ECN: new ECT codepoint %x out of mask\n",
150 if ((einfo->operation & (IPT_ECN_OP_SET_ECE|IPT_ECN_OP_SET_CWR))
151 && e->ip.proto != IPPROTO_TCP) {
152 printk(KERN_WARNING "ECN: cannot use TCP operations on a "
160 static struct ipt_target ipt_ecn_reg = {
163 .checkentry = checkentry,
167 static int __init init(void)
169 return ipt_register_target(&ipt_ecn_reg);
172 static void __exit fini(void)
174 ipt_unregister_target(&ipt_ecn_reg);