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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 | /* iptables module for the IPv4 and TCP ECN bits, Version 1.5
*
* (C) 2002 by Harald Welte <laforge@netfilter.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/in.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <net/ip.h>
#include <linux/tcp.h>
#include <net/checksum.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ipt_ECN.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
MODULE_DESCRIPTION("iptables ECN modification module");
/* set ECT codepoint from IP header.
* return false if there was an error. */
static inline bool
set_ect_ip(struct sk_buff **pskb, const struct ipt_ECN_info *einfo)
{
struct iphdr *iph = ip_hdr(*pskb);
if ((iph->tos & IPT_ECN_IP_MASK) != (einfo->ip_ect & IPT_ECN_IP_MASK)) {
__u8 oldtos;
if (!skb_make_writable(pskb, sizeof(struct iphdr)))
return false;
iph = ip_hdr(*pskb);
oldtos = iph->tos;
iph->tos &= ~IPT_ECN_IP_MASK;
iph->tos |= (einfo->ip_ect & IPT_ECN_IP_MASK);
nf_csum_replace2(&iph->check, htons(oldtos), htons(iph->tos));
}
return true;
}
/* Return false if there was an error. */
static inline bool
set_ect_tcp(struct sk_buff **pskb, const struct ipt_ECN_info *einfo)
{
struct tcphdr _tcph, *tcph;
__be16 oldval;
/* Not enought header? */
tcph = skb_header_pointer(*pskb, ip_hdrlen(*pskb),
sizeof(_tcph), &_tcph);
if (!tcph)
return false;
if ((!(einfo->operation & IPT_ECN_OP_SET_ECE) ||
tcph->ece == einfo->proto.tcp.ece) &&
(!(einfo->operation & IPT_ECN_OP_SET_CWR) ||
tcph->cwr == einfo->proto.tcp.cwr))
return true;
if (!skb_make_writable(pskb, ip_hdrlen(*pskb) + sizeof(*tcph)))
return false;
tcph = (void *)ip_hdr(*pskb) + ip_hdrlen(*pskb);
oldval = ((__be16 *)tcph)[6];
if (einfo->operation & IPT_ECN_OP_SET_ECE)
tcph->ece = einfo->proto.tcp.ece;
if (einfo->operation & IPT_ECN_OP_SET_CWR)
tcph->cwr = einfo->proto.tcp.cwr;
nf_proto_csum_replace2(&tcph->check, *pskb,
oldval, ((__be16 *)tcph)[6], 0);
return true;
}
static unsigned int
target(struct sk_buff **pskb,
const struct net_device *in,
const struct net_device *out,
unsigned int hooknum,
const struct xt_target *target,
const void *targinfo)
{
const struct ipt_ECN_info *einfo = targinfo;
if (einfo->operation & IPT_ECN_OP_SET_IP)
if (!set_ect_ip(pskb, einfo))
return NF_DROP;
if (einfo->operation & (IPT_ECN_OP_SET_ECE | IPT_ECN_OP_SET_CWR)
&& ip_hdr(*pskb)->protocol == IPPROTO_TCP)
if (!set_ect_tcp(pskb, einfo))
return NF_DROP;
return XT_CONTINUE;
}
static bool
checkentry(const char *tablename,
const void *e_void,
const struct xt_target *target,
void *targinfo,
unsigned int hook_mask)
{
const struct ipt_ECN_info *einfo = (struct ipt_ECN_info *)targinfo;
const struct ipt_entry *e = e_void;
if (einfo->operation & IPT_ECN_OP_MASK) {
printk(KERN_WARNING "ECN: unsupported ECN operation %x\n",
einfo->operation);
return false;
}
if (einfo->ip_ect & ~IPT_ECN_IP_MASK) {
printk(KERN_WARNING "ECN: new ECT codepoint %x out of mask\n",
einfo->ip_ect);
return false;
}
if ((einfo->operation & (IPT_ECN_OP_SET_ECE|IPT_ECN_OP_SET_CWR))
&& (e->ip.proto != IPPROTO_TCP || (e->ip.invflags & XT_INV_PROTO))) {
printk(KERN_WARNING "ECN: cannot use TCP operations on a "
"non-tcp rule\n");
return false;
}
return true;
}
static struct xt_target ipt_ecn_reg __read_mostly = {
.name = "ECN",
.family = AF_INET,
.target = target,
.targetsize = sizeof(struct ipt_ECN_info),
.table = "mangle",
.checkentry = checkentry,
.me = THIS_MODULE,
};
static int __init ipt_ecn_init(void)
{
return xt_register_target(&ipt_ecn_reg);
}
static void __exit ipt_ecn_fini(void)
{
xt_unregister_target(&ipt_ecn_reg);
}
module_init(ipt_ecn_init);
module_exit(ipt_ecn_fini);
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