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/*
* iptables module for DCCP protocol header matching
*
* (C) 2005 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/module.h>
#include <linux/skbuff.h>
#include <linux/spinlock.h>
#include <net/ip.h>
#include <linux/dccp.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ipt_dccp.h>
#define DCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
|| (!!((invflag) & (option)) ^ (cond)))
static unsigned char *dccp_optbuf;
static DEFINE_SPINLOCK(dccp_buflock);
static inline int
dccp_find_option(u_int8_t option,
const struct sk_buff *skb,
const struct dccp_hdr *dh,
int *hotdrop)
{
/* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */
unsigned char *op;
unsigned int optoff = __dccp_hdr_len(dh);
unsigned int optlen = dh->dccph_doff*4 - __dccp_hdr_len(dh);
unsigned int i;
if (dh->dccph_doff * 4 < __dccp_hdr_len(dh)) {
*hotdrop = 1;
return 0;
}
if (!optlen)
return 0;
spin_lock_bh(&dccp_buflock);
op = skb_header_pointer(skb,
skb->nh.iph->ihl*4 + optoff,
optlen, dccp_optbuf);
if (op == NULL) {
/* If we don't have the whole header, drop packet. */
spin_unlock_bh(&dccp_buflock);
*hotdrop = 1;
return 0;
}
for (i = 0; i < optlen; ) {
if (op[i] == option) {
spin_unlock_bh(&dccp_buflock);
return 1;
}
if (op[i] < 2)
i++;
else
i += op[i+1]?:1;
}
spin_unlock_bh(&dccp_buflock);
return 0;
}
static inline int
match_types(const struct dccp_hdr *dh, u_int16_t typemask)
{
return (typemask & (1 << dh->dccph_type));
}
static inline int
match_option(u_int8_t option, const struct sk_buff *skb,
const struct dccp_hdr *dh, int *hotdrop)
{
return dccp_find_option(option, skb, dh, hotdrop);
}
static int
match(const struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
const void *matchinfo,
int offset,
int *hotdrop)
{
const struct ipt_dccp_info *info =
(const struct ipt_dccp_info *)matchinfo;
struct dccp_hdr _dh, *dh;
if (offset)
return 0;
dh = skb_header_pointer(skb, skb->nh.iph->ihl*4, sizeof(_dh), &_dh);
if (dh == NULL) {
*hotdrop = 1;
return 0;
}
return DCCHECK(((ntohs(dh->dccph_sport) >= info->spts[0])
&& (ntohs(dh->dccph_sport) <= info->spts[1])),
IPT_DCCP_SRC_PORTS, info->flags, info->invflags)
&& DCCHECK(((ntohs(dh->dccph_dport) >= info->dpts[0])
&& (ntohs(dh->dccph_dport) <= info->dpts[1])),
IPT_DCCP_DEST_PORTS, info->flags, info->invflags)
&& DCCHECK(match_types(dh, info->typemask),
IPT_DCCP_TYPE, info->flags, info->invflags)
&& DCCHECK(match_option(info->option, skb, dh, hotdrop),
IPT_DCCP_OPTION, info->flags, info->invflags);
}
static int
checkentry(const char *tablename,
const struct ipt_ip *ip,
void *matchinfo,
unsigned int matchsize,
unsigned int hook_mask)
{
const struct ipt_dccp_info *info;
info = (const struct ipt_dccp_info *)matchinfo;
return ip->proto == IPPROTO_DCCP
&& !(ip->invflags & IPT_INV_PROTO)
&& matchsize == IPT_ALIGN(sizeof(struct ipt_dccp_info))
&& !(info->flags & ~IPT_DCCP_VALID_FLAGS)
&& !(info->invflags & ~IPT_DCCP_VALID_FLAGS)
&& !(info->invflags & ~info->flags);
}
static struct ipt_match dccp_match =
{
.name = "dccp",
.match = &match,
.checkentry = &checkentry,
.me = THIS_MODULE,
};
static int __init init(void)
{
int ret;
/* doff is 8 bits, so the maximum option size is (4*256). Don't put
* this in BSS since DaveM is worried about locked TLB's for kernel
* BSS. */
dccp_optbuf = kmalloc(256 * 4, GFP_KERNEL);
if (!dccp_optbuf)
return -ENOMEM;
ret = ipt_register_match(&dccp_match);
if (ret)
kfree(dccp_optbuf);
return ret;
}
static void __exit fini(void)
{
ipt_unregister_match(&dccp_match);
kfree(dccp_optbuf);
}
module_init(init);
module_exit(fini);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
MODULE_DESCRIPTION("Match for DCCP protocol packets");
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