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/* Kernel module to match one of a list of TCP/UDP ports: ports are in
the same place so we can treat them as equal. */
#include <linux/module.h>
#include <linux/types.h>
#include <linux/udp.h>
#include <linux/skbuff.h>
#include <linux/netfilter_ipv4/ipt_mport.h>
#include <linux/netfilter_ipv4/ip_tables.h>
MODULE_LICENSE("GPL");
#if 0
#define duprintf(format, args...) printk(format , ## args)
#else
#define duprintf(format, args...)
#endif
/* Returns 1 if the port is matched by the test, 0 otherwise. */
static inline int
ports_match(const struct ipt_mport *minfo, u_int16_t src, u_int16_t dst)
{
unsigned int i;
unsigned int m;
u_int16_t pflags = minfo->pflags;
for (i=0, m=1; i<IPT_MULTI_PORTS; i++, m<<=1) {
u_int16_t s, e;
if (pflags & m
&& minfo->ports[i] == 65535)
return 0;
s = minfo->ports[i];
if (pflags & m) {
e = minfo->ports[++i];
m <<= 1;
} else
e = s;
if (minfo->flags & IPT_MPORT_SOURCE
&& src >= s && src <= e)
return 1;
if (minfo->flags & IPT_MPORT_DESTINATION
&& dst >= s && dst <= e)
return 1;
}
return 0;
}
static int
match(const struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
const void *matchinfo,
int offset,
const void *hdr,
u_int16_t datalen,
int *hotdrop)
{
const struct udphdr *udp = hdr;
const struct ipt_mport *minfo = matchinfo;
/* Must be big enough to read ports. */
if (offset == 0 && datalen < sizeof(struct udphdr)) {
/* We've been asked to examine this packet, and we
can't. Hence, no choice but to drop. */
duprintf("ipt_mport:"
" Dropping evil offset=0 tinygram.\n");
*hotdrop = 1;
return 0;
}
/* Must not be a fragment. */
return !offset
&& ports_match(minfo, ntohs(udp->source), ntohs(udp->dest));
}
/* Called when user tries to insert an entry of this type. */
static int
checkentry(const char *tablename,
const struct ipt_ip *ip,
void *matchinfo,
unsigned int matchsize,
unsigned int hook_mask)
{
if (matchsize != IPT_ALIGN(sizeof(struct ipt_mport)))
return 0;
/* Must specify proto == TCP/UDP, no unknown flags or bad count */
return (ip->proto == IPPROTO_TCP || ip->proto == IPPROTO_UDP)
&& !(ip->invflags & IPT_INV_PROTO)
&& matchsize == IPT_ALIGN(sizeof(struct ipt_mport));
}
static struct ipt_match mport_match
= { { NULL, NULL }, "mport", &match, &checkentry, NULL, THIS_MODULE };
static int __init init(void)
{
return ipt_register_match(&mport_match);
}
static void __exit fini(void)
{
ipt_unregister_match(&mport_match);
}
module_init(init);
module_exit(fini);
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