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#include <linux/types.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/netfilter.h>
#include <linux/in.h>
#include <linux/udp.h>
#include <linux/netfilter_ipv4/ip_conntrack_protocol.h>
 
unsigned long ip_ct_udp_timeout = 30*HZ;
unsigned long ip_ct_udp_timeout_stream = 180*HZ;
 
static int udp_pkt_to_tuple(const void *datah, size_t datalen,
			    struct ip_conntrack_tuple *tuple)
{
	const struct udphdr *hdr = datah;
 
	tuple->src.u.udp.port = hdr->source;
	tuple->dst.u.udp.port = hdr->dest;
 
	return 1;
}
 
static int udp_invert_tuple(struct ip_conntrack_tuple *tuple,
			    const struct ip_conntrack_tuple *orig)
{
	tuple->src.u.udp.port = orig->dst.u.udp.port;
	tuple->dst.u.udp.port = orig->src.u.udp.port;
	return 1;
}
 
/* Print out the per-protocol part of the tuple. */
static unsigned int udp_print_tuple(char *buffer,
				    const struct ip_conntrack_tuple *tuple)
{
	return sprintf(buffer, "sport=%hu dport=%hu ",
		       ntohs(tuple->src.u.udp.port),
		       ntohs(tuple->dst.u.udp.port));
}
 
/* Print out the private part of the conntrack. */
static unsigned int udp_print_conntrack(char *buffer,
					const struct ip_conntrack *conntrack)
{
	return 0;
}
 
/* Returns verdict for packet, and may modify conntracktype */
static int udp_packet(struct ip_conntrack *conntrack,
		      struct iphdr *iph, size_t len,
		      enum ip_conntrack_info conntrackinfo)
{
	/* If we've seen traffic both ways, this is some kind of UDP
	   stream.  Extend timeout. */
	if (test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)) {
		ip_ct_refresh(conntrack, ip_ct_udp_timeout_stream);
		/* Also, more likely to be important, and not a probe */
		set_bit(IPS_ASSURED_BIT, &conntrack->status);
	} else
		ip_ct_refresh(conntrack, ip_ct_udp_timeout);
 
	return NF_ACCEPT;
}
 
/* Called when a new connection for this protocol found. */
static int udp_new(struct ip_conntrack *conntrack,
			     struct iphdr *iph, size_t len)
{
	return 1;
}
 
struct ip_conntrack_protocol ip_conntrack_protocol_udp
= { { NULL, NULL }, IPPROTO_UDP, "udp",
    udp_pkt_to_tuple, udp_invert_tuple, udp_print_tuple, udp_print_conntrack,
    udp_packet, udp_new, NULL, NULL, NULL };