1. 根目录:
2. include
3. uapi
4. linux
5. udp.h

/*
 * INET		An implementation of the TCP/IP protocol suite for the LINUX
 *		operating system.  INET is implemented using the  BSD Socket
 *		interface as the means of communication with the user level.
 *
 *		Definitions for the UDP protocol.
 *
 * Version:	@(#)udp.h	1.0.2	04/28/93
 *
 * Author:	Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 *
 *		This program is free software; you can redistribute it and/or
 *		modify it under the terms of the GNU General Public License
 *		as published by the Free Software Foundation; either version
 *		2 of the License, or (at your option) any later version.
 */
#ifndef _UAPI_LINUX_UDP_H
#define _UAPI_LINUX_UDP_H

#include <linux/types.h>

struct udphdr {
	__be16	source;
	__be16	dest;
	__be16	len;
	__sum16	check;
};

/* UDP socket options */
#define UDP_CORK	1	/* Never send partially complete segments */
#define UDP_ENCAP	100	/* Set the socket to accept encapsulated packets */

/* UDP encapsulation types */
#define UDP_ENCAP_ESPINUDP_NON_IKE	1 /* draft-ietf-ipsec-nat-t-ike-00/01 */
#define UDP_ENCAP_ESPINUDP	2 /* draft-ietf-ipsec-udp-encaps-06 */
#define UDP_ENCAP_L2TPINUDP	3 /* rfc2661 */


#endif /* _UAPI_LINUX_UDP_H */