gre.h

/*
 * Copyright (c) 2003 Niels Provos <provos@citi.umich.edu>
 * All rights reserved.
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifndef _GRE_
#define _GRE_

struct gre_hdr {
	uint16_t gre_flags;
	uint16_t gre_proto;
	uint16_t gre_sum;		/* Optional (RFC 2784) */
	uint16_t gre_reserved;		/* Optional (RFC 2784) */
} __attribute__((__packed__));

#define GRE_CHECKSUM	0x8000		/* Use the checksum field */
#define GRE_VERSION	0
#define GRE_IP4PROTO	0x800		/* Required by RFC */

#define GRE_NOCKSUM_DATA(x)	(u_char *)(&(x)->gre_sum)

int gre_encapsulate(ip_t *, struct addr *, struct addr *,
    struct ip_hdr *, u_int);
int gre_decapsulate(struct ip_hdr *, u_short oiplen, struct ip_hdr **, 
    u_short *);

#endif /* _GRE_ */