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/*
* Copyright 2013 Google Inc.
*
* 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., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*/
/*
* Author: ncardwell@google.com (Neal Cardwell)
*
* Our own GRE header declarations, so we have something that's
* portable and somewhat more readable than a typical system header
* file.
*
* We cannot include the kernel's GRE .h files because this tool tries
* to compile and work for basically any Linux/BSD kernel version. So
* we declare our own version of various GRE-related definitions here.
*/
#ifndef __GRE_HEADERS_H__
#define __GRE_HEADERS_H__
#include "types.h"
/* GRE header. See RFC 1701. */
#define GRE_MINLEN 4 /* smallest possible GRE header */
#define GRE_FLAG_C 0x8000 /* checksum */
#define GRE_FLAG_R 0x4000 /* routing */
#define GRE_FLAG_K 0x2000 /* key */
#define GRE_FLAG_S 0x1000 /* sequence */
struct gre {
union {
__be16 flags;
struct {
#if __BYTE_ORDER == __LITTLE_ENDIAN
__u16 recursion_control:3,
strict_route:1,
has_seq:1,
has_key:1,
has_routing:1,
has_checksum:1,
version:3,
reserved:4,
ack:1;
#elif __BYTE_ORDER == __BIG_ENDIAN
__u16 has_checksum:1,
has_routing:1,
has_key:1,
has_seq:1,
strict_route:1,
recursion_control:3,
ack:1,
reserved:4,
version:3;
#else
# error "Please fix endianness defines"
#endif
};
};
__be16 proto;
/* The optional header fields live here. */
union {
__be16 be16[6];
__be32 be32[3];
};
};
/* Return the length in bytes of a GRE header. */
static inline int gre_len(const struct gre *gre)
{
int bytes = GRE_MINLEN;
assert(gre->version == 0); /* we only support v0 */
assert(!gre->has_routing); /* routing info is variable-length! */
if (gre->has_checksum || gre->has_routing)
bytes += 4;
if (gre->has_key)
bytes += 4;
if (gre->has_seq)
bytes += 4;
return bytes;
}
#endif /* __GRE_HEADERS_H__ */
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