linux/include/net/gue.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __NET_GUE_H
#define __NET_GUE_H

/* Definitions for the GUE header, standard and private flags, lengths
 * of optional fields are below.
 *
 * Diagram of GUE header:
 *
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |Ver|C|  Hlen   | Proto/ctype   |        Standard flags       |P|
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |                                                               |
 * ~                      Fields (optional)                        ~
 * |                                                               |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |            Private flags (optional, P bit is set)             |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |                                                               |
 * ~                   Private fields (optional)                   ~
 * |                                                               |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 * C bit indicates control message when set, data message when unset.
 * For a control message, proto/ctype is interpreted as a type of
 * control message. For data messages, proto/ctype is the IP protocol
 * of the next header.
 *
 * P bit indicates private flags field is present. The private flags
 * may refer to options placed after this field.
 */

#include <asm/byteorder.h>
#include <linux/types.h>

struct guehdr { … };

/* Standard flags in GUE header */

#define GUE_FLAG_PRIV …
#define GUE_LEN_PRIV …

#define GUE_FLAGS_ALL …

/* Private flags in the private option extension */

#define GUE_PFLAG_REMCSUM …
#define GUE_PLEN_REMCSUM …

#define GUE_PFLAGS_ALL …

/* Functions to compute options length corresponding to flags.
 * If we ever have a lot of flags this can be potentially be
 * converted to a more optimized algorithm (table lookup
 * for instance).
 */
static inline size_t guehdr_flags_len(__be16 flags)
{ … }

static inline size_t guehdr_priv_flags_len(__be32 flags)
{ … }

/* Validate standard and private flags. Returns non-zero (meaning invalid)
 * if there is an unknown standard or private flags, or the options length for
 * the flags exceeds the options length specific in hlen of the GUE header.
 */
static inline int validate_gue_flags(struct guehdr *guehdr, size_t optlen)
{ … }

#endif