1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef __NET_GUE_H
  3#define __NET_GUE_H
  4
  5/* Definitions for the GUE header, standard and private flags, lengths
  6 * of optional fields are below.
  7 *
  8 * Diagram of GUE header:
  9 *
 10 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 11 * |Ver|C|  Hlen   | Proto/ctype   |        Standard flags       |P|
 12 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 13 * |                                                               |
 14 * ~                      Fields (optional)                        ~
 15 * |                                                               |
 16 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 17 * |            Private flags (optional, P bit is set)             |
 18 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 19 * |                                                               |
 20 * ~                   Private fields (optional)                   ~
 21 * |                                                               |
 22 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 23 *
 24 * C bit indicates control message when set, data message when unset.
 25 * For a control message, proto/ctype is interpreted as a type of
 26 * control message. For data messages, proto/ctype is the IP protocol
 27 * of the next header.
 28 *
 29 * P bit indicates private flags field is present. The private flags
 30 * may refer to options placed after this field.
 31 */
 32
 33#include <asm/byteorder.h>
 34#include <linux/types.h>
 35
 36struct guehdr {
 37	union {
 38		struct {
 39#if defined(__LITTLE_ENDIAN_BITFIELD)
 40			__u8	hlen:5,
 41				control:1,
 42				version:2;
 43#elif defined (__BIG_ENDIAN_BITFIELD)
 44			__u8	version:2,
 45				control:1,
 46				hlen:5;
 47#else
 48#error  "Please fix <asm/byteorder.h>"
 49#endif
 50			__u8	proto_ctype;
 51			__be16	flags;
 52		};
 53		__be32	word;
 54	};
 55};
 56
 57/* Standard flags in GUE header */
 58
 59#define GUE_FLAG_PRIV	htons(1<<0)	/* Private flags are in options */
 60#define GUE_LEN_PRIV	4
 61
 62#define GUE_FLAGS_ALL	(GUE_FLAG_PRIV)
 63
 64/* Private flags in the private option extension */
 65
 66#define GUE_PFLAG_REMCSUM	htonl(1U << 31)
 67#define GUE_PLEN_REMCSUM	4
 68
 69#define GUE_PFLAGS_ALL	(GUE_PFLAG_REMCSUM)
 70
 71/* Functions to compute options length corresponding to flags.
 72 * If we ever have a lot of flags this can be potentially be
 73 * converted to a more optimized algorithm (table lookup
 74 * for instance).
 75 */
 76static inline size_t guehdr_flags_len(__be16 flags)
 77{
 78	return ((flags & GUE_FLAG_PRIV) ? GUE_LEN_PRIV : 0);
 79}
 80
 81static inline size_t guehdr_priv_flags_len(__be32 flags)
 82{
 83	return 0;
 84}
 85
 86/* Validate standard and private flags. Returns non-zero (meaning invalid)
 87 * if there is an unknown standard or private flags, or the options length for
 88 * the flags exceeds the options length specific in hlen of the GUE header.
 89 */
 90static inline int validate_gue_flags(struct guehdr *guehdr, size_t optlen)
 91{
 92	__be16 flags = guehdr->flags;
 93	size_t len;
 94
 95	if (flags & ~GUE_FLAGS_ALL)
 96		return 1;
 97
 98	len = guehdr_flags_len(flags);
 99	if (len > optlen)
100		return 1;
101
102	if (flags & GUE_FLAG_PRIV) {
103		/* Private flags are last four bytes accounted in
104		 * guehdr_flags_len
105		 */
106		__be32 pflags = *(__be32 *)((void *)&guehdr[1] +
107					    len - GUE_LEN_PRIV);
108
109		if (pflags & ~GUE_PFLAGS_ALL)
110			return 1;
111
112		len += guehdr_priv_flags_len(pflags);
113		if (len > optlen)
114			return 1;
115	}
116
117	return 0;
118}
119
120#endif