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 contol 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
 33struct guehdr {
 34	union {
 35		struct {
 36#if defined(__LITTLE_ENDIAN_BITFIELD)
 37			__u8	hlen:5,
 38				control:1,
 39				version:2;
 40#elif defined (__BIG_ENDIAN_BITFIELD)
 41			__u8	version:2,
 42				control:1,
 43				hlen:5;
 44#else
 45#error  "Please fix <asm/byteorder.h>"
 46#endif
 47			__u8	proto_ctype;
 48			__be16	flags;
 49		};
 50		__be32	word;
 51	};
 52};
 53
 54/* Standard flags in GUE header */
 55
 56#define GUE_FLAG_PRIV	htons(1<<0)	/* Private flags are in options */
 57#define GUE_LEN_PRIV	4
 58
 59#define GUE_FLAGS_ALL	(GUE_FLAG_PRIV)
 60
 61/* Private flags in the private option extension */
 62
 63#define GUE_PFLAG_REMCSUM	htonl(1 << 31)
 64#define GUE_PLEN_REMCSUM	4
 65
 66#define GUE_PFLAGS_ALL	(GUE_PFLAG_REMCSUM)
 67
 68/* Functions to compute options length corresponding to flags.
 69 * If we ever have a lot of flags this can be potentially be
 70 * converted to a more optimized algorithm (table lookup
 71 * for instance).
 72 */
 73static inline size_t guehdr_flags_len(__be16 flags)
 74{
 75	return ((flags & GUE_FLAG_PRIV) ? GUE_LEN_PRIV : 0);
 76}
 77
 78static inline size_t guehdr_priv_flags_len(__be32 flags)
 79{
 80	return 0;
 81}
 82
 83/* Validate standard and private flags. Returns non-zero (meaning invalid)
 84 * if there is an unknown standard or private flags, or the options length for
 85 * the flags exceeds the options length specific in hlen of the GUE header.
 86 */
 87static inline int validate_gue_flags(struct guehdr *guehdr, size_t optlen)
 88{
 89	__be16 flags = guehdr->flags;
 90	size_t len;
 91
 92	if (flags & ~GUE_FLAGS_ALL)
 93		return 1;
 94
 95	len = guehdr_flags_len(flags);
 96	if (len > optlen)
 97		return 1;
 98
 99	if (flags & GUE_FLAG_PRIV) {
100		/* Private flags are last four bytes accounted in
101		 * guehdr_flags_len
102		 */
103		__be32 pflags = *(__be32 *)((void *)&guehdr[1] +
104					    len - GUE_LEN_PRIV);
105
106		if (pflags & ~GUE_PFLAGS_ALL)
107			return 1;
108
109		len += guehdr_priv_flags_len(pflags);
110		if (len > optlen)
111			return 1;
112	}
113
114	return 0;
115}
116
117#endif