1#ifndef __NET_GUE_H
  2#define __NET_GUE_H
  3
  4/* Definitions for the GUE header, standard and private flags, lengths
  5 * of optional fields are below.
  6 *
  7 * Diagram of GUE header:
  8 *
  9 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 10 * |Ver|C|  Hlen   | Proto/ctype   |        Standard flags       |P|
 11 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 12 * |                                                               |
 13 * ~                      Fields (optional)                        ~
 14 * |                                                               |
 15 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 16 * |            Private flags (optional, P bit is set)             |
 17 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 18 * |                                                               |
 19 * ~                   Private fields (optional)                   ~
 20 * |                                                               |
 21 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 22 *
 23 * C bit indicates contol message when set, data message when unset.
 24 * For a control message, proto/ctype is interpreted as a type of
 25 * control message. For data messages, proto/ctype is the IP protocol
 26 * of the next header.
 27 *
 28 * P bit indicates private flags field is present. The private flags
 29 * may refer to options placed after this field.
 30 */
 31
 32struct guehdr {
 33	union {
 34		struct {
 35#if defined(__LITTLE_ENDIAN_BITFIELD)
 36			__u8	hlen:5,
 37				control:1,
 38				version:2;
 39#elif defined (__BIG_ENDIAN_BITFIELD)
 40			__u8	version:2,
 41				control:1,
 42				hlen:5;
 43#else
 44#error  "Please fix <asm/byteorder.h>"
 45#endif
 46			__u8    proto_ctype;
 47			__u16   flags;
 48		};
 49		__u32 word;
 50	};
 51};
 52
 53/* Standard flags in GUE header */
 54
 55#define GUE_FLAG_PRIV	htons(1<<0)	/* Private flags are in options */
 56#define GUE_LEN_PRIV	4
 57
 58#define GUE_FLAGS_ALL	(GUE_FLAG_PRIV)
 59
 60/* Private flags in the private option extension */
 61
 62#define GUE_PFLAG_REMCSUM	htonl(1 << 31)
 63#define GUE_PLEN_REMCSUM	4
 64
 65#define GUE_PFLAGS_ALL	(GUE_PFLAG_REMCSUM)
 66
 67/* Functions to compute options length corresponding to flags.
 68 * If we ever have a lot of flags this can be potentially be
 69 * converted to a more optimized algorithm (table lookup
 70 * for instance).
 71 */
 72static inline size_t guehdr_flags_len(__be16 flags)
 73{
 74	return ((flags & GUE_FLAG_PRIV) ? GUE_LEN_PRIV : 0);
 75}
 76
 77static inline size_t guehdr_priv_flags_len(__be32 flags)
 78{
 79	return 0;
 80}
 81
 82/* Validate standard and private flags. Returns non-zero (meaning invalid)
 83 * if there is an unknown standard or private flags, or the options length for
 84 * the flags exceeds the options length specific in hlen of the GUE header.
 85 */
 86static inline int validate_gue_flags(struct guehdr *guehdr,
 87				     size_t optlen)
 88{
 89	size_t len;
 90	__be32 flags = guehdr->flags;
 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		flags = *(__be32 *)((void *)&guehdr[1] + len - GUE_LEN_PRIV);
104
105		if (flags & ~GUE_PFLAGS_ALL)
106			return 1;
107
108		len += guehdr_priv_flags_len(flags);
109		if (len > optlen)
110			return 1;
111	}
112
113	return 0;
114}
115
116#endif