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
121