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 struct 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(1U << 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  */
guehdr_flags_len(__be16 flags)73 static inline size_t guehdr_flags_len(__be16 flags)
74 {
75 	return ((flags & GUE_FLAG_PRIV) ? GUE_LEN_PRIV : 0);
76 }
77 
guehdr_priv_flags_len(__be32 flags)78 static 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  */
validate_gue_flags(struct guehdr * guehdr,size_t optlen)87 static 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
118