include/net/gue.h

   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
  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  */
  73 static inline size_t guehdr_flags_len(__be16 flags)
  74 {
  75         return ((flags & GUE_FLAG_PRIV) ? GUE_LEN_PRIV : 0);
  76 }
  77
  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  */
  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