include/net/inet_dscp.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3  * inet_dscp.h: helpers for handling differentiated services codepoints (DSCP)
   4  *
   5  * DSCP is defined in RFC 2474:
   6  *
   7  *        0   1   2   3   4   5   6   7
   8  *      +---+---+---+---+---+---+---+---+
   9  *      |         DSCP          |  CU   |
  10  *      +---+---+---+---+---+---+---+---+
  11  *
  12  *        DSCP: differentiated services codepoint
  13  *        CU:   currently unused
  14  *
  15  * The whole DSCP + CU bits form the DS field.
  16  * The DS field is also commonly called TOS or Traffic Class (for IPv6).
  17  *
  18  * Note: the CU bits are now used for Explicit Congestion Notification
  19  *       (RFC 3168).
  20  */
  21
  22 #ifndef _INET_DSCP_H
  23 #define _INET_DSCP_H
  24
  25 #include <linux/types.h>
  26
  27 /* Special type for storing DSCP values.
  28  *
  29  * A dscp_t variable stores a DS field with the CU (ECN) bits cleared.
  30  * Using dscp_t allows to strictly separate DSCP and ECN bits, thus avoiding
  31  * bugs where ECN bits are erroneously taken into account during FIB lookups
  32  * or policy routing.
  33  *
  34  * Note: to get the real DSCP value contained in a dscp_t variable one would
  35  * have to do a bit shift after calling inet_dscp_to_dsfield(). We could have
  36  * a helper for that, but there's currently no users.
  37  */
  38 typedef u8 __bitwise dscp_t;
  39
  40 #define INET_DSCP_MASK 0xfc
  41
  42 static inline dscp_t inet_dsfield_to_dscp(__u8 dsfield)
  43 {
  44         return (__force dscp_t)(dsfield & INET_DSCP_MASK);
  45 }
  46
  47 static inline __u8 inet_dscp_to_dsfield(dscp_t dscp)
  48 {
  49         return (__force __u8)dscp;
  50 }
  51
  52 static inline bool inet_validate_dscp(__u8 val)
  53 {
  54         return !(val & ~INET_DSCP_MASK);
  55 }
  56
  57 #endif /* _INET_DSCP_H */