include/net/inet_dscp.h

0001 /* SPDX-License-Identifier: GPL-2.0-or-later */
0002 /*
0003  * inet_dscp.h: helpers for handling differentiated services codepoints (DSCP)
0004  *
0005  * DSCP is defined in RFC 2474:
0006  *
0007  *        0   1   2   3   4   5   6   7
0008  *      +---+---+---+---+---+---+---+---+
0009  *      |         DSCP          |  CU   |
0010  *      +---+---+---+---+---+---+---+---+
0011  *
0012  *        DSCP: differentiated services codepoint
0013  *        CU:   currently unused
0014  *
0015  * The whole DSCP + CU bits form the DS field.
0016  * The DS field is also commonly called TOS or Traffic Class (for IPv6).
0017  *
0018  * Note: the CU bits are now used for Explicit Congestion Notification
0019  *       (RFC 3168).
0020  */
0021
0022 #ifndef _INET_DSCP_H
0023 #define _INET_DSCP_H
0024
0025 #include <linux/types.h>
0026
0027 /* Special type for storing DSCP values.
0028  *
0029  * A dscp_t variable stores a DS field with the CU (ECN) bits cleared.
0030  * Using dscp_t allows to strictly separate DSCP and ECN bits, thus avoiding
0031  * bugs where ECN bits are erroneously taken into account during FIB lookups
0032  * or policy routing.
0033  *
0034  * Note: to get the real DSCP value contained in a dscp_t variable one would
0035  * have to do a bit shift after calling inet_dscp_to_dsfield(). We could have
0036  * a helper for that, but there's currently no users.
0037  */
0038 typedef u8 __bitwise dscp_t;
0039
0040 #define INET_DSCP_MASK 0xfc
0041
0042 static inline dscp_t inet_dsfield_to_dscp(__u8 dsfield)
0043 {
0044     return (__force dscp_t)(dsfield & INET_DSCP_MASK);
0045 }
0046
0047 static inline __u8 inet_dscp_to_dsfield(dscp_t dscp)
0048 {
0049     return (__force __u8)dscp;
0050 }
0051
0052 static inline bool inet_validate_dscp(__u8 val)
0053 {
0054     return !(val & ~INET_DSCP_MASK);
0055 }
0056
0057 #endif /* _INET_DSCP_H */