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 /* A few places in the IPv4 code need to ignore the three high order bits of 43 * DSCP because of backward compatibility (as these bits used to represent the 44 * IPv4 Precedence in RFC 791's TOS field and were ignored). 45 */ 46 #define INET_DSCP_LEGACY_TOS_MASK ((__force dscp_t)0x1c) 47 48 static inline dscp_t inet_dsfield_to_dscp(__u8 dsfield) 49 { 50 return (__force dscp_t)(dsfield & INET_DSCP_MASK); 51 } 52 53 static inline __u8 inet_dscp_to_dsfield(dscp_t dscp) 54 { 55 return (__force __u8)dscp; 56 } 57 58 static inline bool inet_validate_dscp(__u8 val) 59 { 60 return !(val & ~INET_DSCP_MASK); 61 } 62 63 #endif /* _INET_DSCP_H */ 64