From a410a0cf98854a698a519bfbeb604145da384c0e Mon Sep 17 00:00:00 2001 From: Guillaume Nault Date: Fri, 4 Feb 2022 14:58:11 +0100 Subject: ipv6: Define dscp_t and stop taking ECN bits into account in fib6-rules MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Define a dscp_t type and its appropriate helpers that ensure ECN bits are not taken into account when handling DSCP. Use this new type to replace the tclass field of struct fib6_rule, so that fib6-rules don't get influenced by ECN bits anymore. Before this patch, fib6-rules didn't make any distinction between the DSCP and ECN bits. Therefore, rules specifying a DSCP (tos or dsfield options in iproute2) stopped working as soon a packets had at least one of its ECN bits set (as a work around one could create four rules for each DSCP value to match, one for each possible ECN value). After this patch fib6-rules only compare the DSCP bits. ECN doesn't influence the result anymore. Also, fib6-rules now must have the ECN bits cleared or they will be rejected. Signed-off-by: Guillaume Nault Acked-by: David Ahern Reviewed-by: Toke Høiland-Jørgensen Signed-off-by: Jakub Kicinski --- include/net/inet_dscp.h | 57 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) create mode 100644 include/net/inet_dscp.h (limited to 'include/net/inet_dscp.h') diff --git a/include/net/inet_dscp.h b/include/net/inet_dscp.h new file mode 100644 index 000000000000..72f250dffada --- /dev/null +++ b/include/net/inet_dscp.h @@ -0,0 +1,57 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* + * inet_dscp.h: helpers for handling differentiated services codepoints (DSCP) + * + * DSCP is defined in RFC 2474: + * + * 0 1 2 3 4 5 6 7 + * +---+---+---+---+---+---+---+---+ + * | DSCP | CU | + * +---+---+---+---+---+---+---+---+ + * + * DSCP: differentiated services codepoint + * CU: currently unused + * + * The whole DSCP + CU bits form the DS field. + * The DS field is also commonly called TOS or Traffic Class (for IPv6). + * + * Note: the CU bits are now used for Explicit Congestion Notification + * (RFC 3168). + */ + +#ifndef _INET_DSCP_H +#define _INET_DSCP_H + +#include + +/* Special type for storing DSCP values. + * + * A dscp_t variable stores a DS field with the CU (ECN) bits cleared. + * Using dscp_t allows to strictly separate DSCP and ECN bits, thus avoiding + * bugs where ECN bits are erroneously taken into account during FIB lookups + * or policy routing. + * + * Note: to get the real DSCP value contained in a dscp_t variable one would + * have to do a bit shift after calling inet_dscp_to_dsfield(). We could have + * a helper for that, but there's currently no users. + */ +typedef u8 __bitwise dscp_t; + +#define INET_DSCP_MASK 0xfc + +static inline dscp_t inet_dsfield_to_dscp(__u8 dsfield) +{ + return (__force dscp_t)(dsfield & INET_DSCP_MASK); +} + +static inline __u8 inet_dscp_to_dsfield(dscp_t dscp) +{ + return (__force __u8)dscp; +} + +static inline bool inet_validate_dscp(__u8 val) +{ + return !(val & ~INET_DSCP_MASK); +} + +#endif /* _INET_DSCP_H */ -- cgit v1.2.3