On Mon, Aug 03, 2020 at 04:02:16PM +0800, Hangbin Liu wrote: > In RFC1349 it defined TOS field like > > 0 1 2 3 4 5 6 7 > +-----+-----+-----+-----+-----+-----+-----+-----+ > | PRECEDENCE | TOS | MBZ | > +-----+-----+-----+-----+-----+-----+-----+-----+ > > But this has been obsoleted by RFC2474, and updated by RFC3168 later. > Now the DS Field should be like > > 0 1 2 3 4 5 6 7 > +-----+-----+-----+-----+-----+-----+-----+-----+ > | DS FIELD, DSCP | ECN FIELD | > +-----+-----+-----+-----+-----+-----+-----+-----+ > > DSCP: differentiated services codepoint > ECN: Explicit Congestion Notification > > So the old IPTOS_TOS_MASK 0x1E should be updated. But since > changed the value will break UAPI, let's add a new value > IP_DSCP_MASK 0xFC as a replacement. > > Signed-off-by: Hangbin Liu <liuhang...@gmail.com> > --- > include/uapi/linux/in_route.h | 1 + > include/uapi/linux/ip.h | 2 ++ > 2 files changed, 3 insertions(+) > > diff --git a/include/uapi/linux/in_route.h b/include/uapi/linux/in_route.h > index 0cc2c23b47f8..26ba4efb054d 100644 > --- a/include/uapi/linux/in_route.h > +++ b/include/uapi/linux/in_route.h > @@ -29,5 +29,6 @@ > #define RTCF_NAT (RTCF_DNAT|RTCF_SNAT) > > #define RT_TOS(tos) ((tos)&IPTOS_TOS_MASK) > +#define RT_DSCP(tos) ((tos)&IP_DSCP_MASK) > > #endif /* _LINUX_IN_ROUTE_H */ > diff --git a/include/uapi/linux/ip.h b/include/uapi/linux/ip.h > index e42d13b55cf3..62e4169277eb 100644 > --- a/include/uapi/linux/ip.h > +++ b/include/uapi/linux/ip.h > @@ -22,6 +22,8 @@ > > #define IPTOS_TOS_MASK 0x1E > #define IPTOS_TOS(tos) ((tos)&IPTOS_TOS_MASK) > +#define IP_DSCP_MASK 0xFC > +#define IP_DSCP(tos) ((tos)&IP_DSCP_MASK)
What's the use of IP_DSCP()? It's the same as RT_DSCP(). I guess it's supposed to be the equivalent of IPTOS_TOS(), but that macro is only used once in the tree, where it could be replaced with RT_TOS(). I can't see a reason to copy this pattern.
