Re: [PATCH net v2] fib_semantics: Don't match route with mismatching tclassid

[David Miller <davem@davemloft.net>]

From: Stefano Brivio <sbrivio@redhat.com>
Date: Thu, 15 Feb 2018 09:46:03 +0100

> In fib_nh_match(), if output interface or gateway are passed in
> the FIB configuration, we don't have to check next hops of
> multipath routes to conclude whether we have a match or not.
> 
> However, we might still have routes with different realms
> matching the same output interface and gateway configuration,
> and this needs to cause the match to fail. Otherwise the first
> route inserted in the FIB will match, regardless of the realms:
> 
>  # ip route add 1.1.1.1 dev eth0 table 1234 realms 1/2
>  # ip route append 1.1.1.1 dev eth0 table 1234 realms 3/4
>  # ip route list table 1234
>  1.1.1.1 dev eth0 scope link realms 1/2
>  1.1.1.1 dev eth0 scope link realms 3/4
>  # ip route del 1.1.1.1 dev ens3 table 1234 realms 3/4
>  # ip route list table 1234
>  1.1.1.1 dev ens3 scope link realms 3/4
> 
> whereas route with realms 3/4 should have been deleted instead.
> 
> Explicitly check for fc_flow passed in the FIB configuration
> (this comes from RTA_FLOW extracted by rtm_to_fib_config()) and
> fail matching if it differs from nh_tclassid.
> 
> The handling of RTA_FLOW for multipath routes later in
> fib_nh_match() is still needed, as we can have multiple RTA_FLOW
> attributes that need to be matched against the tclassid of each
> next hop.
> 
> v2: Check that fc_flow is set before discarding the match, so
>     that the user can still select the first matching rule by
>     not specifying any realm, as suggested by David Ahern.
> 
> Reported-by: Jianlin Shi <jishi@redhat.com>
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Applied and queued up for -stable, thanks.