netdev - Re: [PATCH iproute2] iproute2: fix MPLS label parsing

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Message-ID: <20200315095732.034b64e5@hermes.lan>
Date:   Sun, 15 Mar 2020 09:57:32 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Guillaume Nault <gnault@...hat.com>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH iproute2] iproute2: fix MPLS label parsing

On Wed, 11 Mar 2020 16:16:36 +0100
Guillaume Nault <gnault@...hat.com> wrote:

> The initial value of "label" in parse_mpls() is 0xffffffff. Therefore
> we should test for this value, and not 0, to detect if a label has been
> provided. The "!label" test not only fails to detect a missing label
> parameter, it also prevents the use of the IPv4 explicit NULL label,
> which actually equals 0.
> 
> Reproducer:
>   $ ip link add name dm0 type dummy
>   $ tc qdisc add dev dm0 ingress
> 
>   $ tc filter add dev dm0 parent ffff: matchall action mpls push
>   Error: act_mpls: Label is required for MPLS push.
>   We have an error talking to the kernel
>   --> Filter was pushed to the kernel, where it got rejected.  
> 
>   $ tc filter add dev dm0 parent ffff: matchall action mpls push label 0
>   Error: argument "label" is required
>   --> Label 0 was rejected by iproute2.  
> 
> Expected result:
>   $ tc filter add dev dm0 parent ffff: matchall action mpls push
>   Error: argument "label" is required
>   --> Filter was directly rejected by iproute2.  
> 
>   $ tc filter add dev dm0 parent ffff: matchall action mpls push label 0
>   --> Filter is accepted.  
> 
> Signed-off-by: Guillaume Nault <gnault@...hat.com>

Applied, thanks