From: Jamal Hadi Salim <jhs@mojatatu•com>
To: Daniel Borkmann <daniel@iogearbox•net>, stephen@networkplumber•org
Cc: tgraf@suug•ch, netdev@vger•kernel.org
Subject: Re: [PATCH iproute2 -next] ingress, clsact: don't add TCA_OPTIONS to nl msg
Date: Tue, 17 May 2016 07:54:30 -0400 [thread overview]
Message-ID: <573B0676.30500@mojatatu.com> (raw)
In-Reply-To: <192c686bb5e277b9552fe1e5c39b14bed520dddd.1463329895.git.daniel@iogearbox.net>
On 16-05-15 12:36 PM, Daniel Borkmann wrote:
> In ingress and clsact qdisc TCA_OPTIONS are ignored, since it's
> parameterless. In tc, we add an empty addattr_l(... TCA_OPTIONS,
> NULL, 0) to the netlink message nevertheless. This has the
> side effect that when someone tries a 'tc qdisc replace' and
> already an existing such qdisc is present, tc fails with
> EINVAL here.
>
> Reason is that in the kernel, this invokes qdisc_change() when
> such requested qdisc is already present. When TCA_OPTIONS are
> passed to modify parameters, it looks whether qdisc implements
> .change() callback, and if not present (like in both cases here)
> it returns with error. Rather than adding an empty stub to the
> kernel that ignores TCA_OPTIONS again, just don't add TCA_OPTIONS
> to the netlink message in the first place.
>
> Before:
>
> # tc qdisc replace dev foo clsact # first try
> # tc qdisc replace dev foo clsact # second one
> RTNETLINK answers: Invalid argument
>
> After:
>
> # tc qdisc replace dev foo clsact
> # tc qdisc replace dev foo clsact
> # tc qdisc replace dev foo clsact
>
> Signed-off-by: Daniel Borkmann <daniel@iogearbox•net>
Acked-by: Jamal Hadi Salim <jhs@mojatatu•com>
I see need for correctness but was curious of use case
that made you even look at this ;->
cheers,
jamal
next prev parent reply other threads:[~2016-05-17 11:54 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-15 16:36 [PATCH iproute2 -next] ingress, clsact: don't add TCA_OPTIONS to nl msg Daniel Borkmann
2016-05-16 18:22 ` Stephen Hemminger
2016-05-17 11:54 ` Jamal Hadi Salim [this message]
2016-05-17 13:10 ` Daniel Borkmann
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