netdev - Re: re iproute2 - don't return error on success fix

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Date:   Tue, 9 Oct 2018 13:54:31 +0300
From:   Or Gerlitz <gerlitz.or@...il.com>
To:     Phil Sutter <phil@....cc>,
        Stephen Hemminger <stephen@...workplumber.org>,
        David Ahern <dsahern@...il.com>,
        Linux Netdev List <netdev@...r.kernel.org>,
        Roi Dayan <roid@...lanox.com>
Subject: Re: re iproute2 - don't return error on success fix

On Mon, Oct 8, 2018 at 3:41 PM Phil Sutter <phil@....cc> wrote:

> > $ ./tc/tc filter add dev enp33s0f0 protocol ip parent ffff: flower
> > skip_sw ip_flags firstfrag action drop && echo "success" || echo
> > "failed"
> > RTNETLINK answers: Operation not supported
> > success
>
> Interestingly, your output lacks the "We have an error" message mine
> shows. So in your case, the call to rtnl_talk_iov() from
> tc_filter_modify() does not return < 0.
>
> In my case, commands always fail with 'skip_sw' since I only test on a
> dummy interface. So maybe we hit different error paths? Could you please
> check what happens for you in __rtnl_talk_iov()? I guess the "RTNETLINK
> answers:" message should come from rtnl_talk_error(). In my case it does
> at least, and I haven't found an alternative place where that message
> could come from.

I have applied the patch Vlad sent today and it solved the problem:

# ./tc/tc filter add dev enp33s0f0 protocol ip parent ffff: flower
skip_sw ip_flags firstfrag action drop && echo "success" || echo
"failed"
RTNETLINK answers: Operation not supported
We have an error talking to the kernel, -1
failed