netdev - Re: Unexpected behaviour of suppress

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Date:   Mon, 24 Oct 2016 12:47:46 +0200
From:   Matthias Peter Walther <m_walt11@...-muenster.de>
To:     netdev@...r.kernel.org
Subject: Re: Unexpected behaviour of suppress_prefixlength 0

I'm not sure, if this was the right list to ask for this?

It seems to me, that this list is for patches only...

On 21.10.2016 00:00, Matthias Peter Walther wrote:
> Hello,
>
> I'm Matthias and I'm new to this list. I just signed up, to ask the
> following question.
>
> I have a configuration like this:
>
> root@...1 ~ # ip rule
> 0:    from all lookup local
> 32765:    from all iif lo lookup ffnet suppress_prefixlength 0
> 32766:    from all lookup main
> 32767:    from all lookup default
> (ffnet is table 42)
> root@...1 ~ # ip r s
> default via 5.9.86.151 dev eth0
> 5.9.86.151 dev eth0  proto kernel  scope link  src 5.9.86.144
> root@...1 ~ # ip r s t 42
> blackhole default
>
> I have the default routing table, and a routing table number 42. I
> could use an ip rule filtering by destination ip, but I wanted to try
> suppress_prefixlength.
>
> Let's say I want to ping 8.8.8.8. What I expect is, that the package
> is put into routing table 42 by the ip rule 32765. As there is no more
> specific route for 8.8.8.8 than the default route in table 42, I
> expect the suppress_prefixlength 0 option to put it back to the
> default routing table and then to be send out through eth0.
>
> Instead this configuration takes the whole machine offline:
>
> root@...1 ~ # ping 8.8.8.8
> connect: Invalid argument
>
> When I delete the ip rule 32765 containing the suppress_prefixlength,
> the machine is back online.
>
> Do I not understand the suppress_prefixlength-feature correctly or is
> this a bug? I tested with Kernel 4.7 and 4.6, both show the same
> behaviour as described above.
>
> Thanks for any replies in advance.
>
> Regards,
> Matthias