netdev - Re: [PATCH v2 net-next 03/11] net/ipv4: Plumb support for filtering route dumps

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Date:   Fri, 19 Jul 2019 10:55:49 -0600
From:   David Ahern <dsahern@...il.com>
To:     Hangbin Liu <liuhangbin@...il.com>,
        David Ahern <dsahern@...nel.org>
Cc:     netdev@...r.kernel.org, Jianlin Shi <jishi@...hat.com>
Subject: Re: [PATCH v2 net-next 03/11] net/ipv4: Plumb support for filtering
 route dumps

Hi:

On 7/18/19 10:17 PM, Hangbin Liu wrote:
> Hi David,
> 
> Before commit 18a8021a7be3 ("net/ipv4: Plumb support for filtering route
> dumps"), when we dump a non-exist table, ip cmd exits silently.
> 
> # ip -4 route list table 1
> # echo $?
> 0
> 
> After commit 18a8021a7be3 ("net/ipv4: Plumb support for filtering route
> dumps"). When we dump a non-exist table, as we returned -ENOENT, ip route
> shows:
> 
> # ip -4 route show table 1
> Error: ipv4: FIB table does not exist.
> Dump terminated
> # echo $?
> 2
> 
> For me it looks make sense to return -ENOENT if we do not have the route
> table. But this changes the userspace behavior. Do you think if we need to
> keep backward compatible or just let it do as it is right now?
> 

It is not change in userspace behavior; ip opted into the strict
checking. The impact is to 'ip' users.

A couple of people have asked about this, and I am curious as to why
people run a route dump for a table that does not exist and do not like
being told that it does not exist.