netdev - Re: 5.1 `ip route get addr/cidr` regression

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Date:   Fri, 17 May 2019 17:22:47 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     David Ahern <dsahern@...il.com>
Cc:     Michal Kubecek <mkubecek@...e.cz>, Netdev <netdev@...r.kernel.org>,
        emersonbernier@...anota.com,
        Stephen Hemminger <stephen@...workplumber.org>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        David Miller <davem@...emloft.net>, piraty1@...ox.ru
Subject: Re: 5.1 `ip route get addr/cidr` regression

On Fri, May 17, 2019 at 5:21 PM David Ahern <dsahern@...il.com> wrote:
>
> On 5/17/19 8:17 AM, Michal Kubecek wrote:
> > AFAIK the purpose of 'ip route get' always was to let the user check
> > the result of a route lookup, i.e. "what route would be used if I sent
> > a packet to an address". To be honest I would have to check how exactly
> > was "ip route get <addr>/<prefixlen>" implemented before.
> >
>
> The prefixlen was always silently ignored. We are trying to clean up
> this 'silent ignoring' just hitting a few speed bumps.

Indeed what we were after has always been, `ip route show dev <dev>
match <addr>/<prefixlen>`, and the old positive return value from `ip
route get` wasn't always correct for what we were using it for. So
mostly the breakage exposed another bug here.