netdev - Re: Why are IPv6 host and anycast routes referencing lo device?

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Message-ID: <14a4ccfb-11d9-f96b-a741-c8595b81ca45@miraclelinux.com>
Date:   Tue, 8 Nov 2016 11:26:34 +0900
From:   YOSHIFUJI Hideaki <hideaki.yoshifuji@...aclelinux.com>
To:     David Ahern <dsa@...ulusnetworks.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Cc:     hideaki.yoshifuji@...aclelinux.com
Subject: Re: Why are IPv6 host and anycast routes referencing lo device?

Hi,

David Ahern wrote:
> 
> Can anyone explain why host routes and anycast routes for IPv6 are added with the device set to loopback versus the device with the address:
> 
> local ::1 dev lo  proto none  metric 0  pref medium
> local 2000:1:: dev lo  proto none  metric 0  pref medium
> local 2000:1::3 dev lo  proto none  metric 0  pref medium
> local 2100:2:: dev lo  proto none  metric 0  pref medium
> local 2100:2::3 dev lo  proto none  metric 0  pref medium
> 
> 
> This behavior differs from IPv4 where host routes use the device with the address:
> 
> broadcast 10.1.1.0 dev eth0  proto kernel  scope link  src 10.1.1.3
> local 10.1.1.3 dev eth0  proto kernel  scope host  src 10.1.1.3
> broadcast 10.1.1.255 dev eth0  proto kernel  scope link  src 10.1.1.3
> broadcast 10.100.2.0 dev eth2  proto kernel  scope link  src 10.100.2.3
> local 10.100.2.3 dev eth2  proto kernel  scope host  src 10.100.2.3
> broadcast 10.100.2.255 dev eth2  proto kernel  scope link  src 10.100.2.3
> 
> The use of loopback pre-dates the git history, so wondering if someone recalls the reason why. We would like to change that to make it consistent with IPv4 - with a sysctl to maintain backwards compatibility.

Once I tried I did not work.
You could try again to see what happens.

--yoshfuji

> 
> Thanks,
> David
> 

-- 
Hideaki Yoshifuji <hideaki.yoshifuji@...aclelinux.com>
Technical Division, MIRACLE LINUX CORPORATION