netdev - Re: [PATCH net-next] ipv6: Add sysctl for RA default route table number

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Date:   Tue, 29 Jun 2021 09:34:22 -0600
From:   David Ahern <dsahern@...il.com>
To:     Eyal Birger <eyal.birger@...il.com>, antony.antony@...unet.com
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org,
        Christian Perle <christian.perle@...unet.com>
Subject: Re: [PATCH net-next] ipv6: Add sysctl for RA default route table
 number

On 6/29/21 8:05 AM, Eyal Birger wrote:
> Hi Antony,
> 
> On 29/06/2021 15:53, Antony Antony wrote:
>> Hi David,
>>
>> On Fri, Jun 25, 2021 at 22:47:41 -0600, David Ahern wrote:
>>> On 6/25/21 1:04 AM, Antony Antony wrote:
>>>> From: Christian Perle <christian.perle@...unet.com>
>>>>
>>>> Default routes learned from router advertisements(RA) are always placed
>>>> in main routing table. For policy based routing setups one may
>>>> want a different table for default routes. This commit adds a sysctl
>>>> to make table number for RA default routes configurable.
>>>>
>>>> examples:
>>>> sysctl net.ipv6.route.defrtr_table
>>>> sysctl -w net.ipv6.route.defrtr_table=42
>>>> ip -6 route show table 42
>>>
>>> How are the routing tables managed? If the netdevs are connected to a
>>> VRF this just works.
>>
>> The main routing table has no default route. Our scripts add routing
>> rules
>> based on interfaces. These rules use the specific routing table where

That's the VRF use case -- routing rules based on interfaces. Connect
those devices to VRFs and the RA does the right thing.

>> the RA
>> (when using SLAAC) installs the default route. The rest just works.
> 
> Could this be a devconf property instead of a global property? seems
> like the difference would be minor to your patch but the benefit is that
> setups using different routing tables for different policies could
> benefit (as mentioned when not using vrfs).

exactly. This is definitely not a global setting, but a per device
setting if at all.