netdev - Re: [PATCH net-next] net/ipv6: Add knob to skip DELROUTE message on device down

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Message-Id: <20181010.224853.1631138200935263910.davem@davemloft.net>
Date:   Wed, 10 Oct 2018 22:48:53 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     dsahern@...nel.org
Cc:     netdev@...r.kernel.org, roopa@...ulusnetworks.com,
        dsahern@...il.com
Subject: Re: [PATCH net-next] net/ipv6: Add knob to skip DELROUTE message
 on device down

From: David Ahern <dsahern@...nel.org>
Date: Tue,  9 Oct 2018 14:27:51 -0700

> From: David Ahern <dsahern@...il.com>
> 
> Another difference between IPv4 and IPv6 is the generation of RTM_DELROUTE
> notifications when a device is taken down (admin down) or deleted. IPv4
> does not generate a message for routes evicted by the down or delete;
> IPv6 does. A NOS at scale really needs to avoid these messages and have
> IPv4 and IPv6 behave similarly, relying on userspace to handle link
> notifications and evict the routes.
> 
> At this point existing user behavior needs to be preserved. Since
> notifications are a global action (not per app) the only way to preserve
> existing behavior and allow the messages to be skipped is to add a new
> sysctl (net/ipv6/route/skip_notify_on_dev_down) which can be set to
> disable the notificatioons.
> 
> IPv6 route code already supports the option to skip the message (it is
> used for multipath routes for example). Besides the new sysctl we need
> to pass the skip_notify setting through the generic fib6_clean and
> fib6_walk functions to fib6_clean_node and to set skip_notify on calls
> to __ip_del_rt for the addrconf_ifdown path.
> 
> Signed-off-by: David Ahern <dsahern@...il.com>

This doesn't apply cleanly, and you seem to be saying that the anycast
and addrconf bits should be removed anyways.