linux-kernel - Re: [PATCH AUTOSEL for 4.15 058/124] ipv6: Set nexthop flags during route creation

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Date:   Mon, 19 Mar 2018 20:04:34 +0200
From:   Ido Schimmel <idosch@...lanox.com>
To:     Sasha Levin <Alexander.Levin@...rosoft.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH AUTOSEL for 4.15 058/124] ipv6: Set nexthop flags during
 route creation

On Mon, Mar 19, 2018 at 03:48:00PM +0000, Sasha Levin wrote:
> From: Ido Schimmel <idosch@...lanox.com>
> 
> [ Upstream commit 5609b80a37f69f796548339e675256188b29c17d ]
> 
> It is valid to install routes with a nexthop device that does not have a
> carrier, so we need to make sure they're marked accordingly.
> 
> As explained in the previous patch, host and anycast routes are never
> marked with the 'linkdown' flag.
> 
> Note that reject routes are unaffected, as these use the loopback device
> which always has a carrier.
> 
> Signed-off-by: Ido Schimmel <idosch@...lanox.com>
> Acked-by: David Ahern <dsahern@...il.com>
> Signed-off-by: David S. Miller <davem@...emloft.net>
> Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>

Hi Sasha,

It doesn't really make sense to take this patch to 4.15 (and 4.14 from
your other mail). The flag is never used there.

In these kernels the flag is dumped to user space based on a carrier
check. See commit 44c9f2f206f8 ("ipv6: Check nexthop flags in route dump
instead of carrier").

Similarly, during route lookup the carrier is checked and not the flag.
See commit 14c5206c2d02 ("ipv6: Check nexthop flags during route lookup
instead of carrier").

Thanks