netdev - Re: [PATCH net 06/10] wireguard: device: reset peer src endpoint when netns exits

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Date:   Tue, 30 Nov 2021 17:00:45 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>, netdev@...r.kernel.org,
        davem@...emloft.net
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>,
        Hangbin Liu <liuhangbin@...il.com>, Xiumei Mu <xmu@...hat.com>,
        Paolo Abeni <pabeni@...hat.com>, stable@...r.kernel.org
Subject: Re: [PATCH net 06/10] wireguard: device: reset peer src endpoint
 when netns exits

"Jason A. Donenfeld" <Jason@...c4.com> writes:

> Each peer's endpoint contains a dst_cache entry that takes a reference
> to another netdev. When the containing namespace exits, we take down the
> socket and prevent future sockets from being created (by setting
> creating_net to NULL), which removes that potential reference on the
> netns. However, it doesn't release references to the netns that a netdev
> cached in dst_cache might be taking, so the netns still might fail to
> exit. Since the socket is gimped anyway, we can simply clear all the
> dst_caches (by way of clearing the endpoint src), which will release all
> references.
>
> However, the current dst_cache_reset function only releases those
> references lazily. But it turns out that all of our usages of
> wg_socket_clear_peer_endpoint_src are called from contexts that are not
> exactly high-speed or bottle-necked. For example, when there's
> connection difficulty, or when userspace is reconfiguring the interface.
> And in particular for this patch, when the netns is exiting. So for
> those cases, it makes more sense to call dst_release immediately. For
> that, we add a small helper function to dst_cache.
>
> This patch also adds a test to netns.sh from Hangbin Liu to ensure this
> doesn't regress.
>
> Test-by: Hangbin Liu <liuhangbin@...il.com>
> Reported-by: Xiumei Mu <xmu@...hat.com>
> Cc: Hangbin Liu <liuhangbin@...il.com>
> Cc: Toke Høiland-Jørgensen <toke@...hat.com>
> Cc: Paolo Abeni <pabeni@...hat.com>
> Fixes: 900575aa33a3 ("wireguard: device: avoid circular netns references")
> Cc: stable@...r.kernel.org
> Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>

Acked-by: Toke Høiland-Jørgensen <toke@...hat.com>