netdev - Re: [PATCH net] neighbour: allow NUD_NOARP entries to be forced GCed

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Message-ID: <e114a16f-5cb2-472a-e790-a84311481251@nvidia.com>
Date:   Mon, 7 Jun 2021 15:16:22 -0700
From:   Roopa Prabhu <roopa@...dia.com>
To:     David Ahern <dsahern@...il.com>, David Ahern <dsahern@...nel.org>,
        <netdev@...r.kernel.org>, <kuba@...nel.org>, <davem@...emloft.net>
CC:     Kasper Dupont <kasperd@...wv.06.feb.2021.kasperd.net>,
        Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
Subject: Re: [PATCH net] neighbour: allow NUD_NOARP entries to be forced GCed


On 6/7/21 3:04 PM, David Ahern wrote:
> On 6/7/21 12:53 PM, Roopa Prabhu wrote:
>> On 6/7/21 10:35 AM, David Ahern wrote:
>>> IFF_POINTOPOINT interfaces use NUD_NOARP entries for IPv6. It's
>>> possible to
>>> fill up the neighbour table with enough entries that it will overflow for
>>> valid connections after that.
>>>
>>> This behaviour is more prevalent after commit 58956317c8de ("neighbor:
>>> Improve garbage collection") is applied, as it prevents removal from
>>> entries that are not NUD_FAILED, unless they are more than 5s old.
>>>
>>> Fixes: 58956317c8de (neighbor: Improve garbage collection)
>>> Reported-by: Kasper Dupont <kasperd@...wv.06.feb.2021.kasperd.net>
>>> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
>>> Signed-off-by: David Ahern <dsahern@...nel.org>
>>> ---
>>> rebased to net tree
>>
>> There are other use-cases  that use NUD_NOARP as static neighbour
>> entries which should be exempt from forced gc.
>>
>> for example when qualified by NTF_EXT_LEARNED for the E-VPN use-case.
>>
>> The check in your patch below should exclude NTF_EXT_LEARNED entries.
>>
>>
>> (unrelated to the neighbour code ,  but bridge driver also uses
>> NUD_NOARP for static entries)
>>
>>
> Maybe I misunderstand your comment: forced_gc does not apply to static
> entries; those were moved to a separate list to avoid walking them.
>
I think you are right. so just to confirm, NUD_NOARP + NTF_EXT_LEARNED 
will never be included in the list for forced_gc and hence not affected 
by your patch ?

if yes, I am good.