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To:     =?UTF-8?Q?Toke_H=c3=b8iland-J=c3=b8rgensen?= <toke@redhat.com>,
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References: <20201216204316.44498-1-nbd@nbd.name>
 <20201216204316.44498-2-nbd@nbd.name> <87czz8bqbj.fsf@toke.dk>
From:   Felix Fietkau <nbd@nbd.name>
Subject: Re: [PATCH 2/7] mac80211: force calculation of software hash for tx
 fair queueing
Message-ID: <add3d1fa-c2ad-5aaf-83c7-31e919129bbf@nbd.name>
Date:   Thu, 17 Dec 2020 13:20:11 +0100
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On 2020-12-17 12:54, Toke Høiland-Jørgensen wrote:
> Felix Fietkau <nbd@nbd.name> writes:
> 
>> Depending on the source, a hardware calculated hash may not provide the
>> same level of collision resistance.
> 
> This seems like it would have performance implications?
> 
> Also, this can potentially discard information from tunnels that
> preserve the hash before encapsulation (we added support for this to
> Wireguard which had some nice effects on queueing of encapsulated
> traffic).
If the hash was calculated in software using the flow dissector, it will
be preserved, even if it went through a few virtual interfaces.
The only hashes discarded are hardware generated ones.

- Felix