netdev - RE: [PATCH v2 RFC 0/13] Remove UDP Fragmentation Offload support

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Date:   Fri, 7 Jul 2017 13:24:25 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Michal Kubecek' <mkubecek@...e.cz>,
        David Miller <davem@...emloft.net>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "willemdebruijn.kernel@...il.com" <willemdebruijn.kernel@...il.com>
Subject: RE: [PATCH v2 RFC 0/13] Remove UDP Fragmentation Offload support

From: Michal Kubecek
> Sent: 07 July 2017 13:46
> On Fri, Jul 07, 2017 at 10:43:26AM +0100, David Miller wrote:
> >
> > This is an RFC patch series, based upon some discussions with
> > various developers, that removes UFO offloading.
> >
> > Very few devices support this operation, it's usefullness is
> > quesitonable at best, and it adds a non-trivial amount of
> > complexity to our data paths.
> 
> My understanding from the communication with the customer whose reports
> resulted in commits acf8dd0a9d0b ("udp: only allow UFO for packets from
> SOCK_DGRAM sockets") and a5cb659bbc1c ("net: account for current skb
> length when deciding about UFO") was that the real benefit from UFO is
> in the case when UFO allows to avoid the need to actually fragment the
> packets. In their case it's when UDP packets are sent via virtio_net
> either between a guest and its host or between two guests on the same
> host.
> ...

Could that be done with a large path-specific mtu?

	David