Subject: Re: [PATCH net] net: change maximum number of UDP segments to 128

From: Jakub Kicinski <[email-masked]>
Date: Tue, 9 Apr 2024 16:31:16 -0700

CC: netdev@

On Sat,  6 Apr 2024 21:50:29 +0300 Yuri Benditovich wrote:
> Fixes: fc8b2a619469378 ("net: more strict VIRTIO_NET_HDR_GSO_UDP_L4 validation")
> 

Fixes: line goes right above your sign-off, no empty lines in between
them.

> The mentioned above commit adds check of potential number
> of UDP segments vs UDP_MAX_SEGMENTS in linux/virtio_net.h.
> After this change certification test of USO guest-to-guest
> transmit on Windows driver for virtio-net device fails,
> for example with packet size of ~64K and mss of 536 bytes.
> In general the USO should not be more restrictive than TSO.
> Indeed, in case of unreasonably small mss a lot of segments
> can cause queue overflow and packet loss on the destination.
> Limit of 128 segments is good for any practical purpose,
> with minimal meaningful mss of 536 the maximal UDP packet will
> be divided to ~120 segments.
> 
> Signed-off-by: Yuri Benditovich <[email-masked]>