netdev - Re: [PATCH net-next v4] ppp: enable TX scatter-gather

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Message-ID: <fee77ae1-0231-414f-be43-6dca8bdb0e20@redhat.com>
Date: Tue, 3 Feb 2026 17:33:24 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Qingfang Deng <dqfext@...il.com>
Cc: Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, linux-ppp@...r.kernel.org,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 Toke Høiland-Jørgensen <toke@...hat.com>
Subject: Re: [PATCH net-next v4] ppp: enable TX scatter-gather

On 2/3/26 4:08 PM, Qingfang Deng wrote:
> On Tue, Feb 3, 2026 at 6:55 PM Paolo Abeni <pabeni@...hat.com> wrote:
>> I'm sorry for missing this point before, but AFAICS channels with
>> chan->direct_xmit == 0 do not support GSO packets at all, and here such
>> packets will be transmitted after linearization (but still as GSO).
>>
>> I think that while transmitting over !chan->direct_xmit you additionally
>> need to check for GSO packet. If ppp features are recomputed depending
>> on the channels configuration, you could chose to drop such packets.
>> Otherwise you will need to segment them before transmission, and that
>> looks error prone in case of multilink.
> 
> I don't think that's true. Using the current features set (NETIF_F_SG
> | NETIF_F_FRAGLIST), the network core will only enable the generic
> software GSO (NETIF_F_GSO), and a GSO skb will be segmented in
> validate_xmit_skb before being passed to the PPP driver.

Right you are! I thought TSO was enabled here at some point but it's not
the case. No need to resubmit, let me resurrect this patch in PW.

Thanks,

Paolo