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

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Message-ID: <CALW65jYYdX+NQ-6vNBdxDGHxDV1AdKQWenFZNjnqE9VQyC7fog@mail.gmail.com>
Date: Tue, 3 Feb 2026 23:08:29 +0800
From: Qingfang Deng <dqfext@...il.com>
To: Paolo Abeni <pabeni@...hat.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 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.

>
> /P