netdev - Re: [PATCH net] net: ndo_gso_check() must force segmentation

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Message-ID: <CAEP_g=__JrSVYZPafUe-CBAA_m_S9WLAF83xKsOo7EZGsftaeg@mail.gmail.com>
Date:	Mon, 22 Dec 2014 10:59:38 -0500
From:	Jesse Gross <jesse@...ira.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Hayes Wang <hayeswang@...ltek.com>,
	Tom Herbert <therbert@...gle.com>,
	David Miller <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	nic_swsd <nic_swsd@...ltek.com>
Subject: Re: [PATCH net] net: ndo_gso_check() must force segmentation

On Mon, Dec 22, 2014 at 10:21 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> From: Eric Dumazet <edumazet@...gle.com>
>
> If ndo_gso_check() returns true, it means a driver wants the stack
> to perform software segmentation, even if device features initially
> claimed hardware was able handle a TSO packet.
>
> This means netif_needs_gso() needs to modify the features.
>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: Hayes Wang <hayeswang@...ltek.com>
> Tested-by: Hayes Wang <hayeswang@...ltek.com>
> Fixes: 04ffcb255f22 ("net: Add ndo_gso_check")

There's actually another problem with ndo_gso_check() - it doesn't
deal with other features like checksum offloading which usually have
similar constraints. As a result, the GSO code generates segments with
checksums offloading that immediately fails.

I have a patch that I was working on last night that behaves similarly
to yours but is also generalized to handle both cases. Let me send it
out now.
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