netdev - Re: [PATCH][v3] dev : fix mtu check when TSO is enabled

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Message-ID: <AANLkTikhqMdLV4jObYNuFcxmwFMkuLKJ+d1xtjw83Jou@mail.gmail.com>
Date:	Tue, 22 Mar 2011 01:05:46 +0100
From:	Michał Mirosław <mirqus@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	daniel.lezcano@...e.fr, eric.dumazet@...il.com, kaber@...sh.net,
	nightnord@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH][v3] dev : fix mtu check when TSO is enabled

2011/3/15 David Miller <davem@...emloft.net>:
> From: Daniel Lezcano <daniel.lezcano@...e.fr>
> Date: Mon, 14 Mar 2011 21:39:50 +0100
>> +
>> +     /* if TSO is enabled, we don't care about the length as the packet
>> +      * could be forwarded without being segmented before
>> +      */
>> +     if (skb->dev && skb->dev->features & NETIF_F_TSO)
>> +             return true;
> I am trying to understand why you aren't simply checking also if this
> is a segmented frame?  Perhaps skb_is_gso() && device has NETIF_F_TSO
> set?

Is the check of netdev features even necessary? Devices without TSO
enabled the skbs are segmented before ndo_start_xmit() anyway.

With TSO there's a question if the receiving end of macvlan can handle
GRO/LRO packets?

BTW, checking only NETIF_F_TSO will break at least for IPv6 TSO
(NETIF_F_TSO6) or whatever else can be segmented in hardware.

Best Regards,
Michał Mirosław
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