linux-kernel - Re: [PATCHv2 net] i40e: Implement ndo_gso

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Message-ID: <CAEP_g=979u0baWXGmCxo61a-KYEUwkruqBNof_zQpsvJxRFqSA@mail.gmail.com>
Date:	Mon, 1 Dec 2014 15:53:07 -0800
From:	Jesse Gross <jesse@...ira.com>
To:	Tom Herbert <therbert@...gle.com>
Cc:	Joe Stringer <joestringer@...ira.com>,
	netdev <netdev@...r.kernel.org>,
	Shannon Nelson <shannon.nelson@...el.com>,
	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	"linux.nics" <linux.nics@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv2 net] i40e: Implement ndo_gso_check()

On Mon, Dec 1, 2014 at 3:47 PM, Tom Herbert <therbert@...gle.com> wrote:
> On Mon, Dec 1, 2014 at 3:35 PM, Joe Stringer <joestringer@...ira.com> wrote:
>> On 21 November 2014 at 09:59, Joe Stringer <joestringer@...ira.com> wrote:
>>> On 20 November 2014 16:19, Jesse Gross <jesse@...ira.com> wrote:
>>>> I don't know if we need to have the check at all for IPIP though -
>>>> after all the driver doesn't expose support for it all (actually it
>>>> doesn't expose GRE either). This raises kind of an interesting
>>>> question about the checks though - it's pretty easy to add support to
>>>> the driver for a new GSO type (and I imagine that people will be
>>>> adding GRE soon) and forget to update the check.
>>>
>>> If the check is more conservative, then testing would show that it's
>>> not working and lead people to figure out why (and update the check).
>>
>> More concretely, one suggestion would be something like following at
>> the start of each gso_check():
>>
>> +       const int supported = SKB_GSO_TCPV4 | SKB_GSO_TCPV6 | SKB_GSO_FCOE |
>> +                             SKB_GSO_UDP | SKB_GSO_UDP_TUNNEL;
>> +
>> +       if (skb_shinfo(skb)->gso_type & ~supported)
>> +               return false;
>
> This should already be handled by net_gso_ok.

My original point wasn't so much that this isn't handled at the moment
but that it's easy to add a supported GSO type but then forget to
update this check - i.e. if a driver already supports UDP_TUNNEL and
adds support for GRE with the same constraints. It seems not entirely
ideal that this function is acting as a blacklist rather than a
whitelist.
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