netdev - Re: [PATCH net 3/5] fm10k: Implement ndo_gso

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Date:	Fri, 7 Nov 2014 19:49:38 +0000
From:	"Vick, Matthew" <matthew.vick@...el.com>
To:	Joe Stringer <joestringer@...ira.com>
CC:	"alexander.duyck@...il.com" <alexander.duyck@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"Dept-GELinuxNICDev@...gic.com" <Dept-GELinuxNICDev@...gic.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"sathya.perla@...lex.com" <sathya.perla@...lex.com>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	Linux NICS <Linux-nics@...el.com>,
	"amirv@...lanox.com" <amirv@...lanox.com>,
	"shahed.shaikh@...gic.com" <shahed.shaikh@...gic.com>,
	"therbert@...gle.com" <therbert@...gle.com>,
	"Or Gerlitz" <gerlitz.or@...il.com>
Subject: Re: [PATCH net 3/5] fm10k: Implement ndo_gso_check()

On 11/6/14, 9:05 PM, "Joe Stringer" <joestringer@...ira.com> wrote:

>Let's merge both discussions into one thread (pick here or there). We
>have 
>this suggestion or the one which simply checks for tunnels and
>inner+outer 
>header lengths. Do you have a preference between them?

Agreed with merging the thread--consider it merged!

Reflecting on this some more, I prefer the latter option (checking tunnels
and header lengths). I'm leaning towards pushing the header length check
into fm10k_tx_encap_offload and then making fm10k_gso_check call that with
the gso_type. So, it's really the most recent version of the patch you
proposed:

static bool fm10k_gso_check(struct sk_buff *skb, struct net_device *dev)
{
	if ((skb_shinfo(skb)->gso_type & (SKB_GSO_UDP_TUNNEL | SKB_GSO_GRE)) &&
	    !fm10k_tx_encap_offload(skb))
		return false;

	return true;
}

plus the header length being checked in fm10k_tx_encap_offload. The only
nit would be that I'd just return the conditional instead of having
"return true" or "return false" lines.

The tunnel length check really should be there in fm10k_tx_encap_offload
anyway, so I'll get a patch together for that one.

>We could introduce an "skb_is_gso_encap()" or similar for this purpose.
>Checking for SKB_GSO_UDP_TUNNEL or SKB_GSO_GRE is pretty closely tied to
>what 
>fm10k_tx_encap_offload() checks for though; it might not even make sense
>to call 
>it if some of the other SKB_GSO_* flags are raised.

A fair point. On the other hand, we have to check the header length both
in the GSO and non-GSO cases anyway, so only having the check in
fm10k_tx_encap_offload and calling it from fm10k_gso_check wouldn't be as
duplicative. What do you think about that approach?

As an aside: the more I think about this, the more I think Tom's right and
that each driver really should have it's own ndo_gso_check() for this.
With fm10k and i40e being different, we're already at 40% of the current
drivers being different. I'll leave it to Or to comment on whether the
other drivers could share the check in some manner.

Cheers,
Matthew

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