netdev - RE: [PATCH v4 1/5] net: Add support for hardware-offloaded encapsulation

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Date:	Mon, 10 Dec 2012 19:58:34 +0000
From:	"Dmitry Kravkov" <dmitry@...adcom.com>
To:	"saeed bishara" <saeed.bishara@...il.com>,
	"Joseph Gasparakis" <joseph.gasparakis@...el.com>
cc:	"davem@...emloft.net" <davem@...emloft.net>,
	"shemminger@...tta.com" <shemminger@...tta.com>,
	"chrisw@...s-sol.org" <chrisw@...s-sol.org>,
	"gospo@...hat.com" <gospo@...hat.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"bhutchings@...arflare.com" <bhutchings@...arflare.com>,
	"Peter P Waskiewicz Jr" <peter.p.waskiewicz.jr@...el.com>,
	"Alexander Duyck" <alexander.h.duyck@...el.com>
Subject: RE: [PATCH v4 1/5] net: Add support for hardware-offloaded
 encapsulation

> -----Original Message-----
> From: saeed bishara [mailto:saeed.bishara@...il.com]
> Sent: Monday, December 10, 2012 12:04 PM
> To: Joseph Gasparakis
> Cc: davem@...emloft.net; shemminger@...tta.com; chrisw@...s-sol.org;
> gospo@...hat.com; netdev@...r.kernel.org; linux-kernel@...r.kernel.org;
> Dmitry Kravkov; bhutchings@...arflare.com; Peter P Waskiewicz Jr; Alexander
> Duyck
> Subject: Re: [PATCH v4 1/5] net: Add support for hardware-offloaded
> encapsulation
> 
> > +static inline struct iphdr *inner_ip_hdr(const struct sk_buff *skb)
> > +{
> > +       return (struct iphdr *)skb_inner_network_header(skb);
> > +}
> 
> Hi,
> I'm a little bit bothered because of those inner_ functions, what
> about the following approach:
> 1. the skb will have a new state, that state can be outer (normal
> mode) and inner.
> 2. when you change the state to inner, all the helper functions such
> as ip_hdr will return the innter header.
> 
> that's ofcourse the API side. the implementation may still use the
> fields you added to the skb.
> 
> what you think?
> saeed

Some drivers will probably need both inner_ and other_ in same flow, switching between two states will consume cpu cycles.