From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net-next V2] gro: introduce gro_mac_header_len Date: Mon, 06 Feb 2012 14:56:52 -0500 (EST) Message-ID: <20120206.145652.1575591691467905094.davem@davemloft.net> References: <20120206.143230.1415707004934341114.davem@davemloft.net> <20120206.145148.558736903670696169.davem@davemloft.net> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: eric.dumazet-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, ogerlitz-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org, sean.hefty-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, herbert-F6s6mLieUQo7FNHlEwC/lvQIK84fMopw@public.gmane.org, linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, shlomop-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: roland-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org Return-path: In-Reply-To: <20120206.145148.558736903670696169.davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: netdev.vger.kernel.org From: David Miller Date: Mon, 06 Feb 2012 14:51:48 -0500 (EST) > From: David Miller > Date: Mon, 06 Feb 2012 14:32:30 -0500 (EST) > >> From: Roland Dreier >> Date: Mon, 6 Feb 2012 11:23:21 -0800 >> >>> Does the netdev driver own skb->cb between hard_header >>> and start_xmit? If so we could use that instead of stealing >>> some header space, and that would at least let us not lie >>> about hard_header_len. >> >> Unfortunately the packet scheduler sits between the hard_header() >> call (via neigh_*_output() --> dev_hard_header()) and when the >> device xmit method is invoked. >> >> And the packet scheduler can make use of the skb->cb[], for >> include/net/sch_generic.h:qdisc_skb_cb > > Actually there is a way to make this work. > > Define your ipoib_skb_cb something like: > > struct ipoib_skb_cb { > struct qdisc_skb_cb qdisc_cb; > > ... ipoib stuff goes here ... > }; > > That way you can use the SKB cb area for your ipoib info > without interfering with the packet scheduler. But this needs a little bit of work since the qdisc_skb_cb ends with a variable length array, but we can put an upper bound on this just like we do for skb->cb[] itself to fix this issue. I'll toss something together. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html