From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Durrant Subject: Re: network misbehaviour with gplpv and 2.6.30 Date: Tue, 21 Jul 2009 11:13:49 +0100 Message-ID: <4A6594DD.9010808@citrix.com> References: <4A658BE6.4010803@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: James Harper Cc: "xen-devel@lists.xensource.com" , Lyon , Andrew List-Id: xen-devel@lists.xenproject.org James Harper wrote: > >> Are you saying that ring slot n >> has only NETRXF_extra_info and *not* NETRXF_more_data? >> > > Yes. From the debug I have received from Andrew Lyon, NETRXF_more_data > is _never_ set. > > From what Andrew tells me (and it's not unlikely that I misunderstood), > the packets in question come from a physical machine external to the > machine running xen. I can't quite understand how that could be as they > are 'large' packets (>1514 byte total packet length) which should only > be locally originated. Unless he's running with jumbo frames (are you > Andrew?). > It's not unusual for h/w drivers to support 'LRO', i.e. they re-assemble consecutive in-order TCP segments into a large packet before passing up the stack. I believe that these would manifest themselves as TSOs coming into the transmit side of netback, just as locally originated large packets would. > I've asked for some more debug info but he's in a different timezone to > me and probably isn't awake yet. I'm less and less inclined to think > that this is actually a problem with GPLPV and more a problem with > netback (or a physical network driver) in 2.6.30, but a tcpdump in Dom0, > HVM without GPLPV and maybe in a Linux DomU should tell us more. > Yes, a tcpdump of what's being passed into netback in dom0 should tell us what's happening. Paul -- =============================== Paul Durrant, Software Engineer Citrix Systems (R&D) Ltd. First Floor, Building 101 Cambridge Science Park Milton Road Cambridge CB4 0FY United Kingdom TEL: x35957 (+44 1223 225957) ===============================