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 10:35:34 +0100 Message-ID: <4A658BE6.4010803@citrix.com> References: 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: > With GPLPV under 2.6.30, GPLPV gets the following from the ring: > > ring slot n (first buffer): > status (length) = 54 bytes > offset = 0 > flags = NETRXF_extra_info (possibly csum too but not relevant) > ring slot n + 1 (extra info) > gso.size (mss) = 1460 > > Because NETRXF_extra_info is not set, that's all I get for that packet. I assume you mean NETRXF_more_data here? Are you saying that ring slot n has only NETRXF_extra_info and *not* NETRXF_more_data? > In the IP header though, the total length is 1544 (which in itself is a > little strange), but obviously I'm not getting a full packet, just the > ETH+IP+TCP header. > > According to Andrew Lyon it works fine in previous versions, so this > problem only arises on 2.6.30. I don't know if netfront on Linux suffers > from a similar problem. > > I can't identify any changes that could cause this, but if the problem > is in netback either the frags count isn't being set correctly, or > skb->cb (which appears to be used temporarily to hold nr_frags) is > becoming corrupt (set to 0) somehow, but the window where this could > occur is very small and I can't see where it could happen. > > Any suggestions as to where to start looking? > > (one nice thing is that I have identified a crash that would occur when > the IP header lied about its length!) > > Thanks > > James > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel -- =============================== 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) ===============================