From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sergei Shtylyov Subject: Re: [PATCH 2/6] xen-netfront: reduce gso_max_size to account for ethernet header Date: Mon, 25 Mar 2013 19:50:44 +0400 Message-ID: <51507254.1080901@cogentembedded.com> References: <1364209702-12437-1-git-send-email-wei.liu2@citrix.com> <1364209702-12437-3-git-send-email-wei.liu2@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: xen-devel@lists.xen.org, netdev@vger.kernel.org, ian.campbell@citrix.com, annie.li@oracle.com, konrad.wilk@oracle.com, david.vrabel@citrix.com To: Wei Liu Return-path: Received: from mail-la0-f51.google.com ([209.85.215.51]:37006 "EHLO mail-la0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758419Ab3CYPvn (ORCPT ); Mon, 25 Mar 2013 11:51:43 -0400 Received: by mail-la0-f51.google.com with SMTP id fo13so11445336lab.24 for ; Mon, 25 Mar 2013 08:51:41 -0700 (PDT) In-Reply-To: <1364209702-12437-3-git-send-email-wei.liu2@citrix.com> Sender: netdev-owner@vger.kernel.org List-ID: Hello. On 25-03-2013 15:08, Wei Liu wrote: > The maximum packet including ethernet header that can be handled by netfront / > netback wire format is 65535. Reduce gso_max_size accordingly. > Drop skb and print warning when skb->len > 65535. This can 1) save the effort > to send malformed packet to netback, 2) help spotting misconfiguration of > netfront in the future. > Signed-off-by: Wei Liu > --- > drivers/net/xen-netfront.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c > index 5527663..3ae9dc1 100644 > --- a/drivers/net/xen-netfront.c > +++ b/drivers/net/xen-netfront.c > @@ -547,6 +547,18 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev) > unsigned int len = skb_headlen(skb); > unsigned long flags; > > + /* Wire format of xen_netif_tx_request only supports skb->len > + * < 64K, because size field in xen_netif_tx_request is > + * uint16_t. If skb->len is too big, drop it and alert user about > + * misconfiguration. > + */ > + if (unlikely(skb->len >= (uint16_t)(~0))) { Such types as 'uint16_t' are intended for userland -- use 'u16' instead. Better still, just use 0xffffu. WBR, Sergei