From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [Xen-devel] [PATCH 2/6] xen-netfront: reduce gso_max_size to account for ethernet header Date: Mon, 25 Mar 2013 14:23:53 +0000 Message-ID: <51505DF9.4080406@citrix.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" Content-Transfer-Encoding: 7bit Cc: , , , , , To: Wei Liu Return-path: Received: from smtp.citrix.com ([66.165.176.89]:55084 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758259Ab3CYOYP (ORCPT ); Mon, 25 Mar 2013 10:24:15 -0400 In-Reply-To: <1364209702-12437-3-git-send-email-wei.liu2@citrix.com> Sender: netdev-owner@vger.kernel.org List-ID: On 25/03/13 11:08, 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. [...] > --- 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))) { Suggest a #define for this maximum added to include/xen/interface/io/netif.h David