From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jan Beulich" Subject: Re: [PATCH 2/6] xen-netfront: reduce gso_max_size to account for ethernet header Date: Mon, 25 Mar 2013 14:39:02 +0000 Message-ID: <51506F9602000078000C8277__3852.67940951071$1364222436$gmane$org@nat28.tlf.novell.com> References: <1364209702-12437-1-git-send-email-wei.liu2@citrix.com> <1364209702-12437-3-git-send-email-wei.liu2@citrix.com> <51505DF9.4080406@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <51505DF9.4080406@citrix.com> Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: david.vrabel@citrix.com, Wei Liu Cc: netdev@vger.kernel.org, annie.li@oracle.com, konrad.wilk@oracle.com, ian.campbell@citrix.com, xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org >>> On 25.03.13 at 15:23, David Vrabel wrote: > 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 I don't see a point in doing so. If you want the connection to be explicit, just use typeof() here instead of uint16_t. Jan