From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: regression: UFO removal breaks kvm live migration Date: Wed, 8 Nov 2017 16:49:57 +0900 Message-ID: References: <20171107080224.v6z65jvimpa5ohs4@unicorn.suse.cz> <20171108.152624.282888162096095926.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: mkubecek@suse.cz, netdev@vger.kernel.org, "Michael S. Tsirkin" , Vlad Yasevic To: David Miller , willemdebruijn.kernel@gmail.com Return-path: Received: from mx1.redhat.com ([209.132.183.28]:37462 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750953AbdKHHuL (ORCPT ); Wed, 8 Nov 2017 02:50:11 -0500 In-Reply-To: <20171108.152624.282888162096095926.davem@davemloft.net> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 2017年11月08日 15:26, David Miller wrote: > From: Willem de Bruijn > Date: Wed, 8 Nov 2017 12:36:26 +0900 > >> On Tue, Nov 7, 2017 at 5:02 PM, Michal Kubecek wrote: >>> I didn't have time to think it through yet but perhaps we could allow >>> setting TUN_F_UFO and ignore its value. >> If the feature is enabled guests may try to send UFO packets, which >> the host is no longer able to fragment. >> >> virtio_net_hdr_to_skb will drop the packets immediately based on >> gso_type and tun_get_user will return EINVAL. >> >> Still, perhaps that's preferable as migration will succeed and most >> guests won't ever try to send those packets in the first place. > However, this would create the situation where there is no way > to properly probe for the actual presence of UFO support. I think we should not have any assumption on how guest will use the feature. So I could not come a better than bring it back partially for TAP, looks like we only need segment them in tun_get_user(). Thanks