Re: [libvirt] 答复: Re: [PATCH] qemu: change the name of tap device for a tapand bridge network

On Mon, May 08, 2017 at 03:03:30PM +0800, ZhiPeng Lu wrote:＞＞ In qemuProcessStop we explicitly remove the port from the openvswitch bridge after＞＞ qemuProcessKill is called. But there is a certain interval of time between＞＞ deleting tap device and removing it from bridge. The problem occurs when two vms＞＞ start and shutdown with the same name's network interface attached to the same＞＞ openvswitch bridge. When one vm with the nic named "vnet0" stopping, it deleted＞＞tap device without timely removing the port from bridge.＞＞.At this time, another vm created the tap device named "vnet0" and added port to the＞＞ same bridge. Then, the first vm removed the port from the same bridge.＞＞ Finally, the tap device of the second vm did not attached to the bridge.＞＞ We need to delete the bridge port before deleting the tap device instead of after.＞＞ So what's needed is to move the loop in qemuProcessStop that cleans up＞＞ network interfaces so that it happens before qemuProcessKill is called.＞This fix won't work correctly either. You cannot assume that libvirt has＞control over when the QEMU process exits. It may exit itself *before*＞libvirt runs any of its cleanup code. On Mon, May 08, 2017 at 06:18:25PM +0800, lu.zhipeng(a)zte.com.cn wrote:＞ I may not have described it clearly. ＞ ＞ i need to ensure the order of adding port to bridge and deleting from bridge.＞ ＞ i rename tap device to avoid the problem in my first patch.i think it can solve the problem.＞ ＞ my second patch may can't resolve the problem .＞ ＞ Do you have any better ideas?

为了让您的VPlat虚拟化故障得到高效的处理，请上报故障到: $VPlat技术支持。 芦志朋 luzhipeng IT开发工程师 IT Development Engineer 操作系统产品部/中心研究院/系统产品 OS Product Dept./Central R＆D Institute/System Product 深圳市南山区科技南路55号中兴通讯研发大楼33楼 33/F, R&D Building, ZTE Corporation Hi-tech Road South, Hi-tech Industrial Park Nanshan District, Shenzhen, P.R.China, 518057 T: +86 755 xxxxxxxx F:+86 755 xxxxxxxx M: +86 xxxxxxxxxxx E: lu.zhipeng(a)zte.com.cn www.zte.com.cn 原始邮件 发件人： ＜berrange(a)redhat.com> 收件人： ＜laine(a)laine.org> 抄送人： ＜libvir-list(a)redhat.xn--com>10108272-u92xv15exu8g 日 期 ：2017年05月02日 16:41 主 题 ：Re: [libvirt] [PATCH] qemu: change the name of tap device for a tapand bridge network On Fri, Apr 28, 2017 at 01:08:45PM -0400, Laine Stump wrote: ＞ On 04/28/2017 05:33 AM, Daniel P. Berrange wrote: ＞ ＞ On Fri, Apr 28, 2017 at 05:23:19PM +0800, ZhiPeng Lu wrote: ＞ ＞＞ Creating tap device and adding the device to bridge are not atomic operation. ＞ ＞＞ Similarly deleting tap device and removing it from bridge are not atomic operation. ＞ ＞＞ The Problem occurs when two vms start and shutdown. When one vm with the nic ＞ ＞＞ named "vnet0" stopping, it deleted tap device but not removing port from bridge. ＞ ＞＞ At this time, another vm created the tap device named "vnet0" and added port to the ＞ ＞＞ same bridge. Then, the first vm deleted the tap device from the same bridge. ＞ ＞＞ Finally, the tap device of the second vm don't attached to the bridge. ＞ ＞＞ So, we can add domid to vm's nic name. For example, the vm's domid is 1 and vnet0 ＞ ＞＞ is renamed to vnet1.0. ＞ ＞ ＞ ＞ Surely deleting the NIC automatically removes it from the bridge so we ＞ ＞ can just remove the code that delets the bridge port. ＞ ＞ That is true when using a Linux host bridge, but I recall that for ＞ openvswitch (which I think is what ZhiPeng is using, based on an earlier ＞ patch), you must explicitly remove the port from the bridge - apparently ＞ the port is still there in openvswitch's table as some sort of "zombie" ＞ connection even after the tap device itself no longer exists. ＞ ＞ ＞ But instead of changing the naming scheme, maybe we should just delete ＞ the bridge port *before* deleting the tap device instead of after. (Am I ＞ recalling correctly that the tap device is deleted automatically when ＞ the qemu process is killed? If so, then what's needed is to move the ＞ loop in qemuProcessStop() that cleans up network interfaces so that it ＞ happens before qemuProcessKill() is called. Agreed, we should just reverse the order. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|