FYI your replies to messages on the list are almost impossible to read & understand. Your email client is sending HTML and badly mangled plain text. Please make it send plain text only to public mailing lists, with line wrapping and sensibly trim & quote text you are replying to. I can't see any comment you made in this latest message so I can't reply to you. On Tue, May 09, 2017 at 08:44:55AM +0800, lu.zhipeng@zte.com.cn wrote:
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@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?
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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
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原始邮件
发件人： ＜berrange@redhat.com＞ 收件人： ＜laine@laine.org＞ 抄送人： ＜libvir-list@redhat.com＞芦志朋10108272 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 :|
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 :|