Ubuntu KVM's Windows XP Virtual machine cannot be connected to the Internet

Ubuntu KVM's Windows xp Virtual Machine cannot access the Internet to solve a problem that has recently encountered the xp Virtual opportunity, that is, after a network program crashes, the xp Virtual Machine cannot access the Internet, and the cause of the program has been ruled out, this is a bug in the kvm network. Restart the machine, regardless of whether the windows xp Virtual Machine of ubuntu kvm cannot access the Internet.
Recently, the xp Virtual Opportunity encountered a problem: after a network program crashes,

This xp Virtual Machine cannot access the Internet, and the cause of the program has been ruled out, so this is a bug in the kvm network. Restarting the machine does not work. I am using a bridge network. The solution is listed here: sudo brctl show shows whether the vSwitch is normal. generally, an interface is missing. Sudo ifdown br0 disable the switch sudo ifup br0 start the switch and restart xp.