[Xen] UDP transmit under VLAN causes guest freeze

Issue

• If VM is started with VLAN as the vif, UDP transmit in VM will causes very high cpu overload and host is almost frozen until the UDP transmit is finished.

Environment

• Red Hat Enterprise Linux 5.4 GA (x86_64)
• kernel-2.6.18-164.el5xen

Diagnostic Steps

Test this with two machine, link with e1000 network devi...