Re: [libvirt] macvtap - no incoming ipv6 traffic processed on kvm host unless i start tcpdump on interface

On Thu, 2015-04-09 at 10:12 +0200, Michal Privoznik wrote: > I mildly recalls seeing a bug like this. The problem was in intel's > kernel driver. A NIC by defaul checks incoming packets whether they > match NIC's MAC. So if a TAP device was created over a NIC, it had to be > put into promisc mode (automatically done by the driver) to allow > different MACs and the check was done in kernel then. But since this > generates too much interrupts, NICs HW was extended and it can be > programmed with multiple MACs to let through. However, there was a bug > which I recall of, that intel driver was not always putting the TAP MAC > into the NIC HW correctly. Obviously, the bug was not visible if the NIC > was put into promisc mode. And this may be what you are seeing. Let me > see if I can find the bug. FYI - enabling promiscious mode on eth0 does not help. I have to enable it on the macvtap0 which is on top of eth0.