Created attachment 160825 [details]
When trying to set up a tap device for bhyve, I ran into a kernel panic with some combination of the e1000 drivers for my Intel NIC and pf forwarding of IPv6 packets. I was following the instructions on the bhyve page for setting up the tap device and bridge: https://www.freebsd.org/doc/handbook/virtualization-host-bhyve.html which worked fine until I try to bring up the bridge, at which point it will panic shortly after (presumably when it gets an IPv6 multicast packet).
The crash appears to be a bad interaction between the e1000 driver and ip6_forward, where it panics when trying to log that it can't forward multicast messages. The name of the interface in one of the mbufs is null, leading to a fault when it tries to strlen the argument to kvprintf.
core.txt is attached.
Created attachment 160826 [details]
I was able to work around this by adding a pf rule that drops incoming IPv6 multicast traffic to em0. Suboptimal, but no more kernel panics.
*** This bug has been marked as a duplicate of bug 202351 ***