Bug 229990

Summary: FreeBSD 11.2 on Hyper-V: hn0: network changed, change 1
Product: Base System Reporter: bazald <bazald>
Component: kernAssignee: freebsd-virtualization (Nobody) <virtualization>
Status: New ---    
Severity: Affects Some People CC: mwisnicki+freebsd
Priority: ---    
Version: 11.2-STABLE   
Hardware: amd64   
OS: Any   

Description bazald@gmail.com 2018-07-23 19:09:29 UTC
I am attempting to run FreeBSD 11.2 under Hyper-V on Windows 10 1803. I have tried both Gen 1 and Gen 2 virtual machines, as well as both legacy and non-legacy network adapters under Gen 1, and networking seems to be difficult to get right, at least with Wi-Fi.

The only configuration that seems to work at all is using a Gen 2 VM (non-legacy network adapter). I initially attempted to use a virtual switch configured to access the external network, with sharing allowed, and I quickly got MAC collision errors. I'm uncertain as to whether that's the expected result.

Moving on to the default switch, sharing my Wi-Fi with that, I seem to have working Internet access. I added "net.link.ether.inet.max_age=60" to /etc/sysctl.conf, which seems to be important for maintaining the connection. As a new FreeBSD user, it is distressing that https://docs.microsoft.com/en-us/windows-server/virtualization/hyper-v/best-practices-for-running-freebsd-on-hyper-v fails to document that it truly ought to be added to /etc/sysctl.conf.

Finally, even with this apparently working connection, we get to the bug I'm actually here to report. I'm still getting flooded with "hn0: network changed, change 1" messages on the terminal. The patch at https://reviews.freebsd.org/D8295 seems to be to blame? I believe NDIS_NETCHANGE_TYPE_POSSIBLE is being reported to the console, and perhaps correctly so given the networking issues with Hyper-V, but some method to at least suppress the messages would be most welcome.
Comment 1 bazald@gmail.com 2018-07-23 22:01:28 UTC
I take it back. The connection is actually being lost for a great many of these messages. Leaving a ping command going confirms it. Perhaps Hyper-V + Wi-Fi is simply an unusable configuration.
Comment 2 mwisnicki+freebsd 2019-12-25 22:22:45 UTC
This actually makes DHCP unusable as it keeps restarting dhclient due to link down and up events.
Comment 3 mwisnicki+freebsd 2019-12-25 22:23:48 UTC
Keeps happening with Windows 1909 and FreeBSD 12.1-R