https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=289545
Bug ID: 289545
Summary: No option to disable NOCAP leads to network down/up
with em0 when starting bridge.
Product: Base System
Version: 13.5-RELEASE
Hardware: Any
OS: Any
Status: New
Severity: Affects Some People
Priority: ---
Component: kern
Assignee: [email protected]
Reporter: [email protected]
Bug report https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=221122 documented
an unfortunate behavior of Intel network cards and how it's triggered by bhyve
vm's. I stumbled across it having the same problem on a 13.5-RELEASE install
where my em0 would go down and come back up leading to a ~7 second network
pause when the first vm was started or last vm stopped.
I attempted the work-around in the bug report. I checked em0 for the features
enabled, started the vm and checked again to see which features the bridge
disabled. I came up with this /etc/rc.conf line:
ifconfig_em0="DHCP -tso -lro -txcsum -rxcsum -txcsum6 -vlanmtu -vlanhwtag
-vlanhwfilter -vlanhwtso -vlanhwcsum"
Unfortunately this is not a complete solution. Before starting the first vm:
options=4802020<JUMBO_MTU,WOL_MAGIC,NOMAP>
After starting the first VM:
options=802020<JUMBO_MTU,WOL_MAGIC>
The bridge is still removing the option "NOMAP", and I believe that is what is
still causing the network to flap.
Unfortunately there is no ifconfig option to disable NOMAP. In fact, there
appears to be no real documentation about it at all anywhere. Indeed, the only
place I can even find this in the source is
https://github.com/freebsd/freebsd-src/blob/main/sbin/ifconfig/ifconfig.c#L1674
where ifconfig prints it out.
Should there be a "-nocap" for ifconfig? Is there some better solution?
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