Date: Sat, 13 Sep 2025 13:51:09 +0000 From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 289545] No option to disable NOCAP leads to network down/up with em0 when starting bridge. Message-ID: <bug-289545-227@https.bugs.freebsd.org/bugzilla/>
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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: bugs@FreeBSD.org Reporter: bicknell@ufp.org 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? -- You are receiving this mail because: You are the assignee for the bug.home | help
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