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Date:      Wed, 29 Jan 2020 11:46:01 +0000
From:      bugzilla-noreply@freebsd.org
To:        virtualization@FreeBSD.org
Subject:   [Bug 215737] [bhyve] utilizing virtio-net truncates jumbo frames at 4084 bytes length
Message-ID:  <bug-215737-27103-GRHwBECHxv@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-215737-27103@https.bugs.freebsd.org/bugzilla/>
References:  <bug-215737-27103@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D215737

Willem Jan Withagen <wjw@digiware.nl> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |wjw@digiware.nl

--- Comment #22 from Willem Jan Withagen <wjw@digiware.nl> ---
What did not work for me last time I tried is:

Have mtu 9000 on the physical interface, and add bridge to it.
The bridge will automagically get an MTU of 9000

Then try to add a plain TAP to it, you'll get "invallid argument".
Setting the tap MTU to 9000 fixes that problem.

I know this is not a typical bhyve problem, but will fail when using vmrun.=
sh

--WjW


root@zfstest:/tmp # ifconfig re0
re0: flags=3D8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
=20=20=20=20=20=20=20
options=3D8209b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,WOL_MAGIC=
,LINKSTATE>
        ether 9c:5c:8e:84:d6:21
        inet 192.168.10.78 netmask 0xfffffc00 broadcast 192.168.11.255
        inet 192.168.11.78 netmask 0xffffff00 broadcast 192.168.11.255
        inet6 fe80::9e5c:8eff:fe84:d621%re0 prefixlen 64 scopeid 0x1
        inet6 2001:4cb8:3:1::78 prefixlen 64
        inet6 2001:4cb8:3:1::11:78 prefixlen 64
        media: Ethernet autoselect (1000baseT <full-duplex>)
        status: active
        nd6 options=3D21<PERFORMNUD,AUTO_LINKLOCAL>
root@zfstest:/tmp # ifconfig re0 mtu 9000
root@zfstest:/tmp # ifconfig bridge0 create
root@zfstest:/tmp # ifconfig bridge0 addm re0 up
root@zfstest:/tmp # ifconfig bridge0
bridge0: flags=3D8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu =
9000
        ether 02:fe:a0:7f:12:00
        id 00:00:00:00:00:00 priority 32768 hellotime 2 fwddelay 15
        maxage 20 holdcnt 6 proto rstp maxaddr 2000 timeout 1200
        root id 00:00:00:00:00:00 priority 32768 ifcost 0 port 0
        member: re0 flags=3D143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
                ifmaxaddr 0 port 1 priority 128 path cost 20000
        groups: bridge
        nd6 options=3D9<PERFORMNUD,IFDISABLED>
root@zfstest:/tmp # ifconfig tap1213 create
root@zfstest:/tmp # ifconfig bridge0 addm tap1213
ifconfig: BRDGADD tap1213: Invalid argument
root@zfstest:/tmp # ifconfig bridge0 addm t
root@zfstest:/tmp # ifconfig tap1213 mtu 9000
root@zfstest:/tmp # ifconfig bridge0 addm tap1213
root@zfstest:/tmp #

--=20
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