[Bug 215737] [bhyve] utilizing virtio-net truncates jumbo frames at 4084 bytes length

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=215737

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

           What    |Removed                     |Added
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                 CC|                            |wjw at digiware.nl

--- Comment #22 from Willem Jan Withagen <wjw at 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 at zfstest:/tmp # ifconfig re0
re0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
       
options=8209b<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=21<PERFORMNUD,AUTO_LINKLOCAL>
root at zfstest:/tmp # ifconfig re0 mtu 9000
root at zfstest:/tmp # ifconfig bridge0 create
root at zfstest:/tmp # ifconfig bridge0 addm re0 up
root at zfstest:/tmp # ifconfig bridge0
bridge0: flags=8843<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=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
                ifmaxaddr 0 port 1 priority 128 path cost 20000
        groups: bridge
        nd6 options=9<PERFORMNUD,IFDISABLED>
root at zfstest:/tmp # ifconfig tap1213 create
root at zfstest:/tmp # ifconfig bridge0 addm tap1213
ifconfig: BRDGADD tap1213: Invalid argument
root at zfstest:/tmp # ifconfig bridge0 addm t
root at zfstest:/tmp # ifconfig tap1213 mtu 9000
root at zfstest:/tmp # ifconfig bridge0 addm tap1213
root at zfstest:/tmp #

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