Nexus 9k - QEMU NIC - flow control issues

[bucho]

Hi Guys,

Been hoping to post it here asking for help while still trying to work around the issue.

What I have is:

EVE: Community 4.20.17-eve-ng-ukms+

NXOS: Nexus 9000v 9.3(2)
NXOS guest settings: QEMU Version - tlp(default 2.4.0) / QEMU NIC - tlp(e1000)

WinSrv Guest: 2008Srv
WinSrv guest settings: QEMU Version - 2.2.0 / QEMU NIC - e1000

IOL: IOL-L2
IOL guest settings: Default

Topology:

WinSrv Guest (eth1G) >>>> (e1/5) NXOS (e1/6) <<<< (eth1G) WinSrv Guest

WinSrv Guest (eth1G) >>>> (e1/5) IOL (e1/6) <<<< (eth1G) WinSrv Guest

Issue description:

1) WinSrv guests cannot exchange large data portions over TCP traversing the Nexus
2) WinSrv guests can exchange 1500 Byte ICMP echo requests sent over the Nexus
3) No issues transiting IOL over TCP,UDP or ICMP

Troubleshooting:

Found this on Nexus interfaces
>>

2019 Dec 28 00:30:09 dc01-core-sw02 %ETHPORT-5-IF_ADMIN_UP: Interface Ethernet1/5 is admin up .
2019 Dec 28 00:30:09 dc01-core-sw02 %ETHPORT-5-SPEED: Interface Ethernet1/5, operational speed changed to auto
2019 Dec 28 00:30:09 dc01-core-sw02 %ETHPORT-5-IF_DUPLEX: Interface Ethernet1/5, operational duplex mode changed to unknown
2019 Dec 28 00:30:09 dc01-core-sw02 %ETHPORT-5-IF_RX_FLOW_CONTROL: Interface Ethernet1/5, operational Receive Flow Control state changed to off
2019 Dec 28 00:30:09 dc01-core-sw02 %ETHPORT-5-IF_TX_FLOW_CONTROL: Interface Ethernet1/5, operational Transmit Flow Control state changed to off
2019 Dec 28 00:30:09 dc01-core-sw02 %ETHPORT-5-IF_UP: Interface Ethernet1/5 is up in mode access

Interface settings:

NXOS
>>
interface Ethernet1/5
speed 1000
duplex full

WinGuest
>>
1G Full Duplex

Interface status:

NXOS
>>
Ethernet1/5 is up
Hardware: 100/1000/10000 Ethernet
full-duplex, 1000 Mb/s


Well, summarizing, for a some strange reason it cannot negotiate speed/duplex properly and disables flow control on the iface (although it's configured and can be seen in show int output). Have a feeling it might be QEMU related and wonder if anyone has seen this before and managed to work around it x)

Cheers
b

[bucho]

Confirmed to be a known bug if anyone's interested