Big problems with tcp offload

[guilhem]

I use KVM in my company with a mix Linux/WIndows.

I use them with vhost_net, bridge and/or macvtap.

Problems com with macvtap on Windows.
without any management of tcp offload :

1. Windows reject any packet send from another vm on the same host (and in macvtap too). (can be correct by a tricky rule in iptables... but it's quite awful
2. More painful, when GRO is activated on host, ALL packets are dropped by windows...

[YanVugenfirer]

Windows does not support GRO (receive offload). Any such configuration on
host will cause Windows to misbehave.

Those issues should be solved on the host. Windows driver reports that it
has no RX offload capabilities.
I will speak to QEMU guys to see what can be done.

Best regards,
Yan.

On Wed, Feb 8, 2012 at 5:37 PM, Guilhem <
reply@reply.github.com

wrote:

I use KVM in my company with a mix Linux/WIndows.

I use them with vhost_net, bridge and/or macvtap.

Problems com with macvtap on Windows :
without any management of tcp offload :

1. Windows reject any paquet send from another another on the same host
   (and in macvtap too). (can be correct by a tricky rule in iptables... but
   it's quite awful
2. More painful, when GRO is activated on host, ALL packets are dropped by
   windows...

---

Reply to this email directly or view it on GitHub:
YanVugenfirer/kvm-guest-drivers-windows#1

---

Daynix Computing LTD
Yan Vugenfirer, Technology expert and consultant
Email: yan@daynix.com
Phone: +972-54-4758084
Web: www.daynix.com

[guilhem]

Thank you for this information, I hope this will be fix ASAP :)

Don't hesitate to come back to me, I can do some tests on my infrastructure

[iggy]

That's how macvtap is supposed to work.

[vipmike007]

1) Windows reject any packet send from another vm on the same host (and in macvtap too). (can be correct by a tricky rule in iptables... but it's quite awful

Tried this via virt-manager ,did not hit this issue . might be libvirt default firewall rule make it ?

[guilhem]

1. A linux vm send packet without any good checksum (thanks to offload). But with macvtap, packet is directly send to the Windows VM (and so without a good checksum). And Windows reject the package.
   To correct this, I must use this rule on the GUEST Linux :
   -A POSTROUTING -d WINDOWS-GUEST -p tcp -j CHECKSUM --checksum-fill
   Very tricky rule...

[vipmike007]

Hi, guihem

which network type are you using , e1000 + macvtap , Am I right ?

[guilhem]

HOST : e1000e + vhost_net
Guests : macvtap + virtio

EDIT : to be more precise, this is my libvirt conf

    <interface type='direct'>
      <mac address='de:ad:b9:73:7e:33'/>
      <source mode='bridge' dev='eth0.2086'/>
      <target dev='macvtap2'/>
      <model type='virtio'/>
      <alias name='net0'/>
      <address slot='0x03' bus='0x00' domain='0x0000' type='pci' function='0x0'/>
    </interface>

[sameehj]

Hi,

we are currently in a process of closing all github's issues that have been resolved or expired. I'm currently closing this issue, please reopen the issue or else open a new issue if needed.