virtio-net: how to prevent receiving big packages?

virtio-net: how to prevent receiving big packages?

[wangsitan]

Hi all,

A virtual net interface using virtio_net with TSO on may send big TCP packets (up to 64KB). The receiver will get big packets if it's virtio_net, too. But it will get common packets (according to MTU) if the receiver is e1000 (who re-packaged the data?). 

The transfer with big packets is more efficient. But there's something wrong with my "receiver" vm whose net-core has been modified. Strange behaviours came out when it received big packets.

I will look at problems on the modified kernel later. What I want to do now is turning off the feature "can receive big packets" of virtio_net in the guest vm (just like I'm using e1000). Is there an easy way to disable it? Or should I change some code in guest's virtio_net?


Thanks a lot.

--
Best Regards
Wangsitan

Re: virtio-net: how to prevent receiving big packages?

[Jason Wang]

On 11/03/2013 04:07 PM, wangsitan wrote:
> Hi all,
>
> A virtual net interface using virtio_net with TSO on may send big TCP packets (up to 64KB). The receiver will get big packets if it's virtio_net, too. But it will get common packets (according to MTU) if the receiver is e1000 (who re-packaged the data?). 
>
> The transfer with big packets is more efficient. But there's something wrong with my "receiver" vm whose net-core has been modified. Strange behaviours came out when it received big packets.
>
> I will look at problems on the modified kernel later. What I want to do now is turning off the feature "can receive big packets" of virtio_net in the guest vm (just like I'm using e1000). Is there an easy way to disable it? Or should I change some code in guest's virtio_net?

You can disable the feature of VIRTIO_NET_F_HOST_TSO4 and
VIRTIO_NET_F_HOST_TSO6 by specifying host_tso4=off,guest_tso6=off in
qemu command line.
>
> Thanks a lot.
>
> --
> Best Regards
> Wangsitan
> --
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Re: virtio-net: how to prevent receiving big packages?

[Jason Wang]

On 11/04/2013 12:35 PM, Jason Wang wrote:
> On 11/03/2013 04:07 PM, wangsitan wrote:
>> Hi all,
>>
>> A virtual net interface using virtio_net with TSO on may send big TCP packets (up to 64KB). The receiver will get big packets if it's virtio_net, too. But it will get common packets (according to MTU) if the receiver is e1000 (who re-packaged the data?). 
>>
>> The transfer with big packets is more efficient. But there's something wrong with my "receiver" vm whose net-core has been modified. Strange behaviours came out when it received big packets.
>>
>> I will look at problems on the modified kernel later. What I want to do now is turning off the feature "can receive big packets" of virtio_net in the guest vm (just like I'm using e1000). Is there an easy way to disable it? Or should I change some code in guest's virtio_net?
> You can disable the feature of VIRTIO_NET_F_HOST_TSO4 and
> VIRTIO_NET_F_HOST_TSO6 by specifying host_tso4=off,guest_tso6=off in
> qemu command line.

Speak too fast, this is for sender. For receiver, you can do it by
specifying guest_tso4=off,guest_tso6=off in qemu command line.
>> Thanks a lot.
>>
>> --
>> Best Regards
>> Wangsitan
>> --
>> To unsubscribe from this list: send the line "unsubscribe kvm" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html