thr3ads.net - Linux Virtualization - [PATCH] virtio: Work around frames incorrectly marked as gso [Feb 2020]

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Jason Wang

2020-Feb-11 02:51 UTC

[PATCH] virtio: Work around frames incorrectly marked as gso

On 2020/2/11 ??12:55, Anton Ivanov wrote:>
>
> On 09/12/2019 10:48, anton.ivanov at cambridgegreys.com wrote:
>> From: Anton Ivanov <anton.ivanov at cambridgegreys.com>
>>
>> Some of the frames marked as GSO which arrive at
>> virtio_net_hdr_from_skb() have no GSO_TYPE, no
>> fragments (data_len = 0) and length significantly shorter
>> than the MTU (752 in my experiments).
>>
>> This is observed on raw sockets reading off vEth interfaces
>> in all 4.x and 5.x kernels I tested.
>>
>> These frames are reported as invalid while they are in fact
>> gso-less frames.
>>
>> This patch marks the vnet header as no-GSO for them instead
>> of reporting it as invalid.
>>
>> Signed-off-by: Anton Ivanov <anton.ivanov at cambridgegreys.com>
>> ---
>> ? include/linux/virtio_net.h | 8 ++++++--
>> ? 1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
>> index 0d1fe9297ac6..d90d5cff1b9a 100644
>> --- a/include/linux/virtio_net.h
>> +++ b/include/linux/virtio_net.h
>> @@ -112,8 +112,12 @@ static inline int virtio_net_hdr_from_skb(const 
>> struct sk_buff *skb,
>> ????????????? hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
>> ????????? else if (sinfo->gso_type & SKB_GSO_TCPV6)
>> ????????????? hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
>> -??????? else
>> -??????????? return -EINVAL;
>> +??????? else {
>> +??????????? if (skb->data_len == 0)
>> +??????????????? hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE;
>> +??????????? else
>> +??????????????? return -EINVAL;
>> +??????? }
>> ????????? if (sinfo->gso_type & SKB_GSO_TCP_ECN)
>> ????????????? hdr->gso_type |= VIRTIO_NET_HDR_GSO_ECN;
>> ????? } else
>>
>
> ping.
>
Do you mean gso_size is set but gso_type is not? Looks like a bug elsewhere.

Thanks

Anton Ivanov

2020-Feb-11 07:42 UTC

head link

[PATCH] virtio: Work around frames incorrectly marked as gso

On 11/02/2020 02:51, Jason Wang wrote:> 
> On 2020/2/11 ??12:55, Anton Ivanov wrote:
>>
>>
>> On 09/12/2019 10:48, anton.ivanov at cambridgegreys.com wrote:
>>> From: Anton Ivanov <anton.ivanov at cambridgegreys.com>
>>>
>>> Some of the frames marked as GSO which arrive at
>>> virtio_net_hdr_from_skb() have no GSO_TYPE, no
>>> fragments (data_len = 0) and length significantly shorter
>>> than the MTU (752 in my experiments).
>>>
>>> This is observed on raw sockets reading off vEth interfaces
>>> in all 4.x and 5.x kernels I tested.
>>>
>>> These frames are reported as invalid while they are in fact
>>> gso-less frames.
>>>
>>> This patch marks the vnet header as no-GSO for them instead
>>> of reporting it as invalid.
>>>
>>> Signed-off-by: Anton Ivanov <anton.ivanov at
cambridgegreys.com>
>>> ---
>>> ? include/linux/virtio_net.h | 8 ++++++--
>>> ? 1 file changed, 6 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/include/linux/virtio_net.h
b/include/linux/virtio_net.h
>>> index 0d1fe9297ac6..d90d5cff1b9a 100644
>>> --- a/include/linux/virtio_net.h
>>> +++ b/include/linux/virtio_net.h
>>> @@ -112,8 +112,12 @@ static inline int
virtio_net_hdr_from_skb(const
>>> struct sk_buff *skb,
>>> ????????????? hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
>>> ????????? else if (sinfo->gso_type & SKB_GSO_TCPV6)
>>> ????????????? hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
>>> -??????? else
>>> -??????????? return -EINVAL;
>>> +??????? else {
>>> +??????????? if (skb->data_len == 0)
>>> +??????????????? hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE;
>>> +??????????? else
>>> +??????????????? return -EINVAL;
>>> +??????? }
>>> ????????? if (sinfo->gso_type & SKB_GSO_TCP_ECN)
>>> ????????????? hdr->gso_type |= VIRTIO_NET_HDR_GSO_ECN;
>>> ????? } else
>>>
>>
>> ping.
>>
> 
> Do you mean gso_size is set but gso_type is not? Looks like a bug 
> elsewhere.
> 
> Thanks
> 
> Yes.

I could not trace it where it is coming from.

I see it when doing recvmmsg on raw sockets in the UML vector network 
drivers.


-- 
Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/

Michael S. Tsirkin

2020-Feb-11 10:37 UTC

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[PATCH] virtio: Work around frames incorrectly marked as gso

On Tue, Feb 11, 2020 at 07:42:37AM +0000, Anton Ivanov
wrote:> On 11/02/2020 02:51, Jason Wang wrote:
> > 
> > On 2020/2/11 ??12:55, Anton Ivanov wrote:
> > > 
> > > 
> > > On 09/12/2019 10:48, anton.ivanov at cambridgegreys.com wrote:
> > > > From: Anton Ivanov <anton.ivanov at
cambridgegreys.com>
> > > > 
> > > > Some of the frames marked as GSO which arrive at
> > > > virtio_net_hdr_from_skb() have no GSO_TYPE, no
> > > > fragments (data_len = 0) and length significantly shorter
> > > > than the MTU (752 in my experiments).
> > > > 
> > > > This is observed on raw sockets reading off vEth interfaces
> > > > in all 4.x and 5.x kernels I tested.
> > > > 
> > > > These frames are reported as invalid while they are in fact
> > > > gso-less frames.
> > > > 
> > > > This patch marks the vnet header as no-GSO for them instead
> > > > of reporting it as invalid.
> > > > 
> > > > Signed-off-by: Anton Ivanov <anton.ivanov at
cambridgegreys.com>
> > > > ---
> > > > ? include/linux/virtio_net.h | 8 ++++++--
> > > > ? 1 file changed, 6 insertions(+), 2 deletions(-)
> > > > 
> > > > diff --git a/include/linux/virtio_net.h
b/include/linux/virtio_net.h
> > > > index 0d1fe9297ac6..d90d5cff1b9a 100644
> > > > --- a/include/linux/virtio_net.h
> > > > +++ b/include/linux/virtio_net.h
> > > > @@ -112,8 +112,12 @@ static inline int
> > > > virtio_net_hdr_from_skb(const struct sk_buff *skb,
> > > > ????????????? hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
> > > > ????????? else if (sinfo->gso_type & SKB_GSO_TCPV6)
> > > > ????????????? hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
> > > > -??????? else
> > > > -??????????? return -EINVAL;
> > > > +??????? else {
> > > > +??????????? if (skb->data_len == 0)
> > > > +??????????????? hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE;
> > > > +??????????? else
> > > > +??????????????? return -EINVAL;
> > > > +??????? }
> > > > ????????? if (sinfo->gso_type & SKB_GSO_TCP_ECN)
> > > > ????????????? hdr->gso_type |= VIRTIO_NET_HDR_GSO_ECN;
> > > > ????? } else
> > > > 
> > > 
> > > ping.
> > > 
> > 
> > Do you mean gso_size is set but gso_type is not? Looks like a bug
> > elsewhere.
> > 
> > Thanks
> > 
> > 
> Yes.
> 
> I could not trace it where it is coming from.
> 
> I see it when doing recvmmsg on raw sockets in the UML vector network
> drivers.
> 
I think we need to find the culprit and fix it there, lots of other things
can break otherwise.
Just printing out skb->dev->name should do the trick, no?

> -- 
> Anton R. Ivanov
> Cambridgegreys Limited. Registered in England. Company Number 10273661
> https://www.cambridgegreys.com/

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