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

On Thu, Feb 13, 2020 at 07:44:06AM -0800, Eric Dumazet
wrote:
> 
> 
> On 2/13/20 2:00 AM, Michael S. Tsirkin wrote:
> > On Wed, Feb 12, 2020 at 05:38:09PM +0000, Anton Ivanov wrote:
> >>
> >>
> >> On 11/02/2020 10:37, Michael S. Tsirkin wrote:
> >>> 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?
> >>
> >> The printk in virtio_net_hdr_from_skb says NULL.
> >>
> >> That is probably normal for a locally originated frame.
> >>
> >> I cannot reproduce this with network traffic by the way - it
happens only if the traffic is locally originated on the host.
> >>
> >> A,
> > 
> > OK so is it code in __tcp_transmit_skb that sets gso_size to non-null
> > when gso_type is 0?
> >
> 
> Correct way to determine if a packet is a gso one is by looking at
gso_size.
> Then only it is legal looking at gso_type
> 
> 
> static inline bool skb_is_gso(const struct sk_buff *skb)
> {
>     return skb_shinfo(skb)->gso_size;
> }
> 
> /* Note: Should be called only if skb_is_gso(skb) is true */
> static inline bool skb_is_gso_v6(const struct sk_buff *skb)
> ...
> 
> 
> There is absolutely no relation between GSO and skb->data_len, skb can
be linearized
> for various orthogonal reasons.
The reported problem is that virtio gets a packet where gso_size
is !0 but gso_type is 0.

It currently drops these on the assumption that it's some type
of a gso packet it does not know how to handle.


So you are saying if skb_is_gso we can still have gso_type set to 0,
and that's an expected configuration?

So the patch should just be:


-        if (skb_is_gso(skb)) {
+        if (skb_is_gso(skb) && sinfo->gso_type) {



?

On 13/02/2020 15:53, Michael S. Tsirkin wrote:
> On Thu, Feb 13, 2020 at 07:44:06AM -0800, Eric Dumazet wrote:
>>
>> On 2/13/20 2:00 AM, Michael S. Tsirkin wrote:
>>> On Wed, Feb 12, 2020 at 05:38:09PM +0000, Anton Ivanov wrote:
>>>>
>>>> On 11/02/2020 10:37, Michael S. Tsirkin wrote:
>>>>> 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?
>>>> The printk in virtio_net_hdr_from_skb says NULL.
>>>>
>>>> That is probably normal for a locally originated frame.
>>>>
>>>> I cannot reproduce this with network traffic by the way - it
happens only if the traffic is locally originated on the host.
>>>>
>>>> A,
>>> OK so is it code in __tcp_transmit_skb that sets gso_size to
non-null
>>> when gso_type is 0?
>>>
>> Correct way to determine if a packet is a gso one is by looking at
gso_size.
>> Then only it is legal looking at gso_type
>>
>>
>> static inline bool skb_is_gso(const struct sk_buff *skb)
>> {
>>      return skb_shinfo(skb)->gso_size;
>> }
>>
>> /* Note: Should be called only if skb_is_gso(skb) is true */
>> static inline bool skb_is_gso_v6(const struct sk_buff *skb)
>> ...
>>
>>
>> There is absolutely no relation between GSO and skb->data_len, skb
can be linearized
>> for various orthogonal reasons.
> The reported problem is that virtio gets a packet where gso_size
> is !0 but gso_type is 0.
>
> It currently drops these on the assumption that it's some type
> of a gso packet it does not know how to handle.
>
>
> So you are saying if skb_is_gso we can still have gso_type set to 0,
> and that's an expected configuration?
>
> So the patch should just be:
>
>
> -        if (skb_is_gso(skb)) {
> +        if (skb_is_gso(skb) && sinfo->gso_type) {
>
Yes, provided that skb_is_gso(skb) and sinfo->gso_type == 0 is a valid state.

I agree with Jason, there may be something wrong going on here and we need to
find the source which creates these packets.

A.
>
> ?
>
>
> _______________________________________________
> linux-um mailing list
> linux-um at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-um
-- 
Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/

On Thu, Feb 13, 2020 at 04:23:24PM +0000, Anton Ivanov
wrote:
> 
> On 13/02/2020 15:53, Michael S. Tsirkin wrote:
> > On Thu, Feb 13, 2020 at 07:44:06AM -0800, Eric Dumazet wrote:
> > > 
> > > On 2/13/20 2:00 AM, Michael S. Tsirkin wrote:
> > > > On Wed, Feb 12, 2020 at 05:38:09PM +0000, Anton Ivanov
wrote:
> > > > > 
> > > > > On 11/02/2020 10:37, Michael S. Tsirkin wrote:
> > > > > > 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?
> > > > > The printk in virtio_net_hdr_from_skb says NULL.
> > > > > 
> > > > > That is probably normal for a locally originated frame.
> > > > > 
> > > > > I cannot reproduce this with network traffic by the way
- it happens only if the traffic is locally originated on the host.
> > > > > 
> > > > > A,
> > > > OK so is it code in __tcp_transmit_skb that sets gso_size to
non-null
> > > > when gso_type is 0?
> > > > 
> > > Correct way to determine if a packet is a gso one is by looking
at gso_size.
> > > Then only it is legal looking at gso_type
> > > 
> > > 
> > > static inline bool skb_is_gso(const struct sk_buff *skb)
> > > {
> > >      return skb_shinfo(skb)->gso_size;
> > > }
> > > 
> > > /* Note: Should be called only if skb_is_gso(skb) is true */
> > > static inline bool skb_is_gso_v6(const struct sk_buff *skb)
> > > ...
> > > 
> > > 
> > > There is absolutely no relation between GSO and skb->data_len,
skb can be linearized
> > > for various orthogonal reasons.
> > The reported problem is that virtio gets a packet where gso_size
> > is !0 but gso_type is 0.
> > 
> > It currently drops these on the assumption that it's some type
> > of a gso packet it does not know how to handle.
> > 
> > 
> > So you are saying if skb_is_gso we can still have gso_type set to 0,
> > and that's an expected configuration?
> > 
> > So the patch should just be:
> > 
> > 
> > -        if (skb_is_gso(skb)) {
> > +        if (skb_is_gso(skb) && sinfo->gso_type) {
> > 
> Yes, provided that skb_is_gso(skb) and sinfo->gso_type == 0 is a valid
state.
> 
> I agree with Jason, there may be something wrong going on here and we need
to find the source which creates these packets.
> 
> A.
Well Eric will know for sure. Eric is skb_is_gso(skb) and
sinfo->gso_type == 0 a valid state?
> > 
> > ?
> > 
> > 
> > _______________________________________________
> > linux-um mailing list
> > linux-um at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-um
> 
> -- 
> Anton R. Ivanov
> Cambridgegreys Limited. Registered in England. Company Number 10273661
> https://www.cambridgegreys.com/

On Thu, Feb 13, 2020 at 04:23:24PM +0000, Anton Ivanov
wrote:
> 
> On 13/02/2020 15:53, Michael S. Tsirkin wrote:
> > On Thu, Feb 13, 2020 at 07:44:06AM -0800, Eric Dumazet wrote:
> > > 
> > > On 2/13/20 2:00 AM, Michael S. Tsirkin wrote:
> > > > On Wed, Feb 12, 2020 at 05:38:09PM +0000, Anton Ivanov
wrote:
> > > > > 
> > > > > On 11/02/2020 10:37, Michael S. Tsirkin wrote:
> > > > > > 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?
> > > > > The printk in virtio_net_hdr_from_skb says NULL.
> > > > > 
> > > > > That is probably normal for a locally originated frame.
> > > > > 
> > > > > I cannot reproduce this with network traffic by the way
- it happens only if the traffic is locally originated on the host.
> > > > > 
> > > > > A,
> > > > OK so is it code in __tcp_transmit_skb that sets gso_size to
non-null
> > > > when gso_type is 0?
> > > > 
> > > Correct way to determine if a packet is a gso one is by looking
at gso_size.
> > > Then only it is legal looking at gso_type
> > > 
> > > 
> > > static inline bool skb_is_gso(const struct sk_buff *skb)
> > > {
> > >      return skb_shinfo(skb)->gso_size;
> > > }
> > > 
> > > /* Note: Should be called only if skb_is_gso(skb) is true */
> > > static inline bool skb_is_gso_v6(const struct sk_buff *skb)
> > > ...
> > > 
> > > 
> > > There is absolutely no relation between GSO and skb->data_len,
skb can be linearized
> > > for various orthogonal reasons.
> > The reported problem is that virtio gets a packet where gso_size
> > is !0 but gso_type is 0.
> > 
> > It currently drops these on the assumption that it's some type
> > of a gso packet it does not know how to handle.
> > 
> > 
> > So you are saying if skb_is_gso we can still have gso_type set to 0,
> > and that's an expected configuration?
> > 
> > So the patch should just be:
> > 
> > 
> > -        if (skb_is_gso(skb)) {
> > +        if (skb_is_gso(skb) && sinfo->gso_type) {
> > 
> Yes, provided that skb_is_gso(skb) and sinfo->gso_type == 0 is a valid
state.
> 
> I agree with Jason, there may be something wrong going on here and we need
to find the source which creates these packets.
> 
> A.

Want to submit a patch to address this for now?
> > 
> > ?
> > 
> > 
> > _______________________________________________
> > linux-um mailing list
> > linux-um at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-um
> 
> -- 
> Anton R. Ivanov
> Cambridgegreys Limited. Registered in England. Company Number 10273661
> https://www.cambridgegreys.com/