svn commit: r361944 - in head/sys/dev/virtio: . network

[Jessica Clarke]

On 14 Jun 2020, at 20:51, Tom Jones <thj at freebsd.org> wrote:
> On Mon, Jun 08, 2020 at 09:51:36PM +0000, Jessica Clarke wrote:
>> Author: jrtc27
>> Date: Mon Jun  8 21:51:36 2020
>> New Revision: 361944
>> URL: https://svnweb.freebsd.org/changeset/base/361944
>> 
>> Log:
>>  virtio: Support non-legacy network device and queue
>> 
>>  The non-legacy interface always defines num_buffers in the header,
>>  regardless of whether VIRTIO_NET_F_MRG_RXBUF, just leaving it unused. We
>>  also need to ensure our virtqueue doesn't filter out VIRTIO_F_VERSION_1
>>  during negotiation, as it supports non-legacy transports just fine. This
>>  fixes network packet transmission on TinyEMU.
>> 
>>  Reviewed by:	br, brooks (mentor), jhb (mentor)
>>  Approved by:	br, brooks (mentor), jhb (mentor)
>>  Differential Revision:	https://reviews.freebsd.org/D25132
>> 
>> Modified:
>>  head/sys/dev/virtio/network/if_vtnet.c
>>  head/sys/dev/virtio/network/if_vtnetvar.h
>>  head/sys/dev/virtio/virtio.c
>>  head/sys/dev/virtio/virtqueue.c
>> 
> 
> Hi Jessica,
> 
> After updating my current bhyve vm today (on a 12.1 host), networking no longer
> works. Reverting this commit seems to resolve the issue. I think vtnet is not
> passing enough data up to the ip layer.
> 
> If I capture on the tap interface for the vm I see arp requests and arp
> replies, however kern.msgbuf is full of: 
> 
> <5>arp: short packet received on vtnet0
> 
> and netstat does not see any replies to arp requests:
> 
> root at freebsd-current:~ # netstat -s -p arp
> arp:
>        11 ARP requests sent
>        0 ARP requests failed to sent
>        0 ARP replies sent
>        0 ARP requests received
>        0 ARP replies received
>        0 ARP packets received
>        24 total packets dropped due to no ARP entry
>        2 ARP entrys timed out
>        0 Duplicate IPs seen
> 
> If I set up an arp entry manually I can see ICMP echo requests and responses on
> the tap interface, but the vm does not see the responses. 
> 
> root at freebsd-current:~ # netstat -s -p ip
> ip:
>        7 total packets received
>        0 bad header checksums
>        0 with size smaller than minimum
>        7 with data size < data length
>        0 with ip length > max ip packet size
>        0 with header length < data size
>        0 with data length < header length
> 
> The line
> 
>        7 with data size < data length
> 
> makes me think that vtnet is truncating packets. 
> 
> markj pointed me at this bug in irc which might also be related:
> 
> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=247242

Hi Tom,
Sorry about that; it seems bhyve hits the "legacy and no MrgRxBuf"
case. Could you please try the patch below?

Jess

diff --git a/sys/dev/virtio/network/if_vtnet.c b/sys/dev/virtio/network/if_vtnet.c
index 7a0859cc0eb1..7e10b75f7f66 100644
--- a/sys/dev/virtio/network/if_vtnet.c
+++ b/sys/dev/virtio/network/if_vtnet.c
@@ -1819,9 +1819,10 @@ vtnet_rxq_eof(struct vtnet_rxq *rxq)
             adjsz = sizeof(struct vtnet_rx_header);
             /*
              * Account for our pad inserted between the header
-             * and the actual start of the frame.
+             * and the actual start of the frame. This includes
+             * the unused num_buffers when using a legacy device.
              */
-            len += VTNET_RX_HEADER_PAD;
+            len += adjsz - sc->vtnet_hdr_size;
         } else {
             mhdr = mtod(m, struct virtio_net_hdr_mrg_rxbuf *);
             nbufs = mhdr->num_buffers;