Re: [PATCH 1/2] net: Fix announce_self

[Jason Wang]

On Fri, Jan 17, 2025 at 7:17 PM Laurent Vivier <lvivier@redhat.com> wrote:
>
> b9ad513e1876 ("net: Remove receive_raw()") adds an iovec entry
> in qemu_deliver_packet_iov() to add the virtio-net header
> in the data when QEMU_NET_PACKET_FLAG_RAW is set but forgets
> to increase the number of iovec entries in the array, so
> receive_iov() will only send the first entry (the virtio-net
> entry, full of 0) and no data. The packet will be discarded.
>
> The only user of QEMU_NET_PACKET_FLAG_RAW is announce_self.
>
> We can see the problem with tcpdump:
>
> - QEMU parameters:
>
>   .. -monitor stdio \
>      -netdev bridge,id=netdev0,br=virbr0 \
>      -device virtio-net,mac=9a:2b:2c:2d:2e:2f,netdev=netdev0 \
>
> - HMP command:
>
>   (qemu) announce_self
>
> - TCP dump:
>
>   $ sudo tcpdump -nxi virbr0
>
>   without the fix:
>
>     <nothing>
>
>   with the fix:
>
>    ARP, Reverse Request who-is 9a:2b:2c:2d:2e:2f tell 9a:2b:2c:2d:2e:2f, 
> length 46
>         0x0000:  0001 0800 0604 0003 9a2b 2c2d 2e2f 0000
>         0x0010:  0000 9a2b 2c2d 2e2f 0000 0000 0000 0000
>         0x0020:  0000 0000 0000 0000 0000 0000 0000
>
> Reported-by: Xiaohui Li <xiaohli@redhat.com>
> Bug: https://issues.redhat.com/browse/RHEL-73891
> Fixes: b9ad513e1876 ("net: Remove receive_raw()")
> Cc: akihiko.odaki@daynix.com
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> ---

Acked-by: Jason Wang <jasowang@redhat.com>

Thanks