[PATCH] virtio-net: purge queued rx packets on queue deletion

[PATCH] virtio-net: purge queued rx packets on queue deletion

[Yuri Benditovich]

https://bugzilla.redhat.com/show_bug.cgi?id=1829272
When deleting queue pair, purge pending RX packets if any.
Example of problematic flow:
1. Bring up q35 VM with tap (vhost off) and virtio-net or e1000e
2. Run ping flood to the VM NIC ( 1 ms interval)
3. Hot unplug the NIC device (device_del)
   During unplug process one or more packets come, the NIC
   can't receive, tap disables read_poll
4. Hot plug the device (device_add) with the same netdev
The tap stays with read_poll disabled and does not receive
any packets anymore (tap_send never triggered)

Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com>
---
 net/net.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/net/net.c b/net/net.c
index 7a2a0fb5ac..a95b417300 100644
--- a/net/net.c
+++ b/net/net.c
@@ -411,10 +411,14 @@ void qemu_del_nic(NICState *nic)
 
     qemu_macaddr_set_free(&nic->conf->macaddr);
 
-    /* If this is a peer NIC and peer has already been deleted, free it now. */
-    if (nic->peer_deleted) {
-        for (i = 0; i < queues; i++) {
-            qemu_free_net_client(qemu_get_subqueue(nic, i)->peer);
+    for (i = 0; i < queues; i++) {
+        NetClientState *nc = qemu_get_subqueue(nic, i);
+        /* If this is a peer NIC and peer has already been deleted, free it now. */
+        if (nic->peer_deleted) {
+            qemu_free_net_client(nc->peer);
+        } else if (nc->peer) {
+            /* if there are RX packets pending, complete them */
+            qemu_purge_queued_packets(nc->peer);
         }
     }
 
-- 
2.17.1

Re: [PATCH] virtio-net: purge queued rx packets on queue deletion

[Jason Wang]

On 2020/11/12 下午5:46, Yuri Benditovich wrote:
> https://bugzilla.redhat.com/show_bug.cgi?id=1829272
> When deleting queue pair, purge pending RX packets if any.
> Example of problematic flow:
> 1. Bring up q35 VM with tap (vhost off) and virtio-net or e1000e
> 2. Run ping flood to the VM NIC ( 1 ms interval)
> 3. Hot unplug the NIC device (device_del)
>     During unplug process one or more packets come, the NIC
>     can't receive, tap disables read_poll
> 4. Hot plug the device (device_add) with the same netdev
> The tap stays with read_poll disabled and does not receive
> any packets anymore (tap_send never triggered)
>
> Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com>


Applied.

Thanks


> ---
>   net/net.c | 12 ++++++++----
>   1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/net/net.c b/net/net.c
> index 7a2a0fb5ac..a95b417300 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -411,10 +411,14 @@ void qemu_del_nic(NICState *nic)
>   
>       qemu_macaddr_set_free(&nic->conf->macaddr);
>   
> -    /* If this is a peer NIC and peer has already been deleted, free it now. */
> -    if (nic->peer_deleted) {
> -        for (i = 0; i < queues; i++) {
> -            qemu_free_net_client(qemu_get_subqueue(nic, i)->peer);
> +    for (i = 0; i < queues; i++) {
> +        NetClientState *nc = qemu_get_subqueue(nic, i);
> +        /* If this is a peer NIC and peer has already been deleted, free it now. */
> +        if (nic->peer_deleted) {
> +            qemu_free_net_client(nc->peer);
> +        } else if (nc->peer) {
> +            /* if there are RX packets pending, complete them */
> +            qemu_purge_queued_packets(nc->peer);
>           }
>       }
>   

Re: [PATCH] virtio-net: purge queued rx packets on queue deletion

[Yuri Benditovich]

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Hi Jason,
Sorry, there is a mistake in the title: should be 'net' instead of
'virtio-net'.
Can you please fix it?

Thanks,
Yuri Benditovich


On Wed, Nov 18, 2020 at 5:59 AM Jason Wang <jasowang@redhat.com> wrote:

>
> On 2020/11/12 下午5:46, Yuri Benditovich wrote:
> > https://bugzilla.redhat.com/show_bug.cgi?id=1829272
> > When deleting queue pair, purge pending RX packets if any.
> > Example of problematic flow:
> > 1. Bring up q35 VM with tap (vhost off) and virtio-net or e1000e
> > 2. Run ping flood to the VM NIC ( 1 ms interval)
> > 3. Hot unplug the NIC device (device_del)
> >     During unplug process one or more packets come, the NIC
> >     can't receive, tap disables read_poll
> > 4. Hot plug the device (device_add) with the same netdev
> > The tap stays with read_poll disabled and does not receive
> > any packets anymore (tap_send never triggered)
> >
> > Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com>
>
>
> Applied.
>
> Thanks
>
>
> > ---
> >   net/net.c | 12 ++++++++----
> >   1 file changed, 8 insertions(+), 4 deletions(-)
> >
> > diff --git a/net/net.c b/net/net.c
> > index 7a2a0fb5ac..a95b417300 100644
> > --- a/net/net.c
> > +++ b/net/net.c
> > @@ -411,10 +411,14 @@ void qemu_del_nic(NICState *nic)
> >
> >       qemu_macaddr_set_free(&nic->conf->macaddr);
> >
> > -    /* If this is a peer NIC and peer has already been deleted, free it
> now. */
> > -    if (nic->peer_deleted) {
> > -        for (i = 0; i < queues; i++) {
> > -            qemu_free_net_client(qemu_get_subqueue(nic, i)->peer);
> > +    for (i = 0; i < queues; i++) {
> > +        NetClientState *nc = qemu_get_subqueue(nic, i);
> > +        /* If this is a peer NIC and peer has already been deleted,
> free it now. */
> > +        if (nic->peer_deleted) {
> > +            qemu_free_net_client(nc->peer);
> > +        } else if (nc->peer) {
> > +            /* if there are RX packets pending, complete them */
> > +            qemu_purge_queued_packets(nc->peer);
> >           }
> >       }
> >
>
>

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