[PATCH 20.11] net/virtio-user: fix socket non-blocking mode

[Xueming(Steven) Li]

Hi Yuan,

20.11 RC1 test has started, this  patch will queue to the next LTS.

Thanks,
Xueming Li

> -----Original Message-----
> From: Yuan Wang <yuanx.wang at intel.com>
> Sent: Tuesday, August 16, 2022 1:33 AM
> To: Xueming(Steven) Li <xuemingl at nvidia.com>; stable at dpdk.org
> Cc: maxime.coquelin at redhat.com; chenbo.xia at intel.com; jiayu.hu at intel.com; cheng1.jiang at intel.com; qiming.yang at intel.com; Yuan
> Wang <yuanx.wang at intel.com>; Stephen Hemminger <stephen at networkplumber.org>
> Subject: [PATCH 20.11] net/virtio-user: fix socket non-blocking mode
> 
> [ upstream commit 41f9a1757ffc010cc3debaad9a56af8ad88d0c6d ]
> 
> The virtio-user initialization requires unix socket to receive backend messages in block mode. However, virtio_user_read_dev_config() sets
> the same socket to nonblocking via fcntl, which affects all threads.
> Enabling the rxq interrupt can causes both of these behaviors to occur concurrently, with the result that the initialization may fail because
> no messages are received in nonblocking socket.
> 
> Fix that by replacing O_NONBLOCK with the recv per-call option MSG_DONTWAIT.
> 
> Fixes: ef53b6030039 ("net/virtio-user: support LSC")
> 
> Signed-off-by: Yuan Wang <yuanx.wang at intel.com>
> Acked-by: Stephen Hemminger <stephen at networkplumber.org>
> Reviewed-by: Chenbo Xia <chenbo.xia at intel.com>
> ---
>  drivers/net/virtio/virtio_user_ethdev.c | 15 ++-------------
>  1 file changed, 2 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/net/virtio/virtio_user_ethdev.c b/drivers/net/virtio/virtio_user_ethdev.c
> index 04d6d7e2f..347caeef4 100644
> --- a/drivers/net/virtio/virtio_user_ethdev.c
> +++ b/drivers/net/virtio/virtio_user_ethdev.c
> @@ -252,15 +252,9 @@ virtio_user_read_dev_config(struct virtio_hw *hw, size_t offset,
> 
>  		if (dev->vhostfd >= 0) {
>  			int r;
> -			int flags;
> 
> -			flags = fcntl(dev->vhostfd, F_GETFL);
> -			if (fcntl(dev->vhostfd, F_SETFL,
> -					flags | O_NONBLOCK) == -1) {
> -				PMD_DRV_LOG(ERR, "error setting O_NONBLOCK flag");
> -				return;
> -			}
> -			r = recv(dev->vhostfd, buf, 128, MSG_PEEK);
> +			r = recv(dev->vhostfd, buf, 128,
> +				       MSG_PEEK | MSG_DONTWAIT);
>  			if (r == 0 || (r < 0 && errno != EAGAIN)) {
>  				dev->net_status &= (~VIRTIO_NET_S_LINK_UP);
>  				PMD_DRV_LOG(ERR, "virtio-user port %u is down", @@ -276,11 +270,6 @@
> virtio_user_read_dev_config(struct virtio_hw *hw, size_t offset,
>  			} else {
>  				dev->net_status |= VIRTIO_NET_S_LINK_UP;
>  			}
> -			if (fcntl(dev->vhostfd, F_SETFL,
> -					flags & ~O_NONBLOCK) == -1) {
> -				PMD_DRV_LOG(ERR, "error clearing O_NONBLOCK flag");
> -				return;
> -			}
>  		} else if (dev->is_server) {
>  			dev->net_status &= (~VIRTIO_NET_S_LINK_UP);
>  			if (virtio_user_server_reconnect(dev) >= 0)
> --
> 2.25.1