Re: [PATCH] Unlink existing unused sockets at start up

[Ilya Maximets <i.maximets@samsung.com>]

On 17.12.2015 07:21, Zhihong Wang wrote:
> This patch unlinks existing unused sockets (which cause new bindings to fail, e.g. vHost PMD) to ensure smooth startup.
> In a lot of cases DPDK applications are terminated abnormally without proper resource release.

Original OVS related problem discussed previously here
( http://dpdk.org/ml/archives/dev/2015-December/030326.html )
fixed in OVS by

commit 9b5422a98f817b9f2a1f8224cab7e1a8d0bbba1f
Author: Ilya Maximets <i.maximets@samsung.com>
Date:   Wed Dec 16 15:32:21 2015 +0300

    ovs-lib: Try to call exit before killing.
    
    While killing OVS may not free all allocated resources.
    
    Example:
        Socket for vhost-user port will stay in a system
        after 'systemctl stop openvswitch' and opening
        that port after restart will fail.


So, the crash of application is the last point of discussion.

> Therefore, DPDK libs should be able to deal with unclean boot environment.

Why are you think that recovery after crash of application
is a problem of underneath library?

Best regards, Ilya Maximets.

> 
> Signed-off-by: Zhihong Wang <zhihong.wang@intel.com>
> ---
>  lib/librte_vhost/vhost_user/vhost-net-user.c | 28 ++++++++++++++++++++++++----
>  1 file changed, 24 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/librte_vhost/vhost_user/vhost-net-user.c b/lib/librte_vhost/vhost_user/vhost-net-user.c
> index 8b7a448..eac0721 100644
> --- a/lib/librte_vhost/vhost_user/vhost-net-user.c
> +++ b/lib/librte_vhost/vhost_user/vhost-net-user.c
> @@ -120,18 +120,38 @@ uds_socket(const char *path)
>  	sockfd = socket(AF_UNIX, SOCK_STREAM, 0);
>  	if (sockfd < 0)
>  		return -1;
> -	RTE_LOG(INFO, VHOST_CONFIG, "socket created, fd:%d\n", sockfd);
> +	RTE_LOG(INFO, VHOST_CONFIG, "socket created, fd: %d\n", sockfd);
>  
>  	memset(&un, 0, sizeof(un));
>  	un.sun_family = AF_UNIX;
>  	snprintf(un.sun_path, sizeof(un.sun_path), "%s", path);
>  	ret = bind(sockfd, (struct sockaddr *)&un, sizeof(un));
>  	if (ret == -1) {
> -		RTE_LOG(ERR, VHOST_CONFIG, "fail to bind fd:%d, remove file:%s and try again.\n",
> +		RTE_LOG(ERR, VHOST_CONFIG,
> +			"bind fd: %d to file: %s failed, checking socket...\n",
>  			sockfd, path);
> -		goto err;
> +		ret = connect(sockfd, (struct sockaddr *)&un, sizeof(un));
> +		if (ret == -1) {
> +			RTE_LOG(INFO, VHOST_CONFIG,
> +				"socket: %s is inactive, rebinding after unlink...\n", path);
> +			unlink(path);
> +			ret = bind(sockfd, (struct sockaddr *)&un, sizeof(un));
> +			if (ret == -1) {
> +				RTE_LOG(ERR, VHOST_CONFIG,
> +					"bind fd: %d to file: %s failed even after unlink\n",
> +					sockfd, path);
> +				goto err;
> +			}
> +		} else {
> +			RTE_LOG(INFO, VHOST_CONFIG,
> +				"socket: %s is alive, remove it and try again\n", path);
> +			RTE_LOG(ERR, VHOST_CONFIG,
> +				"bind fd: %d to file: %s failed\n", sockfd, path);
> +			goto err;
> +		}
>  	}
> -	RTE_LOG(INFO, VHOST_CONFIG, "bind to %s\n", path);
> +	RTE_LOG(INFO, VHOST_CONFIG,
> +		"bind fd: %d to file: %s successful\n", sockfd, path);
>  
>  	ret = listen(sockfd, MAX_VIRTIO_BACKLOG);
>  	if (ret == -1)
>