Re: [dpdk-dev] [PATCH v8 2/4] telemetry: fix socket path conflicts for in-memory mode

[Kevin Traynor <ktraynor@redhat.com>]

On 12/10/2021 17:39, Bruce Richardson wrote:
> When running using in-memory mode, multiple processes can use the same
> runtime dir, leading to conflicts with the telemetry sockets in that
> directory. We can resolve this by appending a suffix to each socket
> beyond the first, with the suffix being an increasing counter value.
> Each process uses the first unused socket counter value.
> 
> Fixes: 6dd571fd07c3 ("telemetry: introduce new functionality")
> 
> Reported-by: David Marchand <david.marchand@redhat.com>
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> Acked-by: Ciara Power <ciara.power@intel.com>

Thanks Bruce, lgtm. Nice solution to keep existing name where possible 
and to give as predictable as you can names for others.

Acked-by: Kevin Traynor <ktraynor@redhat.com>

> ---
>   lib/telemetry/telemetry.c | 65 +++++++++++++++++++++++++++++----------
>   1 file changed, 49 insertions(+), 16 deletions(-)
> 
> diff --git a/lib/telemetry/telemetry.c b/lib/telemetry/telemetry.c
> index 48f4c7ba46..a7483167d4 100644
> --- a/lib/telemetry/telemetry.c
> +++ b/lib/telemetry/telemetry.c
> @@ -457,28 +457,45 @@ create_socket(char *path)
>   
>   	struct sockaddr_un sun = {.sun_family = AF_UNIX};
>   	strlcpy(sun.sun_path, path, sizeof(sun.sun_path));
> -	unlink(sun.sun_path);
> +	TMTY_LOG(DEBUG, "Attempting socket bind to path '%s'\n", path);
> +
>   	if (bind(sock, (void *) &sun, sizeof(sun)) < 0) {
>   		struct stat st;
>   
> -		TMTY_LOG(ERR, "Error binding socket: %s\n", strerror(errno));
> -		if (stat(socket_dir, &st) < 0 || !S_ISDIR(st.st_mode))
> +		TMTY_LOG(DEBUG, "Initial bind to socket '%s' failed.\n", path);
> +
> +		/* first check if we have a runtime dir */
> +		if (stat(socket_dir, &st) < 0 || !S_ISDIR(st.st_mode)) {
>   			TMTY_LOG(ERR, "Cannot access DPDK runtime directory: %s\n", socket_dir);
> -		sun.sun_path[0] = 0;
> -		goto error;
> +			close(sock);
> +			return -ENOENT;
> +		}
> +
> +		/* check if current socket is active */
> +		if (connect(sock, (void *)&sun, sizeof(sun)) == 0) {
> +			close(sock);
> +			return -EADDRINUSE;
> +		}
> +
> +		/* socket is not active, delete and attempt rebind */
> +		TMTY_LOG(DEBUG, "Attempting unlink and retrying bind\n");
> +		unlink(sun.sun_path);
> +		if (bind(sock, (void *) &sun, sizeof(sun)) < 0) {
> +			TMTY_LOG(ERR, "Error binding socket: %s\n", strerror(errno));
> +			close(sock);
> +			return -errno; /* if unlink failed, this will be -EADDRINUSE as above */
> +		}
>   	}
>   
>   	if (listen(sock, 1) < 0) {
>   		TMTY_LOG(ERR, "Error calling listen for socket: %s\n", strerror(errno));
> -		goto error;
> +		unlink(sun.sun_path);
> +		close(sock);
> +		return -errno;
>   	}
> +	TMTY_LOG(DEBUG, "Socket creation and binding ok\n");
>   
>   	return sock;
> -
> -error:
> -	close(sock);
> -	unlink_sockets();
> -	return -1;
>   }
>   
>   static void
> @@ -511,8 +528,10 @@ telemetry_legacy_init(void)
>   		return -1;
>   	}
>   	v1_socket.sock = create_socket(v1_socket.path);
> -	if (v1_socket.sock < 0)
> +	if (v1_socket.sock < 0) {
> +		v1_socket.path[0] = '\0';
>   		return -1;
> +	}
>   	rc = pthread_create(&t_old, NULL, socket_listener, &v1_socket);
>   	if (rc != 0) {
>   		TMTY_LOG(ERR, "Error with create legcay socket thread: %s\n",
> @@ -533,7 +552,9 @@ telemetry_legacy_init(void)
>   static int
>   telemetry_v2_init(void)
>   {
> +	char spath[sizeof(v2_socket.path)];
>   	pthread_t t_new;
> +	short suffix = 0;
>   	int rc;
>   
>   	v2_socket.num_clients = &v2_clients;
> @@ -544,15 +565,27 @@ telemetry_v2_init(void)
>   	rte_telemetry_register_cmd("/help", command_help,
>   			"Returns help text for a command. Parameters: string command");
>   	v2_socket.fn = client_handler;
> -	if (strlcpy(v2_socket.path, get_socket_path(socket_dir, 2),
> -			sizeof(v2_socket.path)) >= sizeof(v2_socket.path)) {
> +	if (strlcpy(spath, get_socket_path(socket_dir, 2), sizeof(spath)) >= sizeof(spath)) {
>   		TMTY_LOG(ERR, "Error with socket binding, path too long\n");
>   		return -1;
>   	}
> +	memcpy(v2_socket.path, spath, sizeof(v2_socket.path));
>   
>   	v2_socket.sock = create_socket(v2_socket.path);
> -	if (v2_socket.sock < 0)
> -		return -1;
> +	while (v2_socket.sock < 0) {
> +		/* bail out on unexpected error, or suffix wrap-around */
> +		if (v2_socket.sock != -EADDRINUSE || suffix < 0) {
> +			v2_socket.path[0] = '\0'; /* clear socket path */
> +			return -1;
> +		}
> +		/* add a suffix to the path if the basic version fails */
> +		if (snprintf(v2_socket.path, sizeof(v2_socket.path), "%s:%d",
> +				spath, ++suffix) >= (int)sizeof(v2_socket.path)) {
> +			TMTY_LOG(ERR, "Error with socket binding, path too long\n");
> +			return -1;
> +		}
> +		v2_socket.sock = create_socket(v2_socket.path);
> +	}
>   	rc = pthread_create(&t_new, NULL, socket_listener, &v2_socket);
>   	if (rc != 0) {
>   		TMTY_LOG(ERR, "Error with create socket thread: %s\n",
>