[RFC] eal: support systemd service convention for runtime directory

[Morten Brørup]

> From: Stephen Hemminger [mailto:stephen at networkplumber.org]
> Sent: Friday, 24 December 2021 00.39
> 
> Systemd.exec supports configuring the runtime directory of a service
> via RuntimeDirectory=. This creates the directory with the necessary
> permissions which actual service may not have if running in container.
> 
> The change to DPDK is to look for the environment RUNTIME_DIRECTORY
> first and use that in preference to the fallback alternatives.
> 
> Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
> ---
>  lib/eal/linux/eal.c | 23 ++++++++++++-----------
>  1 file changed, 12 insertions(+), 11 deletions(-)
> 
> diff --git a/lib/eal/linux/eal.c b/lib/eal/linux/eal.c
> index 60b49248388e..e729c713b393 100644
> --- a/lib/eal/linux/eal.c
> +++ b/lib/eal/linux/eal.c
> @@ -86,25 +86,26 @@ struct lcore_config lcore_config[RTE_MAX_LCORE];
>  /* used by rte_rdtsc() */
>  int rte_cycles_vmware_tsc_map;
> 
> -static const char *default_runtime_dir = "/var/run";
> -
>  int
>  eal_create_runtime_dir(void)
>  {
> -	const char *directory = default_runtime_dir;
> -	const char *xdg_runtime_dir = getenv("XDG_RUNTIME_DIR");
> -	const char *fallback = "/tmp";
> +	const char *directory;
>  	char run_dir[PATH_MAX];
>  	char tmp[PATH_MAX];
>  	int ret;
> 
> -	if (getuid() != 0) {
> -		/* try XDG path first, fall back to /tmp */
> -		if (xdg_runtime_dir != NULL)
> -			directory = xdg_runtime_dir;
> -		else
> -			directory = fallback;
> +	/* from RuntimeDirectory= see systemd.exec */
> +	directory = getenv("RUNTIME_DIRECTORY");
> +	if (directory == NULL) {
> +		if (getuid() == 0)
> +			directory = "/var/run";
> +		else {
> +			directory = getenv("XDG_RUNTIME_DIR");
> +			if (directory == NULL)
> +				directory = "/tmp";
> +		}
>  	}
> +
>  	/* create DPDK subdirectory under runtime dir */
>  	ret = snprintf(tmp, sizeof(tmp), "%s/dpdk", directory);
>  	if (ret < 0 || ret == sizeof(tmp)) {
> --
> 2.30.2
> 

Reviewed-by: Morten Brørup <mb at smartsharesystems.com>

Also, while reviewing this, I stumbled across eal_set_runtime_dir() in eal_common_config.c, which I think should be fixed:

int
eal_set_runtime_dir(char *run_dir, size_t size)
{
	size_t str_size;

-	str_size = strlcpy(runtime_dir, run_dir, size);
-	if (str_size >= size) {
+	str_size = strlcpy(runtime_dir, run_dir, sizeof(runtime_dir));
+	if (str_size >= sizeof(runtime_dir)) {
		RTE_LOG(ERR, EAL, "Runtime directory string too long\n");
		return -1;
	}

	return 0;
}

And I don't understand why size is passed as a parameter to eal_set_runtime_dir().