Re: [PATCH] child process synchronization NIC startup parameters

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed,  5 Jul 2023 17:35:14 +0800
Kaisen You <kaisenx.you@intel.com> wrote:

>  
> +/* get cmdline form PID. Read process info form /proc/$PID. */
> +static char *get_cmdline_from_pid(pid_t pid, char *buf, int len)
> +{
> +	char filename[PATH_MAX];
> +	char *name = NULL;
> +	int fd;
> +	int ret;
> +
> +	if (pid < 1 || buf == NULL || len < 0) {
> +		printf("%s: illegal param\n", __func__);
> +		return NULL;
> +	}
> +
> +	snprintf(filename, PATH_MAX, "/proc/%d/cmdline", pid);
> +	memset(buf, 0, len);
> +	fd = open(filename, O_RDONLY);
> +	if (fd < 0) {
> +		perror("open:");
> +		return NULL;
> +	}
> +	ret = read(fd, buf, len);
> +	close(fd);
> +
> +	if (ret < 0)
> +		return NULL;
> +
> +	if (buf[ret-1] == '\n')
> +		buf[--ret] = 0;
> +
> +	name = buf;
> +	while (ret) {
> +		if (((unsigned char)*name) < ' ')
> +			*name = ' ';
> +		name++;
> +		ret--;
> +	}
> +	*name = 0;
> +
> +	if (buf[0])
> +		return buf;
> +
> +	return NULL;
> +}

Bad idea, this is not portable, and easily broken by system changes and container
environments. Please use some form of explicit communication like is done
for primary / secondary process support.