netdev - Re: [PATCH iproute2/net-next]tc: B.W limits can now be specified in %

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Date:   Tue, 31 Oct 2017 17:35:52 +0100
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Nishanth Devarajan <ndev2021@...il.com>
Cc:     netdev@...r.kernel.org, doucette@...edu, michel.machado@...il.com
Subject: Re: [PATCH iproute2/net-next]tc: B.W limits can now be specified in
 %

On Sat, 28 Oct 2017 22:57:00 +0530
Nishanth Devarajan <ndev2021@...il.com> wrote:

>  
> +int read_prop(char *dev, char *prop, long *value)
> +{
> +	char fname[41], buf[80], *endp;
> +	ssize_t len;
> +	int fd;
> +	long result;
> +
> +	sprintf(fname, "/sys/class/net/%s/%s", dev, prop);
> +	fd = open(fname, O_RDONLY);
> +	if (fd < 0) {
> +		if (strcmp(prop, "tun_flags"))
> +			fprintf(stderr, "open %s: %s\n", fname,
> +				strerror(errno));
> +		return -1;
> +	}
> +	len = read(fd, buf, sizeof(buf)-1);
> +	close(fd);
> +	if (len < 0) {
> +		fprintf(stderr, "read %s: %s", fname, strerror(errno));
> +		return -1;
> +	}
> +
> +	buf[len] = 0;
> +	result = strtol(buf, &endp, 0);
> +	if (*endp != '\n') {
> +		fprintf(stderr, "Failed to parse %s\n", fname);
> +		return -1;
> +	}
> +	*value = result;
> +	return 0;
> +}

I know you copy and pasted this code, but it was already a mess.
 1. It should use stdio (fopen/fgets)
 2. It should not be looking for signed values (ie use strtoul)
 3. It should not be special casing "tun_flags"
 4. It needs to check for all possible parsing errors, with strtoul.
    (hint read strtoul man page for how errors are reported).