netdev - Re: [PATCH] net: add mac_pton() for parsing MAC address

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Date:	Wed, 4 May 2011 20:39:59 +0300
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH] net: add mac_pton() for parsing MAC address

On Wed, May 04, 2011 at 08:12:25AM -0700, Stephen Hemminger wrote:
> On Wed, 4 May 2011 09:15:51 +0300
> Alexey Dobriyan <adobriyan@...il.com> wrote:
> 
> > +int mac_pton(const char *s, u8 *mac)
> > +{
> > +	int i;
> > +
> > +	/* XX:XX:XX:XX:XX:XX */
> > +	if (strlen(s) < 3 * ETH_ALEN - 1)
> > +		return 0;
> > +
> > +	/* Don't half dirty result. */
> Shouldn't this be "Don't allow dirty result."?

Maybe.
It means "only dirty result, if everything is OK." like inet_pton(3).

> > +	for (i = 0; i < ETH_ALEN; i++) {
> > +		if (!strchr("0123456789abcdefABCDEF", s[i * 3]))
> > +			return 0;
> > +		if (!strchr("0123456789abcdefABCDEF", s[i * 3 + 1]))
> > +			return 0;
> 
> 		if (!isxdigit(s[i*3]) || !isxdigit(s[i*3+1]))
> 			return 0;
> 
> > +		if (i != ETH_ALEN - 1 && s[i * 3 + 2] != ':')
> > +			return 0;
> > +	}
> > +	for (i = 0; i < ETH_ALEN; i++) {
> > +		mac[i] = (hex_to_bin(s[i * 3]) << 4) | hex_to_bin(s[i * 3 + 1]);
> 		hex2bin(&mac[i], &s[i*3], 1);
> > +	}
> > +	return 1;
> > +}
> > +EXPORT_SYMBOL(mac_pton);
> 
> Also don't need two loops, okay to parse partial result.

You need two loops if code is written as sent.
Otherwise, caller need temporary buffer to not corrupt possibly important
previous MAC value.
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