netdev - Re: [PATCH] iproute2: support dotted-quad netmask notation.

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Date:	Thu, 6 Dec 2007 11:53:50 -0800
From:	Stephen Hemminger <shemminger@...ux-foundation.org>
To:	Andreas Henriksson <andreas@...al.se>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] iproute2: support dotted-quad netmask notation.

On Tue, 4 Dec 2007 14:58:18 +0100
Andreas Henriksson <andreas@...al.se> wrote:

> Suggested patch for allowing netmask to be specified in dotted quad format.
> See http://bugs.debian.org/357172
> 
> (Known problem: this will not prevent some invalid syntaxes,
> ie. "255.0.255.0" will be treated as "255.255.255.0")
> 
> Comments? Suggestions? Improvements?

Fix the bug you mentioned?

/* a valid netmask must be 2^n - 1 (n = 1..31) */
static int is_valid_netmask(const inet_prefix *addr)
{
	uint32_t host;

	if (addr->family != AF_INET)
		return 0;

	host = ~ntohl(addr->data[0]);
	if (host == 0 || ~host == 0)
		return 0;

	return (host & (host + 1)) == 0;
}
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