netmask.c,v

来自「TCP-IP红宝书源代码」· C,V 代码 · 共 55 行

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date	97.09.21.19.27.59;	author dls;	state Dist;
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@/* netmask.c - netmask */

#include <conf.h>
#include <kernel.h>
#include <network.h>

/*------------------------------------------------------------------------
 *  netmask  -  set the default mask for the given net
 *------------------------------------------------------------------------
 */
IPaddr netmask(net)
IPaddr	net;
{
	IPaddr	netpart;
	int	i;

	if (net == 0)
		return net;
	/* check for net match (for subnets) */

	netpart = netnum(net);
	for (i=0; i<Net.nif; ++i)
		if (nif[i].ni_svalid && nif[i].ni_ivalid &&
		    nif[i].ni_net == netpart)
			return nif[i].ni_mask;
	if (IP_CLASSA(net)) return hl2net(0xff000000);
	if (IP_CLASSB(net)) return hl2net(0xffff0000);
	if (IP_CLASSC(net)) return hl2net(0xffffff00);
	return ~0;
}
@