cidr_addr.c

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/*
 * Functions to generate various addresses based on a CIDR
 */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <errno.h>
#include <string.h>
#include "../include/cidr.h"


/* Create a network address */
CIDR *
cidr_addr_network(const CIDR *addr)
{
        int i, j;
        CIDR *toret;

        /* Quick check */
        if(addr==NULL)
        {
                errno = EFAULT;
                return(NULL);
        }
        
        toret = cidr_alloc();
        if(toret==NULL)
                return(NULL); /* Preserve errno */
        toret->proto = addr->proto;
        
        /* The netmask is the same */
        memcpy(toret->mask, addr->mask, (16 * sizeof(toret->mask[0])) );

        /* Now just figure out the network address and spit it out */
        for(i=0 ; i<=15 ; i++)
        {
                for(j=7 ; j>=0 ; j--)
                {
                        /* If we're into host bits, hop out */
                        if( (addr->mask[i] & 1<<j) == 0)
                                return(toret);

                        /* Else, copy this network bit */
                        toret->addr[i] |= (addr->addr[i] & 1<<j);
                }
        }

        /*
         * We only get here on host (/32 or /128) addresses; shorter masks
         * return earlier.  But it's as correct as can be to just say the
         * same here, so...
         */
        return(toret);
}


/* And a broadcast */
CIDR *
cidr_addr_broadcast(const CIDR *addr)
{
        int i, j;
        CIDR *toret;

        /* Quick check */
        if(addr==NULL)
        {
                errno = EFAULT;
                return(NULL);
        }
        
        toret = cidr_alloc();
        if(toret==NULL)
                return(NULL); /* Preserve errno */
        toret->proto = addr->proto;
        
        /* The netmask is the same */
        memcpy(toret->mask, addr->mask, (16 * sizeof(toret->mask[0])) );

        /* Copy all the network bits */
        for(i=0 ; i<=15 ; i++)
        {
                for(j=7 ; j>=0 ; j--)
                {
                        /* If we're into host bits, hop out */
                        if( (addr->mask[i] & 1<<j) == 0)
                                goto post;

                        /* Else, copy this network bit */
                        toret->addr[i] |= (addr->addr[i] & 1<<j);

                }
        }

post:
        /* Now set the remaining bits to 1 */
        for( /* i */ ; i<=15 ; i++)
        {
                for( /* j */ ; j>=0 ; j--)
                        toret->addr[i] |= (1<<j);

                j=7;
        }

        /* And send it back */
        return(toret);
}


/* Get the first host in a CIDR block */
CIDR *
cidr_addr_hostmin(const CIDR *addr)
{
        CIDR *toret;

        toret = cidr_addr_network(addr);
        if(toret==NULL)
                return(NULL); /* Preserve errno */
        
        toret->addr[15] |= 1;

        return(toret);
}


/* Get the last host in a CIDR block */
CIDR *
cidr_addr_hostmax(const CIDR *addr)
{
        CIDR *toret;

        toret = cidr_addr_broadcast(addr);
        if(toret==NULL)
                return(NULL); /* Preserve errno */
        
        toret->addr[15] &= 0xfe;

        return(toret);
}