cidr_net.c

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

#include <errno.h>
#include <stdlib.h>
#include <string.h>

#include "cidr.h"
#include "abstract_mem.h"


/* Get the CIDR's immediate supernet */
CIDR *
cidr_net_supernet(const CIDR *addr)
{
        int i, j;
        int pflen;
        CIDR *toret;

        /* Quick check */
        if(addr==NULL)
        {
                errno = EFAULT;
                return(NULL);
        }
        
        /* If it's already a /0 in its protocol, return nothing */
        pflen = cidr_get_pflen(addr);
        if(pflen==0)
        {
                errno = 0;
                return(NULL);
        }
        
        toret = cidr_dup(addr);
        if(toret==NULL)
                return(NULL); /* Preserve errno */
        
        /* Chop a bit off the netmask */
        /* This gets the last network bit */
        if(toret->proto==CIDR_IPV4)
                pflen += 96;
        pflen--;
        i = pflen / 8;
        j = 7 - (pflen % 8);

        /* Make that bit a host bit */
        (toret->mask)[i] &= ~(1<<j);

        /*
         * Now zero out the host bits in the addr.  Do this manually instead
         * of calling cidr_addr_network() to save some extra copies and
         * allocationss and so forth.
         */
        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 CIDR's two children */
CIDR **
cidr_net_subnets(const CIDR *addr)
{
        int i, j;
        int pflen;
        CIDR **toret;

        if(addr==NULL)
        {
                errno = EFAULT;
                return(NULL);
        }
        
        /* You can't split a host address! */
        pflen = cidr_get_pflen(addr);
        if(  (addr->proto==CIDR_IPV4 && pflen==32)
          || (addr->proto==CIDR_IPV6 && pflen==128))
        {
                errno = 0;
                return(NULL);
        }

        toret = gsh_calloc(2, sizeof(CIDR *));
        if(toret==NULL)
        {
                errno = ENOMEM;
                return(NULL);
        }
        
        /* Get a blank-ish slate for the first kid */
        toret[0] = cidr_addr_network(addr);
        if(toret[0]==NULL)
        {
                gsh_free(toret);
                return(NULL); /* Preserve errno */
        }

        /* Find its first host bit */
        if(toret[0]->proto==CIDR_IPV4)
                pflen += 96;
        i = pflen / 8;
        j = 7 - (pflen % 8);

        /* Make it a network bit */
        (toret[0])->mask[i] |= 1<<j;

        /* Now dup the second kid off that */
        toret[1] = cidr_dup(toret[0]);
        if(toret[1]==NULL)
        {
                cidr_free(toret[0]);
                gsh_free(toret);
                return(NULL); /* Preserve errno */
        }

        /* And set that first host bit */
        (toret[1])->addr[i] |= 1<<j;


        /* Return the pair */
        return(toret);
}