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inet.c revision 1.1 
      1 /*
      2  * The mrouted program is covered by the license in the accompanying file
      3  * named "LICENSE".  Use of the mrouted program represents acceptance of
      4  * the terms and conditions listed in that file.
      5  *
      6  * The mrouted program is COPYRIGHT 1989 by The Board of Trustees of
      7  * Leland Stanford Junior University.
      8  *
      9  *
     10  * from: Id: inet.c,v 1.4 1993/05/30 01:36:38 deering Exp
     11  *      $Id: inet.c,v 1.1 1994/01/11 20:15:55 brezak Exp $
     12  */
     13 
     14 #ifndef lint
     15 static char rcsid[] = "$Id: inet.c,v 1.1 1994/01/11 20:15:55 brezak Exp $";
     16 #endif
     17 
     18 #include "defs.h"
     19 
     20 
     21 /*
     22  * Exported variables.
     23  */
     24 char s1[16];		/* buffers to hold the string representations  */
     25 char s2[16];		/* of IP addresses, to be passed to inet_fmt() */
     26 char s3[16];		/* or inet_fmts().                             */
     27 
     28 
     29 /*
     30  * Verify that a given IP address is credible as a host address.
     31  * (Without a mask, cannot detect addresses of the form {subnet,0} or
     32  * {subnet,-1}.)
     33  */
     34 int inet_valid_host(naddr)
     35     u_long naddr;
     36 {
     37     register u_long addr;
     38 
     39     addr = ntohl(naddr);
     40 
     41     return (!(IN_MULTICAST(addr) ||
     42 	      IN_BADCLASS (addr) ||
     43 	      (addr & 0xff000000) == 0));
     44 }
     45 
     46 
     47 /*
     48  * Verify that a given subnet number and mask pair are credible.
     49  */
     50 int inet_valid_subnet(nsubnet, nmask)
     51     u_long nsubnet, nmask;
     52 {
     53     register u_long subnet, mask;
     54 
     55     subnet = ntohl(nsubnet);
     56     mask   = ntohl(nmask);
     57 
     58     if ((subnet & mask) != subnet) return (FALSE);
     59 
     60     if (IN_CLASSA(subnet)) {
     61 	if (mask < 0xff000000 ||
     62 	   (subnet & 0xff000000) == 0 ||
     63 	   (subnet & 0xff000000) == 0x7f000000) return (FALSE);
     64     }
     65     else if (IN_CLASSB(subnet)) {
     66 	if (mask < 0xffff0000) return (FALSE);
     67     }
     68     else if (IN_CLASSC(subnet)) {
     69 	if (mask < 0xffffff00) return (FALSE);
     70     }
     71     else return (FALSE);
     72 
     73     return (TRUE);
     74 }
     75 
     76 
     77 /*
     78  * Convert an IP address in u_long (network) format into a printable string.
     79  */
     80 char *inet_fmt(addr, s)
     81     u_long addr;
     82     char *s;
     83 {
     84     register u_char *a;
     85 
     86     a = (u_char *)&addr;
     87     sprintf(s, "%u.%u.%u.%u", a[0], a[1], a[2], a[3]);
     88     return (s);
     89 }
     90 
     91 
     92 /*
     93  * Convert an IP subnet number in u_long (network) format into a printable
     94  * string.
     95  */
     96 char *inet_fmts(addr, mask, s)
     97     u_long addr, mask;
     98     char *s;
     99 {
    100     register u_char *a, *m;
    101 
    102     a = (u_char *)&addr;
    103     m = (u_char *)&mask;
    104 
    105     if      (m[3] != 0) sprintf(s, "%u.%u.%u.%u", a[0], a[1], a[2], a[3]);
    106     else if (m[2] != 0) sprintf(s, "%u.%u.%u",    a[0], a[1], a[2]);
    107     else if (m[1] != 0) sprintf(s, "%u.%u",       a[0], a[1]);
    108     else                sprintf(s, "%u",          a[0]);
    109 
    110     return (s);
    111 }
    112 
    113 
    114 /*
    115  * Convert the printable string representation of an IP address into the
    116  * u_long (network) format.  Return 0xffffffff on error.  (To detect the
    117  * legal address with that value, you must explicitly compare the string
    118  * with "255.255.255.255".)
    119  */
    120 u_long inet_parse(s)
    121     char *s;
    122 {
    123     u_long a;
    124     u_int a0, a1, a2, a3;
    125     char c;
    126 
    127     if (sscanf(s, "%u.%u.%u.%u%c", &a0, &a1, &a2, &a3, &c) != 4 ||
    128 	a0 > 255 || a1 > 255 || a2 > 255 || a3 > 255)
    129 	return (0xffffffff);
    130 
    131     ((u_char *)&a)[0] = a0;
    132     ((u_char *)&a)[1] = a1;
    133     ((u_char *)&a)[2] = a2;
    134     ((u_char *)&a)[3] = a3;
    135 
    136     return (a);
    137 }
    138 
    139 
    140 /*
    141  * inet_cksum extracted from:
    142  *			P I N G . C
    143  *
    144  * Author -
    145  *	Mike Muuss
    146  *	U. S. Army Ballistic Research Laboratory
    147  *	December, 1983
    148  * Modified at Uc Berkeley
    149  *
    150  * (ping.c) Status -
    151  *	Public Domain.  Distribution Unlimited.
    152  *
    153  *			I N _ C K S U M
    154  *
    155  * Checksum routine for Internet Protocol family headers (C Version)
    156  *
    157  */
    158 int inet_cksum(addr, len)
    159 	u_short *addr;
    160 	u_int len;
    161 {
    162 	register int nleft = (int)len;
    163 	register u_short *w = addr;
    164 	u_short answer = 0;
    165 	register int sum = 0;
    166 
    167 	/*
    168 	 *  Our algorithm is simple, using a 32 bit accumulator (sum),
    169 	 *  we add sequential 16 bit words to it, and at the end, fold
    170 	 *  back all the carry bits from the top 16 bits into the lower
    171 	 *  16 bits.
    172 	 */
    173 	while( nleft > 1 )  {
    174 		sum += *w++;
    175 		nleft -= 2;
    176 	}
    177 
    178 	/* mop up an odd byte, if necessary */
    179 	if( nleft == 1 ) {
    180 		*(u_char *) (&answer) = *(u_char *)w ;
    181 		sum += answer;
    182 	}
    183 
    184 	/*
    185 	 * add back carry outs from top 16 bits to low 16 bits
    186 	 */
    187 	sum = (sum >> 16) + (sum & 0xffff);	/* add hi 16 to low 16 */
    188 	sum += (sum >> 16);			/* add carry */
    189 	answer = ~sum;				/* truncate to 16 bits */
    190 	return (answer);
    191 }
    192