usr.sbin/mrouted/inet.c

   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  * inet.c,v 3.8.4.2 1998/01/06 01:57:44 fenner Exp
  11  *
  12  * $FreeBSD: src/usr.sbin/mrouted/inet.c,v 1.11 1999/08/28 01:17:04 peter Exp $
  13  * $DragonFly: src/usr.sbin/mrouted/inet.c,v 1.3 2004/03/15 18:10:28 dillon Exp $
  14  */
  15
  16 #include "defs.h"
  17
  18 /*
  19  * Exported variables.
  20  */
  21 char s1[19];            /* buffers to hold the string representations  */
  22 char s2[19];            /* of IP addresses, to be passed to inet_fmt() */
  23 char s3[19];            /* or inet_fmts().                             */
  24 char s4[19];
  25
  26
  27 /*
  28  * Verify that a given IP address is credible as a host address.
  29  * (Without a mask, cannot detect addresses of the form {subnet,0} or
  30  * {subnet,-1}.)
  31  */
  32 int
  33 inet_valid_host(u_int32 naddr)
  34 {
  35     u_int32 addr;
  36
  37     addr = ntohl(naddr);
  38
  39     return (!(IN_MULTICAST(addr) ||
  40               IN_BADCLASS (addr) ||
  41               (addr & 0xff000000) == 0));
  42 }
  43
  44 /*
  45  * Verify that a given netmask is plausible;
  46  * make sure that it is a series of 1's followed by
  47  * a series of 0's with no discontiguous 1's.
  48  */
  49 int
  50 inet_valid_mask(u_int32 mask)
  51 {
  52     if (~(((mask & -mask) - 1) | mask) != 0) {
  53         /* Mask is not contiguous */
  54         return (FALSE);
  55     }
  56
  57     return (TRUE);
  58 }
  59
  60 /*
  61  * Verify that a given subnet number and mask pair are credible.
  62  *
  63  * With CIDR, almost any subnet and mask are credible.  mrouted still
  64  * can't handle aggregated class A's, so we still check that, but
  65  * otherwise the only requirements are that the subnet address is
  66  * within the [ABC] range and that the host bits of the subnet
  67  * are all 0.
  68  */
  69 int
  70 inet_valid_subnet(u_int32 nsubnet, u_int32 nmask)
  71 {
  72     u_int32 subnet, mask;
  73
  74     subnet = ntohl(nsubnet);
  75     mask   = ntohl(nmask);
  76
  77     if ((subnet & mask) != subnet) return (FALSE);
  78
  79     if (subnet == 0)
  80         return (mask == 0);
  81
  82     if (IN_CLASSA(subnet)) {
  83         if (mask < 0xff000000 ||
  84             (subnet & 0xff000000) == 0x7f000000 ||
  85             (subnet & 0xff000000) == 0x00000000) return (FALSE);
  86     }
  87     else if (IN_CLASSD(subnet) || IN_BADCLASS(subnet)) {
  88         /* Above Class C address space */
  89         return (FALSE);
  90     }
  91     if (subnet & ~mask) {
  92         /* Host bits are set in the subnet */
  93         return (FALSE);
  94     }
  95     if (!inet_valid_mask(mask)) {
  96         /* Netmask is not contiguous */
  97         return (FALSE);
  98     }
  99
 100     return (TRUE);
 101 }
 102
 103
 104 /*
 105  * Convert an IP address in u_long (network) format into a printable string.
 106  */
 107 char *
 108 inet_fmt(u_int32 addr, char *s)
 109 {
 110     u_char *a;
 111
 112     a = (u_char *)&addr;
 113     sprintf(s, "%u.%u.%u.%u", a[0], a[1], a[2], a[3]);
 114     return (s);
 115 }
 116
 117
 118 /*
 119  * Convert an IP subnet number in u_long (network) format into a printable
 120  * string including the netmask as a number of bits.
 121  */
 122 char *
 123 inet_fmts(u_int32 addr, u_int32 mask, char *s)
 124 {
 125     u_char *a, *m;
 126     int bits;
 127
 128     if ((addr == 0) && (mask == 0)) {
 129         sprintf(s, "default");
 130         return (s);
 131     }
 132     a = (u_char *)&addr;
 133     m = (u_char *)&mask;
 134     bits = 33 - ffs(ntohl(mask));
 135
 136     if      (m[3] != 0) sprintf(s, "%u.%u.%u.%u/%d", a[0], a[1], a[2], a[3],
 137                                                 bits);
 138     else if (m[2] != 0) sprintf(s, "%u.%u.%u/%d",    a[0], a[1], a[2], bits);
 139     else if (m[1] != 0) sprintf(s, "%u.%u/%d",       a[0], a[1], bits);
 140     else                sprintf(s, "%u/%d",          a[0], bits);
 141
 142     return (s);
 143 }
 144
 145 /*
 146  * Convert the printable string representation of an IP address into the
 147  * u_long (network) format.  Return 0xffffffff on error.  (To detect the
 148  * legal address with that value, you must explicitly compare the string
 149  * with "255.255.255.255".)
 150  */
 151 u_int32
 152 inet_parse(char *s, int n)
 153 {
 154     u_int32 a = 0;
 155     u_int a0 = 0, a1 = 0, a2 = 0, a3 = 0;
 156     int i;
 157     char c;
 158
 159     i = sscanf(s, "%u.%u.%u.%u%c", &a0, &a1, &a2, &a3, &c);
 160     if (i < n || i > 4 || a0 > 255 || a1 > 255 || a2 > 255 || a3 > 255)
 161         return (0xffffffff);
 162
 163     ((u_char *)&a)[0] = a0;
 164     ((u_char *)&a)[1] = a1;
 165     ((u_char *)&a)[2] = a2;
 166     ((u_char *)&a)[3] = a3;
 167
 168     return (a);
 169 }
 170
 171
 172 /*
 173  * inet_cksum extracted from:
 174  *                      P I N G . C
 175  *
 176  * Author -
 177  *      Mike Muuss
 178  *      U. S. Army Ballistic Research Laboratory
 179  *      December, 1983
 180  * Modified at Uc Berkeley
 181  *
 182  * (ping.c) Status -
 183  *      Public Domain.  Distribution Unlimited.
 184  *
 185  *                      I N _ C K S U M
 186  *
 187  * Checksum routine for Internet Protocol family headers (C Version)
 188  *
 189  */
 190 int
 191 inet_cksum(u_short *addr, u_int len)
 192 {
 193         int nleft = (int)len;
 194         u_short *w = addr;
 195         u_short answer = 0;
 196         int sum = 0;
 197
 198         /*
 199          *  Our algorithm is simple, using a 32 bit accumulator (sum),
 200          *  we add sequential 16 bit words to it, and at the end, fold
 201          *  back all the carry bits from the top 16 bits into the lower
 202          *  16 bits.
 203          */
 204         while (nleft > 1)  {
 205                 sum += *w++;
 206                 nleft -= 2;
 207         }
 208
 209         /* mop up an odd byte, if necessary */
 210         if (nleft == 1) {
 211                 *(u_char *) (&answer) = *(u_char *)w ;
 212                 sum += answer;
 213         }
 214
 215         /*
 216          * add back carry outs from top 16 bits to low 16 bits
 217          */
 218         sum = (sum >> 16) + (sum & 0xffff);     /* add hi 16 to low 16 */
 219         sum += (sum >> 16);                     /* add carry */
 220         answer = ~sum;                          /* truncate to 16 bits */
 221         return (answer);
 222 }