Annotation of embedaddon/mrouted/inet.c, revision 1.1
1.1 ! misho 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: #include "defs.h"
! 11:
! 12: /*
! 13: * Exported variables.
! 14: */
! 15: char s1[MAX_INET_BUF_LEN]; /* buffers to hold the string representations */
! 16: char s2[MAX_INET_BUF_LEN]; /* of IP addresses, to be passed to inet_fmt() */
! 17: char s3[MAX_INET_BUF_LEN]; /* or inet_fmts(). */
! 18: char s4[MAX_INET_BUF_LEN];
! 19:
! 20:
! 21: /*
! 22: * Verify that a given IP address is credible as a host address.
! 23: * (Without a mask, cannot detect addresses of the form {subnet,0} or
! 24: * {subnet,-1}.)
! 25: */
! 26: int inet_valid_host(u_int32 naddr)
! 27: {
! 28: u_int32 addr;
! 29:
! 30: addr = ntohl(naddr);
! 31:
! 32: return (!(IN_MULTICAST(addr) ||
! 33: IN_BADCLASS (addr) ||
! 34: (addr & 0xff000000) == 0));
! 35: }
! 36:
! 37: /*
! 38: * Verify that a given netmask is plausible;
! 39: * make sure that it is a series of 1's followed by
! 40: * a series of 0's with no discontiguous 1's.
! 41: */
! 42: int inet_valid_mask(u_int32 mask)
! 43: {
! 44: if (~(((mask & -mask) - 1) | mask) != 0) {
! 45: /* Mask is not contiguous */
! 46: return FALSE;
! 47: }
! 48:
! 49: return TRUE;
! 50: }
! 51:
! 52: /*
! 53: * Verify that a given subnet number and mask pair are credible.
! 54: *
! 55: * With CIDR, almost any subnet and mask are credible. mrouted still
! 56: * can't handle aggregated class A's, so we still check that, but
! 57: * otherwise the only requirements are that the subnet address is
! 58: * within the [ABC] range and that the host bits of the subnet
! 59: * are all 0.
! 60: */
! 61: int inet_valid_subnet(u_int32 nsubnet, u_int32 nmask)
! 62: {
! 63: u_int32 subnet, mask;
! 64:
! 65: subnet = ntohl(nsubnet);
! 66: mask = ntohl(nmask);
! 67:
! 68: if ((subnet & mask) != subnet) return FALSE;
! 69:
! 70: if (subnet == 0)
! 71: return mask == 0;
! 72:
! 73: if (IN_CLASSA(subnet)) {
! 74: if (mask < 0xff000000 ||
! 75: (subnet & 0xff000000) == 0x7f000000 ||
! 76: (subnet & 0xff000000) == 0x00000000) return FALSE;
! 77: }
! 78: else if (IN_CLASSD(subnet) || IN_BADCLASS(subnet)) {
! 79: /* Above Class C address space */
! 80: return FALSE;
! 81: }
! 82: if (subnet & ~mask) {
! 83: /* Host bits are set in the subnet */
! 84: return FALSE;
! 85: }
! 86: if (!inet_valid_mask(mask)) {
! 87: /* Netmask is not contiguous */
! 88: return FALSE;
! 89: }
! 90:
! 91: return TRUE;
! 92: }
! 93:
! 94:
! 95: /*
! 96: * Convert an IP address in u_long (network) format into a printable string.
! 97: */
! 98: char *inet_fmt(u_int32 addr, char *s, size_t len)
! 99: {
! 100: u_char *a;
! 101:
! 102: a = (u_char *)&addr;
! 103: snprintf(s, len, "%u.%u.%u.%u", a[0], a[1], a[2], a[3]);
! 104:
! 105: return s;
! 106: }
! 107:
! 108:
! 109: /*
! 110: * Convert an IP subnet number in u_long (network) format into a printable
! 111: * string including the netmask as a number of bits.
! 112: */
! 113: char *inet_fmts(u_int32 addr, u_int32 mask, char *s, size_t len)
! 114: {
! 115: u_char *a, *m;
! 116: int bits;
! 117:
! 118: if ((addr == 0) && (mask == 0)) {
! 119: snprintf(s, len, "default");
! 120: return s;
! 121: }
! 122: a = (u_char *)&addr;
! 123: m = (u_char *)&mask;
! 124: bits = 33 - ffs(ntohl(mask));
! 125:
! 126: if (m[3] != 0) snprintf(s, len, "%u.%u.%u.%u/%d", a[0], a[1], a[2], a[3],
! 127: bits);
! 128: else if (m[2] != 0) snprintf(s, len, "%u.%u.%u/%d", a[0], a[1], a[2], bits);
! 129: else if (m[1] != 0) snprintf(s, len, "%u.%u/%d", a[0], a[1], bits);
! 130: else snprintf(s, len, "%u/%d", a[0], bits);
! 131:
! 132: return s;
! 133: }
! 134:
! 135: /*
! 136: * Convert the printable string representation of an IP address into the
! 137: * u_long (network) format. Return 0xffffffff on error. (To detect the
! 138: * legal address with that value, you must explicitly compare the string
! 139: * with "255.255.255.255".)
! 140: */
! 141: u_int32 inet_parse(char *s, int n)
! 142: {
! 143: u_int32 a = 0;
! 144: u_int a0 = 0, a1 = 0, a2 = 0, a3 = 0;
! 145: int i;
! 146: char c;
! 147:
! 148: i = sscanf(s, "%u.%u.%u.%u%c", &a0, &a1, &a2, &a3, &c);
! 149: if (i < n || i > 4 || a0 > 255 || a1 > 255 || a2 > 255 || a3 > 255)
! 150: return 0xffffffff;
! 151:
! 152: ((u_char *)&a)[0] = a0;
! 153: ((u_char *)&a)[1] = a1;
! 154: ((u_char *)&a)[2] = a2;
! 155: ((u_char *)&a)[3] = a3;
! 156:
! 157: return a;
! 158: }
! 159:
! 160:
! 161: /*
! 162: * inet_cksum extracted from:
! 163: * P I N G . C
! 164: *
! 165: * Author -
! 166: * Mike Muuss
! 167: * U. S. Army Ballistic Research Laboratory
! 168: * December, 1983
! 169: * Modified at Uc Berkeley
! 170: *
! 171: * (ping.c) Status -
! 172: * Public Domain. Distribution Unlimited.
! 173: *
! 174: * I N _ C K S U M
! 175: *
! 176: * Checksum routine for Internet Protocol family headers (C Version)
! 177: *
! 178: */
! 179: int inet_cksum(u_int16_t *addr, u_int len)
! 180: {
! 181: int nleft = (int)len;
! 182: u_int16_t *w = addr;
! 183: u_int16_t answer = 0;
! 184: int32_t sum = 0;
! 185:
! 186: /*
! 187: * Our algorithm is simple, using a 32 bit accumulator (sum),
! 188: * we add sequential 16 bit words to it, and at the end, fold
! 189: * back all the carry bits from the top 16 bits into the lower
! 190: * 16 bits.
! 191: */
! 192: while (nleft > 1) {
! 193: sum += *w++;
! 194: nleft -= 2;
! 195: }
! 196:
! 197: /* mop up an odd byte, if necessary */
! 198: if (nleft == 1) {
! 199: *(u_char *) (&answer) = *(u_char *)w ;
! 200: sum += answer;
! 201: }
! 202:
! 203: /*
! 204: * add back carry outs from top 16 bits to low 16 bits
! 205: */
! 206: sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */
! 207: sum += (sum >> 16); /* add carry */
! 208: answer = ~sum; /* truncate to 16 bits */
! 209:
! 210: return answer;
! 211: }
! 212:
! 213: /**
! 214: * Local Variables:
! 215: * version-control: t
! 216: * indent-tabs-mode: t
! 217: * c-file-style: "ellemtel"
! 218: * c-basic-offset: 4
! 219: * End:
! 220: */
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