1 /* $NetBSD: inet.c,v 1.4 1995/12/10 10:07:03 mycroft Exp $ */ 2 3 /* 4 * The mrouted program is covered by the license in the accompanying file 5 * named "LICENSE". Use of the mrouted program represents acceptance of 6 * the terms and conditions listed in that file. 7 * 8 * The mrouted program is COPYRIGHT 1989 by The Board of Trustees of 9 * Leland Stanford Junior University. 10 */ 11 12 13 #include "defs.h" 14 15 16 /* 17 * Exported variables. 18 */ 19 char s1[19]; /* buffers to hold the string representations */ 20 char s2[19]; /* of IP addresses, to be passed to inet_fmt() */ 21 char s3[19]; /* or inet_fmts(). */ 22 char s4[19]; 23 24 25 /* 26 * Verify that a given IP address is credible as a host address. 27 * (Without a mask, cannot detect addresses of the form {subnet,0} or 28 * {subnet,-1}.) 29 */ 30 int 31 inet_valid_host(naddr) 32 u_int32_t naddr; 33 { 34 register u_int32_t addr; 35 36 addr = ntohl(naddr); 37 38 return (!(IN_MULTICAST(addr) || 39 IN_BADCLASS (addr) || 40 (addr & 0xff000000) == 0)); 41 } 42 43 /* 44 * Verify that a given netmask is plausible; 45 * make sure that it is a series of 1's followed by 46 * a series of 0's with no discontiguous 1's. 47 */ 48 int 49 inet_valid_mask(mask) 50 u_int32_t 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(nsubnet, nmask) 71 u_int32_t nsubnet, nmask; 72 { 73 register u_int32_t subnet, mask; 74 75 subnet = ntohl(nsubnet); 76 mask = ntohl(nmask); 77 78 if ((subnet & mask) != subnet) return (FALSE); 79 80 if (subnet == 0) 81 return (mask == 0); 82 83 if (IN_CLASSA(subnet)) { 84 if (mask < 0xff000000 || 85 (subnet & 0xff000000) == 0x7f000000 || 86 (subnet & 0xff000000) == 0x00000000) return (FALSE); 87 } 88 else if (IN_CLASSD(subnet) || IN_BADCLASS(subnet)) { 89 /* Above Class C address space */ 90 return (FALSE); 91 } 92 if (subnet & ~mask) { 93 /* Host bits are set in the subnet */ 94 return (FALSE); 95 } 96 if (!inet_valid_mask(mask)) { 97 /* Netmask is not contiguous */ 98 return (FALSE); 99 } 100 101 return (TRUE); 102 } 103 104 105 /* 106 * Convert an IP address in u_long (network) format into a printable string. 107 */ 108 char * 109 inet_fmt(addr, s) 110 u_int32_t addr; 111 char *s; 112 { 113 register u_char *a; 114 115 a = (u_char *)&addr; 116 sprintf(s, "%u.%u.%u.%u", a[0], a[1], a[2], a[3]); 117 return (s); 118 } 119 120 121 /* 122 * Convert an IP subnet number in u_long (network) format into a printable 123 * string including the netmask as a number of bits. 124 */ 125 char * 126 inet_fmts(addr, mask, s) 127 u_int32_t addr, mask; 128 char *s; 129 { 130 register u_char *a, *m; 131 int bits; 132 133 if ((addr == 0) && (mask == 0)) { 134 sprintf(s, "default"); 135 return (s); 136 } 137 a = (u_char *)&addr; 138 m = (u_char *)&mask; 139 bits = 33 - ffs(ntohl(mask)); 140 141 if (m[3] != 0) sprintf(s, "%u.%u.%u.%u/%d", a[0], a[1], a[2], a[3], 142 bits); 143 else if (m[2] != 0) sprintf(s, "%u.%u.%u/%d", a[0], a[1], a[2], bits); 144 else if (m[1] != 0) sprintf(s, "%u.%u/%d", a[0], a[1], bits); 145 else sprintf(s, "%u/%d", a[0], bits); 146 147 return (s); 148 } 149 150 /* 151 * Convert the printable string representation of an IP address into the 152 * u_long (network) format. Return 0xffffffff on error. (To detect the 153 * legal address with that value, you must explicitly compare the string 154 * with "255.255.255.255".) 155 */ 156 u_int32_t 157 inet_parse(s) 158 char *s; 159 { 160 u_int32_t a = 0; 161 u_int a0, a1, a2, a3; 162 char c; 163 164 if (sscanf(s, "%u.%u.%u.%u%c", &a0, &a1, &a2, &a3, &c) != 4 || 165 a0 > 255 || a1 > 255 || a2 > 255 || a3 > 255) 166 return (0xffffffff); 167 168 ((u_char *)&a)[0] = a0; 169 ((u_char *)&a)[1] = a1; 170 ((u_char *)&a)[2] = a2; 171 ((u_char *)&a)[3] = a3; 172 173 return (a); 174 } 175 176 177 /* 178 * inet_cksum extracted from: 179 * P I N G . C 180 * 181 * Author - 182 * Mike Muuss 183 * U. S. Army Ballistic Research Laboratory 184 * December, 1983 185 * Modified at Uc Berkeley 186 * 187 * (ping.c) Status - 188 * Public Domain. Distribution Unlimited. 189 * 190 * I N _ C K S U M 191 * 192 * Checksum routine for Internet Protocol family headers (C Version) 193 * 194 */ 195 int 196 inet_cksum(addr, len) 197 u_short *addr; 198 u_int len; 199 { 200 register int nleft = (int)len; 201 register u_short *w = addr; 202 u_short answer = 0; 203 register int sum = 0; 204 205 /* 206 * Our algorithm is simple, using a 32 bit accumulator (sum), 207 * we add sequential 16 bit words to it, and at the end, fold 208 * back all the carry bits from the top 16 bits into the lower 209 * 16 bits. 210 */ 211 while (nleft > 1) { 212 sum += *w++; 213 nleft -= 2; 214 } 215 216 /* mop up an odd byte, if necessary */ 217 if (nleft == 1) { 218 *(u_char *) (&answer) = *(u_char *)w ; 219 sum += answer; 220 } 221 222 /* 223 * add back carry outs from top 16 bits to low 16 bits 224 */ 225 sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */ 226 sum += (sum >> 16); /* add carry */ 227 answer = ~sum; /* truncate to 16 bits */ 228 return (answer); 229 } 230