1/* $NetBSD: inet.c,v 1.11 2003/05/16 22:59:50 dsl 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/* buffers to hold the string representations */ 17/* of IP addresses, returned by inet_fmt{s}() */ 18#define SS_MASK ((1 << 3) - 1) 19static char ss[SS_MASK + 1][32]; 20static int ss_index = 0; /* index into above */ 21 22 23/* 24 * Verify that a given IP address is credible as a host address. 25 * (Without a mask, cannot detect addresses of the form {subnet,0} or 26 * {subnet,-1}.) 27 */ 28int 29inet_valid_host(u_int32_t naddr) 30{ 31 u_int32_t addr; 32 33 addr = ntohl(naddr); 34 35 return (!(IN_MULTICAST(addr) || 36 IN_BADCLASS (addr) || 37 (addr & 0xff000000) == 0)); 38} 39 40/* 41 * Verify that a given netmask is plausible; 42 * make sure that it is a series of 1's followed by 43 * a series of 0's with no discontiguous 1's. 44 */ 45int 46inet_valid_mask(u_int32_t mask) 47{ 48 if (~(((mask & -mask) - 1) | mask) != 0) { 49 /* Mask is not contiguous */ 50 return (FALSE); 51 } 52 53 return (TRUE); 54} 55 56/* 57 * Verify that a given subnet number and mask pair are credible. 58 * 59 * With CIDR, almost any subnet and mask are credible. mrouted still 60 * can't handle aggregated class A's, so we still check that, but 61 * otherwise the only requirements are that the subnet address is 62 * within the [ABC] range and that the host bits of the subnet 63 * are all 0. 64 */ 65int 66inet_valid_subnet(u_int32_t nsubnet, u_int32_t nmask) 67{ 68 u_int32_t subnet, mask; 69 70 subnet = ntohl(nsubnet); 71 mask = ntohl(nmask); 72 73 if ((subnet & mask) != subnet) return (FALSE); 74 75 if (subnet == 0) 76 return (mask == 0); 77 78 if (IN_CLASSA(subnet)) { 79 if (mask < 0xff000000 || 80 (subnet & 0xff000000) == 0x7f000000 || 81 (subnet & 0xff000000) == 0x00000000) return (FALSE); 82 } 83 else if (IN_CLASSD(subnet) || IN_BADCLASS(subnet)) { 84 /* Above Class C address space */ 85 return (FALSE); 86 } 87 if (subnet & ~mask) { 88 /* Host bits are set in the subnet */ 89 return (FALSE); 90 } 91 if (!inet_valid_mask(mask)) { 92 /* Netmask is not contiguous */ 93 return (FALSE); 94 } 95 96 return (TRUE); 97} 98 99 100/* 101 * Convert an IP address in u_long (network) format into a printable string. 102 */ 103char * 104inet_fmt(u_int32_t addr) 105{ 106 u_char *a; 107 char *s = ss[++ss_index & SS_MASK]; 108 109 a = (u_char *)&addr; 110 snprintf(s, sizeof ss[0], "%u.%u.%u.%u", a[0], a[1], a[2], a[3]); 111 return (s); 112} 113 114 115/* 116 * Convert an IP subnet number in u_long (network) format into a printable 117 * string including the netmask as a number of bits. 118 */ 119char * 120inet_fmts(u_int32_t addr, u_int32_t mask) 121{ 122 u_char *a, *m; 123 int bits; 124 char *s = ss[++ss_index & SS_MASK]; 125 126 if ((addr == 0) && (mask == 0)) { 127 snprintf(s, sizeof ss[0], "default"); 128 return (s); 129 } 130 a = (u_char *)&addr; 131 m = (u_char *)&mask; 132 bits = 33 - ffs(ntohl(mask)); 133 134 if (m[3] != 0) snprintf(s, sizeof ss[0], "%u.%u.%u.%u/%d", a[0], a[1], a[2], a[3], 135 bits); 136 else if (m[2] != 0) snprintf(s, sizeof ss[0], "%u.%u.%u/%d", a[0], a[1], a[2], bits); 137 else if (m[1] != 0) snprintf(s, sizeof ss[0], "%u.%u/%d", a[0], a[1], bits); 138 else snprintf(s, sizeof ss[0], "%u/%d", a[0], bits); 139 140 return (s); 141} 142 143/* 144 * Convert the printable string representation of an IP address into the 145 * u_long (network) format. Return 0xffffffff on error. (To detect the 146 * legal address with that value, you must explicitly compare the string 147 * with "255.255.255.255".) 148 */ 149u_int32_t 150inet_parse(char *s, int *mask_p) 151{ 152 u_int32_t a = 0; 153 u_int a0, a1, a2, a3; 154 char c; 155 int n; 156 157 if (sscanf(s, "%u.%u.%u.%u%n", &a0, &a1, &a2, &a3, &n) != 4) 158 return 0xffffffff; 159 if (a0 > 255 || a1 > 255 || a2 > 255 || a3 > 255) 160 return 0xffffffff; 161 162 if (mask_p == 0) { 163 if (s[n] != 0) 164 return 0xffffffff; 165 } else { 166 if (sscanf(s + n, "/%u%c", &n, &c) != 1 || n > 32) 167 return 0xffffffff; 168 *mask_p = n; 169 } 170 171 ((u_char *)&a)[0] = a0; 172 ((u_char *)&a)[1] = a1; 173 ((u_char *)&a)[2] = a2; 174 ((u_char *)&a)[3] = a3; 175 176 return (a); 177} 178 179 180/* 181 * inet_cksum extracted from: 182 * P I N G . C 183 * 184 * Author - 185 * Mike Muuss 186 * U. S. Army Ballistic Research Laboratory 187 * December, 1983 188 * Modified at Uc Berkeley 189 * 190 * (ping.c) Status - 191 * Public Domain. Distribution Unlimited. 192 * 193 * I N _ C K S U M 194 * 195 * Checksum routine for Internet Protocol family headers (C Version) 196 * 197 */ 198int 199inet_cksum(u_int16_t *addr, u_int len) 200{ 201 int nleft = (int)len; 202 u_int16_t *w = addr; 203 int32_t sum = 0; 204 union { 205 u_int16_t w; 206 u_int8_t b[2]; 207 } answer; 208 209 /* 210 * Our algorithm is simple, using a 32 bit accumulator (sum), 211 * we add sequential 16 bit words to it, and at the end, fold 212 * back all the carry bits from the top 16 bits into the lower 213 * 16 bits. 214 */ 215 while (nleft > 1) { 216 sum += *w++; 217 nleft -= 2; 218 } 219 220 /* mop up an odd byte, if necessary */ 221 if (nleft == 1) { 222 answer.w = 0; 223 answer.b[0] = *(u_char *)w ; 224 sum += answer.w; 225 } 226 227 /* 228 * add back carry outs from top 16 bits to low 16 bits 229 */ 230 sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */ 231 sum += (sum >> 16); /* add carry */ 232 answer.w = ~sum; /* truncate to 16 bits */ 233 return (answer.w); 234} 235