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 #define SNAMLEN 19
20 char s1[SNAMLEN]; /* buffers to hold the string representations */
21 char s2[SNAMLEN]; /* of IP addresses, to be passed to inet_fmt() */
22 char s3[SNAMLEN]; /* or inet_fmts(). */
23 char s4[SNAMLEN];
24
25
26 /*
27 * Verify that a given IP address is credible as a host address.
28 * (Without a mask, cannot detect addresses of the form {subnet,0} or
29 * {subnet,-1}.)
30 */
31 int
inet_valid_host(u_int32_t naddr)32 inet_valid_host(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
inet_valid_mask(u_int32_t mask)49 inet_valid_mask(u_int32_t mask)
50 {
51 if (~(((mask & -mask) - 1) | mask) != 0) {
52 /* Mask is not contiguous */
53 return (FALSE);
54 }
55
56 return (TRUE);
57 }
58
59 /*
60 * Verify that a given subnet number and mask pair are credible.
61 *
62 * With CIDR, almost any subnet and mask are credible. mrouted still
63 * can't handle aggregated class A's, so we still check that, but
64 * otherwise the only requirements are that the subnet address is
65 * within the [ABC] range and that the host bits of the subnet
66 * are all 0.
67 */
68 int
inet_valid_subnet(u_int32_t nsubnet,u_int32_t nmask)69 inet_valid_subnet(u_int32_t nsubnet, u_int32_t nmask)
70 {
71 register u_int32_t subnet, mask;
72
73 subnet = ntohl(nsubnet);
74 mask = ntohl(nmask);
75
76 if ((subnet & mask) != subnet) return (FALSE);
77
78 if (subnet == 0)
79 return (mask == 0);
80
81 if (IN_CLASSA(subnet)) {
82 if (mask < 0xff000000 ||
83 (subnet & 0xff000000) == 0x7f000000 ||
84 (subnet & 0xff000000) == 0x00000000) return (FALSE);
85 }
86 else if (IN_CLASSD(subnet) || IN_BADCLASS(subnet)) {
87 /* Above Class C address space */
88 return (FALSE);
89 }
90 if (subnet & ~mask) {
91 /* Host bits are set in the subnet */
92 return (FALSE);
93 }
94 if (!inet_valid_mask(mask)) {
95 /* Netmask is not contiguous */
96 return (FALSE);
97 }
98
99 return (TRUE);
100 }
101
102
103 /*
104 * Convert an IP address in u_long (network) format into a printable string.
105 */
106 char *
inet_fmt(u_int32_t addr,char * s)107 inet_fmt(u_int32_t addr, char *s)
108 {
109 register u_char *a;
110
111 a = (u_char *)&addr;
112 snprintf(s, SNAMLEN, "%u.%u.%u.%u", a[0], a[1], a[2], a[3]);
113 return (s);
114 }
115
116
117 /*
118 * Convert an IP subnet number in u_long (network) format into a printable
119 * string including the netmask as a number of bits.
120 */
121 char *
inet_fmts(u_int32_t addr,u_int32_t mask,char * s)122 inet_fmts(u_int32_t addr, u_int32_t mask, char *s)
123 {
124 register u_char *a, *m;
125 int bits;
126
127 if ((addr == 0) && (mask == 0)) {
128 snprintf(s, SNAMLEN, "default");
129 return (s);
130 }
131 a = (u_char *)&addr;
132 m = (u_char *)&mask;
133 bits = 33 - ffs(ntohl(mask));
134
135 if (m[3] != 0)
136 snprintf(s, SNAMLEN, "%u.%u.%u.%u/%d", a[0], a[1], a[2], a[3], bits);
137 else if (m[2] != 0)
138 snprintf(s, SNAMLEN, "%u.%u.%u/%d", a[0], a[1], a[2], bits);
139 else if (m[1] != 0)
140 snprintf(s, SNAMLEN, "%u.%u/%d", a[0], a[1], bits);
141 else
142 snprintf(s, SNAMLEN, "%u/%d", a[0], bits);
143
144 return (s);
145 }
146
147 /*
148 * Convert the printable string representation of an IP address into the
149 * u_long (network) format. Return 0xffffffff on error. (To detect the
150 * legal address with that value, you must explicitly compare the string
151 * with "255.255.255.255".)
152 */
153 u_int32_t
inet_parse(char * s)154 inet_parse(char *s)
155 {
156 u_int32_t a = 0;
157 u_int a0, a1, a2, a3;
158 char c;
159
160 if (sscanf(s, "%u.%u.%u.%u%c", &a0, &a1, &a2, &a3, &c) != 4 ||
161 a0 > 255 || a1 > 255 || a2 > 255 || a3 > 255)
162 return (0xffffffff);
163
164 ((u_char *)&a)[0] = a0;
165 ((u_char *)&a)[1] = a1;
166 ((u_char *)&a)[2] = a2;
167 ((u_char *)&a)[3] = a3;
168
169 return (a);
170 }
171
172
173 /*
174 * inet_cksum extracted from:
175 * P I N G . C
176 *
177 * Author -
178 * Mike Muuss
179 * U. S. Army Ballistic Research Laboratory
180 * December, 1983
181 * Modified at Uc Berkeley
182 *
183 * (ping.c) Status -
184 * Public Domain. Distribution Unlimited.
185 *
186 * I N _ C K S U M
187 *
188 * Checksum routine for Internet Protocol family headers (C Version)
189 *
190 */
191 int
inet_cksum(u_int16_t * addr,u_int len)192 inet_cksum(u_int16_t *addr, u_int len)
193 {
194 register int nleft = (int)len;
195 register u_int16_t *w = addr;
196 u_int16_t answer = 0;
197 register int32_t sum = 0;
198
199 /*
200 * Our algorithm is simple, using a 32 bit accumulator (sum),
201 * we add sequential 16 bit words to it, and at the end, fold
202 * back all the carry bits from the top 16 bits into the lower
203 * 16 bits.
204 */
205 while (nleft > 1) {
206 sum += *w++;
207 nleft -= 2;
208 }
209
210 /* mop up an odd byte, if necessary */
211 if (nleft == 1) {
212 *(u_char *) (&answer) = *(u_char *)w ;
213 sum += answer;
214 }
215
216 /*
217 * add back carry outs from top 16 bits to low 16 bits
218 */
219 sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */
220 sum += (sum >> 16); /* add carry */
221 answer = ~sum; /* truncate to 16 bits */
222 return (answer);
223 }
224