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