Annotation of embedaddon/mrouted/inet.c, revision 1.1.1.1
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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