/* $NetBSD: inet.c,v 1.13 2020/09/07 18:37:21 christos Exp $ */
/*
* The mrouted program is covered by the license in the accompanying file
* named "LICENSE". Use of the mrouted program represents acceptance of
* the terms and conditions listed in that file.
*
* The mrouted program is COPYRIGHT 1989 by The Board of Trustees of
* Leland Stanford Junior University.
*/
#include <assert.h>
#include "defs.h"
/* buffers to hold the string representations */
/* of IP addresses, returned by inet_fmt{s}() */
#define SS_MASK ((1 << 3) - 1)
static char ss[SS_MASK + 1][32];
static int ss_index = 0; /* index into above */
/*
* Verify that a given IP address is credible as a host address.
* (Without a mask, cannot detect addresses of the form {subnet,0} or
* {subnet,-1}.)
*/
int
inet_valid_host(u_int32_t naddr)
{
u_int32_t addr;
addr = ntohl(naddr);
return (!(IN_MULTICAST(addr) ||
IN_BADCLASS (addr) ||
(addr & 0xff000000) == 0));
}
/*
* Verify that a given netmask is plausible;
* make sure that it is a series of 1's followed by
* a series of 0's with no discontiguous 1's.
*/
int
inet_valid_mask(u_int32_t mask)
{
if (~(((mask & -mask) - 1) | mask) != 0) {
/* Mask is not contiguous */
return (FALSE);
}
return (TRUE);
}
/*
* Verify that a given subnet number and mask pair are credible.
*
* With CIDR, almost any subnet and mask are credible. mrouted still
* can't handle aggregated class A's, so we still check that, but
* otherwise the only requirements are that the subnet address is
* within the [ABC] range and that the host bits of the subnet
* are all 0.
*/
int
inet_valid_subnet(u_int32_t nsubnet, u_int32_t nmask)
{
u_int32_t subnet, mask;
subnet = ntohl(nsubnet);
mask = ntohl(nmask);
if ((subnet & mask) != subnet) return (FALSE);
if (subnet == 0)
return (mask == 0);
if (IN_CLASSA(subnet)) {
if (mask < 0xff000000 ||
(subnet & 0xff000000) == 0x7f000000 ||
(subnet & 0xff000000) == 0x00000000) return (FALSE);
}
else if (IN_CLASSD(subnet) || IN_BADCLASS(subnet)) {
/* Above Class C address space */
return (FALSE);
}
if (subnet & ~mask) {
/* Host bits are set in the subnet */
return (FALSE);
}
if (!inet_valid_mask(mask)) {
/* Netmask is not contiguous */
return (FALSE);
}
return (TRUE);
}
/*
* Convert an IP address in u_long (network) format into a printable string.
*/
char *
inet_fmt(u_int32_t addr)
{
u_char *a;
char *s = ss[++ss_index & SS_MASK];
a = (u_char *)&addr;
snprintf(s, sizeof ss[0], "%u.%u.%u.%u", a[0], a[1], a[2], a[3]);
return (s);
}
/*
* Convert an IP subnet number in u_long (network) format into a printable
* string including the netmask as a number of bits.
*/
char *
inet_fmts(u_int32_t addr, u_int32_t mask)
{
u_char *a, *m;
int bits;
char *s = ss[++ss_index & SS_MASK];
if ((addr == 0) && (mask == 0)) {
snprintf(s, sizeof ss[0], "default");
return (s);
}
a = (u_char *)&addr;
m = (u_char *)&mask;
bits = 33 - ffs(ntohl(mask));
if (m[3] != 0) snprintf(s, sizeof ss[0], "%u.%u.%u.%u/%d", a[0], a[1], a[2], a[3],
bits);
else if (m[2] != 0) snprintf(s, sizeof ss[0], "%u.%u.%u/%d", a[0], a[1], a[2], bits);
else if (m[1] != 0) snprintf(s, sizeof ss[0], "%u.%u/%d", a[0], a[1], bits);
else snprintf(s, sizeof ss[0], "%u/%d", a[0], bits);
return (s);
}
/*
* Convert the printable string representation of an IP address into the
* u_long (network) format. Return 0xffffffff on error. (To detect the
* legal address with that value, you must explicitly compare the string
* with "255.255.255.255".)
*/
u_int32_t
inet_parse(char *s, int *mask_p)
{
u_int32_t a = 0;
u_int a0, a1, a2, a3;
char c;
int n;
if (sscanf(s, "%u.%u.%u.%u%n", &a0, &a1, &a2, &a3, &n) != 4)
return 0xffffffff;
if (a0 > 255 || a1 > 255 || a2 > 255 || a3 > 255)
return 0xffffffff;
if (mask_p == 0) {
if (s[n] != 0)
return 0xffffffff;
} else {
if (sscanf(s + n, "/%u%c", &n, &c) != 1 || n > 32)
return 0xffffffff;
*mask_p = n;
}
((u_char *)&a)[0] = a0;
((u_char *)&a)[1] = a1;
((u_char *)&a)[2] = a2;
((u_char *)&a)[3] = a3;
return (a);
}
/*
* inet_cksum extracted from:
* P I N G . C
*
* Author -
* Mike Muuss
* U. S. Army Ballistic Research Laboratory
* December, 1983
* Modified at Uc Berkeley
*
* (ping.c) Status -
* Public Domain. Distribution Unlimited.
*
* I N _ C K S U M
*
* Checksum routine for Internet Protocol family headers (C Version)
*
*/
int
inet_cksum(const void *addr, u_int len)
{
int nleft = (int)len;
const u_int16_t *w = addr;
int32_t sum = 0;
union {
u_int16_t w;
u_int8_t b[2];
} answer;
assert(((uintptr_t)w & 1) == 0);
/*
* Our algorithm is simple, using a 32 bit accumulator (sum),
* we add sequential 16 bit words to it, and at the end, fold
* back all the carry bits from the top 16 bits into the lower
* 16 bits.
*/
while (nleft > 1) {
sum += *w++;
nleft -= 2;
}
/* mop up an odd byte, if necessary */
if (nleft == 1) {
answer.w = 0;
answer.b[0] = *(const u_char *)w;
sum += answer.w;
}
/*
* add back carry outs from top 16 bits to low 16 bits
*/
sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */
sum += (sum >> 16); /* add carry */
answer.w = ~sum; /* truncate to 16 bits */
return (answer.w);
}
