inet.c

/*
 * The mrouted program is covered by the license in the accompanying file
 * named "LICENSE.mrouted". 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.
 *
 *
 * inet.c,v 3.8.4.1 1997/01/29 19:49:33 fenner Exp
 */
#define C(x)    ((x) & 0xff)

#include "defs.h"


/*
 * Exported variables.
 */
char s1[19];		/* buffers to hold the string representations  */
char s2[19];		/* of IP addresses, to be passed to inet_fmt() */
char s3[19];
char s4[19];


/*
 * 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(naddr)
u_int32 naddr;
{
	register u_int32 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(mask)
u_int32 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(nsubnet, nmask)
u_int32 nsubnet, nmask;
{
	register u_int32 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_int32 (network) format into a printable string.
 */
char *
inet_fmt(addr, s)
u_int32 addr;
char *s;
{
	register u_char *a;

	a = (u_char *)&addr;
	sprintf(s, "%u.%u.%u.%u", a[0], a[1], a[2], a[3]);
	return (s);
}


/*
 * Convert an IP subnet number in u_int32 (network) format into a printable
 * string including the netmask as a number of bits.
 */
#ifdef NOSUCHDEF	/* replaced by netname() */
char *
inet_fmts(addr, mask, s)
u_int32 addr, mask;
char *s;
{
	register u_char *a, *m;
	int bits;

	if ((addr == 0) && (mask == 0)) {
		sprintf(s, "default");
		return (s);
	}
	a = (u_char *)&addr;
	m = (u_char *)&mask;
	bits = 33 - ffs(ntohl(mask));

	if (m[3] != 0) sprintf(s, "%u.%u.%u.%u/%d", a[0], a[1], a[2], a[3],
							   bits);
	else if (m[2] != 0) sprintf(s, "%u.%u.%u/%d",    a[0], a[1], a[2], bits);
	else if (m[1] != 0) sprintf(s, "%u.%u/%d",       a[0], a[1], bits);
	else                sprintf(s, "%u/%d",          a[0], bits);

	return (s);
}
#endif /* NOSUCHDEF */

/*
 * Convert the printable string representation of an IP address into the
 * u_int32 (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".)
 * The return value is in network order.
 */
u_int32
inet_parse(s, n)
char *s;
int n;
{
	u_int32 a = 0;
	u_int a0 = 0, a1 = 0, a2 = 0, a3 = 0;
	int i;
	char c;

	i = sscanf(s, "%u.%u.%u.%u%c", &a0, &a1, &a2, &a3, &c);
	if (i < n || i > 4 || a0 > 255 || a1 > 255 || a2 > 255 || a3 > 255)
		return (0xffffffff);

	((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(addr, len)
u_int16 *addr;
u_int len;
{
	register int nleft = (int)len;
	register u_int16 *w = addr;
	u_int16 answer = 0;
	register int sum = 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) {
		*(u_char *)(&answer) = *(u_char *)w ;
		sum += answer;
	}

	/*
	 * 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 = ~sum;				/* truncate to 16 bits */
	return (answer);
}

/*
 * Called by following netname() to create a mask specified network address.
 */
void
trimdomain(cp)
char *cp;
{
	static char domain[MAXHOSTNAMELEN + 1];
	static int first = 1;
	char *s;

	if (first) {
		first = 0;
		if (gethostname(domain, MAXHOSTNAMELEN) == 0 &&
			(s = strchr(domain, '.')))
			(void) strcpy(domain, s + 1);
		else
			domain[0] = 0;
	}

	if (domain[0]) {
		while ((cp = strchr(cp, '.'))) {
			if (!strcasecmp(cp + 1, domain)) {
				*cp = 0;        /* hit it */
				break;
			} else {
				cp++;
			}
		}
	}
}

static u_long
forgemask(a)
u_long a;
{
	u_long m;

	if (IN_CLASSA(a))
		m = IN_CLASSA_NET;
	else if (IN_CLASSB(a))
		m = IN_CLASSB_NET;
	else
		m = IN_CLASSC_NET;
	return (m);
}

static void
domask(dst, addr, mask)
char *dst;
u_long addr, mask;
{
	int b, i;

	if (!mask || (forgemask(addr) == mask)) {
		*dst = '\0';
		return;
	}
	i = 0;
	for (b = 0; b < 32; b++)
		if (mask & (1 << b)) {
			int bb;

			i = b;
			for (bb = b + 1; bb < 32; bb++)
				if (!(mask & (1 << bb))) {
					i = -1; /* noncontig */
					break;
				}
			break;
		}
	if (i == -1)
		sprintf(dst, "&0x%lx", mask);
	else
		sprintf(dst, "/%d", 32 - i);
}

/*
 * Return the name of the network whose address is given.
 * The address is assumed to be that of a net or subnet, not a host.
 */
char *
netname(addr, mask)
u_int32 addr, mask;
{
	static char line[MAXHOSTNAMELEN + 4];
	u_int32 omask;
	u_int32 i;

	i = ntohl(addr);
	omask = mask = ntohl(mask);
	if ((i & 0xffffff) == 0)
		sprintf(line, "%u", C(i >> 24));
	else if ((i & 0xffff) == 0)
		sprintf(line, "%u.%u", C(i >> 24), C(i >> 16));
	else if ((i & 0xff) == 0)
		sprintf(line, "%u.%u.%u", C(i >> 24), C(i >> 16), C(i >> 8));
	else
		sprintf(line, "%u.%u.%u.%u", C(i >> 24),
				C(i >> 16), C(i >> 8), C(i));
	domask(line + strlen(line), i, omask);
	return (line);
}