Re: linux-ipsec: apps/utils/libs that parse IP/netbits

From: Henry Spencer <henry(at)spsystems.net>
Date: Wed Jul 15 1998 - 18:09:54 EDT

> Can anyone think of any applications/utils/libraries that do IP/netbits
> parsing? ...

Try the enclosed. I just wrote it, as a first contribution to a set of utility routines for our user interface. No manpage yet -- let me know if you can't figure it out. It provides network address and mask, with the non-mask bits in the network address forced to 0. It does depend on a couple of existing library routines; that dependency can be removed if it proves awkward.

If you compile with -DATOSUBNET_MAIN, it becomes a self-contained test program.

                                                          Henry Spencer
                                                       henry@spsystems.net
                                                     (henry@zoo.toronto.edu)

#! /bin/sh
echo 'atosubnet.c':
sed 's/^X//' >'atosubnet.c' <<'!'

X#include 
X#include 
X#include 
X#include 
X
X#define	ABITS	32	/* bits in an address or mask */

X
X/*
X - atosubnet - convert ASCII "addr/mask" to address and mask

X * Mask can be either dotted quad or integer bit count.
X * Results are in network byte order.
X */
Xint				/* 0 success, -1 failure */

Xatosubnet(s, addrp, maskp)
Xconst char *s;
Xstruct in_addr *addrp;
Xstruct in_addr *maskp;
X{

X	char *slash;
X	char *mask;
X	unsigned long m;
X	int n;
X
X	slash = strchr(s, '/');
X	if (slash == NULL)
X		return -1;
X	mask = slash + 1;
X	*slash = '\0';
X
X	if (inet_aton(s, addrp) == 0)
X		return -1;
X
X	if (strchr(mask, '.') != NULL) {	/* mask is dotted quad too */
X		if (inet_aton(mask, maskp) == 0)
X			return -1;
X		addrp->s_addr &= maskp->s_addr;
X		return 0;
X	}
X
X	/* uh-oh, mask must be a bit count */
X	if (*(mask + strspn(mask, "1234567890")) != '\0')
X		return -1;
X	n = atoi(mask);
X	if (n > ABITS)
X		return -1;
X	m = 0;
X	m--;				/* all 1s */
X	m <<= ABITS - n;
X	maskp->s_addr = htonl(m);
X	addrp->s_addr &= maskp->s_addr;
X
X	return 0;

X}
X
X
X
X/*
X - subnettoa - convert address and mask to ASCII "addr/mask"

X * Inputs are in network byte order.  Note that they're structs, not
X * pointers to structs.
X * Output expresses the mask as a bit count if possible, else dotted quad.
X * It is an error for there not to be enough room.
X */
Xint				/* 0 success, -1 failure */

Xsubnettoa(addr, mask, dst, dstlen)
Xstruct in_addr addr;
Xstruct in_addr mask;

Xchar *dst;			/* where to put the ASCII */
Xsize_t dstlen;			/* how big dst is */
X{
X	unsigned long m;
X	int n;
X	char *s;
X	char c;
X	char *stop = dst + dstlen;
X	char buf[5];
X
X	s = inet_ntoa(addr);
X	while ((c = *s++) != '\0') {
X		if (dst >= stop)
X			return -1;
X		*dst++ = c;
X	}
X	if (dst >= stop)
X		return -1;
X	*dst++ = '/';
X
X	m = 0;
X	m--;				/* all 1s */
X	for (n = 0; n <= ABITS && htonl(m<
Do you need help?
In addition to our free technical library, Pantek provides professional IT services to companies who utilize Open Source software:
Learn more about Pantek's Technical Support offerings
Place an order for 24/7/365 Technical Support here
Learn more about Pantek, who we are, and what we do
Chat with a Live Operator
Related lists.freeswan.org Links
1998-fall
1998-spring
1998-summer
1998-winter
1999-winter
announce
briefs
bugs
design
freeswan-list
hipsec
ietf-sectest
users
users-admin
Request more information about Pantek

X	struct in_addr a;
X	struct in_addr m;
X	char buf[100];
X
X	if (argc < 2) {
X		fprintf(stderr, "Usage: %s addr/mask\n", argv[0]);
X		exit(2);
X	}
X
X	if (atosubnet(argv[1], &a, &m) < 0) {
X		fprintf(stderr, "%s: conversion failed\n", argv[0]);
X		exit(1);
X	}
X	if (subnettoa(a, m, buf, sizeof(buf)) < 0) {
X		fprintf(stderr, "%s: reverse conversion failed: ", argv[0]);
X		fprintf(stderr, "%s/", inet_ntoa(a));
X		fprintf(stderr, "%s\n", inet_ntoa(m));
X		exit(1);
X	}
X	printf("%s\n", buf);
X
X	exit(0);