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/*
* Check format of network prefix
*/
#include <stdio.h>
#include <stdarg.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
typedef struct
{
uint8_t family;
uint8_t bytelen;
unsigned int plen;
uint32_t data[4];
} inet_prefix;
static void err(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
vfprintf(stderr, fmt, ap);
va_end(ap);
exit(1);
}
static void usage(void)
{
fprintf(stderr, "Usage: check-prefix-boundary [-4|-6] address/prefix\n");
exit(1);
}
static void get_addr_1(inet_prefix *addr, const char *name, int family)
{
memset(addr, 0, sizeof(*addr));
if (strchr(name, ':')) {
addr->family = AF_INET6;
addr->bytelen = 16;
if (family != AF_UNSPEC && family != AF_INET6)
err("IPV6 address not allowed\n");
if (inet_pton(AF_INET6, name, addr->data) <= 0)
err("Invalid IPV6 address: %s\n", name);
return;
}
addr->family = AF_INET;
addr->bytelen = 4;
if (family != AF_UNSPEC && family != AF_INET)
err("IPV4 address not allowed\n");
if (inet_pton(AF_INET, name, addr->data) <= 0)
err("Invalid IPV4 address: %s\n", name);
return;
}
static void get_prefix_1(inet_prefix *dst, char *arg, int family)
{
char *slash, *endp;
memset(dst, 0, sizeof(*dst));
slash = strchr(arg, '/');
if (!slash || slash[1] == '\0')
err("Missing prefix length\n");
*slash = 0;
get_addr_1(dst, arg, family);
dst->plen = strtoul(slash+1, &endp, 0);
if (*endp != '\0')
err("Invalid character in prefix length\n");
if (dst->plen > 8 * dst->bytelen)
err("Prefix length is too large\n");
*slash = '/';
}
static void get_netmask(inet_prefix *msk, const inet_prefix *dst)
{
int i, plen = dst->plen;
memset(msk, 0, sizeof(*msk));
msk->family = dst->family;
msk->bytelen = dst->bytelen;
for (i = 0; plen > 0 && i < dst->bytelen / sizeof(uint32_t); i++) {
uint32_t m = (plen > 32) ? ~0 : htonl(~0 << (32 - plen));
msk->data[i] = dst->data[i] & m;
plen -= 32;
}
}
int main(int argc, char **argv)
{
int family = AF_UNSPEC;
while (--argc) {
char *arg = *++argv;
inet_prefix dst, msk;
if (arg[0] == '-') {
switch(arg[1]) {
case '4':
family = AF_INET;
break;
case '6':
family = AF_INET6;
break;
default:
usage();
}
continue;
}
get_prefix_1(&dst, arg, family);
get_netmask(&msk, &dst);
if (memcmp(msk.data, dst.data, dst.bytelen) != 0) {
char buf[INET_ADDRSTRLEN];
err("Prefix not on a natural network boundary."
"Did you mean %s?\n",
inet_ntop(msk.family, msk.data, buf, sizeof buf));
}
}
return 0;
}
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