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rev_res4.c
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rev_res4.c
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/*
* dietsniff - a slim and static network sniffer for Linux
* Copyright (C) 2005 Hynek Schlawack <hynek@ularx.de>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
/* rev_res4.c - Contains everything concerning reverse resolution of
* IPv4-addresses.
*/
#ifdef USE_REV_RES
/* ANSI */
#include <stdlib.h>
/* POSIX */
#include <errno.h>
/* libowfat */
#include <dns.h>
#include <stralloc.h>
/* Custom */
#include "dietsniff.h"
#define HASHSIZE 257
struct node {
struct node *n;
int addr;
char *hn;
};
static inline int
hash(int x)
{
return x % HASHSIZE;
}
static struct node *hashtable[HASHSIZE];
static void
append(int addr, char *hn)
{
int q = hash(addr);
struct node *n = malloc(sizeof(struct node));
if (!n) error("Allocation of memory failed");
n->n = NULL;
n->addr = addr;
n->hn = hn;
if (__unlikely(hashtable[q])) {
struct node *p = hashtable[q];
for (;p->n; p = p->n);
p->n = n;
} else {
hashtable[q] = n;
}
}
char *
addr2name4(int addr)
{
struct node *n = hashtable[hash(addr)];
for (;n; n = n->n) {
if (__unlikely(addr == n->addr)) {
break;
}
}
if (__likely(n)) {
return n->hn;
} else {
stralloc out = { 0 };
if (dns_name4(&out, (char *) &addr) == -1) error("Reverse resolving failed");
append(addr, out.s);
return out.s;
}
}
#endif /* REV_RES */