src/fragroute/mod_ip_ttl.c
/*
* mod_ip_ttl.c
*
* Copyright (c) 2001 Dug Song <dugsong@monkey.org>
*
* $Id$
*/
#include "config.h"
#include "argv.h"
#include "mod.h"
#include "pkt.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct ip_ttl_data {
int ttl;
};
void *
ip_ttl_close(void *d)
{
if (d != NULL)
free(d);
return (NULL);
}
void *
ip_ttl_open(int argc, char *argv[])
{
struct ip_ttl_data *data;
if (argc != 2)
return (NULL);
if ((data = calloc(1, sizeof(*data))) == NULL)
return (NULL);
if ((data->ttl = strtol(argv[1], NULL, 10)) <= 0 || data->ttl > 255)
return (ip_ttl_close(data));
return (data);
}
int
ip_ttl_apply(void *d, struct pktq *pktq)
{
struct ip_ttl_data *data = (struct ip_ttl_data *)d;
struct pkt *pkt;
int ttldec;
TAILQ_FOREACH(pkt, pktq, pkt_next)
{
uint16_t eth_type = htons(pkt->pkt_eth->eth_type);
if (eth_type == ETH_TYPE_IP) {
ttldec = pkt->pkt_ip->ip_ttl - data->ttl;
pkt->pkt_ip->ip_ttl = data->ttl;
if (pkt->pkt_ip->ip_sum >= htons(0xffff - (ttldec << 8)))
pkt->pkt_ip->ip_sum += htons(ttldec << 8) + 1;
else
pkt->pkt_ip->ip_sum += htons(ttldec << 8);
} else if (eth_type == ETH_TYPE_IPV6) {
pkt->pkt_ip6->ip6_hlim = data->ttl;
}
}
return (0);
}
struct mod mod_ip_ttl = {
"ip_ttl", /* name */
"ip_ttl <ttl>", /* usage */
ip_ttl_open, /* open */
ip_ttl_apply, /* apply */
ip_ttl_close /* close */
};