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Copy pathgre.c
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167 lines (135 loc) · 4.34 KB
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/*
* Copyright (c) 2003 Niels Provos <provos@citi.umich.edu>
* All rights reserved.
*
* 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
* 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
*/
#include <sys/types.h>
#include <sys/param.h>
#include "config.h"
#include <sys/queue.h>
#include <sys/tree.h>
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
#include <err.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <ctype.h>
#include <syslog.h>
#include <dnet.h>
#undef timeout_pending
#undef timeout_initialized
#include <event.h>
#include "honeyd.h"
#include "gre.h"
extern rand_t *honeyd_rand;
extern int honeyd_ttl;
static u_char pkt[IP_LEN_MAX];
int
gre_decapsulate(struct ip_hdr *oip, u_short oiplen,
struct ip_hdr **pip, u_short *piplen)
{
struct gre_hdr *gre;
struct ip_hdr *ip;
u_char *end = (u_char *)oip + oiplen;
u_char *data;
uint16_t flags, proto, iplen;
gre = (struct gre_hdr *)((u_char *)oip + (oip->ip_hl << 2));
data = (u_char *)(gre + 1);
if (end <= data)
return (-1);
/* We support only RFC 2784 */
flags = ntohs(gre->gre_flags);
if ((flags & ~GRE_CHECKSUM) != 0) {
syslog(LOG_DEBUG,
"%s: dropping RFC 1701 encapsulation: flags = %x",
__func__, flags);
return (-1);
}
proto = ntohs(gre->gre_proto);
if (proto != GRE_IP4PROTO) {
syslog(LOG_DEBUG,
"%s: dropping encapsulated packet: bad protocol %d",
__func__, proto);
return (-1);
}
if (!(flags & GRE_CHECKSUM))
data = GRE_NOCKSUM_DATA(gre);
/* Check for the proper length of the packet */
ip = (struct ip_hdr *)data;
if (data + sizeof(struct ip_hdr) > end)
return (-1);
iplen = ntohs(ip->ip_len);
if (data + iplen > end)
return (-1);
if (flags & GRE_CHECKSUM) {
u_int sum = gre->gre_sum, tmp;
gre->gre_sum = 0;
tmp = ip_cksum_add(gre, sizeof(struct gre_hdr) + iplen, 0);
tmp = ip_cksum_carry(tmp);
if (sum != tmp) {
syslog(LOG_INFO,
"%s: dropping encapsulated packet: bad checksum: %x vs %x",
__func__, ntohs(sum), ntohs(tmp));
return (-1);
}
}
*pip = ip;
*piplen = iplen;
return (0);
}
int
gre_encapsulate(ip_t *honeyd_ip, struct addr *src, struct addr *dst,
struct ip_hdr *iip, u_int iiplen)
{
struct ip_hdr *oip = (struct ip_hdr *)pkt;
struct gre_hdr *gre = (struct gre_hdr *)(oip + 1);
u_char *data = (u_char *)(gre + 1);
u_int iplen, sum;
iplen = sizeof(struct ip_hdr) + sizeof(struct gre_hdr) + iiplen;
if (iplen > sizeof(pkt)) {
syslog(LOG_ERR, "%s: packet too long: %d", __func__, iplen);
return (-1);
}
ip_pack_hdr(pkt, 0, iplen, rand_uint16(honeyd_rand),
0, honeyd_ttl, IP_PROTO_GRE, src->addr_ip, dst->addr_ip);
memset(gre, 0, sizeof(struct gre_hdr));
gre->gre_flags = htons(GRE_CHECKSUM | GRE_VERSION);
gre->gre_proto = htons(GRE_IP4PROTO);
/* Copy the payload */
memcpy(data, iip, iiplen);
/* Calculate the checksum */
sum = ip_cksum_add(gre, iiplen + sizeof(struct gre_hdr), 0);
gre->gre_sum = ip_cksum_carry(sum);
ip_checksum(oip, iplen);
return (ip_send(honeyd_ip, pkt, iplen) != iplen ? -1 : 0);
}