/*
  *  OpenVPN -- An application to securely tunnel IP networks
  *             over a single TCP/UDP port, with support for SSL/TLS-based
  *             session authentication and key exchange,
  *             packet encryption, packet authentication, and
  *             packet compression.
  *

  *  Copyright (C) 2002-2010 OpenVPN Technologies, Inc. <sales@openvpn.net>

  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License version 2
  *  as published by the Free Software Foundation.
  *
  *  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 (see the file COPYING included with this
  *  distribution); if not, write to the Free Software Foundation, Inc.,
  *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */
 
 #include "syshead.h"
 
 #include "proto.h"

 #include "error.h"

 
 #include "memdbg.h"
 
 /*
  * If raw tunnel packet is IPv4, return true and increment
  * buffer offset to start of IP header.
  */
 bool
 is_ipv4 (int tunnel_type, struct buffer *buf)
 {
   int offset;
   const struct openvpn_iphdr *ih;
 
   verify_align_4 (buf);
   if (tunnel_type == DEV_TYPE_TUN)
     {
       if (BLEN (buf) < (int) sizeof (struct openvpn_iphdr))
 	return false;
       offset = 0;
     }
   else if (tunnel_type == DEV_TYPE_TAP)
     {
       const struct openvpn_ethhdr *eh;
       if (BLEN (buf) < (int)(sizeof (struct openvpn_ethhdr)
 	  + sizeof (struct openvpn_iphdr)))
 	return false;
       eh = (const struct openvpn_ethhdr *) BPTR (buf);
       if (ntohs (eh->proto) != OPENVPN_ETH_P_IPV4)
 	return false;
       offset = sizeof (struct openvpn_ethhdr);
     }
   else
     return false;
 
   ih = (const struct openvpn_iphdr *) (BPTR (buf) + offset);
 
   if (OPENVPN_IPH_GET_VER (ih->version_len) == 4)
     return buf_advance (buf, offset);
   else
     return false;
 }

 
 #ifdef PACKET_TRUNCATION_CHECK
 
 void
 ipv4_packet_size_verify (const uint8_t *data,
 			 const int size,
 			 const int tunnel_type,
 			 const char *prefix,
 			 counter_type *errors)
 {
   if (size > 0)
     {
       struct buffer buf;
 
       buf_set_read (&buf, data, size);
 
       if (is_ipv4 (tunnel_type, &buf))
 	{
 	  const struct openvpn_iphdr *pip;
 	  int hlen;
 	  int totlen;
 	  const char *msgstr = "PACKET SIZE INFO";
 	  unsigned int msglevel = D_PACKET_TRUNC_DEBUG;
 
 	  if (BLEN (&buf) < (int) sizeof (struct openvpn_iphdr))
 	    return;
   
 	  verify_align_4 (&buf);
 	  pip = (struct openvpn_iphdr *) BPTR (&buf);
 	  
 	  hlen = OPENVPN_IPH_GET_LEN (pip->version_len);
 	  totlen = ntohs (pip->tot_len);
 	  
 	  if (BLEN (&buf) != totlen)
 	    {
 	      msgstr = "PACKET TRUNCATION ERROR";
 	      msglevel = D_PACKET_TRUNC_ERR;
 	      if (errors)
 		++(*errors);
 	    }
 
 	  msg (msglevel, "%s %s: size=%d totlen=%d hlen=%d errcount=" counter_format,
 	       msgstr,
 	       prefix,
 	       BLEN (&buf),
 	       totlen,
 	       hlen,
 	       errors ? *errors : (counter_type)0);
 	}
     }
 }
 
 #endif