/*
  *  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) 2002-2018 OpenVPN 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; if not, write to the Free Software Foundation, Inc.,
  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

  */
 

 #ifdef HAVE_CONFIG_H
 #include "config.h"
 #elif defined(_MSC_VER)
 #include "config-msvc.h"
 #endif
 

 #include "syshead.h"
 
 #include "proto.h"

 #include "error.h"

 
 #include "memdbg.h"
 
 /*

  * If raw tunnel packet is IPv<X>, return true and increment

  * buffer offset to start of IP header.
  */

 static

 bool

 is_ipv_X( int tunnel_type, struct buffer *buf, int ip_ver )

 {

     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) != (ip_ver == 6 ? OPENVPN_ETH_P_IPV6 : OPENVPN_ETH_P_IPV4))
         {
             return false;
         }
         offset = sizeof(struct openvpn_ethhdr);
     }
     else
     {
         return false;

     }
 

     ih = (const struct openvpn_iphdr *) (BPTR(buf) + offset);

     /* IP version is stored in the same bits for IPv4 or IPv6 header */
     if (OPENVPN_IPH_GET_VER(ih->version_len) == ip_ver)
     {
         return buf_advance(buf, offset);
     }
     else
     {
         return false;
     }

 }

 bool

 is_ipv4(int tunnel_type, struct buffer *buf)

 {
     return is_ipv_X( tunnel_type, buf, 4 );
 }
 bool

 is_ipv6(int tunnel_type, struct buffer *buf)

 {
     return is_ipv_X( tunnel_type, buf, 6 );
 }
 

 #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 /* ifdef PACKET_TRUNCATION_CHECK */