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-rw-r--r--proto.c74
1 files changed, 74 insertions, 0 deletions
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+/*
+ * 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) 2002-2005 OpenVPN Solutions LLC <info@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
+ */
+
+#ifdef WIN32
+#include "config-win32.h"
+#else
+#include "config.h"
+#endif
+
+#include "syshead.h"
+
+#include "proto.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;
+}