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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
+ */
+
+#ifndef PROTO_H
+#define PROTO_H
+
+#include "buffer.h"
+
+/*
+ * Tunnel types
+ */
+#define DEV_TYPE_UNDEF 0
+#define DEV_TYPE_NULL 1
+#define DEV_TYPE_TUN 2 /* point-to-point IP tunnel */
+#define DEV_TYPE_TAP 3 /* ethernet (802.3) tunnel */
+
+/*
+ * IP and Ethernet protocol structs. For portability,
+ * OpenVPN needs its own definitions of these structs, and
+ * names have been adjusted to avoid collisions with
+ * native structs.
+ */
+
+#define OPENVPN_ETH_ALEN 6 /* ethernet address length */
+struct openvpn_ethhdr
+{
+ uint8_t dest[OPENVPN_ETH_ALEN]; /* destination ethernet addr */
+ uint8_t source[OPENVPN_ETH_ALEN]; /* source ethernet addr */
+
+# define OPENVPN_ETH_P_IPV4 0x0800 /* IPv4 protocol */
+# define OPENVPN_ETH_P_IPV6 0x86DD /* IPv6 protocol */
+# define OPENVPN_ETH_P_ARP 0x0806 /* ARP protocol */
+ uint16_t proto; /* packet type ID field */
+};
+
+struct openvpn_iphdr {
+# define OPENVPN_IPH_GET_VER(v) (((v) >> 4) & 0x0F)
+# define OPENVPN_IPH_GET_LEN(v) (((v) & 0x0F) << 2)
+ uint8_t version_len;
+
+ uint8_t tos;
+ uint16_t tot_len;
+ uint16_t id;
+
+# define OPENVPN_IP_OFFMASK 0x1fff
+ uint16_t frag_off;
+
+ uint8_t ttl;
+
+# define OPENVPN_IPPROTO_IGMP 2 /* IGMP protocol */
+# define OPENVPN_IPPROTO_TCP 6 /* TCP protocol */
+# define OPENVPN_IPPROTO_UDP 17 /* UDP protocol */
+ uint8_t protocol;
+
+ uint16_t check;
+ uint32_t saddr;
+ uint32_t daddr;
+ /*The options start here. */
+};
+
+/*
+ * UDP header
+ */
+struct openvpn_udphdr {
+ uint16_t source;
+ uint16_t dest;
+ uint16_t len;
+ uint16_t check;
+};
+
+/*
+ * TCP header, per RFC 793.
+ */
+struct openvpn_tcphdr {
+ uint16_t source; /* source port */
+ uint16_t dest; /* destination port */
+ uint32_t seq; /* sequence number */
+ uint32_t ack_seq; /* acknowledgement number */
+
+# define OPENVPN_TCPH_GET_DOFF(d) (((d) & 0xF0) >> 2)
+ uint8_t doff_res;
+
+# define OPENVPN_TCPH_FIN_MASK (1<<0)
+# define OPENVPN_TCPH_SYN_MASK (1<<1)
+# define OPENVPN_TCPH_RST_MASK (1<<2)
+# define OPENVPN_TCPH_PSH_MASK (1<<3)
+# define OPENVPN_TCPH_ACK_MASK (1<<4)
+# define OPENVPN_TCPH_URG_MASK (1<<5)
+# define OPENVPN_TCPH_ECE_MASK (1<<6)
+# define OPENVPN_TCPH_CWR_MASK (1<<7)
+ uint8_t flags;
+
+ uint16_t window;
+ uint16_t check;
+ uint16_t urg_ptr;
+};
+
+#define OPENVPN_TCPOPT_EOL 0
+#define OPENVPN_TCPOPT_NOP 1
+#define OPENVPN_TCPOPT_MAXSEG 2
+#define OPENVPN_TCPOLEN_MAXSEG 4
+
+/*
+ * The following macro is used to update an
+ * internet checksum. "acc" is a 32-bit
+ * accumulation of all the changes to the
+ * checksum (adding in old 16-bit words and
+ * subtracting out new words), and "cksum"
+ * is the checksum value to be updated.
+ */
+#define ADJUST_CHECKSUM(acc, cksum) { \
+ (acc) += (cksum); \
+ if ((acc) < 0) { \
+ (acc) = -(acc); \
+ (acc) = ((acc) >> 16) + ((acc) & 0xffff); \
+ (acc) += (acc) >> 16; \
+ (cksum) = (uint16_t) ~(acc); \
+ } else { \
+ (acc) = ((acc) >> 16) + ((acc) & 0xffff); \
+ (acc) += (acc) >> 16; \
+ (cksum) = (uint16_t) (acc); \
+ } \
+}
+
+/*
+ * We are in a "liberal" position with respect to MSS,
+ * i.e. we assume that MSS can be calculated from MTU
+ * by subtracting out only the IP and TCP header sizes
+ * without options.
+ *
+ * (RFC 879, section 7).
+ */
+#define MTU_TO_MSS(mtu) (mtu - sizeof(struct openvpn_iphdr) \
+ - sizeof(struct openvpn_tcphdr))
+
+/*
+ * 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);
+
+#endif