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1 office 1 /**
2 * @file msgproto.h
3 * @author Ambroz Bizjak <ambrop7@gmail.com>
4 *
5 * @section LICENSE
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * 3. Neither the name of the author nor the
15 * names of its contributors may be used to endorse or promote products
16 * derived from this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
20 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
21 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
22 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
23 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
24 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
25 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
27 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 *
29 * @section DESCRIPTION
30 *
31 * MsgProto is used by each pair of VPN peers as messages through the server, in order to
32 * establish a direct data connection. MsgProto operates on top of the SCProto message
33 * service, optionally secured with SSL; see {@link scproto.h} for details.
34 *
35 * MsgProto is built with BProto, the protocol and code generator for building
36 * custom message protocols. The BProto specification file is msgproto.bproto.
37 *
38 * It goes roughly like that:
39 *
40 * We name one peer the master and the other the slave. The master is the one with
41 * greater ID.
42 * When the peers get to know about each other, the master starts the binding procedure.
43 * It binds/listens to an address, and sends the slave the "youconnect" message. It
44 * contains a list of external addresses for that bind address and additional parameters.
45 * Each external address includes a string called a scope name. The slave, which receives
46 * the "youconnect" message, finds the first external address whose scope it recognizes,
47 * and attempts to establish connection to that address. If it finds an address, buf fails
48 * at connecting, it sends "youretry", which makes the master restart the binding procedure
49 * after some time. If it however does not recognize any external address, it sends
50 * "cannotconnect" back to the master.
51 * When the master receives the "cannotconnect", it tries the next bind address, as described
52 * above. When the master runs out of bind addresses, it sends "cannotbind" to the slave.
53 * When the slave receives the "cannotbind", it starts its own binding procedure, similarly
54 * to what is described above, with master and slave reversed. First difference is if the
55 * master fails to connect to a recognized address, it doesn't send "youretry", but rather
56 * simply restarts the whole procedure after some time. The other difference is when the
57 * slave runs out of bind addresses, it not only sends "cannotbind" to the master, but
58 * registers relaying to the master. And in this case, when the master receives the "cannotbind",
59 * it doesn't start the binding procedure all all over, but registers relaying to the slave.
60 */
61  
62 #ifndef BADVPN_PROTOCOL_MSGPROTO_H
63 #define BADVPN_PROTOCOL_MSGPROTO_H
64  
65 #include <generated/bproto_msgproto.h>
66  
67 #define MSGID_YOUCONNECT 1
68 #define MSGID_CANNOTCONNECT 2
69 #define MSGID_CANNOTBIND 3
70 #define MSGID_YOURETRY 5
71 #define MSGID_SEED 6
72 #define MSGID_CONFIRMSEED 7
73  
74 #define MSG_MAX_PAYLOAD (SC_MAX_MSGLEN - msg_SIZEtype - msg_SIZEpayload(0))
75  
76 #endif