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