-@c ==================================================================
-@node The Protocol, , Security, Technical information
-@section Detailed protocol specifications
-
-
-
-@menu
-* Data protocol::
-* Meta protocol::
-@end menu
-
-@c ==================================================================
-@node Data protocol, Meta protocol, The Protocol, The Protocol
-@subsection The data protocol
-
-The data that is sent through the UDP connection is formatted as follows:
-
-@example
-
- bytes | Contents
-----------------------
- 0-1 | The length of this packet, including all leading fields
- 2-5 | The destination IP address
- 6-... | The encrypted data
-
-@end example
-
-The method that was used to encrypt the data should be made known via
-the meta-protocol, during early identification stages.
-
-
-@c ==================================================================
-@node Meta protocol, , Data protocol, The Protocol
-@subsection The Meta protocol
-
-This protocol consists of separate packets of information, that are
-generally formatted thusly:
-
-@example
-
- bytes | Contents
-----------------------
- 0 | The request ID
- 1-... | (Optional: arguments)
-
-@end example
-
-What follows is a listing of possible request IDs.
-
-@table @samp
-@item ACK
-Acknowledge. This generally means that the authentication has been
-accepted by the remote computer. Takes no arguments.
-
-@example
-
- bytes | Contents
-----------------------
- 0 | `1'
-
-@end example
-
-@item AUTH_S_INIT
-@itemx AUTH_C_INIT
-Obsolete. Use @samp{BASIC_INFO}.
-
-@item AUTH_S_SPP
-@itemx AUTH_C_SPP
-Obsolete. Use @samp{PASSPHRASE}.
-
-@item AUTH_S_SKEY
-@itemx AUTH_C_SKEY
-Obsolete. Use @samp{PUBLIC_KEY}, @samp{REQ_KEY} and @samp{ANS_KEY}.
-
-@item AUTH_S_SACK
-@itemx AUTH_C_RACK
-Obsolete. Use @samp{ACK}.
-
-@item TERMREQ
-A request to terminate this connection, for whatever reason.
-
-@example
-
- bytes | Contents
-----------------------
- 0 | `30'
- 1-4 | The VPN IP address of the host that has exited
-
-@end example
-
-
-@item PINGTIMEOUT
-Terminate connection, but the reason must be a ping timeout.
-
-@example
-
- bytes | Contents
-----------------------
- 0 | `31'
- 1-4 | The VPN IP address of the host that has exited
-
-@end example
-
-
-@item PING
-Send probe to the other end, if he hasn't returned a @samp{PONG} within
-10 seconds, the connection is considered to be dead and will be
-terminated, we should try to notify the other by sending a
-@samp{PINGTIMEOUT} packet.
-
-@example
-
- bytes | Contents
-----------------------
- 0 | `40'
-
-@end example
-
-
-@item PONG
-See explanation for @samp{PING}
-
-@example
-
- bytes | Contents
-----------------------
- 0 | `41'
-
-@end example
-
-
-@item ADD_HOST
-Send an @samp{ADD_HOST} packet if you want to propagate all your current
-connections to a new computer on a network. If we get this request, we
-must forward it to everyone that hasn't got it yet.
-
-@example
-
- bytes | Contents
-----------------------
- 0 | `60'
- 1-4 | The real IP address of the new host
- 5-8 | The VPN IP address of the new host
- 9-12 | The VPN netmask
- 13-14 | The port number that the new host listens on
-
-@end example
-
-
-@item BASIC_INFO
-This packet will contain all necessary basic information about
-ourselves, such as the port we listen on and our desired VPN IP address.
-
-@example
-
- bytes | Contents
-----------------------
- 0 | `61'
- 1 | The protocol version.
- | This chapter describes version 4.
- 2-3 | The port number that the new host listens on
- 4-7 | The VPN IP address of the new host
- 8-11 | The VPN netmask
-
-@end example
-
-
-@item PASSPHRASE
-Send an encrypted passphrase. Should be encrypted with our
-@strong{public} key, and it must reach us before a @samp{PUBLIC_KEY}
-request.
-
-@example
-
- bytes | Contents
-----------------------
- 0 | `62'
- 1-2 | The length of the encrypted passphrase
- 3-... | The encrypted passphrase
-
-@end example
-
-
-@item PUBLIC_KEY
-This is only used during authentication of a new connection, later on we
-may use @samp{REQ_KEY} and @samp{ANS_KEY}.
-
-@example
-
- bytes | Contents
-----------------------
- 0 | `63'
- 1-2 | The length of the key
- 3-... | The public key, given in base-36
-
-@end example
-
-
-@item HOLD
-@itemx RESUME
-Unused.
-
-@item CALCULATE
-@itemx CALC_RES
-@itemx ALMOST_KEY
-Never been in use.
-
-@item REQ_KEY
-Request a public key from someone and return it to the sender of this
-request using a @samp{ANS_KEY} packet. If we get such request, we must
-forward it to the connection that leads to the destination.
-
-@example
-
- bytes | Contents
-----------------------
- 0 | `160'
- 1-4 | The source VPN IP address
- 5-8 | The destination VPN IP address
- 9-14 | `0'
-
-@end example
-
-
-@item ANS_KEY
-Answer to a @samp{REQ_KEY} request, forward it to the destination if it
-is not meant for us.
-
-@example
-
- bytes | Contents
-----------------------
- 0 | `161'
- 1-4 | The source VPN IP address
- 5-8 | The destination VPN IP address
- 9-12 | The expiration date/time in seconds
- 13-14 | The key length
- 15-... | The public key in base-36
-
-@end example
-
-
-@item KEY_CHANGED
-The source computer wants to tell that it has regenerated its private
-and public keys, so anything going there must be encrypted with a new
-shared key.
-
-@example
-
- bytes | Contents
-----------------------
- 0 | `162'
- 1-4 | The source VPN IP address
-
-@end example
-
-
-@end table
-
-
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