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https://github.com/OpenVPN/openvpn.git
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34cb9132ef
Suitable for mature project. root - administrative stuff doc - documents src - sources tests - tests distro - distro specific files sample - samples SIDE EFFECT: many changes to rpm spec. Signed-off-by: Alon Bar-Lev <alon.barlev@gmail.com> Acked-by: Adriaan de Jong <dejong@fox-it.com> Signed-off-by: David Sommerseth <davids@redhat.com>
97 lines
4.5 KiB
C
97 lines
4.5 KiB
C
/*
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* OpenVPN -- An application to securely tunnel IP networks
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* over a single TCP/UDP port, with support for SSL/TLS-based
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* session authentication and key exchange,
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* packet encryption, packet authentication, and
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* packet compression.
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*
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* Copyright (C) 2010 Fox Crypto B.V. <openvpn@fox-it.com>
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*
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program (see the file COPYING included with this
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* distribution); if not, write to the Free Software Foundation, Inc.,
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* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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/**
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* @file
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* Data Channel Fragmentation module documentation file.
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*/
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/**
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* @defgroup fragmentation Data Channel Fragmentation module
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*
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* The Data Channel Fragmentation module offers fragmentation of data
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* channel packets.
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*
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* @par State structures
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* The Data Channel Fragmentation module stores its internal state in a \c
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* fragment_master structure. One such structure is present for each VPN
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* tunnel, and is stored in \c context.c2.fragment of the \c context
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* associated with that VPN tunnel.
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*
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* @par
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* The \c fragment_master structure contains one \c fragment_list
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* structure \c fragment_master.incoming. This is a list of \c fragment
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* structures, each of which can store the parts of one fragmented packet
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* while it is being reassembled. The \c fragment_master structure also
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* contains one \c buffer called \c fragment_master.outgoing, in which a
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* data channel large packet to be sent to a remote OpenVPN peer can be
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* broken up into parts to be sent one by one.
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*
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* @par Initialization and cleanup
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* Every time a new \c fragment_master is needed, it must be allocated and
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* initialized by the \c fragment_init() function. Similarly, every time
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* a \c fragment_master is no longer needed, it must be cleaned up using
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* the \c fragment_free() function. These functions take care of the
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* allocation and freeing of the \c fragment_master structure itself and
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* all internal memory required for the use of that structure. Note that
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* this behavior is different from that displayed by the \link compression
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* Data Channel Compression module\endlink.
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*
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* @par
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* Because of the one-to-one relationship between \c fragment_master
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* structures and VPN tunnels, the above-mentioned initialization and
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* cleanup functions are called directly from the \c init_instance() and
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* \c close_instance() functions, which control the initialization and
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* cleanup of VPN tunnel instances and their associated \c context
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* structures.
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*
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* @par Packet processing functions
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* This module receives data channel packets from the \link data_control
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* Data Channel Control module\endlink and processes them according to the
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* settings of the packet's VPN tunnel. The \link data_control Data
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* Channel Control module\endlink uses the following interface functions:
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* - For packets which will be sent to a remote OpenVPN peer: \c
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* fragment_outgoing() \n This function inspects data channel packets as
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* they are being made ready to be sent as VPN tunnel packets to a
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* remote OpenVPN peer. If a packet's size is larger than its
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* destination VPN tunnel's maximum transmission unit (MTU), then this
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* module breaks that packet up into smaller parts, each of which is
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* smaller than or equal to the VPN tunnel's MTU. See \c
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* fragment_outgoing() for details.
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* - For packets which have been received from a remote OpenVPN peer: \c
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* fragment_incoming() \n This function inspects data channel packets
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* that have been received from a remote OpenVPN peer through a VPN
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* tunnel. It reads the fragmentation header of the packet, and
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* depending on its value performs the appropriate action. See \c
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* fragment_incoming() for details.
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*
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* @par Settings that control this module's activity
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* Whether the Data Channel Fragmentation module is active or not depends
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* on the compile-time \c ENABLE_FRAGMENT preprocessor macro and the
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* runtime flag \c options.fragment, which gets its value from the
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* process's configuration sources, such as the configuration file and
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* commandline %options.
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*/
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