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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>
100 lines
4.6 KiB
C
100 lines
4.6 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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* Memory management strategies documentation file.
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*/
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/**
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* @page memory_management OpenVPN's memory management strategies
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*
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* This section describes several implementation details relating to
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* OpenVPN's memory management strategies.
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*
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* During operation, the OpenVPN process performs all kinds of operations
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* on blocks of data. Receiving packets, encrypting content, prepending
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* headers, etc. To make the programmer's job easier and to decrease the
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* likelihood of memory-related bugs, OpenVPN uses its own memory %buffer
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* library and garbage collection facilities. These are described in
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* brief here.
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*
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* @section memory_management_buffer The buffer structure
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*
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* The \c buffer structure is a wrapper around a block of dynamically
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* allocated memory which keeps track of the block's capacity \c
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* buffer.capacity and location in memory \c buffer.data. This structure
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* supports efficient prepending and appending within the allocated memory
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* through the use of offset \c buffer.offset and length \c buffer.len
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* fields. See the \c buffer documentation for more details on the
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* structure itself.
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*
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* OpenVPN's %buffer library, implemented in the \c buffer.h and \c
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* buffer.c files, contains many utility functions for working with \c
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* buffer structures. These functions facilitate common operations, such
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* as allocating, freeing, reading and writing to \c buffer structures,
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* and even offer several more advanced operations, such as string
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* matching and creating sub-buffers.
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*
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* Not only do these utility functions make working with \c buffer
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* structures easy, they also perform extensive error checking. Each
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* function, where necessary, checks whether enough space is available
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* before performing its actions. This minimizes the chance of bugs
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* leading to %buffer overflows and other vulnerabilities.
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*
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* @section memory_management_frame The frame structure
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*
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* The \c frame structure keeps track of the maximum allowed packet
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* geometries of a network connection.
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*
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* It is used, for example, to determine the size of \c buffer structures
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* in which to store data channel packets. This is done by having each
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* data channel processing module register the maximum amount of extra
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* space it will need for header prepending and content expansion in the
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* \c frame structure. Once these parameters are known, \c buffer
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* structures can be allocated, based on the \c frame parameters, so that
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* they are large enough to allow efficient prepending of headers and
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* processing of content.
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*
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* @section memory_management_garbage Garbage collection
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*
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* OpenVPN has many sizable functions which perform various actions
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* depending on their %context. This makes it difficult to know in advance
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* exactly how much memory must be allocated. The garbage collection
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* facilities are used to keep track of dynamic allocations, thereby
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* allowing easy collective freeing of the allocated memory.
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*
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* The garbage collection system is implemented by the \c gc_arena and \c
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* gc_entry structures. The arena represents a garbage collecting unit,
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* and contains a linked list of entries. Each entry represents one block
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* of dynamically allocated memory.
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*
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* The garbage collection system also contains various utility functions
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* for working with the garbage collection structures. These include
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* functions for initializing new arenas, allocating memory of a given
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* size and registering the allocation in an arena, and freeing all the
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* allocated memory associated with an arena.
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*/
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