mirror/openvpn
0
0
Fork 0
mirror of https://github.com/OpenVPN/openvpn.git synced 2024-09-20 03:52:28 +02:00
Code

Added memory management documentation

Browse Source 
Signed-off-by: Adriaan de Jong <dejong@fox-it.com>
Acked-by: James Yonan <james@openvpn.net>
Signed-off-by: David Sommerseth <dazo@users.sourceforge.net>
This commit is contained in:
David Sommerseth 2011-07-28 23:25:07 +02:00
parent 0332b951ce
commit 5959e9def6
2 changed files with 147 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

57
buffer.h
View File

@ -42,14 +42,30 @@
#define BUF_INIT_TRACKING
#endif
/* basic buffer class for OpenVPN */
/**************************************************************************/
/**
* Wrapper structure for dynamically allocated memory.
*
* The actual content stored in a \c buffer structure starts at the memory
* location \c buffer.data \c + \c buffer.offset, and has a length of \c
* buffer.len bytes. This, together with the space available before and
* after the content, is represented in the pseudocode below:
@code
uint8_t *content_start = buffer.data + buffer.offset;
uint8_t *content_end = buffer.data + buffer.offset + buffer.len;
int prepend_capacity = buffer.offset;
int append_capacity = buffer.capacity - (buffer.offset + buffer.len);
@endcode
*/
struct buffer
{
int capacity; /* size of buffer allocated by malloc */
int offset; /* data starts at data + offset, offset > 0 to allow for efficient prepending */
int len; /* length of data that starts at data + offset */
uint8_t *data;
int capacity; /**< Size in bytes of memory allocated by
* \c malloc(). */
int offset; /**< Offset in bytes of the actual content
* within the allocated memory. */
int len; /**< Length in bytes of the actual content
* within the allocated memory. */
uint8_t *data; /**< Pointer to the allocated memory. */
#ifdef BUF_INIT_TRACKING
const char *debug_file;
@ -57,18 +73,41 @@ struct buffer
#endif
};
/* for garbage collection */
/**************************************************************************/
/**
* Garbage collection entry for one dynamically allocated block of memory.
*
* This structure represents one link in the linked list contained in a \c
* gc_arena structure. Each time the \c gc_malloc() function is called,
* it allocates \c sizeof(gc_entry) + the requested number of bytes. The
* \c gc_entry is then stored as a header in front of the memory address
* returned to the caller.
*/
struct gc_entry
{
struct gc_entry *next;
struct gc_entry *next; /**< Pointer to the next item in the
* linked list. */
};
/**
* Garbage collection arena used to keep track of dynamically allocated
* memory.
*
* This structure contains a linked list of \c gc_entry structures. When
* a block of memory is allocated using the \c gc_malloc() function, the
* allocation is registered in the function's \c gc_arena argument. All
* the dynamically allocated memory registered in a \c gc_arena can be
* freed using the \c gc_free() function.
*/
struct gc_arena
{
struct gc_entry *list;
struct gc_entry *list; /**< First element of the linked list of
* \c gc_entry structures. */
};
#define BPTR(buf) (buf_bptr(buf))
#define BEND(buf) (buf_bend(buf))
#define BLAST(buf) (buf_blast(buf))

99
doc_memory_management.h Normal file
View File

@ -0,0 +1,99 @@
/*
* OpenVPN -- An application to securely tunnel IP networks
* over a single TCP/UDP port, with support for SSL/TLS-based
* session authentication and key exchange,
* packet encryption, packet authentication, and
* packet compression.
*
* Copyright (C) 2010 Fox Crypto B.V. <openvpn@fox-it.com>
*
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program (see the file COPYING included with this
* distribution); if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/**
* @file
* Memory management strategies documentation file.
*/
/**
* @page memory_management OpenVPN's memory management strategies
*
* This section describes several implementation details relating to
* OpenVPN's memory management strategies.
*
* During operation, the OpenVPN process performs all kinds of operations
* on blocks of data. Receiving packets, encrypting content, prepending
* headers, etc. To make the programmer's job easier and to decrease the
* likelihood of memory-related bugs, OpenVPN uses its own memory %buffer
* library and garbage collection facilities. These are described in
* brief here.
*
* @section memory_management_buffer The buffer structure
*
* The \c buffer structure is a wrapper around a block of dynamically
* allocated memory which keeps track of the block's capacity \c
* buffer.capacity and location in memory \c buffer.data. This structure
* supports efficient prepending and appending within the allocated memory
* through the use of offset \c buffer.offset and length \c buffer.len
* fields. See the \c buffer documentation for more details on the
* structure itself.
*
* OpenVPN's %buffer library, implemented in the \c buffer.h and \c
* buffer.c files, contains many utility functions for working with \c
* buffer structures. These functions facilitate common operations, such
* as allocating, freeing, reading and writing to \c buffer structures,
* and even offer several more advanced operations, such as string
* matching and creating sub-buffers.
*
* Not only do these utility functions make working with \c buffer
* structures easy, they also perform extensive error checking. Each
* function, where necessary, checks whether enough space is available
* before performing its actions. This minimizes the chance of bugs
* leading to %buffer overflows and other vulnerabilities.
*
* @section memory_management_frame The frame structure
*
* The \c frame structure keeps track of the maximum allowed packet
* geometries of a network connection.
*
* It is used, for example, to determine the size of \c buffer structures
* in which to store data channel packets. This is done by having each
* data channel processing module register the maximum amount of extra
* space it will need for header prepending and content expansion in the
* \c frame structure. Once these parameters are known, \c buffer
* structures can be allocated, based on the \c frame parameters, so that
* they are large enough to allow efficient prepending of headers and
* processing of content.
*
* @section memory_management_garbage Garbage collection
*
* OpenVPN has many sizable functions which perform various actions
* depending on their %context. This makes it difficult to know in advance
* exactly how much memory must be allocated. The garbage collection
* facilities are used to keep track of dynamic allocations, thereby
* allowing easy collective freeing of the allocated memory.
*
* The garbage collection system is implemented by the \c gc_arena and \c
* gc_entry structures. The arena represents a garbage collecting unit,
* and contains a linked list of entries. Each entry represents one block
* of dynamically allocated memory.
*
* The garbage collection system also contains various utility functions
* for working with the garbage collection structures. These include
* functions for initializing new arenas, allocating memory of a given
* size and registering the allocation in an arena, and freeing all the
* allocated memory associated with an arena.
*/