OpenVPN
comp.h
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1 /*
2  * OpenVPN -- An application to securely tunnel IP networks
3  * over a single UDP port, with support for SSL/TLS-based
4  * session authentication and key exchange,
5  * packet encryption, packet authentication, and
6  * packet compression.
7  *
8  * Copyright (C) 2002-2021 OpenVPN Inc <sales@openvpn.net>
9  *
10  * This program is free software; you can redistribute it and/or modify
11  * it under the terms of the GNU General Public License version 2
12  * as published by the Free Software Foundation.
13  *
14  * This program is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17  * GNU General Public License for more details.
18  *
19  * You should have received a copy of the GNU General Public License along
20  * with this program; if not, write to the Free Software Foundation, Inc.,
21  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
22  */
23 
24 /*
25  * Generic compression support. Currently we support
26  * LZO 2 and LZ4.
27  */
28 #ifndef OPENVPN_COMP_H
29 #define OPENVPN_COMP_H
30 
31 #ifdef USE_COMP
32 
33 #include "buffer.h"
34 #include "mtu.h"
35 #include "common.h"
36 #include "status.h"
37 
38 /* algorithms */
39 #define COMP_ALG_UNDEF 0
40 #define COMP_ALG_STUB 1 /* support compression command byte and framing without actual compression */
41 #define COMP_ALG_LZO 2 /* LZO algorithm */
42 #define COMP_ALG_SNAPPY 3 /* Snappy algorithm (no longer supported) */
43 #define COMP_ALG_LZ4 4 /* LZ4 algorithm */
44 
45 
46 /* algorithm v2 */
47 #define COMP_ALGV2_UNCOMPRESSED 10
48 #define COMP_ALGV2_LZ4 11
49 /*
50  #define COMP_ALGV2_LZO 12
51  #define COMP_ALGV2_SNAPPY 13
52  */
53 
54 /* Compression flags */
55 #define COMP_F_ADAPTIVE (1<<0) /* COMP_ALG_LZO only */
56 #define COMP_F_ALLOW_COMPRESS (1<<1) /* not only downlink is compressed but also uplink */
57 #define COMP_F_SWAP (1<<2) /* initial command byte is swapped with last byte in buffer to preserve payload alignment */
58 #define COMP_F_ADVERTISE_STUBS_ONLY (1<<3) /* tell server that we only support compression stubs */
59 #define COMP_F_ALLOW_STUB_ONLY (1<<4) /* Only accept stub compression, even with COMP_F_ADVERTISE_STUBS_ONLY
60  * we still accept other compressions to be pushed */
61 #define COMP_F_MIGRATE (1<<5) /* push stub-v2 or comp-lzo no when we see a client with comp-lzo in occ */
62 #define COMP_F_ALLOW_ASYM (1<<6) /* Compression was explicitly set to allow asymetric compression */
63 
64 
65 /*
66  * Length of prepended prefix on compressed packets
67  */
68 #define COMP_PREFIX_LEN 1
69 
70 /*
71  * Prefix bytes
72  */
73 
74 /* V1 on wire codes */
75 /* Initial command byte to tell our peer if we compressed */
76 #define LZO_COMPRESS_BYTE 0x66
77 #define LZ4_COMPRESS_BYTE 0x69
78 #define NO_COMPRESS_BYTE 0xFA
79 #define NO_COMPRESS_BYTE_SWAP 0xFB /* to maintain payload alignment, replace this byte with last byte of packet */
80 
81 /* V2 on wire code */
82 #define COMP_ALGV2_INDICATOR_BYTE 0x50
83 #define COMP_ALGV2_UNCOMPRESSED_BYTE 0
84 #define COMP_ALGV2_LZ4_BYTE 1
85 #define COMP_ALGV2_LZO_BYTE 2
86 #define COMP_ALGV2_SNAPPY_BYTE 3
87 
88 /*
89  * Compress worst case size expansion (for any algorithm)
90  *
91  * LZO: len + len/8 + 128 + 3
92  * Snappy: len + len/6 + 32
93  * LZ4: len + len/255 + 16 (LZ4_COMPRESSBOUND(len))
94  */
95 #define COMP_EXTRA_BUFFER(len) ((len)/6 + 128 + 3 + COMP_PREFIX_LEN)
96 
97 /*
98  * Don't try to compress any packet smaller than this.
99  */
100 #define COMPRESS_THRESHOLD 100
101 
102 /* Forward declaration of compression context */
103 struct compress_context;
104 
105 /*
106  * Virtual methods and other static info for each compression algorithm
107  */
108 struct compress_alg
109 {
110  const char *name;
111  void (*compress_init)(struct compress_context *compctx);
112  void (*compress_uninit)(struct compress_context *compctx);
113  void (*compress)(struct buffer *buf, struct buffer work,
114  struct compress_context *compctx,
115  const struct frame *frame);
116 
117  void (*decompress)(struct buffer *buf, struct buffer work,
118  struct compress_context *compctx,
119  const struct frame *frame);
120 };
121 
122 /*
123  * Headers for each compression implementation
124  */
125 #ifdef ENABLE_LZO
126 #include "lzo.h"
127 #endif
128 
129 #ifdef ENABLE_LZ4
130 #include "comp-lz4.h"
131 #endif
132 
133 /*
134  * Information that basically identifies a compression
135  * algorithm and related flags.
136  */
137 struct compress_options
138 {
139  int alg;
140  unsigned int flags;
141 };
142 
143 /*
144  * Workspace union of all supported compression algorithms
145  */
146 union compress_workspace_union
147 {
148 #ifdef ENABLE_LZO
149  struct lzo_compress_workspace lzo;
150 #endif
151 #ifdef ENABLE_LZ4
152  struct lz4_workspace lz4;
153 #endif
154 };
155 
156 /*
157  * Context for active compression session
158  */
159 struct compress_context
160 {
161  unsigned int flags;
162  struct compress_alg alg;
163  union compress_workspace_union wu;
164 
165  /* statistics */
166  counter_type pre_decompress;
167  counter_type post_decompress;
168  counter_type pre_compress;
169  counter_type post_compress;
170 };
171 
172 extern const struct compress_alg comp_stub_alg;
173 extern const struct compress_alg compv2_stub_alg;
174 
175 struct compress_context *comp_init(const struct compress_options *opt);
176 
177 void comp_uninit(struct compress_context *compctx);
178 
179 void comp_add_to_extra_frame(struct frame *frame);
180 
181 void comp_add_to_extra_buffer(struct frame *frame);
182 
183 void comp_print_stats(const struct compress_context *compctx, struct status_output *so);
184 
185 void comp_generate_peer_info_string(const struct compress_options *opt, struct buffer *out);
186 
187 void compv2_escape_data_ifneeded(struct buffer *buf);
188 
189 static inline bool
190 comp_enabled(const struct compress_options *info)
191 {
192  return info->alg != COMP_ALG_UNDEF;
193 }
194 
195 static inline bool
196 comp_non_stub_enabled(const struct compress_options *info)
197 {
198  return info->alg != COMP_ALGV2_UNCOMPRESSED
199  && info->alg != COMP_ALG_STUB
200  && info->alg != COMP_ALG_UNDEF;
201 }
202 
203 #endif /* USE_COMP */
204 #endif /* ifndef OPENVPN_COMP_H */
Packet geometry parameters.
Definition: mtu.h:93
list flags
uint64_t counter_type
Definition: common.h:30
Wrapper structure for dynamically allocated memory.
Definition: buffer.h:60
Data Channel Compression module header file.