1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3  * ppp-comp.h - Definitions for doing PPP packet compression.
4  *
5  * Copyright 1994-1998 Paul Mackerras.
6  */
7 #ifndef _NET_PPP_COMP_H
8 #define _NET_PPP_COMP_H
9 
10 #include <uapi/linux/ppp-comp.h>
11 
12 
13 struct module;
14 
15 /*
16  * The following symbols control whether we include code for
17  * various compression methods.
18  */
19 
20 #ifndef DO_BSD_COMPRESS
21 #define DO_BSD_COMPRESS	1	/* by default, include BSD-Compress */
22 #endif
23 #ifndef DO_DEFLATE
24 #define DO_DEFLATE	1	/* by default, include Deflate */
25 #endif
26 #define DO_PREDICTOR_1	0
27 #define DO_PREDICTOR_2	0
28 
29 /*
30  * Structure giving methods for compression/decompression.
31  */
32 
33 struct compressor {
34 	int	compress_proto;	/* CCP compression protocol number */
35 
36 	/* Allocate space for a compressor (transmit side) */
37 	void	*(*comp_alloc) (unsigned char *options, int opt_len);
38 
39 	/* Free space used by a compressor */
40 	void	(*comp_free) (void *state);
41 
42 	/* Initialize a compressor */
43 	int	(*comp_init) (void *state, unsigned char *options,
44 			      int opt_len, int unit, int opthdr, int debug);
45 
46 	/* Reset a compressor */
47 	void	(*comp_reset) (void *state);
48 
49 	/* Compress a packet */
50 	int     (*compress) (void *state, unsigned char *rptr,
51 			      unsigned char *obuf, int isize, int osize);
52 
53 	/* Return compression statistics */
54 	void	(*comp_stat) (void *state, struct compstat *stats);
55 
56 	/* Allocate space for a decompressor (receive side) */
57 	void	*(*decomp_alloc) (unsigned char *options, int opt_len);
58 
59 	/* Free space used by a decompressor */
60 	void	(*decomp_free) (void *state);
61 
62 	/* Initialize a decompressor */
63 	int	(*decomp_init) (void *state, unsigned char *options,
64 				int opt_len, int unit, int opthdr, int mru,
65 				int debug);
66 
67 	/* Reset a decompressor */
68 	void	(*decomp_reset) (void *state);
69 
70 	/* Decompress a packet. */
71 	int	(*decompress) (void *state, unsigned char *ibuf, int isize,
72 				unsigned char *obuf, int osize);
73 
74 	/* Update state for an incompressible packet received */
75 	void	(*incomp) (void *state, unsigned char *ibuf, int icnt);
76 
77 	/* Return decompression statistics */
78 	void	(*decomp_stat) (void *state, struct compstat *stats);
79 
80 	/* Used in locking compressor modules */
81 	struct module *owner;
82 	/* Extra skb space needed by the compressor algorithm */
83 	unsigned int comp_extra;
84 };
85 
86 /*
87  * The return value from decompress routine is the length of the
88  * decompressed packet if successful, otherwise DECOMP_ERROR
89  * or DECOMP_FATALERROR if an error occurred.
90  *
91  * We need to make this distinction so that we can disable certain
92  * useful functionality, namely sending a CCP reset-request as a result
93  * of an error detected after decompression.  This is to avoid infringing
94  * a patent held by Motorola.
95  * Don't you just lurve software patents.
96  */
97 
98 #define DECOMP_ERROR		-1	/* error detected before decomp. */
99 #define DECOMP_FATALERROR	-2	/* error detected after decomp. */
100 
101 extern int ppp_register_compressor(struct compressor *);
102 extern void ppp_unregister_compressor(struct compressor *);
103 #endif /* _NET_PPP_COMP_H */
104