Merge branch 't/gui_improvements'
[paraslash.git] / sideband.h
1 /*
2 * Copyright (C) 2012-2013 Andre Noll <maan@systemlinux.org>
3 *
4 * Licensed under the GPL v2. For licencing details see COPYING.
5 */
6
7 /** \file sideband.h exported symbols from sideband.c */
8
9 /**
10 * The valid sideband designators.
11 *
12 * A sideband packet consists of a header and a body. The header is sent prior
13 * to the data and contains the length of the buffer and the sideband
14 * designator, an integer. This scheme allows receivers to never read more data
15 * than what was specified in the header.
16 *
17 * The sideband designator indicates the type of the data. The authentication
18 * handshake between the command handler (child of para_server) and the client
19 * requires to exchange several small packages. Each such package is sent as a
20 * sideband package with a dedicated designator.
21 *
22 * Other designators are employed for normal command output and for log
23 * messages, where each loglevel corresponds to a sideband designator.
24 *
25 * Note that the values of this enum are part of the ABI, so never change
26 * or remove entries. Appending is OK though.
27 */
28 #define SB_DESIGNATORS \
29 /* Special value for receiving only: Accept any band. */ \
30 DESIGNATOR(ANY), \
31 /* This packet contains the authentication challenge. */ \
32 DESIGNATOR(CHALLENGE), \
33 /* I solved your challenge and here is the proof. */ \
34 DESIGNATOR(CHALLENGE_RESPONSE), \
35 /* Congratulations, you are authenticated. */ \
36 DESIGNATOR(PROCEED), \
37 /* This is the command I want you to execute. */ \
38 DESIGNATOR(COMMAND), \
39 /* Ready to receive a blob (addblob commands only). */ \
40 DESIGNATOR(AWAITING_DATA), \
41 /* Normal command output (default). */ \
42 DESIGNATOR(OUTPUT), \
43 /* LL_DEBUG. */ \
44 DESIGNATOR(DEBUG_LOG), \
45 /* LL_INFO. */ \
46 DESIGNATOR(INFO_LOG), \
47 /* LL_NOTICE. */ \
48 DESIGNATOR(NOTICE_LOG), \
49 /* LL_WARNING, */ \
50 DESIGNATOR(WARNING_LOG), \
51 /* LL_ERROR. */ \
52 DESIGNATOR(ERROR_LOG), \
53 /* LL_CRIT. */ \
54 DESIGNATOR(CRIT_LOG), \
55 /* LL_EMERG. */ \
56 DESIGNATOR(EMERG_LOG), \
57 /* Command terminated successfully. */ \
58 DESIGNATOR(EXIT__SUCCESS), \
59 /* Command failed. */ \
60 DESIGNATOR(EXIT__FAILURE), \
61
62 /** Just prefix with \p SBD_. */
63 #define DESIGNATOR(x) SBD_ ## x
64
65 /** All valid sideband designators. */
66 enum sb_designator {SB_DESIGNATORS NUM_SB_DESIGNATORS};
67 #undef DESIGNATOR
68 /** One stringified sideband designator. */
69 #define DESIGNATOR(x) #x
70 /** List of stringified sidedband designators. */
71 #define SB_DESIGNATORS_ARRAY SB_DESIGNATORS
72
73 /**
74 * The information contained in a sideband buffer.
75 *
76 * This structure is used for both sending and receiving data through a
77 * sideband channel. A pointer to a sideband buffer is passed to the sending
78 * side of a sideband while the receiving end yields a filled out structure
79 * once all data has been received.
80 */
81 struct sb_buffer {
82 /** Data and length. */
83 struct iovec iov;
84 /** The band designator. */
85 uint8_t band;
86 };
87
88 /**
89 * The opaque sideband context structure.
90 *
91 * A pointer to a structure of this type is returned by the two \a sb_new_xxx
92 * functions as an opaque handle. Other public functions of the sideband API
93 * take such a handle as a parameter.
94 */
95 struct sb_context;
96
97 /**
98 * The type of a sideband transformation.
99 *
100 * The sideband API allows to filter all data through an arbitrary
101 * transformation, which is useful for crypto purposes. The transformation may
102 * either transform the data in place, or return a pointer to a new buffer
103 * which contains the transformed source buffer. The internal sideband
104 * functions can tell the two types of transformations apart by checking
105 * whether the destination buffer coincides with the source buffer.
106 *
107 * If the transformation allocates a new buffer, it _must_ allocate one extra
108 * byte for \p NULL termination.
109 */
110 typedef void (*sb_transformation)(struct iovec *src, struct iovec *dst,
111 void *trafo_context);
112
113
114 /** Initialize a sideband buffer. */
115 #define SBB_INIT(_band, _buf, _numbytes) \
116 { \
117 .band = _band, \
118 .iov = { \
119 .iov_base = _buf, \
120 .iov_len = _numbytes \
121 } \
122 };
123
124 /* receiving */
125 struct sb_context *sb_new_recv(size_t max_size, sb_transformation t,
126 void *trafo_context);
127 void sb_get_recv_buffer(struct sb_context *c, struct iovec *iov);
128 int sb_received(struct sb_context *c, size_t nbytes, struct sb_buffer *result);
129
130 /* sending */
131 struct sb_context *sb_new_send(struct sb_buffer *sbb, bool dont_free,
132 sb_transformation t, void *trafo_context);
133 int sb_get_send_buffers(struct sb_context *c, struct iovec iov[2]);
134 bool sb_sent(struct sb_context *c, size_t nbytes);
135
136 void sb_free(struct sb_context *c);