2 * dnstap/dnstap_fstrm.h - Frame Streams protocol for dnstap
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40 * Definitions for the Frame Streams data transport protocol for
41 * dnstap message logs.
44 #ifndef DNSTAP_FSTRM_H
45 #define DNSTAP_FSTRM_H
47 /* Frame Streams data transfer protocol encode for DNSTAP messages.
48 * The protocol looks to be specified in the libfstrm library.
50 * Quick writeup for DNSTAP usage, from reading fstrm/control.h eloquent
51 * comments and fstrm/control.c for some bytesize details (the content type
54 * The Frame Streams can be unidirectional or bi-directional.
55 * bi-directional streams use control frame types READY, ACCEPT and FINISH.
56 * uni-directional streams use control frame types START and STOP.
57 * unknown control frame types should be ignored by the receiver, they
58 * do not change the data frame encoding.
60 * bi-directional control frames implement a simple handshake protocol
61 * between sender and receiver.
63 * The uni-directional control frames have one start and one stop frame,
64 * before and after the data. The start frame can have a content type.
65 * The start and stop frames are not optional.
67 * data frames are preceded by 4byte length, bigendian.
68 * zero length data frames are not possible, they are an escape that
69 * signals the presence of a control frame.
71 * a control frame consists of 0 value in 4byte bigendian, this is really
72 * the data frame length, with 0 the escape sequence that indicates one
73 * control frame follows.
74 * Then, 4byte bigendian, length of the control frame message.
75 * Then, the control frame payload (of that length). with in it:
76 * 4byte bigendian, control type (eg. START, STOP, READY, ACCEPT, FINISH).
77 * perhaps nothing more (STOP, FINISH), but for other types maybe
79 * 4byte bigendian, the control-field-type, currently only content-type.
80 * 4byte bigendian, length of the string for this option.
81 * .. bytes of that string.
83 * The START type can have only one field. Field max len 256.
84 * control frame max frame length 512 (excludes the 0-escape and control
85 * frame length bytes).
87 * the bidirectional type of transmission is like this:
88 * client sends READY (with content type included),
89 * client waits for ACCEPT (with content type included),
90 * client sends START (with matched content type from ACCEPT)
93 * client waits for FINISH frame.
97 /** max length of Frame Streams content type field string */
98 #define FSTRM_CONTENT_TYPE_LENGTH_MAX 256
99 /** control frame value to denote the control frame ACCEPT */
100 #define FSTRM_CONTROL_FRAME_ACCEPT 0x01
101 /** control frame value to denote the control frame START */
102 #define FSTRM_CONTROL_FRAME_START 0x02
103 /** control frame value to denote the control frame STOP */
104 #define FSTRM_CONTROL_FRAME_STOP 0x03
105 /** control frame value to denote the control frame READY */
106 #define FSTRM_CONTROL_FRAME_READY 0x04
107 /** control frame value to denote the control frame FINISH */
108 #define FSTRM_CONTROL_FRAME_FINISH 0x05
109 /** the constant that denotes the control field type that is the
110 * string for the content type of the stream. */
111 #define FSTRM_CONTROL_FIELD_TYPE_CONTENT_TYPE 0x01
112 /** the content type for DNSTAP frame streams */
113 #define DNSTAP_CONTENT_TYPE "protobuf:dnstap.Dnstap"
116 * This creates an FSTRM control frame of type START.
117 * @param contenttype: a zero delimited string with the content type.
118 * eg. use the constant DNSTAP_CONTENT_TYPE, which is defined as
119 * "protobuf:dnstap.Dnstap", for a dnstap frame stream.
120 * @param len: if a buffer is returned this is the length of that buffer.
121 * @return NULL on malloc failure. Returns a malloced buffer with the
122 * protocol message. The buffer starts with the 4 bytes of 0 that indicate
123 * a control frame. The buffer should be sent without preceding it with
124 * the 'len' variable (like data frames are), but straight the content of the
125 * buffer, because the lengths are included in the buffer. This is so that
126 * the zero control indicator can be included before the control frame length.
128 void* fstrm_create_control_frame_start(char* contenttype, size_t* len);
131 * This creates an FSTRM control frame of type READY.
132 * @param contenttype: a zero delimited string with the content type.
133 * eg. use the constant DNSTAP_CONTENT_TYPE, which is defined as
134 * "protobuf:dnstap.Dnstap", for a dnstap frame stream.
135 * @param len: if a buffer is returned this is the length of that buffer.
136 * @return NULL on malloc failure. Returns a malloced buffer with the
137 * protocol message. The buffer starts with the 4 bytes of 0 that indicate
138 * a control frame. The buffer should be sent without preceding it with
139 * the 'len' variable (like data frames are), but straight the content of the
140 * buffer, because the lengths are included in the buffer. This is so that
141 * the zero control indicator can be included before the control frame length.
143 void* fstrm_create_control_frame_ready(char* contenttype, size_t* len);
146 * This creates an FSTRM control frame of type STOP.
147 * @param len: if a buffer is returned this is the length of that buffer.
148 * @return NULL on malloc failure. Returns a malloced buffer with the
149 * protocol message. The buffer starts with the 4 bytes of 0 that indicate
150 * a control frame. The buffer should be sent without preceding it with
151 * the 'len' variable (like data frames are), but straight the content of the
152 * buffer, because the lengths are included in the buffer. This is so that
153 * the zero control indicator can be included before the control frame length.
155 void* fstrm_create_control_frame_stop(size_t* len);
158 * This creates an FSTRM control frame of type ACCEPT.
159 * @param contenttype: a zero delimited string with the content type.
160 * for dnstap streams use DNSTAP_CONTENT_TYPE.
161 * @param len: if a buffer is returned this is the length of that buffer.
162 * @return NULL on malloc failure. Returns a malloced buffer with the
163 * protocol message. The buffer starts with the 4 bytes of 0 that indicate
164 * a control frame. The buffer should be sent without preceding it with
165 * the 'len' variable (like data frames are), but straight the content of the
166 * buffer, because the lengths are included in the buffer. This is so that
167 * the zero control indicator can be included before the control frame length.
169 void* fstrm_create_control_frame_accept(char* contenttype, size_t* len);
172 * This creates an FSTRM control frame of type FINISH.
173 * @param len: if a buffer is returned this is the length of that buffer.
174 * @return NULL on malloc failure. Returns a malloced buffer with the
175 * protocol message. The buffer starts with the 4 bytes of 0 that indicate
176 * a control frame. The buffer should be sent without preceding it with
177 * the 'len' variable (like data frames are), but straight the content of the
178 * buffer, because the lengths are included in the buffer. This is so that
179 * the zero control indicator can be included before the control frame length.
181 void* fstrm_create_control_frame_finish(size_t* len);
184 * Return string that describes a control packet. For debug, logs.
185 * Like 'start content-type(protobuf:dnstap.Dnstap)' or 'stop'.
186 * @param pkt: the packet data, that is the data after the 4 zero start
187 * bytes and 4 length bytes.
188 * @param len: the length of the control packet data, in pkt. This is the
189 * ntohl of the 4 bytes length preceding the data.
190 * @return zero delimited string, malloced. Or NULL on malloc failure.
192 char* fstrm_describe_control(void* pkt, size_t len);
194 #endif /* DNSTAP_FSTRM_H */