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/*
* Copyright (c) 2014 by Farsight Security, Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
*/
#ifndef FSTRM_CONTROL_H
#define FSTRM_CONTROL_H
/**
* \defgroup fstrm_control fstrm_control
*
* `fstrm_control` is an interface for encoding and decoding Frame Streams
* control frames.
*
* Two types of frames are possible in a Frame Streams byte stream: **data
* frames** and **control frames**. Both are variable length byte sequences
* prefixed by a 32-bit big endian unsigned integer (the **frame length**)
* specifying the length of the following byte sequence. If this frame length
* value is greater than zero, the **frame length** specifies the **data frame
* length**, and a data frame follows it. If the frame length is zero (i.e., it
* is the four byte sequence `00 00 00 00`), this is an **escape sequence**,
* which means that a control frame follows. The control frame itself is
* prefixed by a 32-bit big endian unsigned integer (the **control frame
* length**) specifying the length of the following **control frame payload**.
*
* There are two types of control frames used for uni-directional streams:
* `START` and `STOP`. These control frame types bracket the stream of data
* frames. `START` indicates the beginning of the stream and communicates
* metadata about the stream to follow, and `STOP` indicates the end of the
* stream.
*
* Bi-directional streams make use of three additional control frame types:
* `READY`, `ACCEPT`, and `FINISH`. These control frame types are used in a
* simple handshake protocol between sender and receiver.
*
* A uni-directional Frame Streams byte stream normally consists of the
* following:
*
* 1. The `START` control frame.
* 2. A sequence of zero or more data frames or control frames that are not of
* the control frame types `START`, `STOP`, `ACCEPT`, `READY`, or
* `FINISH`.
* 3. The `STOP` control frame.
*
* The `START` and `STOP` control frames are not optional. The `START` control
* frame must appear at the beginning of the byte stream, and the `STOP` control
* frame must appear at the end of the byte stream. (If the byte stream has an
* end.) `START` control frames must not appear anywhere other than at the
* beginning of the byte stream, and `STOP` control frames must not appear
* anywhere other than at the end of the byte stream. Only one `START` control
* frame and only one `STOP` control frame may appear in a Frame Streams byte
* stream.
*
* Control frames may optionally include zero or more **control frame fields**.
* There is currently one type of control frame field defined: `CONTENT_TYPE`.
* This field specifies a variable length byte sequence describing the encoding
* of data frames that appear in the Frame Streams byte stream. This field is
* used by cooperating programs to unambiguously identify how to interpret the
* data frames in a particular Frame Streams byte stream. For instance, this
* field may specify a particular schema to use to interpret the data frames
* appearing in the byte stream. Zero, one, or more `CONTENT_TYPE` fields may
* appear in `READY` or `ACCEPT` control frames. Zero or one `CONTENT_TYPE`
* fields may appear in `START` control frames. No `CONTENT_TYPE` fields may
* appear in `STOP` or `FINISH` control frames.
*
* A uni-directional Frame Streams encoder would normally produce a byte stream
* as follows:
*
* 1. Write the `START` **control frame**.
* + At the start of the byte stream, write the four byte **escape
* sequence** `00 00 00 00` that precedes control frames.
* + Write the **control frame length** as a 32-bit big endian unsigned
* integer.
* + Write the **control frame payload**. It must be a `START` control
* frame. It may optionally specify a `CONTENT_TYPE` field.
* 2. Write zero or more **data frames**.
* 3. Write the `STOP` **control frame**.
* + At the start of the byte stream, write the four byte **escape
* sequence** `00 00 00 00` that precedes control frames.
* + Write the **control frame length** as a 32-bit big endian unsigned
* integer.
* + Write the **control frame payload**. It must be a `STOP` control
* frame.
*
* A uni-directional Frame Streams decoder would normally process the byte
* stream as follows:
*
* 1. Read the `START` control frame.
* + At the start of the byte stream, read the four byte **escape
* sequence** `00 00 00 00` that precedes control frames.
* + Read the 32-bit big endian unsigned integer specifying the **control
* frame length**.
* + Decode the **control frame payload**. It must be a `START` control
* frame. It may optionally specify a `CONTENT_TYPE` field.
* 2. Repeatedly read data frames or control frames following the `START`
* control frame.
* + Read the **frame length**, a 32-bit big endian unsigned integer.
* + If the **frame length** is zero, a control frame follows:
* + Read the 32-bit big endian unsigned integer specifying the
* **control frame length**.
* + Decode the **control frame payload**. If it is a `STOP`
* control frame, the end of the Frame Streams byte stream has
* occurred, and no frames follow. Break out of the decoding loop
* and halt processing. (`READY`, `ACCEPT`, `START`, and `FINISH`
* may not occur here. For forward compatibility, control frames of
* types other than the types `READY`, `ACCEPT`, `START`, `STOP`,
* and `FINISH` must be ignored here. No control frames specified
* in the future may alter the encoding of succeeding frames.)
* + If the **frame length** is non-zero, it specifies the number of bytes
* in the following **data frame**. Consume these bytes from the byte
* stream.
*
* The functions fstrm_control_encode() and fstrm_control_decode() are provided
* to encode and decode control frames. See the detailed descriptions of those
* functions for code examples showing their usage.
*
* @{
*/
/**
* The maximum length in bytes of an "Accept", "Start", or "Stop" control frame
* payload. This excludes the escape sequence and the control frame length.
*/
#define FSTRM_CONTROL_FRAME_LENGTH_MAX 512
/**
* The maximum length in bytes of a "Content Type" control frame field payload.
* This excludes the field type and payload length.
*/
#define FSTRM_CONTROL_FIELD_CONTENT_TYPE_LENGTH_MAX 256
/**
* Control frame types.
*/
typedef enum {
/** Control frame type value for "Accept" control frames. */
FSTRM_CONTROL_ACCEPT = 0x01,
/** Control frame type value for "Start" control frames. */
FSTRM_CONTROL_START = 0x02,
/** Control frame type value for "Stop" control frames. */
FSTRM_CONTROL_STOP = 0x03,
/** Control frame type value for "Ready" control frames. */
FSTRM_CONTROL_READY = 0x04,
/** Control frame type value for "Finish" control frames. */
FSTRM_CONTROL_FINISH = 0x05,
} fstrm_control_type;
/**
* Control frame field types. These are optional fields that can appear in
* control frames.
*/
typedef enum {
/**
* Control frame field type value for the "Content Type" control frame
* option.
*/
FSTRM_CONTROL_FIELD_CONTENT_TYPE = 0x01,
} fstrm_control_field;
/**
* Flags for controlling the behavior of the encoding and decoding functions.
*/
typedef enum {
/**
* Set to control whether to include the control frame header in
* encoding/decoding operations.
*
* Causes fstrm_control_encode() and fstrm_control_encoded_size() to
* include the control frame header containing the escape sequence and
* control frame payload length in the encoded output. Otherwise, only
* the control frame payload itself is encoded.
*
* Tells fstrm_control_decode() that the input buffer to be decoded
* begins with the control frame header containing the escape sequence
* and control frame payload length. (Note that this requires the caller
* to peek at the input buffer to calculate the right buffer length.)
* Otherwise, the input buffer begins with the control frame payload.
*/
FSTRM_CONTROL_FLAG_WITH_HEADER = (1 << 0),
} fstrm_control_flag;
/**
* Convert an `fstrm_control_type` enum value to a string representation.
* Unknown values are represented as `"FSTRM_CONTROL_UNKNOWN"`.
*
* \param type The `fstrm_control_type` enum value.
* \return The string representation of the enum value. (Always non-NULL.)
*/
const char *
fstrm_control_type_to_str(fstrm_control_type type);
/**
* Convert an `fstrm_control_field` enum value to a string representation.
* Unknown values are represented as `"FSTRM_CONTROL_FIELD_UNKNOWN"`.
*
* \param f_type The `fstrm_control_field` enum value.
* \return The string representation of the enum value. (Always non-NULL.)
*/
const char *
fstrm_control_field_type_to_str(fstrm_control_field f_type);
/**
* Initialize an `fstrm_control` object. This object represents Frame Streams
* control frames and is used for encoding and decoding control frames.
*
* \return
* An `fstrm_control` object.
*/
struct fstrm_control *
fstrm_control_init(void);
/**
* Destroy an `fstrm_control` object.
*
* \param[in] c
* Pointer to an `fstrm_control` object.
*/
void
fstrm_control_destroy(struct fstrm_control **c);
/**
* Reinitialize an `fstrm_control` object. This resets the internal state to
* default values.
*
* \param c
* `fstrm_control` object.
*/
void
fstrm_control_reset(struct fstrm_control *c);
/**
* Retrieve the type of the control frame.
*
* \param c
* `fstrm_control` object.
* \param[out] type
* Type of the control frame.
*
* \retval #fstrm_res_success
* \retval #fstrm_res_failure
*/
fstrm_res
fstrm_control_get_type(
const struct fstrm_control *c,
fstrm_control_type *type);
/**
* Set the type of the control frame.
*
* \param c
* `fstrm_control` object.
* \param[in] type
* Type of the control frame.
*
* \retval #fstrm_res_success
* \retval #fstrm_res_failure
*/
fstrm_res
fstrm_control_set_type(
struct fstrm_control *c,
fstrm_control_type type);
/**
* Retrieve the number of "Content Type" fields present in the control frame.
*
* \param c
* `fstrm_control` object.
* \param[out] n_content_type
* The number of "Content Type" fields.
*
* \retval #fstrm_res_success
* \retval #fstrm_res_failure
*/
fstrm_res
fstrm_control_get_num_field_content_type(
const struct fstrm_control *c,
size_t *n_content_type);
/**
* Retrieve a "Content Type" field from the control frame. This function
* returns a reference which must not be modified. Control frames may contain
* zero, one, or more "Content Type" fields.
*
* \see fstrm_control_get_num_field_content_type()
*
* \param c
* `fstrm_control` object.
* \param[in] idx
* The index of the "Content Type" field to retrieve.
* \param[out] content_type
* Pointer to where the reference to the "Content Type" string will be
* stored. Note that this string is not NUL-terminated and may contain
* embedded NULs.
* \param[out] len_content_type
* The number of bytes in `content_type`.
*
* \retval #fstrm_res_success
* The control frame has a "Content Type" field.
* \retval #fstrm_res_failure
* The control frame does not have a "Content Type" field.
*/
fstrm_res
fstrm_control_get_field_content_type(
const struct fstrm_control *c,
const size_t idx,
const uint8_t **content_type,
size_t *len_content_type);
/**
* Add a "Content Type" field to the control frame. This function makes a copy
* of the provided string. This function may be called multiple times, in which
* case multiple "Content Type" fields will be added to the control frame.
*
* The "Content Type" fields are removed on a call to fstrm_control_reset().
*
* \param c
* `fstrm_control` object.
* \param[in] content_type
* The "Content Type" string to copy. Note that this string is not
* NUL-terminated and may contain embedded NULs.
* \param[in] len_content_type
* The number of bytes in `content_type`.
*
* \retval #fstrm_res_success
* The "Content Type" field was successfully added.
* \retval #fstrm_res_failure
* The "Content Type" string is too long.
*/
fstrm_res
fstrm_control_add_field_content_type(
struct fstrm_control *c,
const uint8_t *content_type,
size_t len_content_type);
/**
* Check if the control frame matches a particular content type value. That is,
* the content type given in the `match` and `len_match` parameters is checked
* for compatibility with the content types (if any) specified in the control
* frame.
*
* \param c
* `fstrm_control` object.
* \param match
* The "Content Type" string to match. Note that this string is not
* NUL-terminated and may contain embedded NULs. May be NULL, in which case
* the control frame must not have any content type fields in order to
* match.
* \param len_match
* The number of bytes in `match`.
*
* \retval #fstrm_res_success
* A match was found.
* \retval #fstrm_res_failure
* A match was not found.
*/
fstrm_res
fstrm_control_match_field_content_type(
const struct fstrm_control *c,
const uint8_t *match,
const size_t len_match);
/**
* Decode a control frame from a buffer. The buffer starts with either the
* escape sequence or the control frame payload depending on whether the
* `FSTRM_CONTROL_FLAG_WITH_HEADER` flag is set or not. In either case, the
* 'len_control_frame' parameter must be exact. Underflow or overflow is not
* permitted.
*
* The following code example shows a function that decodes a control frame
* payload:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
static fstrm_res
decode_control_frame(const void *control_frame, size_t len_control_frame)
{
fstrm_res res;
fstrm_control_type c_type;
struct fstrm_control *c;
uint32_t flags = 0;
c = fstrm_control_init();
res = fstrm_control_decode(c, control_frame, len_control_frame, flags);
if (res != fstrm_res_success) {
puts("fstrm_control_decode() failed.");
fstrm_control_destroy(&c);
return res;
}
res = fstrm_control_get_type(c, &c_type);
if (res != fstrm_res_success) {
puts("fstrm_control_get_type() failed.");
fstrm_control_destroy(&c);
return res;
}
printf("The control frame is of type %s (%u).\n",
fstrm_control_type_to_str(c_type), c_type);
size_t n_content_type;
res = fstrm_control_get_num_field_content_type(c, &n_content_type);
if (res != fstrm_res_success) {
puts("fstrm_control_get_num_field_content_type() failed.");
fstrm_control_destroy(&c);
return res;
}
const uint8_t *content_type;
size_t len_content_type;
for (size_t idx = 0; idx < n_content_type; idx++) {
res = fstrm_control_get_field_content_type(c, idx,
&content_type, &len_content_type);
if (res == fstrm_res_success) {
printf("The control frame has a CONTENT_TYPE field of length %zd.\n",
len_content_type);
}
}
fstrm_control_destroy(&c);
return fstrm_res_success;
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* \param c
* `fstrm_control` object. Its state will be overwritten.
* \param[in] control_frame
* Buffer containing the serialized control frame.
* \param[in] len_control_frame
* The number of bytes in `control_frame`. This parameter must specify the
* exact number of bytes in the control frame.
* \param flags
* Flags controlling the decoding process. See #fstrm_control_flag.
*
* \retval #fstrm_res_success
* \retval #fstrm_res_failure
*/
fstrm_res
fstrm_control_decode(
struct fstrm_control *c,
const void *control_frame,
size_t len_control_frame,
const uint32_t flags);
/**
* Calculate the number of bytes needed to serialize the control frame.
*
* \param c
* `fstrm_control` object.
* \param[out] len_control_frame
* The number of bytes needed to encode `c`.
* \param flags
* Flags controlling the encoding process. See #fstrm_control_flag.
*
* \retval #fstrm_res_success
* \retval #fstrm_res_failure
*/
fstrm_res
fstrm_control_encoded_size(
const struct fstrm_control *c,
size_t *len_control_frame,
const uint32_t flags);
/**
* Encode a control frame into a buffer. Since a Frame Streams control frame is
* a variable length byte sequence of up to #FSTRM_CONTROL_FRAME_LENGTH_MAX
* bytes, this function can be used in two different ways. The first way is to
* call fstrm_control_encoded_size() to obtain the exact number of bytes needed
* to encode the frame, and then pass a buffer of this exact size to
* fstrm_control_encode(). The following example shows this usage:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fstrm_res res;
struct fstrm_control *c;
uint8_t *control_frame;
size_t len_control_frame;
uint32_t flags = 0;
c = fstrm_control_init();
res = fstrm_control_set_type(c, FSTRM_CONTROL_START);
if (res != fstrm_res_success) {
// Error handling goes here.
}
// Calculate the number of bytes needed.
res = fstrm_control_encoded_size(c, &len_control_frame, flags);
if (res != fstrm_res_success) {
// Error handling goes here.
}
// 'len_control_frame' now specifies the number of bytes required for
// the control frame. Allocate the needed space.
control_frame = malloc(len_control_frame);
if (!control_frame) {
// Error handling goes here.
}
// Serialize the control frame into the allocated buffer.
res = fstrm_control_encode(c, control_frame, &len_control_frame, 0);
if (res != fstrm_res_success) {
// Error handling goes here.
}
// Do something with 'control_frame' and 'len_control_frame'.
// Clean up.
free(control_frame);
fstrm_control_destroy(&c);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* The second way to use fstrm_control_encode() is to allocate a statically
* sized buffer of #FSTRM_CONTROL_FRAME_LENGTH_MAX bytes. The exact number of
* bytes serialized by the encoder will be returned in the `len_control_frame`
* parameter. The following example shows this usage:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fstrm_res res;
struct fstrm_control *c;
uint8_t control_frame[FSTRM_CONTROL_FRAME_LENGTH_MAX];
size_t len_control_frame = sizeof(control_frame);
c = fstrm_control_init();
res = fstrm_control_set_type(c, FSTRM_CONTROL_START);
if (res != fstrm_res_success) {
// Error handling.
}
// Serialize the control frame.
res = fstrm_control_encode(c, control_frame, &len_control_frame, 0);
if (res != fstrm_res_success) {
// Error handling goes here.
}
// Do something with 'control_frame' and 'len_control_frame'.
// Clean up.
fstrm_control_destroy(&c);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* \param c
* `fstrm_control` object.
* \param[out] control_frame
* The buffer in which to serialize the control frame.
* \param[in,out] len_control_frame
* The size in bytes of `control_frame`. On a successful return, contains
* the number of bytes actually written into `control_frame`.
* \param flags
* Flags controlling the encoding process. See #fstrm_control_flag.
*
* \retval #fstrm_res_success
* \retval #fstrm_res_failure
*/
fstrm_res
fstrm_control_encode(
const struct fstrm_control *c,
void *control_frame,
size_t *len_control_frame,
const uint32_t flags);
/**@}*/
#endif /* FSTRM_CONTROL_H */
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