// -*- mode:doc; -*- // vim: set syntax=asciidoc,tw=0: coap_pdu_access(3) ================= :doctype: manpage :man source: coap_pdu_access :man version: @PACKAGE_VERSION@ :man manual: libcoap Manual NAME ---- coap_pdu_access, coap_check_option, coap_decode_var_bytes, coap_decode_var_bytes8, coap_get_data, coap_opt_length, coap_opt_value, coap_option_filter_clear, coap_option_filter_get, coap_option_filter_set, coap_option_filter_unset, coap_option_iterator_init, coap_option_next, coap_pdu_get_code, coap_pdu_get_mid, coap_pdu_get_token, coap_pdu_get_type - Accessing CoAP PDUs SYNOPSIS -------- *#include * *coap_opt_t *coap_check_option(const coap_pdu_t *_pdu_, coap_option_num_t _number_, coap_opt_iterator_t *_oi_);* *unsigned int coap_decode_var_bytes(const uint8_t *_buf_, size_t _length_);* *uint64_t coap_decode_var_bytes8(const uint8_t *_buf_, size_t _length_);* *int coap_get_data(const coap_pdu_t *_pdu_, size_t *_length, const uint8_t **_data_);* *uint32_t coap_opt_length(const coap_opt_t *_opt_);* *const uint8_t *coap_opt_value(const coap_opt_t *_opt_);* *void coap_option_filter_clear(coap_opt_filter_t *_filter_);* *int coap_option_filter_get(coap_opt_filter_t *_filter_, coap_option_num_t _number_);* *int coap_option_filter_set(coap_opt_filter_t *_filter_, coap_option_num_t _number_)*; *int coap_option_filter_unset(coap_opt_filter_t *_filter_, coap_option_num_t _number_);* *coap_opt_iterator_t *coap_option_iterator_init(const coap_pdu_t *_pdu_, coap_opt_iterator_t *_oi_, const coap_opt_filter_t *_filter_);* *coap_opt_t *coap_option_next(coap_opt_iterator_t *_oi_);* *coap_pdu_code_t coap_pdu_get_code(const coap_pdu_t *_pdu_);* *coap_mid_t coap_pdu_get_mid(const coap_pdu_t *_pdu_);* *coap_bin_const_t coap_pdu_get_token(const coap_pdu_t *_pdu_);* *coap_pdu_type_t coap_pdu_get_type(const coap_pdu_t *_pdu_);* For specific (D)TLS library support, link with *-lcoap-@LIBCOAP_API_VERSION@-notls*, *-lcoap-@LIBCOAP_API_VERSION@-gnutls*, *-lcoap-@LIBCOAP_API_VERSION@-openssl*, *-lcoap-@LIBCOAP_API_VERSION@-mbedtls* or *-lcoap-@LIBCOAP_API_VERSION@-tinydtls*. Otherwise, link with *-lcoap-@LIBCOAP_API_VERSION@* to get the default (D)TLS library support. DESCRIPTION ----------- The CoAP PDU is of the form --header--|--optional token--|--optional options--|--optional payload-- The terminology used is taken mainly from https://tools.ietf.org/html/rfc7252#section-1.2 The following functions provide access to the information held within a PDU. *Header:* The *coap_pdu_get_type*() function returns one of the messages types below from the PDU _pdu_. [source, c] ---- COAP_MESSAGE_CON Type confirmable. COAP_MESSAGE_NON Type non-confirmable. COAP_MESSAGE_ACK Type acknowledge COAP_MESSAGE_RST Type reset. ---- The *coap_pdu_get_code*() function returns one of the codes below from the PDU _pdu_. It is possible that new codes are added in over time. [source, c] ---- COAP_EMPTY_CODE 0.00 COAP_REQUEST_CODE_GET 0.01 COAP_REQUEST_CODE_POST 0.02 COAP_REQUEST_CODE_PUT 0.03 COAP_REQUEST_CODE_DELETE 0.04 COAP_REQUEST_CODE_FETCH 0.05 COAP_REQUEST_CODE_PATCH 0.06 COAP_REQUEST_CODE_IPATCH 0.07 COAP_RESPONSE_CODE_OK 2.00 COAP_RESPONSE_CODE_CREATED 2.01 COAP_RESPONSE_CODE_DELETED 2.02 COAP_RESPONSE_CODE_VALID 2.03 COAP_RESPONSE_CODE_CHANGED 2.04 COAP_RESPONSE_CODE_CONTENT 2.05 COAP_RESPONSE_CODE_CONTINUE 2.31 COAP_RESPONSE_CODE_BAD_REQUEST 4.00 COAP_RESPONSE_CODE_UNAUTHORIZED 4.01 COAP_RESPONSE_CODE_BAD_OPTION 4.02 COAP_RESPONSE_CODE_FORBIDDEN 4.03 COAP_RESPONSE_CODE_NOT_FOUND 4.04 COAP_RESPONSE_CODE_NOT_ALLOWED 4.05 COAP_RESPONSE_CODE_NOT_ACCEPTABLE 4.06 COAP_RESPONSE_CODE_INCOMPLETE 4.08 COAP_RESPONSE_CODE_CONFLICT 4.09 COAP_RESPONSE_CODE_PRECONDITION_FAILED 4.12 COAP_RESPONSE_CODE_REQUEST_TOO_LARGE 4.13 COAP_RESPONSE_CODE_UNSUPPORTED_CONTENT_FORMAT 4.15 COAP_RESPONSE_CODE_UNPROCESSABLE 4.22 COAP_RESPONSE_CODE_TOO_MANY_REQUESTS 4.29 COAP_RESPONSE_CODE_INTERNAL_ERROR 5.00 COAP_RESPONSE_CODE_NOT_IMPLEMENTED 5.01 COAP_RESPONSE_CODE_BAD_GATEWAY 5.02 COAP_RESPONSE_CODE_SERVICE_UNAVAILABLE 5.03 COAP_RESPONSE_CODE_GATEWAY_TIMEOUT 5.04 COAP_RESPONSE_CODE_PROXYING_NOT_SUPPORTED 5.05 COAP_RESPONSE_CODE_HOP_LIMIT_REACHED 5.08 COAP_SIGNALING_CODE_CSM 7.01 COAP_SIGNALING_CODE_PING 7.02 COAP_SIGNALING_CODE_PONG 7.03 COAP_SIGNALING_CODE_RELEASE 7.04 COAP_SIGNALING_CODE_ABORT 7.05 ---- The *coap_pdu_get_mid*() returns the message id from the PDU _pdu_. *Token:* The *coap_pdu_get_token*() returns the token information held in the PDU _pdu_ which may be zero length. *Options:* The following is the current list of options with their numeric value ---- /* * The C, U, and N flags indicate the properties * Critical, Unsafe, and NoCacheKey, respectively. * If U is set, then N has no meaning as per * https://tools.ietf.org/html/rfc7252#section-5.10 * and is set to a -. * Separately, R is for the options that can be repeated * * The least significant byte of the option is set as followed * as per https://tools.ietf.org/html/rfc7252#section-5.4.6 * * 0 1 2 3 4 5 6 7 * --+---+---+---+---+---+---+---+ * | NoCacheKey| U | C | * --+---+---+---+---+---+---+---+ * * https://tools.ietf.org/html/rfc8613#section-4 goes on to define E, I and U * properties Encrypted and Integrity Protected, Integrity Protected Only and * Unprotected respectively. Integrity Protected Only is not currently used. * * An Option is tagged with CUNREIU with any of the letters replaced with _ if * not set, or - for N if U is set (see above) for aiding understanding of the * Option. */ COAP_OPTION_IF_MATCH 1 /* C__RE__, opaque, 0-8 B, RFC7252 */ COAP_OPTION_URI_HOST 3 /* CU-___U, String, 1-255 B, RFC7252 */ COAP_OPTION_ETAG 4 /* ___RE__, opaque, 1-8 B, RFC7252 */ COAP_OPTION_IF_NONE_MATCH 5 /* C___E__, empty, 0 B, RFC7252 */ COAP_OPTION_OBSERVE 6 /* _U-_E_U, empty/uint, 0 B/0-3 B, RFC7641 */ COAP_OPTION_URI_PORT 7 /* CU-___U, uint, 0-2 B, RFC7252 */ COAP_OPTION_LOCATION_PATH 8 /* ___RE__, String, 0-255 B, RFC7252 */ COAP_OPTION_OSCORE 9 /* C_____U, *, 0-255 B, RFC8613 */ COAP_OPTION_URI_PATH 11 /* CU-RE__, String, 0-255 B, RFC7252 */ COAP_OPTION_CONTENT_FORMAT 12 /* ____E__, uint, 0-2 B, RFC7252 */ /* COAP_OPTION_MAXAGE default 60 seconds if not set */ COAP_OPTION_MAXAGE 14 /* _U-_E_U, uint, 0-4 B, RFC7252 */ COAP_OPTION_URI_QUERY 15 /* CU-RE__, String, 1-255 B, RFC7252 */ COAP_OPTION_HOP_LIMIT 16 /* ______U, uint, 1 B, RFC8768 */ COAP_OPTION_ACCEPT 17 /* C___E__, uint, 0-2 B, RFC7252 */ COAP_OPTION_LOCATION_QUERY 20 /* ___RE__, String, 0-255 B, RFC7252 */ COAP_OPTION_BLOCK2 23 /* CU-_E_U, uint, 0-3 B, RFC7959 */ COAP_OPTION_BLOCK1 27 /* CU-_E_U, uint, 0-3 B, RFC7959 */ COAP_OPTION_SIZE2 28 /* __N_E_U, uint, 0-4 B, RFC7959 */ COAP_OPTION_PROXY_URI 35 /* CU-___U, String, 1-1034 B, RFC7252 */ COAP_OPTION_PROXY_SCHEME 39 /* CU-___U, String, 1-255 B, RFC7252 */ COAP_OPTION_SIZE1 60 /* __N_E_U, uint, 0-4 B, RFC7252 */ COAP_OPTION_NORESPONSE 258 /* _U-_E_U, uint, 0-1 B, RFC7967 */ ---- See FURTHER INFORMATION as to how to get the latest list. The *coap_check_option*() function is used to check whether the specified option _number_ is in the PDU _pdu_. The option iterator _oi_ is used as an internal storage location while iterating through the options looking for the specific _number_. If the _number_ is repeated in the _pdu_, only the first occurrence will be returned. If the option is not found, NULL is returned. Alternatively, the *coap_option_iterator_init*() function can be used to initialize option iterator _oi_, applying a filter _filter_ to indicate which options are to be ignored when iterating through the options. The _filter_ can be NULL (or COAP_OPT_ALL) if all of the options are required. Then this is followed by using the *coap_option_next*() function in a loop to return all the appropriate options until NULL is returned - indicating the end of available the options. See EXAMPLES below for further information. To set up the filter, the following 4 functions are available. The *coap_option_filter_clear*() function initializes _filter_ to have no options set. The *coap_option_filter_get*() function is used to check whether option _number_ is set in _filter_. The *coap_option_filter_set*() function is used to set option _number_ in _filter_. The *coap_option_filter_unset*() function is used to remove option _number_ in _filter_. The *coap_opt_length*() function returns the length of the option _opt_. The *coap_opt_val*() function returns a pointer to the start of the data for the option. The *coap_decode_var_bytes*() function will decode an option up to 4 bytes long from _buf_ and _length_ into an unsigned 32bit number. The *coap_decode_var_bytes*8() function will decode an option up to 8 bytes long from _buf_ and _length_ into an unsigned 64bit number. *Payload:* The *coap_get_data*() function is used abstract from the _pdu_ information about the received data by updating _length_ with the length of data available, and _data_ with a pointer to where the data is located. *NOTE:* This function has been updated by *coap_get_data_large*() when large transfers may take place. See coap_block(3). EXAMPLES -------- *Abstract information from PDU* [source, c] ---- #include static void get_pdu_information(coap_pdu_t *pdu) { int ret; /* Header variables */ coap_pdu_type_t pdu_type; coap_pdu_code_t pdu_code; coap_mid_t pdu_mid; /* Token variables */ coap_bin_const_t pdu_token; /* Option variables */ coap_opt_iterator_t opt_iter; coap_opt_t *option; coap_opt_filter_t ignore_options; /* Data payload variables */ size_t pdu_data_length; const uint8_t *pdu_data; size_t pdu_data_offset; size_t pdu_data_total_length; /* Pull in the header information */ pdu_type = coap_pdu_get_type(pdu); pdu_code = coap_pdu_get_code(pdu); pdu_mid = coap_pdu_get_mid(pdu); /* Pull in the token information */ pdu_token = coap_pdu_get_token(pdu); /* Pull in the option information */ /* Specific option check */ option = coap_check_option(pdu, COAP_OPTION_OBSERVE, &opt_iter); if (option) { uint32_t value = coap_decode_var_bytes(coap_opt_value(option), coap_opt_length(option)); coap_log(LOG_INFO, "Option OBSERVE, value %u\n", value); } /* Iterate through all options */ coap_option_iterator_init(pdu, &opt_iter, COAP_OPT_ALL); while ((option = coap_option_next(&opt_iter))) { coap_log(LOG_INFO, "A: Option %d, Length %u\n", opt_iter.number, coap_opt_length(option)); } /* Iterate through options, some ignored */ coap_option_filter_clear(&ignore_options); coap_option_filter_set(&ignore_options, COAP_OPTION_OBSERVE); coap_option_iterator_init(pdu, &opt_iter, &ignore_options); while ((option = coap_option_next(&opt_iter))) { coap_log(LOG_INFO, "I: Option %d, Length %u\n", opt_iter.number, coap_opt_length(option)); } /* Pull in the payload information */ ret = coap_get_data(pdu, &pdu_data_length, &pdu_data); /* or */ ret = coap_get_data_large(pdu, &pdu_data_length, &pdu_data, &pdu_data_offset, &pdu_data_total_length); } ---- SEE ALSO -------- *coap_block*(3) and *coap_pdu_setup*(3) FURTHER INFORMATION ------------------- See "RFC7252: The Constrained Application Protocol (CoAP)" "RFC8613: Object Security for Constrained RESTful Environments (OSCORE)" for further information. See https://www.iana.org/assignments/core-parameters/core-parameters.xhtml#option-numbers for the current set of defined CoAP Options. BUGS ---- Please report bugs on the mailing list for libcoap: libcoap-developers@lists.sourceforge.net or raise an issue on GitHub at https://github.com/obgm/libcoap/issues AUTHORS ------- The libcoap project