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RIOT/sys/include/net/gcoap.h
Pekka Nikander 8f10d65ad5 net/gcoap: Make references to coap_resource_t const in gcoap 
A CoAP resource is a primary object between the application
    and CoAP library.  The Library needs the paths, methods,
    and handlers from it, so that it can call the right handler.
    However, it never needs to change any of them.

    The application also needs the resources.  The application
    may want to declare the resources as const, since it may
    want to store them in flash.
2018-07-30 09:00:21 +03:00

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/*
* Copyright (c) 2015-2017 Ken Bannister. All rights reserved.
* 2017 Freie Universität Berlin
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @defgroup net_gcoap CoAP
* @ingroup net
* @brief High-level interface to CoAP messaging
*
* gcoap provides a high-level interface for writing CoAP messages via RIOT's
* sock networking API. gcoap internalizes network event processing so an
* application only needs to focus on request/response handling. For a server,
* gcoap accepts a list of resource paths with callbacks for writing the
* response. For a client, gcoap provides a function to send a request, with a
* callback for reading the server response. Generation of the request or
* response requires from one to three well-defined steps, depending on
* inclusion of a payload.
*
* gcoap allocates a RIOT message processing thread, so a single instance can
* serve multiple applications. This approach also means gcoap uses a single UDP
* port, which supports RFC 6282 compression. Internally, gcoap depends on the
* nanocoap package for base level structs and functionality.
*
* gcoap also supports the Observe extension (RFC 7641) for a server. gcoap
* provides functions to generate and send an observe notification that are
* similar to the functions to send a client request.
*
* *Contents*
*
* - Server Operation
* - Client Operation
* - Observe Server Operation
* - Implementation Notes
* - Implementation Status
*
* ## Server Operation ##
*
* gcoap listens for requests on GCOAP_PORT, 5683 by default. You can redefine
* this by uncommenting the appropriate lines in gcoap's make file.
*
* gcoap allows an application to specify a collection of request resource paths
* it wants to be notified about. Create an array of resources (coap_resource_t
* structs). Note that the elements must be ordered alphabetically with respect
* to the resource path. Use gcoap_register_listener() at application startup
* to pass in these resources, wrapped in a gcoap_listener_t.
*
* gcoap itself defines a resource for `/.well-known/core` discovery, which
* lists all of the registered paths.
*
* ### Creating a response ###
*
* An application resource includes a callback function, a coap_handler_t. After
* reading the request, the callback must use one or two functions provided by
* gcoap to format the response, as described below. The callback *must* read
* the request thoroughly before calling the functions, because the response
* buffer likely reuses the request buffer. See `examples/gcoap/gcoap_cli.c`
* for a simple example of a callback.
*
* Here is the expected sequence for a callback function:
*
* Read request completely and parse request payload, if any. Use the
* coap_pkt_t _payload_ and _payload_len_ attributes.
*
* If there is a payload, follow the three steps below.
*
* -# Call gcoap_resp_init() to initialize the response.
* -# Write the response payload, starting at the updated _payload_ pointer
* in the coap_pkt_t. If some error occurs, return a negative errno
* code from the handler, and gcoap will send a server error (5.00).
* -# Call gcoap_finish() to complete the PDU after writing the payload,
* and return the result. gcoap will send the message.
*
* If no payload, call only gcoap_response() to write the full response.
* Alternatively, you still can use gcoap_resp_init() and gcoap_finish(), as
* described above. In fact, the gcoap_response() function is inline, and uses
* those two functions.
*
* ## Client Operation ##
*
* Client operation includes two phases: creating and sending a request, and
* handling the response aynchronously in a client supplied callback. See
* `examples/gcoap/gcoap_cli.c` for a simple example of sending a request and
* reading the response.
*
* ### Creating a request ###
*
* Here is the expected sequence to prepare and send a request:
*
* Allocate a buffer and a coap_pkt_t for the request.
*
* If there is a payload, follow the steps below.
*
* -# Call gcoap_req_init() to initialize the request.
* -# Optionally, mark the request confirmable by calling
* coap_hdr_set_type() with COAP_TYPE_CON.
* -# Write the request payload, starting at the updated _payload_ pointer
* in the coap_pkt_t.
* -# Call gcoap_finish(), which updates the packet for the payload.
*
* If no payload, call only gcoap_request() to write the full request.
* Alternatively, you still can use gcoap_req_init() and gcoap_finish(),
* as described above. The gcoap_request() function is inline, and uses those
* two functions.
*
* Finally, call gcoap_req_send2() for the destination endpoint, as well as a
* callback function for the host's response.
*
* ### Handling the response ###
*
* When gcoap receives the response to a request, it executes the callback from
* the request. gcoap also executes the callback when a response is not
* received within GCOAP_RESPONSE_TIMEOUT.
*
* Here is the expected sequence for handling a response in the callback.
*
* -# Test for a server response or timeout in the _req_state_ callback
* parameter. See the GCOAP_MEMO... constants.
* -# Test the response with coap_get_code_class() and coap_get_code_detail().
* -# Test the response payload with the coap_pkt_t _payload_len_ and
* _content_type_ attributes.
* -# Read the payload, if any.
*
* ## Observe Server Operation
*
* A CoAP client may register for Observe notifications for any resource that
* an application has registered with gcoap. An application does not need to
* take any action to support Observe client registration. However, gcoap
* limits registration for a given resource to a _single_ observer.
*
* An Observe notification is considered a response to the original client
* registration request. So, the Observe server only needs to create and send
* the notification -- no further communication or callbacks are required.
*
* ### Creating a notification ###
*
* Here is the expected sequence to prepare and send a notification:
*
* Allocate a buffer and a coap_pkt_t for the notification, then follow the
* steps below.
*
* -# Call gcoap_obs_init() to initialize the notification for a resource.
* Test the return value, which may indicate there is not an observer for
* the resource. If so, you are done.
* -# Write the notification payload, starting at the updated _payload_ pointer
* in the coap_pkt_t.
* -# Call gcoap_finish(), which updates the packet for the payload.
*
* Finally, call gcoap_obs_send() for the resource.
*
* ### Other considerations ###
*
* By default, the value for the Observe option in a notification is three
* bytes long. For resources that change slowly, this length can be reduced via
* GCOAP_OBS_VALUE_WIDTH.
*
* A client always may re-register for a resource with the same token or with
* a new token to indicate continued interest in receiving notifications about
* it. Of course the client must not already be using any new token in the
* registration for a different resource. Successful registration always is
* indicated by the presence of the Observe option in the response.
*
* To cancel registration, the server expects to receive a GET request with
* the Observe option value set to 1. The server does not support cancellation
* via a reset (RST) response to a non-confirmable notification.
*
* ## Implementation Notes ##
*
* ### Building a packet ###
*
* The sequence and functions described above to build a request or response
* is designed to provide a relatively simple API for the user.
*
* The structure of a CoAP PDU requires that options are placed between the
* header and the payload. So, gcoap provides space in the buffer for them in
* the request/response ...init() function, and then writes them during
* gcoap_finish(). We trade some inefficiency/work in the buffer for
* simplicity in the API.
*
* ### Waiting for a response ###
*
* We take advantage of RIOT's asynchronous messaging by using an xtimer to wait
* for a response, so the gcoap thread does not block while waiting. The user is
* notified via the same callback, whether the message is received or the wait
* times out. We track the response with an entry in the
* `_coap_state.open_reqs` array.
*
* ## Implementation Status ##
* gcoap includes server and client capability. Available features include:
*
* - Message Type: Supports non-confirmable (NON) messaging. Additionally
* provides a callback on timeout. Provides piggybacked ACK response to a
* confirmable (CON) request.
* - Observe extension: Provides server-side registration and notifications.
* - Server and Client provide helper functions for writing the
* response/request. See the CoAP topic in the source documentation for
* details. See the gcoap example for sample implementations.
* - Server allows an application to register a 'listener', which includes an
* array of endpoint paths and function callbacks used to write a response.
* - Server listens on a port at startup; defaults to 5683.
* - Client operates asynchronously; sends request and then handles response
* in a user provided callback.
* - Client generates token; length defined at compile time.
* - Options: Supports Content-Format for payload.
*
* @{
*
* @file
* @brief gcoap definition
*
* @author Ken Bannister <kb2ma@runbox.com>
* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
*/
#ifndef NET_GCOAP_H
#define NET_GCOAP_H
#include <stdint.h>
#include "net/ipv6/addr.h"
#include "net/sock/udp.h"
#include "net/nanocoap.h"
#include "xtimer.h"
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief Size for module message queue
*/
#ifndef GCOAP_MSG_QUEUE_SIZE
#define GCOAP_MSG_QUEUE_SIZE (4)
#endif
/**
* @brief Server port; use RFC 7252 default if not defined
*/
#ifndef GCOAP_PORT
#define GCOAP_PORT (5683)
#endif
/**
* @brief Size of the buffer used to build a CoAP request or response
*/
#ifndef GCOAP_PDU_BUF_SIZE
#define GCOAP_PDU_BUF_SIZE (128)
#endif
/**
* @brief Size of the buffer used to write options, other than Uri-Path, in a
* request
*
* Accommodates Content-Format and Uri-Queries
*/
#define GCOAP_REQ_OPTIONS_BUF (40)
/**
* @brief Size of the buffer used to write options in a response
*
* Accommodates Content-Format.
*/
#define GCOAP_RESP_OPTIONS_BUF (8)
/**
* @brief Size of the buffer used to write options in an Observe notification
*
* Accommodates Content-Format and Observe.
*/
#define GCOAP_OBS_OPTIONS_BUF (8)
/**
* @brief Maximum number of requests awaiting a response
*/
#ifndef GCOAP_REQ_WAITING_MAX
#define GCOAP_REQ_WAITING_MAX (2)
#endif
/**
* @brief Maximum length in bytes for a token
*/
#define GCOAP_TOKENLEN_MAX (8)
/**
* @brief Maximum length in bytes for a header, including the token
*/
#define GCOAP_HEADER_MAXLEN (sizeof(coap_hdr_t) + GCOAP_TOKENLEN_MAX)
/**
* @brief Length in bytes for a token; use 2 if not defined
*/
#ifndef GCOAP_TOKENLEN
#define GCOAP_TOKENLEN (2)
#endif
/**
* @brief Marks the boundary between header and payload
*/
#define GCOAP_PAYLOAD_MARKER (0xFF)
/**
* @name States for the memo used to track waiting for a response
* @{
*/
#define GCOAP_MEMO_UNUSED (0) /**< This memo is unused */
#define GCOAP_MEMO_WAIT (1) /**< Request sent; awaiting response */
#define GCOAP_MEMO_RESP (2) /**< Got response */
#define GCOAP_MEMO_TIMEOUT (3) /**< Timeout waiting for response */
#define GCOAP_MEMO_ERR (4) /**< Error processing response packet */
/** @} */
/**
* @brief Value for send_limit in request memo when non-confirmable type
*/
#define GCOAP_SEND_LIMIT_NON (-1)
/**
* @brief Time in usec that the event loop waits for an incoming CoAP message
*/
#ifndef GCOAP_RECV_TIMEOUT
#define GCOAP_RECV_TIMEOUT (1 * US_PER_SEC)
#endif
/**
* @brief Default time to wait for a non-confirmable response [in usec]
*
* Set to 0 to disable timeout.
*/
#ifndef GCOAP_NON_TIMEOUT
#define GCOAP_NON_TIMEOUT (5000000U)
#endif
/**
* @brief Identifies waiting timed out for a response to a sent message
*/
#define GCOAP_MSG_TYPE_TIMEOUT (0x1501)
/**
* @brief Identifies a request to interrupt listening for an incoming message
* on a sock
*
* Allows the event loop to process IPC messages.
*/
#define GCOAP_MSG_TYPE_INTR (0x1502)
/**
* @brief Maximum number of Observe clients; use 2 if not defined
*/
#ifndef GCOAP_OBS_CLIENTS_MAX
#define GCOAP_OBS_CLIENTS_MAX (2)
#endif
/**
* @brief Maximum number of registrations for Observable resources; use 2 if
* not defined
*/
#ifndef GCOAP_OBS_REGISTRATIONS_MAX
#define GCOAP_OBS_REGISTRATIONS_MAX (2)
#endif
/**
* @name States for the memo used to track Observe registrations
* @{
*/
#define GCOAP_OBS_MEMO_UNUSED (0) /**< This memo is unused */
#define GCOAP_OBS_MEMO_IDLE (1) /**< Registration OK; no current activity */
#define GCOAP_OBS_MEMO_PENDING (2) /**< Resource changed; notification pending */
/** @} */
/**
* @brief Width in bytes of the Observe option value for a notification
*
* This width is used to determine the length of the 'tick' used to measure
* the time between observable changes to a resource. A tick is expressed
* internally as GCOAP_OBS_TICK_EXPONENT, which is the base-2 log value of the
* tick length in microseconds.
*
* The canonical setting for the value width is 3 (exponent 5), which results
* in a tick length of 32 usec, per sec. 3.4, 4.4 of the RFC. Width 2
* (exponent 16) results in a tick length of ~65 msec, and width 1 (exponent
* 24) results in a tick length of ~17 sec.
*
* The tick length must be short enough so that the Observe value strictly
* increases for each new notification. The purpose of the value is to allow a
* client to detect message reordering within the network latency period (128
* sec). For resources that change only slowly, the reduced message length is
* useful when packet size is limited.
*/
#ifndef GCOAP_OBS_VALUE_WIDTH
#define GCOAP_OBS_VALUE_WIDTH (3)
#endif
/**
* @brief See GCOAP_OBS_VALUE_WIDTH
*/
#if (GCOAP_OBS_VALUE_WIDTH == 3)
#define GCOAP_OBS_TICK_EXPONENT (5)
#elif (GCOAP_OBS_VALUE_WIDTH == 2)
#define GCOAP_OBS_TICK_EXPONENT (16)
#elif (GCOAP_OBS_VALUE_WIDTH == 1)
#define GCOAP_OBS_TICK_EXPONENT (24)
#endif
/**
* @name Return values for gcoap_obs_init()
* @{
*/
#define GCOAP_OBS_INIT_OK (0)
#define GCOAP_OBS_INIT_ERR (-1)
#define GCOAP_OBS_INIT_UNUSED (-2)
/** @} */
/**
* @brief Stack size for module thread
*/
#ifndef GCOAP_STACK_SIZE
#define GCOAP_STACK_SIZE (THREAD_STACKSIZE_DEFAULT + DEBUG_EXTRA_STACKSIZE \
+ sizeof(coap_pkt_t))
#endif
/**
* @brief Count of PDU buffers available for resending confirmable messages
*/
#ifndef GCOAP_RESEND_BUFS_MAX
#define GCOAP_RESEND_BUFS_MAX (1)
#endif
/**
* @brief A modular collection of resources for a server
*/
typedef struct gcoap_listener {
const coap_resource_t *resources; /**< First element in the array of
* resources; must order alphabetically */
size_t resources_len; /**< Length of array */
struct gcoap_listener *next; /**< Next listener in list */
} gcoap_listener_t;
/**
* @brief Handler function for a server response, including the state for the
* originating request
*
* If request timed out, the packet header is for the request.
*/
typedef void (*gcoap_resp_handler_t)(unsigned req_state, coap_pkt_t* pdu,
sock_udp_ep_t *remote);
/**
* @brief Extends request memo for resending a confirmable request.
*/
typedef struct {
uint8_t *pdu_buf; /**< Buffer containing the PDU */
size_t pdu_len; /**< Length of pdu_buf */
} gcoap_resend_t;
/**
* @brief Memo to handle a response for a request
*/
typedef struct {
unsigned state; /**< State of this memo, a GCOAP_MEMO... */
int send_limit; /**< Remaining resends, 0 if none;
GCOAP_SEND_LIMIT_NON if non-confirmable */
union {
uint8_t hdr_buf[GCOAP_HEADER_MAXLEN];
/**< Copy of PDU header, if no resends */
gcoap_resend_t data; /**< Endpoint and PDU buffer, for resend */
} msg; /**< Request message data; if confirmable,
supports resending message */
sock_udp_ep_t remote_ep; /**< Remote endpoint */
gcoap_resp_handler_t resp_handler; /**< Callback for the response */
xtimer_t response_timer; /**< Limits wait for response */
msg_t timeout_msg; /**< For response timer */
} gcoap_request_memo_t;
/**
* @brief Memo for Observe registration and notifications
*/
typedef struct {
sock_udp_ep_t *observer; /**< Client endpoint; unused if null */
const coap_resource_t *resource; /**< Entity being observed */
uint8_t token[GCOAP_TOKENLEN_MAX]; /**< Client token for notifications */
unsigned token_len; /**< Actual length of token attribute */
} gcoap_observe_memo_t;
/**
* @brief Initializes the gcoap thread and device
*
* Must call once before first use.
*
* @return PID of the gcoap thread on success.
* @return -EEXIST, if thread already has been created.
* @return -EINVAL, if the IP port already is in use.
*/
kernel_pid_t gcoap_init(void);
/**
* @brief Starts listening for resource paths
*
* @param[in] listener Listener containing the resources.
*/
void gcoap_register_listener(gcoap_listener_t *listener);
/**
* @brief Initializes a CoAP request PDU on a buffer.
*
* @param[out] pdu Request metadata
* @param[out] buf Buffer containing the PDU
* @param[in] len Length of the buffer
* @param[in] code Request code: GCOAP_[GET|POST|PUT|DELETE]
* @param[in] path Resource path, *must* start with '/'
*
* @pre @p path not `NULL`
* @pre @p path must start with `/`
*
* @return 0 on success
* @return < 0 on error
*/
int gcoap_req_init(coap_pkt_t *pdu, uint8_t *buf, size_t len,
unsigned code, const char *path);
/**
* @brief Finishes formatting a CoAP PDU after the payload has been written
*
* Assumes the PDU has been initialized with gcoap_req_init() or
* gcoap_resp_init().
*
* @param[in,out] pdu Request metadata
* @param[in] payload_len Length of the payload, or 0 if none
* @param[in] format Format code for the payload; use COAP_FORMAT_NONE if
* not specified
*
* @return size of the PDU
* @return < 0 on error
*/
ssize_t gcoap_finish(coap_pkt_t *pdu, size_t payload_len, unsigned format);
/**
* @brief Writes a complete CoAP request PDU when there is not a payload
*
* @param[in,out] pdu Request metadata
* @param[in,out] buf Buffer containing the PDU
* @param[in] len Length of the buffer
* @param[in] code Request code: GCOAP_[GET|POST|PUT|DELETE]
* @param[in] path Resource path, *must* start with '/'
*
* @return size of the PDU within the buffer
* @return < 0 on error
*/
static inline ssize_t gcoap_request(coap_pkt_t *pdu, uint8_t *buf, size_t len,
unsigned code, char *path)
{
return (gcoap_req_init(pdu, buf, len, code, path) == 0)
? gcoap_finish(pdu, 0, COAP_FORMAT_NONE)
: -1;
}
/**
* @brief Sends a buffer containing a CoAP request to the provided endpoint
*
* @param[in] buf Buffer containing the PDU
* @param[in] len Length of the buffer
* @param[in] remote Destination for the packet
* @param[in] resp_handler Callback when response received, may be NULL
*
* @return length of the packet
* @return 0 if cannot send
*/
size_t gcoap_req_send2(const uint8_t *buf, size_t len,
const sock_udp_ep_t *remote,
gcoap_resp_handler_t resp_handler);
/**
* @brief Sends a buffer containing a CoAP request to the provided host/port
*
* @deprecated Please use @ref gcoap_req_send2() instead
*
* @param[in] buf Buffer containing the PDU
* @param[in] len Length of the buffer
* @param[in] addr Destination for the packet
* @param[in] port Port at the destination
* @param[in] resp_handler Callback when response received, may be NULL
*
* @return length of the packet
* @return 0 if cannot send
*/
size_t gcoap_req_send(const uint8_t *buf, size_t len, const ipv6_addr_t *addr,
uint16_t port, gcoap_resp_handler_t resp_handler);
/**
* @brief Initializes a CoAP response packet on a buffer
*
* Initializes payload location within the buffer based on packet setup.
*
* @param[out] pdu Response metadata
* @param[in] buf Buffer containing the PDU
* @param[in] len Length of the buffer
* @param[in] code Response code
*
* @return 0 on success
* @return < 0 on error
*/
int gcoap_resp_init(coap_pkt_t *pdu, uint8_t *buf, size_t len, unsigned code);
/**
* @brief Writes a complete CoAP response PDU when there is no payload
*
* @param[out] pdu Response metadata
* @param[out] buf Buffer containing the PDU
* @param[in] len Length of the buffer
* @param[in] code Response code
*
* @return size of the PDU within the buffer
* @return < 0 on error
*/
static inline ssize_t gcoap_response(coap_pkt_t *pdu, uint8_t *buf,
size_t len, unsigned code)
{
return (gcoap_resp_init(pdu, buf, len, code) == 0)
? gcoap_finish(pdu, 0, COAP_FORMAT_NONE)
: -1;
}
/**
* @brief Initializes a CoAP Observe notification packet on a buffer, for the
* observer registered for a resource
*
* First verifies that an observer has been registered for the resource.
*
* @param[out] pdu Notification metadata
* @param[out] buf Buffer containing the PDU
* @param[in] len Length of the buffer
* @param[in] resource Resource for the notification
*
* @return GCOAP_OBS_INIT_OK on success
* @return GCOAP_OBS_INIT_ERR on error
* @return GCOAP_OBS_INIT_UNUSED if no observer for resource
*/
int gcoap_obs_init(coap_pkt_t *pdu, uint8_t *buf, size_t len,
const coap_resource_t *resource);
/**
* @brief Sends a buffer containing a CoAP Observe notification to the
* observer registered for a resource
*
* Assumes a single observer for a resource.
*
* @param[in] buf Buffer containing the PDU
* @param[in] len Length of the buffer
* @param[in] resource Resource to send
*
* @return length of the packet
* @return 0 if cannot send
*/
size_t gcoap_obs_send(const uint8_t *buf, size_t len,
const coap_resource_t *resource);
/**
* @brief Provides important operational statistics
*
* Useful for monitoring.
*
* @return count of unanswered requests
*/
uint8_t gcoap_op_state(void);
/**
* @brief Get the resource list, currently only `CoRE Link Format`
* (COAP_FORMAT_LINK) supported
*
* If @p buf := NULL, nothing will be written but the size of the resulting
* resource list is computed and returned.
*
* @param[out] buf output buffer to write resource list into, my be NULL
* @param[in] maxlen length of @p buf, ignored if @p buf is NULL
* @param[in] cf content format to use for the resource list, currently
* only COAP_FORMAT_LINK supported
*
* @todo add support for `JSON CoRE Link Format`
* @todo add support for 'CBOR CoRE Link Format`
*
* @return the number of bytes written to @p buf
* @return -1 on error
*/
int gcoap_get_resource_list(void *buf, size_t maxlen, uint8_t cf);
/**
* @brief Adds a single Uri-Query option to a CoAP request
*
* To add multiple Uri-Query options, simply call this function multiple times.
* The Uri-Query options will be added in the order those calls.
*
* @param[out] pdu The package that is being build
* @param[in] key Key to add to the query string
* @param[in] val Value to assign to @p key (may be NULL)
*
* @pre ((pdu != NULL) && (key != NULL))
*
* @return overall length of new query string
* @return -1 on error
*/
int gcoap_add_qstring(coap_pkt_t *pdu, const char *key, const char *val);
#ifdef __cplusplus
}
#endif
#endif /* NET_GCOAP_H */
/** @} */
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