Hi Arman,
> This patch introduces struct bt_att, which handles the transport and
> encoding/decoding for the ATT protocol. The structure of the code
> follows that of src/shared/mgmt and lib/mgmt.h, where individual
> parameter structures are defined for all ATT protocol requests, responses,
> commands, indications, and notifications. The serialization and
> endianness conversion for all parameters are handled by bt_att.
>
> struct bt_att is based around struct io and operates on a raw file
> descriptor. The initial patch implements the Exchange MTU request &
> response and the Error Response. Currently, only requests that are
> initiated locally are supported.
> ---
> Makefile.am | 3 +-
> src/shared/att.c | 531 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
> src/shared/att.h | 101 +++++++++++
> 3 files changed, 634 insertions(+), 1 deletion(-)
> create mode 100644 src/shared/att.c
> create mode 100644 src/shared/att.h
>
> diff --git a/Makefile.am b/Makefile.am
> index f96c700..0c3424f 100644
> --- a/Makefile.am
> +++ b/Makefile.am
> @@ -155,7 +155,8 @@ src_bluetoothd_SOURCES = $(builtin_sources) \
> src/shared/timeout.h src/shared/timeout-glib.c \
> src/shared/queue.h src/shared/queue.c \
> src/shared/util.h src/shared/util.c \
> - src/shared/mgmt.h src/shared/mgmt.c
> + src/shared/mgmt.h src/shared/mgmt.c \
> + src/shared/att.h src/shared/att.c
> src_bluetoothd_LDADD = lib/libbluetooth-internal.la gdbus/libgdbus-internal.la \
> @GLIB_LIBS@ @DBUS_LIBS@ -ldl -lrt
> src_bluetoothd_LDFLAGS = $(AM_LDFLAGS) -Wl,--export-dynamic \
> diff --git a/src/shared/att.c b/src/shared/att.c
> new file mode 100644
> index 0000000..8b10c30
> --- /dev/null
> +++ b/src/shared/att.c
> @@ -0,0 +1,531 @@
> +/*
> + *
> + * BlueZ - Bluetooth protocol stack for Linux
> + *
> + * Copyright (C) 2014 Google Inc.
> + * Copyright (C) 2014 Intel Corporation.
> + *
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
> + *
> + */
> +
> +#ifdef HAVE_CONFIG_H
> +#include <config.h>
> +#endif
> +
> +#include <stdio.h>
> +#include <unistd.h>
> +#include <string.h>
> +#include <errno.h>
> +
> +#include "src/shared/io.h"
> +#include "src/shared/queue.h"
> +#include "src/shared/util.h"
> +#include "src/shared/att.h"
> +
> +#define ATT_MAX_VALUE_LEN 512
> +#define ATT_DEFAULT_LE_MTU 23
> +#define ATT_MIN_PDU_LEN 1 /* At least 1 byte for the opcode. */
> +
> +struct bt_att {
> + int ref_count;
> + int fd;
> + bool close_on_unref;
> + struct io *io;
> + bool writer_active;
> + struct queue *request_queue;
> + struct queue *pending_list;
> + unsigned int next_request_id;
> + bool destroyed;
> + void *buf;
> + uint16_t len;
> + bt_att_debug_func_t debug_callback;
> + bt_att_destroy_func_t debug_destroy;
> + void *debug_data;
> +};
> +
> +struct bt_att_request {
> + unsigned int id;
> + uint8_t opcode;
> + void *pdu;
> + uint16_t len;
> + bt_att_request_func_t callback;
> + bt_att_destroy_func_t destroy;
> + void *user_data;
> +};
> +
> +static void destroy_request(void *data)
> +{
> + struct bt_att_request *request = data;
> +
> + if (request->destroy)
> + request->destroy(request->user_data);
> +
> + free(request->pdu);
> + free(request);
> +}
> +
> +static bool match_request_opcode(const void *a, const void *b)
> +{
> + const struct bt_att_request *request = a;
> + const uint8_t opcode = PTR_TO_UINT(b);
> +
> + return request->opcode == opcode;
> +}
> +
> +static void write_watch_destroy(void *user_data)
> +{
> + struct bt_att *att = user_data;
> +
> + att->writer_active = false;
> +}
> +
> +static bool can_write_data(struct io *io, void *user_data)
> +{
> + struct bt_att *att = user_data;
> + struct bt_att_request *request;
> + ssize_t bytes_written;
> +
> + if (!queue_isempty(att->pending_list))
> + return false;
> +
> + request = queue_pop_head(att->request_queue);
> + if (!request)
> + return false;
> +
> + bytes_written = write(att->fd, request->pdu, request->len);
> + if (bytes_written < 0) {
> + util_debug(att->debug_callback, att->debug_data,
> + "write failed: %s", strerror(errno));
a few projects started to use %m these days. Might be a good idea to just go with it as well.
> + if (request->callback)
> + request->callback(BT_ATT_OP_ERROR_RESP, NULL, 0,
> + request->user_data);
> +
> + destroy_request(request);
> + return true;
> + }
> +
> + util_debug(att->debug_callback, att->debug_data,
> + "ATT command 0x%02x", request->opcode);
> +
> + util_hexdump('<', request->pdu, bytes_written,
> + att->debug_callback, att->debug_data);
> +
> + queue_push_tail(att->pending_list, request);
> +
> + return false;
> +}
> +
> +static void wakeup_writer(struct bt_att *att)
> +{
> + if (!queue_isempty(att->pending_list))
> + return;
> +
> + if (att->writer_active)
> + return;
> +
> + io_set_write_handler(att->io, can_write_data, att, write_watch_destroy);
> +}
> +
> +static void request_complete(struct bt_att *att, uint8_t req_opcode,
> + uint8_t rsp_opcode, const void *param,
> + uint16_t length)
> +{
> + struct bt_att_request *request;
> +
> + request = queue_remove_if(att->pending_list,
> + match_request_opcode,
> + UINT_TO_PTR(req_opcode));
Please do not have these extra empty lines between the function and the if checking if the result is valid. If we accidentally have this in some other code, please send patches to fix it since that is an oversight.
> +
> + if (request) {
> + if (request->callback)
> + request->callback(rsp_opcode, param, length,
> + request->user_data);
> +
> + destroy_request(request);
> + }
> +
> + if (att->destroyed)
> + return;
> +
> + wakeup_writer(att);
> +}
> +
> +static bool handle_error_rsp(struct bt_att *att, const uint8_t *pdu,
> + uint16_t pdu_length)
> +{
> + struct bt_att_error_rsp_param param;
> +
> + if (pdu_length != 5)
> + return false;
> +
> + memset(¶m, 0, sizeof(param));
> +
> + param.request_opcode = pdu[1];
> + param.handle = get_le16(pdu + 2);
> + param.error_code = pdu[4];
> +
> + request_complete(att, param.request_opcode, pdu[0],
> + ¶m, sizeof(param));
> +
> + return true;
> +}
> +
> +static bool handle_exchange_mtu_rsp(struct bt_att *att, const uint8_t *pdu,
> + uint16_t pdu_length)
> +{
> + struct bt_att_exchange_mtu_rsp_param param;
> +
> + if (pdu_length != 3)
> + return false;
> +
> + param.server_rx_mtu = get_le16(pdu + 1);
> +
> + request_complete(att, BT_ATT_OP_EXCHANGE_MTU_REQ, pdu[0],
> + ¶m, sizeof(param));
> +
> + return true;
> +}
> +
> +static bool handle_response(struct bt_att *att, const uint8_t *pdu,
> + uint16_t pdu_length)
> +{
> + uint8_t opcode = pdu[0];
> +
> + if (opcode == BT_ATT_OP_ERROR_RESP)
> + return handle_error_rsp(att, pdu, pdu_length);
> +
> + if (opcode == BT_ATT_OP_EXCHANGE_MTU_RESP)
> + return handle_exchange_mtu_rsp(att, pdu, pdu_length);
> +
> + return false;
> +}
> +
> +static void read_watch_destroy(void *user_data)
> +{
> + struct bt_att *att = user_data;
> +
> + if (att->destroyed) {
> + queue_destroy(att->pending_list, NULL);
> + free(att);
> + }
> +}
> +
> +static bool can_read_data(struct io *io, void *user_data)
> +{
> + struct bt_att *att = user_data;
> + uint8_t *pdu;
> + ssize_t bytes_read;
> +
> + bytes_read = read(att->fd, att->buf, att->len);
> + if (bytes_read < 0)
> + return false;
> +
> + util_hexdump('>', att->buf, bytes_read,
> + att->debug_callback, att->debug_data);
> +
> + if (bytes_read < ATT_MIN_PDU_LEN)
> + return true;
> +
> + pdu = att->buf;
> +
> + /* The opcode is either a response to a pending request, a new request
> + * from a client, or a notification/indication. Handle them separately
> + * here.
> + */
> + /* TODO: Handle other types of data here. */
> + handle_response(att, pdu, bytes_read);
> +
> + if (att->destroyed)
> + return false;
> +
> + return true;
> +}
> +
> +struct bt_att *bt_att_new(int fd)
> +{
> + struct bt_att *att;
> +
> + if (fd < 0)
> + return NULL;
> +
> + att = new0(struct bt_att, 1);
> + if (!att)
> + return NULL;
> +
> + att->fd = fd;
> + att->close_on_unref = false;
> +
> + att->len = ATT_DEFAULT_LE_MTU;
> + att->buf = malloc(att->len);
> + if (!att->buf)
> + goto fail;
> +
> + att->io = io_new(fd);
> + if (!att->io)
> + goto fail;
> +
> + att->request_queue = queue_new();
> + if (!att->request_queue)
> + goto fail;
> +
> + att->pending_list = queue_new();
> + if (!att->pending_list)
> + goto fail;
> +
> + if (!io_set_read_handler(att->io, can_read_data,
> + att, read_watch_destroy))
> + goto fail;
> +
> + att->writer_active = false;
> +
> + return bt_att_ref(att);
> +
> +fail:
> + queue_destroy(att->pending_list, NULL);
> + queue_destroy(att->request_queue, NULL);
> + io_destroy(att->io);
> + free(att->buf);
> + free(att);
> +
> + return NULL;
> +}
> +
> +struct bt_att *bt_att_ref(struct bt_att *att)
> +{
> + if (!att)
> + return NULL;
> +
> + __sync_fetch_and_add(&att->ref_count, 1);
> +
> + return att;
> +}
> +
> +void bt_att_unref(struct bt_att *att)
> +{
> + if (!att)
> + return;
> +
> + if (__sync_sub_and_fetch(&att->ref_count, 1))
> + return;
> +
> + bt_att_cancel_all(att);
> +
> + queue_destroy(att->request_queue, NULL);
> +
> + io_set_write_handler(att->io, NULL, NULL, NULL);
> + io_set_read_handler(att->io, NULL, NULL, NULL);
> +
> + io_destroy(att->io);
> + att->io = NULL;
> +
> + if (att->close_on_unref)
> + close(att->fd);
> +
> + if (att->debug_destroy)
> + att->debug_destroy(att->debug_data);
> +
> + free(att->buf);
> + att->buf = NULL;
> +
> + att->destroyed = true;
> +}
> +
> +bool bt_att_set_debug(struct bt_att *att, bt_att_debug_func_t callback,
> + void *user_data, bt_att_destroy_func_t destroy)
> +{
> + if (!att)
> + return false;
> +
> + if (att->debug_destroy)
> + att->debug_destroy(att->debug_data);
> +
> + att->debug_callback = callback;
> + att->debug_destroy = destroy;
> + att->debug_data = user_data;
> +
> + return true;
> +}
> +
> +bool bt_att_set_close_on_unref(struct bt_att *att, bool do_close)
> +{
> + if (!att)
> + return false;
> +
> + att->close_on_unref = do_close;
> +
> + return true;
> +}
> +
> +uint16_t bt_att_get_mtu(struct bt_att *att)
> +{
> + if (!att)
> + return 0;
> +
> + return att->len;
> +}
> +
> +bool bt_att_set_mtu(struct bt_att *att, uint16_t mtu)
> +{
> + char *buf;
> +
> + if (!att)
> + return false;
> +
> + if (mtu < ATT_DEFAULT_LE_MTU)
> + return false;
> +
> + buf = malloc(mtu);
> + if (!buf)
> + return false;
> +
> + free(att->buf);
> +
> + att->len = mtu;
> + att->buf = buf;
> +
> + return true;
> +}
> +
> +static bool encode_mtu_req(const void *param, uint16_t length, void *buf,
> + uint16_t mtu, uint16_t *pdu_length)
> +{
> + const struct bt_att_exchange_mtu_req_param *cp = param;
> + const uint16_t len = 3;
> +
> + if (length != sizeof(struct bt_att_exchange_mtu_req_param))
> + return false;
> +
> + if (len > mtu)
> + return false;
> +
> + put_le16(cp->client_rx_mtu, buf);
> + *pdu_length = len;
> +
> + return true;
> +}
> +
> +static bool encode_pdu(uint8_t opcode, const void *param, uint16_t length,
> + uint16_t mtu, void *pdu, uint16_t *pdu_length)
> +{
> + uint8_t *bytes = pdu;
> +
> + if (!bytes)
> + return false;
> +
> + bytes[0] = opcode;
> +
> + /* The length of the PDU depends on the specific ATT method. Special
> + * case the operations with variable-length PDU's here.
> + */
> + if (length == 0) {
> + *pdu_length = 1;
> + return true;
> + }
> +
> + if (!param)
> + return false;
> +
> + if (opcode == BT_ATT_OP_EXCHANGE_MTU_REQ) {
> + return encode_mtu_req(param, length, bytes + 1,
> + mtu, pdu_length);
> + }
> +
> + return false;
> +}
> +
> +static struct bt_att_request *create_request(uint8_t opcode, const void *param,
> + uint16_t length, void *buf, uint16_t mtu,
> + bt_att_request_func_t callback, void *user_data,
> + bt_att_destroy_func_t destroy)
> +{
> + struct bt_att_request *request;
> +
> + if (!opcode)
> + return NULL;
> +
> + if (length > 0 && !param)
> + return NULL;
> +
> + request = new0(struct bt_att_request, 1);
> + if (!request)
> + return NULL;
> +
> + if (!encode_pdu(opcode, param, length, mtu, buf, &request->len)) {
> + free(request);
> + return NULL;
> + }
> +
> + /* request->len is at least 1 due to the opcode */
> + request->pdu = malloc(request->len);
> + if (!request->pdu) {
> + free(request);
> + return NULL;
> + }
> +
> + if (request->len > 0)
> + memcpy(request->pdu, buf, request->len);
> +
> + request->opcode = opcode;
> + request->callback = callback;
> + request->destroy = destroy;
> + request->user_data = user_data;
> +
> + return request;
> +}
> +
> +unsigned int bt_att_send_sequential(struct bt_att *att, uint8_t opcode,
> + const void *param, uint16_t length,
> + bt_att_request_func_t callback, void *user_data,
> + bt_att_destroy_func_t destroy)
> +{
> + struct bt_att_request *request;
> +
> + if (!att)
> + return 0;
> +
> + request = create_request(opcode, param, length, att->buf, att->len,
> + callback, user_data, destroy);
> +
> + if (!request)
> + return 0;
> +
> + if (att->next_request_id < 1)
> + att->next_request_id = 1;
> +
> + request->id = att->next_request_id++;
> +
> + if (!queue_push_tail(att->request_queue, request)) {
> + free(request->pdu);
> + free(request);
> + return 0;
> + }
> +
> + wakeup_writer(att);
> +
> + return request->id;
> +}
> +
> +bool bt_att_cancel_all(struct bt_att *att)
> +{
> + if (!att)
> + return false;
> +
> + queue_remove_all(att->pending_list, NULL, NULL, destroy_request);
> + queue_remove_all(att->request_queue, NULL, NULL, destroy_request);
> +
> + return true;
> +}
> diff --git a/src/shared/att.h b/src/shared/att.h
> new file mode 100644
> index 0000000..8fe8805
> --- /dev/null
> +++ b/src/shared/att.h
> @@ -0,0 +1,101 @@
> +/*
> + *
> + * BlueZ - Bluetooth protocol stack for Linux
> + *
> + * Copyright (C) 2014 Google Inc.
> + *
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
> + *
> + */
> +
> +#include <stdbool.h>
> +#include <stdint.h>
> +
> +/* Error response */
> +#define BT_ATT_OP_ERROR_RESP 0x01
> +struct bt_att_error_rsp_param {
> + uint8_t request_opcode;
> + uint16_t handle;
> + uint8_t error_code;
> +};
> +
> +/* Exchange MTU */
> +#define BT_ATT_OP_EXCHANGE_MTU_REQ 0x02
> +struct bt_att_exchange_mtu_req_param {
> + uint16_t client_rx_mtu;
> +};
> +
> +#define BT_ATT_OP_EXCHANGE_MTU_RESP 0x03
> +struct bt_att_exchange_mtu_rsp_param {
> + uint16_t server_rx_mtu;
> +};
> +
> +/* Error codes for Error response PDU */
> +#define BT_ATT_ERROR_INVALID_HANDLE 0x01
> +#define BT_ATT_ERROR_READ_NOT_PERMITTED 0x02
> +#define BT_ATT_ERROR_WRITE_NOT_PERMITTED 0x03
> +#define BT_ATT_ERROR_INVALID_PDU 0x04
> +#define BT_ATT_ERROR_AUTHENTICATION 0x05
> +#define BT_ATT_ERROR_REQUEST_NOT_SUPPORTED 0x06
> +#define BT_ATT_ERROR_INVALID_OFFSET 0x07
> +#define BT_ATT_ERROR_AUTHORIZATION 0x08
> +#define BT_ATT_ERROR_PREPARE_QUEUE_FULL 0x09
> +#define BT_ATT_ERROR_ATTRIBUTE_NOT_FOUND 0x0A
> +#define BT_ATT_ERROR_ATTRIBUTE_NOT_LONG 0x0B
> +#define BT_ATT_ERROR_INSUFFICIENT_ENCRYPTION_KEY_SIZE 0x0C
> +#define BT_ATT_ERROR_INVALID_ATTRIBUTE_VALUE_LEN 0x0D
> +#define BT_ATT_ERROR_UNLIKELY 0x0E
> +#define BT_ATT_ERROR_INSUFFICIENT_ENCRYPTION 0x0F
> +#define BT_ATT_ERROR_UNSUPPORTED_GROUP_TYPE 0x10
> +#define BT_ATT_ERROR_INSUFFICIENT_RESOURCES 0x11
> +
> +typedef void (*bt_att_destroy_func_t)(void *user_data);
> +
> +struct bt_att;
> +
> +struct bt_att *bt_att_new(int fd);
> +
> +struct bt_att *bt_att_ref(struct bt_att *att);
> +void bt_att_unref(struct bt_att *att);
> +
> +typedef void (*bt_att_debug_func_t)(const char *str, void *user_data);
> +
> +bool bt_att_set_debug(struct bt_att *att, bt_att_debug_func_t callback,
> + void *user_data, bt_att_destroy_func_t destroy);
> +
> +bool bt_att_set_close_on_unref(struct bt_att *att, bool do_close);
> +
> +uint16_t bt_att_get_mtu(struct bt_att *att);
> +bool bt_att_set_mtu(struct bt_att *att, uint16_t mtu);
> +
> +typedef void (*bt_att_request_func_t)(uint8_t opcode, const void *param,
> + uint16_t length, void *user_data);
> +
> +/*
> + * bt_att_send_sequential is used to send ATT protocol requests and
> + * indications which invoke a response or confirmation from the remote device.
> + * All commands issued through this function will be queued and processed
> + * sequentially as a response/confirmation for each one is received from the
> + * remote device. Note that a client implementation would use this to only send
> + * ATT protocol requests whereas a server implementation would use this to only
> + * send ATT protocol indications.
> + */
> +unsigned int bt_att_send_sequential(struct bt_att *att, uint8_t opcode,
> + const void *param, uint16_t length,
> + bt_att_request_func_t callback, void *user_data,
> + bt_att_destroy_func_t destroy);
That is the implied behavior for _send functions. So I would not use _send_sequential here at all.
I am still not sure that we should be doing it like this. We tried this with gattrib and it did not turn out that great. I really like the approach of I send this command and expect this PDU back or an error. The reason here is that in theory you can get interleaved commands/response on the same channel.
So this is what you would normally expect:
-> command
<- response
Straight forward and simple, right. However nothing is stopping the other side from issues the same command in the other direction.
-> command
<- command
<- response
-> response
And this is not to mention notifications and confirmations that can happen as well.
I am thinking out loud here. What might help is a table that classifies which opcode is a command, response, notification or confirmation and based on that we just do the right thing.
Unfortunately we need to get this one right and I know that rebasing patches can be a pain. So if you just want to send the initial 01/01 patch for this then that is fine with me as well. I think some units tests with this overlapping bi-directional communication would be amazingly great to have. I do wonder if other OSes handle this well.
Regards
Marcel
--
To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
