It can be useful for programs using GATT to be aware of the maximum
transmittable packet size, as negotiated by bluetoothd. This change
exposes the negotiated MTU over D-Bus, if such a negotiation has
occurred.
---
client/main.c | 1 +
doc/device-api.txt | 5 +++++
src/device.c | 31 +++++++++++++++++++++++++++++++
src/shared/gatt-server.c | 15 +++++++++++++++
src/shared/gatt-server.h | 3 +++
5 files changed, 55 insertions(+)
diff --git a/client/main.c b/client/main.c
index 255cbd5..6435674 100644
--- a/client/main.c
+++ b/client/main.c
@@ -1372,6 +1372,7 @@ static void cmd_info(const char *arg)
print_property(proxy, "ServiceData");
print_property(proxy, "RSSI");
print_property(proxy, "TxPower");
+ print_property(proxy, "NegotiatedMTU");
}
static void pair_reply(DBusMessage *message, void *user_data)
diff --git a/doc/device-api.txt b/doc/device-api.txt
index 13b2881..908616b 100644
--- a/doc/device-api.txt
+++ b/doc/device-api.txt
@@ -234,3 +234,8 @@ Properties string Address [readonly]
array{byte} AdvertisingFlags [readonly, experimental]
The Advertising Data Flags of the remote device.
+
+ int16 NegotiatedMTU [readonly, optional, experimental]
+
+ The ATT MTU negotiated with the connected host.
+ Available only once MTU negotiation is complete.
diff --git a/src/device.c b/src/device.c
index 8693eb8..1b171ee 100644
--- a/src/device.c
+++ b/src/device.c
@@ -930,6 +930,35 @@ static gboolean
dev_property_exists_tx_power(const GDBusPropertyTable *property,
return TRUE;
}
+static gboolean dev_property_get_negotiated_mtu(
+ const GDBusPropertyTable * property,
+ DBusMessageIter *iter, void *data)
+{
+ const struct btd_device *dev = data;
+ dbus_int16_t val = 0;
+ int err;
+
+ err = bt_gatt_server_get_negotiated_mtu(dev->server, &val);
+ if (err != 0)
+ return FALSE;
+
+ dbus_message_iter_append_basic(iter, DBUS_TYPE_INT16, &val);
+
+ return TRUE;
+}
+
+static gboolean dev_property_exists_negotiated_mtu(
+ const GDBusPropertyTable * property,
+ void *data)
+{
+ const struct btd_device *dev = data;
+ int err;
+
+ err = bt_gatt_server_get_negotiated_mtu(dev->server, NULL);
+
+ return err == 0;
+}
+
static gboolean
dev_property_get_svc_resolved(const GDBusPropertyTable *property,
DBusMessageIter *iter, void *data)
@@ -2561,6 +2590,8 @@ static const GDBusPropertyTable
device_properties[] = {
NULL, dev_property_service_data_exist },
{ "TxPower", "n", dev_property_get_tx_power, NULL,
dev_property_exists_tx_power },
+ { "NegotiatedMTU", "n", dev_property_get_negotiated_mtu, NULL,
+ dev_property_exists_negotiated_mtu },
{ "ServicesResolved", "b", dev_property_get_svc_resolved, NULL, NULL
},
{ "AdvertisingFlags", "ay", dev_property_get_flags, NULL,
dev_property_flags_exist,
diff --git a/src/shared/gatt-server.c b/src/shared/gatt-server.c
index 79e01c8..2727f09 100644
--- a/src/shared/gatt-server.c
+++ b/src/shared/gatt-server.c
@@ -89,6 +89,7 @@ struct bt_gatt_server {
struct bt_att *att;
int ref_count;
uint16_t mtu;
+ bool mtu_negotiated;
unsigned int mtu_id;
unsigned int read_by_grp_type_id;
@@ -1378,12 +1379,25 @@ static void exchange_mtu_cb(uint8_t opcode,
const void *pdu,
/* Set MTU to be the minimum */
server->mtu = final_mtu;
+ server->mtu_negotiated = true;
bt_att_set_mtu(server->att, final_mtu);
util_debug(server->debug_callback, server->debug_data,
"MTU exchange complete, with MTU: %u", final_mtu);
}
+int bt_gatt_server_get_negotiated_mtu(const struct bt_gatt_server
*server,
+ int16_t *mtu)
+{
+ if (!server || !server->mtu_negotiated)
+ return -1;
+
+ if (mtu)
+ *mtu = server->mtu;
+
+ return 0;
+}
+
static bool gatt_server_register_att_handlers(struct bt_gatt_server
*server)
{
/* Exchange MTU */
@@ -1493,6 +1507,7 @@ struct bt_gatt_server *bt_gatt_server_new(struct
gatt_db *db,
server->db = gatt_db_ref(db);
server->att = bt_att_ref(att);
server->mtu = MAX(mtu, BT_ATT_DEFAULT_LE_MTU);
+ server->mtu_negotiated = false;
server->max_prep_queue_len = DEFAULT_MAX_PREP_QUEUE_LEN;
server->prep_queue = queue_new();
diff --git a/src/shared/gatt-server.h b/src/shared/gatt-server.h
index 0e480e1..0b99da5 100644
--- a/src/shared/gatt-server.h
+++ b/src/shared/gatt-server.h
@@ -31,6 +31,9 @@ struct bt_gatt_server *bt_gatt_server_new(struct
gatt_db *db,
struct bt_gatt_server *bt_gatt_server_ref(struct bt_gatt_server
*server);
void bt_gatt_server_unref(struct bt_gatt_server *server);
+int bt_gatt_server_get_negotiated_mtu(const struct bt_gatt_server
*server,
+ int16_t *mtu);
+
typedef void (*bt_gatt_server_destroy_func_t)(void *user_data);
typedef void (*bt_gatt_server_debug_func_t)(const char *str, void
*user_data);
typedef void (*bt_gatt_server_conf_func_t)(void *user_data);
