From 88e0af714a9d7d8b0b3e22930898e57dcffec158 Mon Sep 17 00:00:00 2001
From: Szymon Janc <szymon.janc@tieto.com>
Date: Sat, 7 Feb 2015 16:18:17 +0100
Subject: [PATCH] android/gatt: Add helper for getting local MTU

This helper makes code easier to follow. Also local MTU is now
MIN(IMTU,OMTU) to avoid situation that where local OMTU is
lower than negotiated MTU.
---
 android/gatt.c | 97 ++++++++++++++++++++++++--------------------------
 1 file changed, 46 insertions(+), 51 deletions(-)

diff --git a/android/gatt.c b/android/gatt.c
index 45d70fdcf..d5f3d7df9 100644
--- a/android/gatt.c
+++ b/android/gatt.c
@@ -954,15 +954,38 @@ static gboolean disconnected_cb(GIOChannel *io, GIOCondition cond,
 	return FALSE;
 }
 
+static bool get_local_mtu(struct gatt_device *dev, uint16_t *mtu)
+{
+	GIOChannel *io;
+	uint16_t imtu, omtu;
+
+	io = g_attrib_get_channel(dev->attrib);
+
+	if (!bt_io_get(io, NULL, BT_IO_OPT_IMTU, &imtu, BT_IO_OPT_OMTU, &omtu,
+							BT_IO_OPT_INVALID)) {
+		error("gatt: Failed to get local MTU");
+		return false;
+	}
+
+	/*
+	 * Limit MTU to  MIN(IMTU, OMTU). This is to avoid situation where
+	 * local OMTU < MIN(remote MTU, IMTU)
+	 */
+	if (mtu)
+		*mtu = MIN(imtu, omtu);
+
+	DBG("mtu %u", *mtu);
+
+	return true;
+}
+
 static void att_handler(const uint8_t *ipdu, uint16_t len, gpointer user_data);
 
 static void exchange_mtu_cb(guint8 status, const guint8 *pdu, guint16 plen,
 							gpointer user_data)
 {
 	struct gatt_device *device = user_data;
-	GIOChannel *io;
-	GError *gerr = NULL;
-	uint16_t rmtu, mtu, imtu;
+	uint16_t rmtu, lmtu, mtu;
 
 	if (status) {
 		error("gatt: MTU exchange: %s", att_ecode2str(status));
@@ -975,28 +998,22 @@ static void exchange_mtu_cb(guint8 status, const guint8 *pdu, guint16 plen,
 	}
 
 	if (rmtu < ATT_DEFAULT_LE_MTU) {
-		error("gatt: MTU exchange: mtu error");
+		error("gatt: MTU exchange: remote MTU invalid (%u)", rmtu);
 		goto failed;
 	}
 
-	io = g_attrib_get_channel(device->attrib);
+	if (!get_local_mtu(device, &lmtu))
+		goto failed;
 
-	bt_io_get(io, &gerr, BT_IO_OPT_IMTU, &imtu, BT_IO_OPT_INVALID);
-	if (gerr) {
-		error("gatt: Could not get imtu: %s", gerr->message);
-		g_error_free(gerr);
+	mtu = MIN(lmtu, rmtu);
 
-		return;
-	}
-
-	mtu = MIN(rmtu, imtu);
-	if (mtu != imtu && !g_attrib_set_mtu(device->attrib, mtu)) {
+	if (mtu != ATT_DEFAULT_LE_MTU &&
+				!g_attrib_set_mtu(device->attrib, mtu)) {
 		error("gatt: MTU exchange failed");
 		goto failed;
 	}
 
-	DBG("MTU exchange succeeded: rmtu:%d, old mtu:%d, new mtu:%d", rmtu,
-								imtu, mtu);
+	DBG("MTU exchange succeeded: remote mtu:%d local mtu:%d", rmtu, lmtu);
 
 failed:
 	device_unref(device);
@@ -1004,21 +1021,12 @@ failed:
 
 static void send_exchange_mtu_request(struct gatt_device *device)
 {
-	GIOChannel *io;
-	GError *gerr = NULL;
-	uint16_t imtu;
-
-	io = g_attrib_get_channel(device->attrib);
-
-	bt_io_get(io, &gerr, BT_IO_OPT_IMTU, &imtu, BT_IO_OPT_INVALID);
-	if (gerr) {
-		error("gatt: Could not get imtu: %s", gerr->message);
-		g_error_free(gerr);
+	uint16_t mtu;
 
+	if (!get_local_mtu(device, &mtu))
 		return;
-	}
 
-	if (!gatt_exchange_mtu(device->attrib, imtu, exchange_mtu_cb,
+	if (!gatt_exchange_mtu(device->attrib, mtu, exchange_mtu_cb,
 							device_ref(device)))
 		device_unref(device);
 }
@@ -6131,50 +6139,37 @@ static uint8_t read_request(const uint8_t *cmd, uint16_t cmd_len,
 static uint8_t mtu_att_handle(const uint8_t *cmd, uint16_t cmd_len,
 							struct gatt_device *dev)
 {
-	uint16_t mtu, imtu, omtu, cid;
+	uint16_t rmtu, mtu, len;
 	size_t length;
-	GIOChannel *io;
-	GError *gerr = NULL;
-	uint16_t len;
 	uint8_t *rsp;
 
 	DBG("");
 
-	len = dec_mtu_req(cmd, cmd_len, &mtu);
+	len = dec_mtu_req(cmd, cmd_len, &rmtu);
 	if (!len)
 		return ATT_ECODE_INVALID_PDU;
 
-	if (mtu < ATT_DEFAULT_LE_MTU)
+	if (rmtu < ATT_DEFAULT_LE_MTU)
 		return ATT_ECODE_REQ_NOT_SUPP;
 
-	io = g_attrib_get_channel(dev->attrib);
-
-	bt_io_get(io, &gerr,
-			BT_IO_OPT_CID, &cid,
-			BT_IO_OPT_IMTU, &imtu,
-			BT_IO_OPT_OMTU, &omtu,
-			BT_IO_OPT_INVALID);
-	if (gerr) {
-		error("bt_io_get: %s", gerr->message);
-		g_error_free(gerr);
+	/* MTU exchange shall not be used on BR/EDR - Vol 3. Part G. 4.3.1 */
+	if (get_cid(dev) != ATT_CID)
 		return ATT_ECODE_UNLIKELY;
-	}
 
-	/* MTU exchange shall not be used on BR/EDR - Vol 3. Part G. 4.3.1 */
-	if (cid != ATT_CID)
+	if (!get_local_mtu(dev, &mtu))
 		return ATT_ECODE_UNLIKELY;
 
 	rsp = g_attrib_get_buffer(dev->attrib, &length);
 
-	/* Respond with our IMTU */
-	len = enc_mtu_resp(imtu, rsp, length);
+	/* Respond with our MTU */
+	len = enc_mtu_resp(mtu, rsp, length);
 	if (!len)
 		return ATT_ECODE_UNLIKELY;
 
 	g_attrib_send(dev->attrib, 0, rsp, len, NULL, NULL, NULL);
 
-	/* Limit OMTU to received value */
-	mtu = MIN(mtu, omtu);
+	/* Limit MTU to received value */
+	mtu = MIN(mtu, rmtu);
 	g_attrib_set_mtu(dev->attrib, mtu);
 
 	return 0;
-- 
2.47.3