From cd1111e16f6f5edb48e23a5d8acd9dd54727bd97 Mon Sep 17 00:00:00 2001
From: Johan Hedberg <johan.hedberg@intel.com>
Date: Wed, 6 Jun 2018 16:28:01 +0200
Subject: [PATCH] mgmt: Reduce net_buf user data requirement

Instead of storing a bt_addr_le_t, just store a pointer to the bt_conn
object (which is what the code is interested in anyway). This way the
user data size requirement drops from 7 to 4, which is the default
that all current users are happy with.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
---
 subsys/mgmt/Kconfig  |  4 ++--
 subsys/mgmt/smp_bt.c | 37 +++++++++++++++++++++++++++----------
 2 files changed, 29 insertions(+), 12 deletions(-)

diff --git a/subsys/mgmt/Kconfig b/subsys/mgmt/Kconfig
index 3c35684385..99e22d1e96 100644
--- a/subsys/mgmt/Kconfig
+++ b/subsys/mgmt/Kconfig
@@ -87,10 +87,10 @@ config MCUMGR_BUF_SIZE
 config MCUMGR_BUF_USER_DATA_SIZE
 	int
 	prompt "Size of mcumgr buffer user data"
-	default 7
+	default 4
 	help
 	  The size, in bytes, of user data to allocate for each mcumgr buffer.
 	  Different mcumgr transports impose different requirements for this
-	  setting.  A value of 7 is sufficient for UART, shell, and bluetooth.
+	  setting.  A value of 4 is sufficient for UART, shell, and bluetooth.
 
 endmenu
diff --git a/subsys/mgmt/smp_bt.c b/subsys/mgmt/smp_bt.c
index c667f4e87c..44d5a55c2f 100644
--- a/subsys/mgmt/smp_bt.c
+++ b/subsys/mgmt/smp_bt.c
@@ -23,6 +23,10 @@
 
 struct device;
 
+struct smp_bt_user_data {
+	struct bt_conn *conn;
+};
+
 static struct zephyr_smp_transport smp_bt_transport;
 
 /* SMP service.
@@ -47,14 +51,14 @@ static ssize_t smp_bt_chr_write(struct bt_conn *conn,
 				const void *buf, u16_t len, u16_t offset,
 				u8_t flags)
 {
-	const bt_addr_le_t *addr;
+	struct smp_bt_user_data *ud;
 	struct net_buf *nb;
 
 	nb = mcumgr_buf_alloc();
 	net_buf_add_mem(nb, buf, len);
 
-	addr = bt_conn_get_dst(conn);
-	memcpy(net_buf_user_data(nb), addr, sizeof(*addr));
+	ud = net_buf_user_data(nb);
+	ud->conn = bt_conn_ref(conn);
 
 	zephyr_smp_rx_req(&smp_bt_transport, nb);
 
@@ -89,16 +93,17 @@ static int smp_bt_tx_rsp(struct bt_conn *conn, const void *data, u16_t len)
 }
 
 /**
- * Extracts the peer address from a net_buf's user data and looks up the
- * corresponding conection.
+ * Extracts the Bluetooth connection from a net_buf's user data.
  */
 static struct bt_conn *smp_bt_conn_from_pkt(const struct net_buf *nb)
 {
-	bt_addr_le_t addr;
+	struct smp_bt_user_data *ud = net_buf_user_data(nb);
 
-	/* Cast away const. */
-	memcpy(&addr, net_buf_user_data((void *)nb), sizeof(addr));
-	return bt_conn_lookup_addr_le(&addr);
+	if (!ud->conn) {
+		return NULL;
+	}
+
+	return bt_conn_ref(ud->conn);
 }
 
 /**
@@ -122,6 +127,18 @@ static u16_t smp_bt_get_mtu(const struct net_buf *nb)
 	return mtu - 3;
 }
 
+static void smp_bt_buf_free(struct net_buf *nb)
+{
+	struct smp_bt_user_data *ud = net_buf_user_data(nb);
+
+	if (ud->conn) {
+		bt_conn_unref(ud->conn);
+		ud->conn = NULL;
+	}
+
+	mcumgr_buf_free(nb);
+}
+
 /**
  * Transmits the specified SMP response.
  */
@@ -138,7 +155,7 @@ static int smp_bt_tx_pkt(struct zephyr_smp_transport *zst, struct net_buf *nb)
 		bt_conn_unref(conn);
 	}
 
-	mcumgr_buf_free(nb);
+	smp_bt_buf_free(nb);
 
 	return rc;
 }