Bluetooth: Mesh: Transport length checks should account for MIC

The Transport layer would previously rely on the access layer to check
whether there's room for the full message and a MIC in the available
buffer space, and its own checks would ignore the MIC. This should be
handled by the Transport layer checks, so the access layer doesn't have
to.

Signed-off-by: Trond Einar Snekvik <[email protected]>

Author: trond-snekvik

subsys/bluetooth/mesh/transport.c

@@ -632,12 +632,12 @@ int bt_mesh_trans_send(struct bt_mesh_net_tx *tx, struct net_buf_simple *msg,
 		return -EINVAL;
 	}
 
-	if (msg->len > BT_MESH_TX_SDU_MAX) {
-		BT_ERR("Not enough segment buffers for length %u", msg->len);
+	if (msg->len > BT_MESH_TX_SDU_MAX - BT_MESH_MIC_SHORT) {
+		BT_ERR("Message too big: %u", msg->len);
 		return -EMSGSIZE;
 	}
 
-	if (net_buf_simple_tailroom(msg) < 4) {
+	if (net_buf_simple_tailroom(msg) < BT_MESH_MIC_SHORT) {
 		BT_ERR("Insufficient tailroom for Transport MIC");
 		return -EINVAL;
 	}