| // +build !windows |
| |
| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| |
| package bll |
| |
| import ( |
| "runtime" |
| "time" |
| |
| log "github.com/Sirupsen/logrus" |
| "github.com/go-ble/ble" |
| |
| "mynewt.apache.org/newtmgr/nmxact/bledefs" |
| ) |
| |
| func exchangeMtu(cln ble.Client, preferredMtu uint16) (uint16, error) { |
| log.Debugf("Exchanging MTU") |
| |
| // We loop three times here to workaround an library issue with macOS. In |
| // macOS, the request to exchange MTU doesn't actually do anything. The |
| // BLE library relies on the assumption that the OS already exchanged MTUs |
| // on its own. If this assumption is incorrect, the number that was |
| // returned is the default out of date value (23). In this case, sleep and |
| // retry. |
| var mtu int |
| for i := 0; i < 3; i++ { |
| var err error |
| mtu, err = cln.ExchangeMTU(int(preferredMtu)) |
| if err != nil { |
| return 0, err |
| } |
| |
| // If this isn't macOS, accept the MTU the library reported. |
| if runtime.GOOS != "darwin" { |
| break |
| } |
| |
| // If macOS returned a value other than 23, then MTU exchange has |
| // completed. |
| if mtu != bledefs.BLE_ATT_MTU_DFLT { |
| break |
| } |
| |
| // Otherwise, give the OS some time to perform the exchange. |
| log.Debugf("macOS reports an MTU of 23. " + |
| "Assume exchange hasn't completed; wait and requery.") |
| time.Sleep(time.Second) |
| } |
| |
| log.Debugf("Exchanged MTU; ATT MTU = %d", mtu) |
| return uint16(mtu), nil |
| } |