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      1 /*
      2  * Copyright (C) 2016 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #include "adb_mdns.h"
     18 #include "sysdeps.h"
     19 
     20 #include <dns_sd.h>
     21 #include <endian.h>
     22 #include <unistd.h>
     23 
     24 #include <chrono>
     25 #include <mutex>
     26 #include <thread>
     27 
     28 #include <android-base/logging.h>
     29 #include <android-base/properties.h>
     30 
     31 using namespace std::chrono_literals;
     32 
     33 static std::mutex& mdns_lock = *new std::mutex();
     34 static int port;
     35 static DNSServiceRef mdns_ref;
     36 static bool mdns_registered = false;
     37 
     38 static void start_mdns() {
     39     if (android::base::GetProperty("init.svc.mdnsd", "") == "running") {
     40         return;
     41     }
     42 
     43     android::base::SetProperty("ctl.start", "mdnsd");
     44 
     45     if (! android::base::WaitForProperty("init.svc.mdnsd", "running", 5s)) {
     46         LOG(ERROR) << "Could not start mdnsd.";
     47     }
     48 }
     49 
     50 static void mdns_callback(DNSServiceRef /*ref*/,
     51                           DNSServiceFlags /*flags*/,
     52                           DNSServiceErrorType errorCode,
     53                           const char* /*name*/,
     54                           const char* /*regtype*/,
     55                           const char* /*domain*/,
     56                           void* /*context*/) {
     57     if (errorCode != kDNSServiceErr_NoError) {
     58         LOG(ERROR) << "Encountered mDNS registration error ("
     59             << errorCode << ").";
     60     }
     61 }
     62 
     63 static void setup_mdns_thread() {
     64     start_mdns();
     65     std::lock_guard<std::mutex> lock(mdns_lock);
     66 
     67     std::string hostname = "adb-";
     68     hostname += android::base::GetProperty("ro.serialno", "unidentified");
     69 
     70     auto error = DNSServiceRegister(&mdns_ref, 0, 0, hostname.c_str(),
     71                                     kADBServiceType, nullptr, nullptr,
     72                                     htobe16((uint16_t)port), 0, nullptr,
     73                                     mdns_callback, nullptr);
     74 
     75     if (error != kDNSServiceErr_NoError) {
     76         LOG(ERROR) << "Could not register mDNS service (" << error << ").";
     77         mdns_registered = false;
     78     }
     79 
     80     mdns_registered = true;
     81 }
     82 
     83 static void teardown_mdns() {
     84     std::lock_guard<std::mutex> lock(mdns_lock);
     85 
     86     if (mdns_registered) {
     87         DNSServiceRefDeallocate(mdns_ref);
     88     }
     89 }
     90 
     91 void setup_mdns(int port_in) {
     92     port = port_in;
     93     std::thread(setup_mdns_thread).detach();
     94 
     95     // TODO: Make this more robust against a hard kill.
     96     atexit(teardown_mdns);
     97 }
     98