1 /*
2  * Copyright (C) 2020 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 "client/mdns_utils.h"
18 
19 #include <android-base/strings.h>
20 
21 namespace mdns {
22 
23 // <Instance>.<Service>.<Domain>
24 std::optional<MdnsInstance> mdns_parse_instance_name(std::string_view name) {
25     CHECK(!name.empty());
26 
27     // Return the whole name if it doesn't fall under <Instance>.<Service>.<Domain> or
28     // <Instance>.<Service>
29     bool has_local_suffix = false;
30     // Strip the local suffix, if any
31     {
32         std::string local_suffix = ".local";
33         local_suffix += android::base::EndsWith(name, ".") ? "." : "";
34 
35         if (android::base::ConsumeSuffix(&name, local_suffix)) {
36             if (name.empty()) {
37                 return std::nullopt;
38             }
39             has_local_suffix = true;
40         }
41     }
42 
43     std::string transport;
44     // Strip the transport suffix, if any
45     {
46         std::string add_dot = (!has_local_suffix && android::base::EndsWith(name, ".")) ? "." : "";
47         std::array<std::string, 2> transport_suffixes{"._tcp", "._udp"};
48 
49         for (const auto& t : transport_suffixes) {
50             if (android::base::ConsumeSuffix(&name, t + add_dot)) {
51                 if (name.empty()) {
52                     return std::nullopt;
53                 }
54                 transport = t.substr(1);
55                 break;
56             }
57         }
58 
59         if (has_local_suffix && transport.empty()) {
60             return std::nullopt;
61         }
62     }
63 
64     if (!has_local_suffix && transport.empty()) {
65         return std::make_optional<MdnsInstance>(name, "", "");
66     }
67 
68     // Split the service name from the instance name
69     auto pos = name.rfind(".");
70     if (pos == 0 || pos == std::string::npos || pos == name.size() - 1) {
71         return std::nullopt;
72     }
73 
74     return std::make_optional<MdnsInstance>(name.substr(0, pos), name.substr(pos + 1), transport);
75 }
76 
77 }  // namespace mdns
78