1 /*
2 * Copyright 2007-2021 CM4all GmbH
3 * All rights reserved.
4 *
5 * author: Max Kellermann <mk@cm4all.com>
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 *
11 * - Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 *
14 * - Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the
17 * distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
21 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
22 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
23 * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
24 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
25 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
26 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
28 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
29 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
30 * OF THE POSSIBILITY OF SUCH DAMAGE.
31 */
32
33 #include "Publisher.hxx"
34 #include "Service.hxx"
35 #include "Client.hxx"
36 #include "Error.hxx"
37 #include "ErrorHandler.hxx"
38 #include "net/SocketAddress.hxx"
39
40 #include <avahi-common/error.h>
41 #include <avahi-common/malloc.h>
42 #include <avahi-common/alternative.h>
43
44 #include <cassert>
45
46 #include <stdio.h>
47 #include <unistd.h>
48
49 namespace Avahi {
50
51 /**
52 * Append the process id to the given prefix string. This is used as
53 * a workaround for an avahi-daemon bug/problem: when a service gets
54 * restarted, and then binds to a new port number (e.g. beng-proxy
55 * with automatic port assignment), we don't get notified, and so we
56 * never query the new port. By appending the process id to the
57 * client name, we ensure that the exiting old process broadcasts
58 * AVAHI_BROWSER_REMOVE, and hte new process broadcasts
59 * AVAHI_BROWSER_NEW.
60 */
61 static std::string
MakePidName(const char * prefix)62 MakePidName(const char *prefix)
63 {
64 char buffer[256];
65 snprintf(buffer, sizeof(buffer), "%s[%u]", prefix, (unsigned)getpid());
66 return buffer;
67 }
68
Publisher(Client & _client,const char * _name,std::forward_list<Service> _services,ErrorHandler & _error_handler)69 Publisher::Publisher(Client &_client, const char *_name,
70 std::forward_list<Service> _services,
71 ErrorHandler &_error_handler) noexcept
72 :error_handler(_error_handler),
73 name(MakePidName(_name)),
74 client(_client), services(std::move(_services))
75 {
76 assert(!services.empty());
77
78 client.AddListener(*this);
79
80 auto *c = client.GetClient();
81 if (c != nullptr)
82 RegisterServices(c);
83 }
84
~Publisher()85 Publisher::~Publisher() noexcept
86 {
87 client.RemoveListener(*this);
88 }
89
90 inline void
GroupCallback(AvahiEntryGroup * g,AvahiEntryGroupState state)91 Publisher::GroupCallback(AvahiEntryGroup *g,
92 AvahiEntryGroupState state) noexcept
93 {
94 switch (state) {
95 case AVAHI_ENTRY_GROUP_ESTABLISHED:
96 break;
97
98 case AVAHI_ENTRY_GROUP_COLLISION:
99 if (!visible)
100 /* meanwhile, HideServices() has been called */
101 return;
102
103 /* pick a new name */
104
105 {
106 char *new_name = avahi_alternative_service_name(name.c_str());
107 name = new_name;
108 avahi_free(new_name);
109 }
110
111 /* And recreate the services */
112 RegisterServices(avahi_entry_group_get_client(g));
113 break;
114
115 case AVAHI_ENTRY_GROUP_FAILURE:
116 error_handler.OnAvahiError(std::make_exception_ptr(MakeError(*avahi_entry_group_get_client(g),
117 "Avahi service group failure")));
118 break;
119
120 case AVAHI_ENTRY_GROUP_UNCOMMITED:
121 case AVAHI_ENTRY_GROUP_REGISTERING:
122 break;
123 }
124 }
125
126 void
GroupCallback(AvahiEntryGroup * g,AvahiEntryGroupState state,void * userdata)127 Publisher::GroupCallback(AvahiEntryGroup *g,
128 AvahiEntryGroupState state,
129 void *userdata) noexcept
130 {
131 auto &publisher = *(Publisher *)userdata;
132 publisher.GroupCallback(g, state);
133 }
134
135 static void
AddService(AvahiEntryGroup & group,const Service & service,const char * name)136 AddService(AvahiEntryGroup &group, const Service &service,
137 const char *name)
138 {
139 int error = avahi_entry_group_add_service(&group,
140 service.interface,
141 service.protocol,
142 AvahiPublishFlags(0),
143 name, service.type.c_str(),
144 nullptr, nullptr,
145 service.port, nullptr);
146 if (error != AVAHI_OK)
147 throw MakeError(error, "Failed to add Avahi service");
148 }
149
150 static void
AddServices(AvahiEntryGroup & group,const std::forward_list<Service> & services,const char * name)151 AddServices(AvahiEntryGroup &group,
152 const std::forward_list<Service> &services, const char *name)
153 {
154 for (const auto &i : services)
155 AddService(group, i, name);
156 }
157
158 static EntryGroupPtr
MakeEntryGroup(AvahiClient & c,const std::forward_list<Service> & services,const char * name,AvahiEntryGroupCallback callback,void * userdata)159 MakeEntryGroup(AvahiClient &c,
160 const std::forward_list<Service> &services, const char *name,
161 AvahiEntryGroupCallback callback, void *userdata)
162 {
163 EntryGroupPtr group(avahi_entry_group_new(&c, callback, userdata));
164 if (!group)
165 throw MakeError(c, "Failed to create Avahi service group");
166
167 AddServices(*group, services, name);
168
169 int error = avahi_entry_group_commit(group.get());
170 if (error != AVAHI_OK)
171 throw MakeError(error, "Failed to commit Avahi service group");
172
173 return group;
174 }
175
176 void
RegisterServices(AvahiClient * c)177 Publisher::RegisterServices(AvahiClient *c) noexcept
178 {
179 assert(visible);
180
181 try {
182 group = MakeEntryGroup(*c, services, name.c_str(),
183 GroupCallback, this);
184 } catch (...) {
185 error_handler.OnAvahiError(std::current_exception());
186 }
187 }
188
189 void
HideServices()190 Publisher::HideServices() noexcept
191 {
192 if (!visible)
193 return;
194
195 visible = false;
196 group.reset();
197 }
198
199 void
ShowServices()200 Publisher::ShowServices() noexcept
201 {
202 if (visible)
203 return;
204
205 visible = true;
206
207 auto *c = client.GetClient();
208 if (c != nullptr)
209 RegisterServices(c);
210 }
211
212 void
OnAvahiConnect(AvahiClient * c)213 Publisher::OnAvahiConnect(AvahiClient *c) noexcept
214 {
215 if (group == nullptr && visible)
216 RegisterServices(c);
217 }
218
219 void
OnAvahiDisconnect()220 Publisher::OnAvahiDisconnect() noexcept
221 {
222 group.reset();
223 }
224
225 void
OnAvahiChanged()226 Publisher::OnAvahiChanged() noexcept
227 {
228 group.reset();
229 }
230
231 } // namespace Avahi
232