zeroconf/avahi: move generic sources to lib/avahi

src/lib/avahi/Publisher.cxx

@@ -0,0 +1,231 @@
+/*
+ * Copyright 2007-2021 CM4all GmbH
+ * All rights reserved.
+ *
+ * author: Max Kellermann <mk@cm4all.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "Publisher.hxx"
+#include "Service.hxx"
+#include "Client.hxx"
+#include "Error.hxx"
+#include "ErrorHandler.hxx"
+#include "net/SocketAddress.hxx"
+
+#include <avahi-common/error.h>
+#include <avahi-common/malloc.h>
+#include <avahi-common/alternative.h>
+
+#include <cassert>
+
+#include <stdio.h>
+#include <unistd.h>
+
+namespace Avahi {
+
+/**
+ * Append the process id to the given prefix string.  This is used as
+ * a workaround for an avahi-daemon bug/problem: when a service gets
+ * restarted, and then binds to a new port number (e.g. beng-proxy
+ * with automatic port assignment), we don't get notified, and so we
+ * never query the new port.  By appending the process id to the
+ * client name, we ensure that the exiting old process broadcasts
+ * AVAHI_BROWSER_REMOVE, and hte new process broadcasts
+ * AVAHI_BROWSER_NEW.
+ */
+static std::string
+MakePidName(const char *prefix)
+{
+	char buffer[256];
+	snprintf(buffer, sizeof(buffer), "%s[%u]", prefix, (unsigned)getpid());
+	return buffer;
+}
+
+Publisher::Publisher(Client &_client, const char *_name,
+		     std::forward_list<Service> _services,
+		     ErrorHandler &_error_handler) noexcept
+	:error_handler(_error_handler),
+	 name(MakePidName(_name)),
+	 client(_client), services(std::move(_services))
+{
+	assert(!services.empty());
+
+	client.AddListener(*this);
+
+	auto *c = client.GetClient();
+	if (c != nullptr)
+		RegisterServices(c);
+}
+
+Publisher::~Publisher() noexcept
+{
+	client.RemoveListener(*this);
+}
+
+inline void
+Publisher::GroupCallback(AvahiEntryGroup *g,
+			 AvahiEntryGroupState state) noexcept
+{
+	switch (state) {
+	case AVAHI_ENTRY_GROUP_ESTABLISHED:
+		break;
+
+	case AVAHI_ENTRY_GROUP_COLLISION:
+		if (!visible)
+			/* meanwhile, HideServices() has been called */
+			return;
+
+		/* pick a new name */
+
+		{
+			char *new_name = avahi_alternative_service_name(name.c_str());
+			name = new_name;
+			avahi_free(new_name);
+		}
+
+		/* And recreate the services */
+		RegisterServices(avahi_entry_group_get_client(g));
+		break;
+
+	case AVAHI_ENTRY_GROUP_FAILURE:
+		error_handler.OnAvahiError(std::make_exception_ptr(MakeError(*avahi_entry_group_get_client(g),
+									     "Avahi service group failure")));
+		break;
+
+	case AVAHI_ENTRY_GROUP_UNCOMMITED:
+	case AVAHI_ENTRY_GROUP_REGISTERING:
+		break;
+	}
+}
+
+void
+Publisher::GroupCallback(AvahiEntryGroup *g,
+			 AvahiEntryGroupState state,
+			 void *userdata) noexcept
+{
+	auto &publisher = *(Publisher *)userdata;
+	publisher.GroupCallback(g, state);
+}
+
+static void
+AddService(AvahiEntryGroup &group, const Service &service,
+	   const char *name)
+{
+	int error = avahi_entry_group_add_service(&group,
+						  service.interface,
+						  service.protocol,
+						  AvahiPublishFlags(0),
+						  name, service.type.c_str(),
+						  nullptr, nullptr,
+						  service.port, nullptr);
+	if (error != AVAHI_OK)
+		throw MakeError(error, "Failed to add Avahi service");
+}
+
+static void
+AddServices(AvahiEntryGroup &group,
+	    const std::forward_list<Service> &services, const char *name)
+{
+	for (const auto &i : services)
+		AddService(group, i, name);
+}
+
+static EntryGroupPtr
+MakeEntryGroup(AvahiClient &c,
+	       const std::forward_list<Service> &services, const char *name,
+	       AvahiEntryGroupCallback callback, void *userdata)
+{
+	EntryGroupPtr group(avahi_entry_group_new(&c, callback, userdata));
+	if (!group)
+		throw MakeError(c, "Failed to create Avahi service group");
+
+	AddServices(*group, services, name);
+
+	int error = avahi_entry_group_commit(group.get());
+	if (error != AVAHI_OK)
+		throw MakeError(error, "Failed to commit Avahi service group");
+
+	return group;
+}
+
+void
+Publisher::RegisterServices(AvahiClient *c) noexcept
+{
+	assert(visible);
+
+	try {
+		group = MakeEntryGroup(*c, services, name.c_str(),
+				       GroupCallback, this);
+	} catch (...) {
+		error_handler.OnAvahiError(std::current_exception());
+	}
+}
+
+void
+Publisher::HideServices() noexcept
+{
+	if (!visible)
+		return;
+
+	visible = false;
+	group.reset();
+}
+
+void
+Publisher::ShowServices() noexcept
+{
+	if (visible)
+		return;
+
+	visible = true;
+
+	auto *c = client.GetClient();
+	if (c != nullptr)
+		RegisterServices(c);
+}
+
+void
+Publisher::OnAvahiConnect(AvahiClient *c) noexcept
+{
+	if (group == nullptr && visible)
+		RegisterServices(c);
+}
+
+void
+Publisher::OnAvahiDisconnect() noexcept
+{
+	group.reset();
+}
+
+void
+Publisher::OnAvahiChanged() noexcept
+{
+	group.reset();
+}
+
+} // namespace Avahi