zeroconf/avahi/Publisher: new class, replacing lots of code from ZeroconfAvahi.cxx

src/zeroconf/ZeroconfAvahi.cxx

@@ -21,41 +21,30 @@
 #include "avahi/Client.hxx"
 #include "avahi/ConnectionListener.hxx"
 #include "avahi/ErrorHandler.hxx"
+#include "avahi/Publisher.hxx"
+#include "avahi/Service.hxx"
 #include "ZeroconfInternal.hxx"
 #include "Listen.hxx"
 #include "util/Domain.hxx"
 #include "util/RuntimeError.hxx"
 #include "Log.hxx"
 
-#include <avahi-client/client.h>
-#include <avahi-client/publish.h>
-
-#include <avahi-common/alternative.h>
 #include <avahi-common/domain.h>
-#include <avahi-common/malloc.h>
-#include <avahi-common/error.h>
 
 static constexpr Domain avahi_domain("avahi");
 
-class AvahiGlue final : Avahi::ErrorHandler, Avahi::ConnectionListener {
+class AvahiGlue final : Avahi::ErrorHandler {
 public:
 	Avahi::Client client;
+	Avahi::Publisher publisher;
 
-	explicit AvahiGlue(EventLoop &event_loop)
-		:client(event_loop, *this)
+	AvahiGlue(EventLoop &event_loop,
+		  const char *name, std::forward_list<Avahi::Service> services)
+		:client(event_loop, *this),
+		 publisher(client, name, std::move(services), *this)
 	{
-		client.AddListener(*this);
-	}
-
-	~AvahiGlue() noexcept {
-		client.RemoveListener(*this);
 	}
 
-	/* virtual methods from class AvahiConnectionListener */
-	void OnAvahiConnect(AvahiClient *client) noexcept override;
-	void OnAvahiDisconnect() noexcept override;
-	void OnAvahiChanged() noexcept override;
-
 	/* virtual methods from class Avahi::ErrorHandler */
 	bool OnAvahiError(std::exception_ptr e) noexcept override {
 		LogError(e);
@@ -63,141 +52,7 @@ public:
 	}
 };
 
-static char *avahi_name;
 static AvahiGlue *avahi_glue;
-static AvahiEntryGroup *avahi_group;
-
-static void
-AvahiRegisterService(AvahiClient *c);
-
-/**
- * Callback when the EntryGroup changes state.
- */
-static void
-AvahiGroupCallback(AvahiEntryGroup *g,
-		   AvahiEntryGroupState state,
-		   [[maybe_unused]] void *userdata)
-{
-	assert(g != nullptr);
-
-	FormatDebug(avahi_domain,
-		    "Service group changed to state %d", state);
-
-	switch (state) {
-	case AVAHI_ENTRY_GROUP_ESTABLISHED:
-		/* The entry group has been established successfully */
-		FormatNotice(avahi_domain,
-			     "Service '%s' successfully established.",
-			     avahi_name);
-		break;
-
-	case AVAHI_ENTRY_GROUP_COLLISION:
-		/* A service name collision happened. Let's pick a new name */
-		{
-			char *n = avahi_alternative_service_name(avahi_name);
-			avahi_free(avahi_name);
-			avahi_name = n;
-		}
-
-		FormatNotice(avahi_domain,
-			     "Service name collision, renaming service to '%s'",
-			     avahi_name);
-
-		/* And recreate the services */
-		AvahiRegisterService(avahi_entry_group_get_client(g));
-		break;
-
-	case AVAHI_ENTRY_GROUP_FAILURE:
-		FormatError(avahi_domain,
-			    "Entry group failure: %s",
-			    avahi_strerror(avahi_client_errno(avahi_entry_group_get_client(g))));
-		/* Some kind of failure happened while we were
-		   registering our services */
-		break;
-
-	case AVAHI_ENTRY_GROUP_UNCOMMITED:
-		LogDebug(avahi_domain, "Service group is UNCOMMITED");
-		break;
-
-	case AVAHI_ENTRY_GROUP_REGISTERING:
-		LogDebug(avahi_domain, "Service group is REGISTERING");
-	}
-}
-
-/**
- * Registers a new service with avahi.
- */
-static void
-AvahiRegisterService(AvahiClient *c)
-{
-	assert(c != nullptr);
-
-	FormatDebug(avahi_domain, "Registering service %s/%s",
-		    SERVICE_TYPE, avahi_name);
-
-	/* If this is the first time we're called,
-	 * let's create a new entry group */
-	if (!avahi_group) {
-		avahi_group = avahi_entry_group_new(c, AvahiGroupCallback, nullptr);
-		if (!avahi_group) {
-			FormatError(avahi_domain,
-				    "Failed to create avahi EntryGroup: %s",
-				    avahi_strerror(avahi_client_errno(c)));
-			return;
-		}
-	}
-
-	/* Add the service */
-	/* TODO: This currently binds to ALL interfaces.
-	 *       We could maybe add a service per actual bound interface,
-	 *       if that's better. */
-	int result = avahi_entry_group_add_service(avahi_group,
-						   AVAHI_IF_UNSPEC,
-						   AVAHI_PROTO_UNSPEC,
-						   AvahiPublishFlags(0),
-						   avahi_name, SERVICE_TYPE,
-						   nullptr, nullptr,
-						   listen_port, nullptr);
-	if (result < 0) {
-		FormatError(avahi_domain, "Failed to add service %s: %s",
-			    SERVICE_TYPE, avahi_strerror(result));
-		return;
-	}
-
-	/* Tell the server to register the service group */
-	result = avahi_entry_group_commit(avahi_group);
-	if (result < 0) {
-		FormatError(avahi_domain, "Failed to commit service group: %s",
-			    avahi_strerror(result));
-		return;
-	}
-}
-
-void
-AvahiGlue::OnAvahiConnect(AvahiClient *c) noexcept
-{
-	if (avahi_group == nullptr)
-		AvahiRegisterService(c);
-}
-
-void
-AvahiGlue::OnAvahiDisconnect() noexcept
-{
-	if (avahi_group != nullptr) {
-		avahi_entry_group_free(avahi_group);
-		avahi_group = nullptr;
-	}
-}
-
-void
-AvahiGlue::OnAvahiChanged() noexcept
-{
-	if (avahi_group != nullptr) {
-		LogDebug(avahi_domain, "Resetting group");
-		avahi_entry_group_reset(avahi_group);
-	}
-}
-
 
 void
 AvahiInit(EventLoop &loop, const char *serviceName)
@@ -207,9 +62,12 @@ AvahiInit(EventLoop &loop, const char *serviceName)
 	if (!avahi_is_valid_service_name(serviceName))
 		throw FormatRuntimeError("Invalid zeroconf_name \"%s\"", serviceName);
 
-	avahi_name = avahi_strdup(serviceName);
+	std::forward_list<Avahi::Service> services;
+	services.emplace_front(AVAHI_IF_UNSPEC,
+			       AVAHI_PROTO_UNSPEC,
+			       SERVICE_TYPE, listen_port);
 
-	avahi_glue = new AvahiGlue(loop);
+	avahi_glue = new AvahiGlue(loop, serviceName, std::move(services));
 }
 
 void
@@ -217,13 +75,5 @@ AvahiDeinit()
 {
 	LogDebug(avahi_domain, "Shutting down interface");
 
-	if (avahi_group != nullptr) {
-		avahi_entry_group_free(avahi_group);
-		avahi_group = nullptr;
-	}
-
 	delete avahi_glue;
-
-	avahi_free(avahi_name);
-	avahi_name = nullptr;
 }

src/zeroconf/avahi/EntryGroup.hxx

+/*
+ * 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.
+ */
+
+#pragma once
+
+#include <avahi-client/publish.h>
+
+#include <memory>
+
+namespace Avahi {
+
+struct EntryGroupDeleter {
+	void operator()(AvahiEntryGroup *g) noexcept {
+		avahi_entry_group_free(g);
+	}
+};
+
+using EntryGroupPtr = std::unique_ptr<AvahiEntryGroup, EntryGroupDeleter>;
+
+} // namespace Avahi

src/zeroconf/avahi/Publisher.cxx

+/*
+ * 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

src/zeroconf/avahi/Publisher.hxx

+/*
+ * 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.
+ */
+
+#pragma once
+
+#include "EntryGroup.hxx"
+#include "ConnectionListener.hxx"
+
+#include <avahi-client/publish.h>
+
+#include <string>
+#include <forward_list>
+
+class SocketAddress;
+
+namespace Avahi {
+
+struct Service;
+class ErrorHandler;
+class Client;
+
+/**
+ * A helper class which manages a list of services to be published via
+ * Avahi/Zeroconf.
+ */
+class Publisher final : ConnectionListener {
+	ErrorHandler &error_handler;
+
+	std::string name;
+
+	Client &client;
+
+	EntryGroupPtr group;
+
+	const std::forward_list<Service> services;
+
+	/**
+	 * Shall the published services be visible?  This is controlled by
+	 * HideServices() and ShowServices().
+	 */
+	bool visible = true;
+
+public:
+	Publisher(Client &client, const char *_name,
+		  std::forward_list<Service> _services,
+		  ErrorHandler &_error_handler) noexcept;
+	~Publisher() noexcept;
+
+	Publisher(const Publisher &) = delete;
+	Publisher &operator=(const Publisher &) = delete;
+
+	/**
+	 * Temporarily hide all registered services.  You can undo this
+	 * with ShowServices().
+	 */
+	void HideServices() noexcept;
+
+	/**
+	 * Undo HideServices().
+	 */
+	void ShowServices() noexcept;
+
+private:
+	void GroupCallback(AvahiEntryGroup *g,
+			   AvahiEntryGroupState state) noexcept;
+	static void GroupCallback(AvahiEntryGroup *g,
+				  AvahiEntryGroupState state,
+				  void *userdata) noexcept;
+
+	void RegisterServices(AvahiClient *c) noexcept;
+
+	/* virtual methods from class AvahiConnectionListener */
+	void OnAvahiConnect(AvahiClient *client) noexcept override;
+	void OnAvahiDisconnect() noexcept override;
+	void OnAvahiChanged() noexcept override;
+};
+
+} // namespace Avahi

src/zeroconf/avahi/Service.hxx

+/*
+ * 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.
+ */
+
+#pragma once
+
+#include <avahi-common/address.h>
+
+#include <cstdint>
+#include <string>
+
+namespace Avahi {
+
+struct Service {
+	AvahiIfIndex interface = AVAHI_IF_UNSPEC;
+	AvahiProtocol protocol = AVAHI_PROTO_UNSPEC;
+	std::string type;
+	uint16_t port;
+
+	Service(AvahiIfIndex _interface, AvahiProtocol _protocol,
+		const char *_type, uint16_t _port) noexcept
+		:interface(_interface), protocol(_protocol),
+		 type(_type), port(_port) {}
+};
+
+} // namespace Avahi

src/zeroconf/avahi/meson.build

@@ -9,6 +9,7 @@ avahi = static_library(
   'Client.cxx',
   'Error.cxx',
   'Poll.cxx',
+  'Publisher.cxx',
   include_directories: inc,
   dependencies: [
     libavahi_client,