iiod: Move Avahi support to its own dns-sd.c source file

Avoid having a huge #ifdef block in iiod.c by moving this code to a
dns-sd.c source file, that will be compiled conditionally.

Signed-off-by: Paul Cercueil <[email protected]>

iiod/CMakeLists.txt

@@ -60,6 +60,10 @@ endif ()
 
 add_definitions(-D_GNU_SOURCE=1)
 
+if (HAVE_AVAHI)
+	target_sources(iiod PRIVATE dns-sd.c)
+endif()
+
 if(NOT SKIP_INSTALL_ALL)
 	install(TARGETS iiod RUNTIME DESTINATION ${CMAKE_INSTALL_SBINDIR})
 endif()

iiod/dns-sd.c

@@ -0,0 +1,334 @@
+// SPDX-license-identifier: LGPL-v2-or-later
+/*
+ * libiio - Library for interfacing industrial I/O (IIO) devices
+ *
+ * Copyright (C) 2021 Analog Devices, Inc.
+ * Author: Paul Cercueil <[email protected]>
+ */
+
+#include "dns-sd.h"
+#include "ops.h"
+#include "thread-pool.h"
+
+#include "../debug.h"
+#include "../iio.h"
+
+#include <avahi-common/thread-watch.h>
+#include <avahi-common/error.h>
+#include <avahi-common/alternative.h>
+#include <avahi-common/malloc.h>
+#include <avahi-client/client.h>
+#include <avahi-client/publish.h>
+#include <avahi-common/domain.h>
+
+#include <stddef.h>
+#include <time.h>
+
+/***
+ * Parts of the avahi code are borrowed from the client-publish-service.c
+ * https://www.avahi.org/doxygen/html/client-publish-service_8c-example.html
+ * which is an example in the avahi library. Copyright Lennart Poettering
+ * released under the LGPL 2.1 or (at your option) any later version.
+ */
+
+/* Global Data */
+
+static struct avahi_data {
+	AvahiThreadedPoll *poll;
+	AvahiClient *client;
+	AvahiEntryGroup *group;
+	char * name;
+} avahi;
+
+static void create_services(AvahiClient *c);
+static AvahiClient * client_new(void);
+
+static void client_free()
+{
+	/* This also frees the entry group, if any. */
+	if (avahi.client) {
+		avahi_client_free(avahi.client);
+		avahi.client = NULL;
+		avahi.group = NULL;
+	}
+}
+
+static void shutdown_avahi()
+{
+	/* Stop the avahi client, if it's running. */
+	if (avahi.poll)
+		avahi_threaded_poll_stop(avahi.poll);
+
+	/* Clean up the avahi objects. The order is significant. */
+	client_free();
+	if (avahi.poll) {
+		avahi_threaded_poll_free(avahi.poll);
+		avahi.poll = NULL;
+	}
+	if (avahi.name) {
+		IIO_INFO("Avahi: Removing service '%s'\n", avahi.name);
+		avahi_free(avahi.name);
+		avahi.name = NULL;
+	}
+}
+
+static void __avahi_group_cb(AvahiEntryGroup *group,
+		AvahiEntryGroupState state, void *d)
+{
+	/* Called whenever the entry group state changes */
+	if (!group)  {
+		IIO_ERROR("__avahi_group_cb with no valid group\n");
+		return;
+	}
+
+	avahi.group = group;
+
+	switch (state) {
+		case AVAHI_ENTRY_GROUP_ESTABLISHED :
+			IIO_INFO("Avahi: Service '%s' successfully established.\n",
+					avahi.name);
+			break;
+		case AVAHI_ENTRY_GROUP_COLLISION : {
+			char *n;
+			/* A service name collision, pick a new name */
+			n = avahi_alternative_service_name(avahi.name);
+			avahi_free(avahi.name);
+			avahi.name = n;
+			IIO_INFO("Avahi: Group Service name collision, renaming service to '%s'\n",
+					avahi.name);
+			create_services(avahi_entry_group_get_client(group));
+			break;
+		}
+		case AVAHI_ENTRY_GROUP_FAILURE :
+			IIO_ERROR("Entry group failure: %s\n",
+					avahi_strerror(avahi_client_errno(
+						avahi_entry_group_get_client(group))));
+			break;
+		case AVAHI_ENTRY_GROUP_UNCOMMITED:
+			/* This is normal,
+			 * since we commit things in the create_services()
+			 */
+			IIO_DEBUG("Avahi: Group uncommitted\n");
+			break;
+		case AVAHI_ENTRY_GROUP_REGISTERING:
+			IIO_DEBUG("Avahi: Group registering\n");
+			break;
+	}
+}
+
+static void __avahi_client_cb(AvahiClient *client,
+		AvahiClientState state, void *d)
+{
+	if (!client) {
+		IIO_ERROR("__avahi_client_cb with no valid client\n");
+		return;
+	}
+
+	switch (state) {
+		case AVAHI_CLIENT_S_RUNNING:
+			/* Same as AVAHI_SERVER_RUNNING */
+			IIO_DEBUG("Avahi: create services\n");
+			/* The server has startup successfully, so create our services */
+			create_services(client);
+			break;
+		case AVAHI_CLIENT_FAILURE:
+			if (avahi_client_errno(client) != AVAHI_ERR_DISCONNECTED) {
+				IIO_ERROR("Avahi: Client failure: %s\n",
+					avahi_strerror(avahi_client_errno(client)));
+				break;
+			}
+			IIO_INFO("Avahi: server disconnected\n");
+			avahi_client_free(client);
+			avahi.group = NULL;
+			avahi.client = client_new();
+			break;
+		case AVAHI_CLIENT_S_COLLISION:
+			/* Same as AVAHI_SERVER_COLLISION */
+			/* When the server is back in AVAHI_SERVER_RUNNING state
+			 * we will register them again with the new host name. */
+			IIO_DEBUG("Avahi: Client collision\n");
+			/* Let's drop our registered services.*/
+			if (avahi.group)
+				avahi_entry_group_reset(avahi.group);
+			break;
+		case AVAHI_CLIENT_S_REGISTERING:
+			/* Same as AVAHI_SERVER_REGISTERING */
+			IIO_DEBUG("Avahi: Client group reset\n");
+			if (avahi.group)
+				avahi_entry_group_reset(avahi.group);
+			break;
+		case AVAHI_CLIENT_CONNECTING:
+			IIO_DEBUG("Avahi: Client Connecting\n");
+			break;
+	}
+
+	/* NOTE: group is freed by avahi_client_free */
+}
+
+static AvahiClient * client_new(void)
+{
+	int ret;
+	AvahiClient * client;
+
+	client = avahi_client_new(avahi_threaded_poll_get(avahi.poll),
+			AVAHI_CLIENT_NO_FAIL, __avahi_client_cb, NULL, &ret);
+
+	/* No Daemon is handled by the avahi_start thread */
+	if (!client && ret != AVAHI_ERR_NO_DAEMON) {
+		IIO_ERROR("Avahi: failure creating client: %s (%d)\n",
+				avahi_strerror(ret), ret);
+	}
+
+	return client;
+}
+
+
+static void create_services(AvahiClient *c)
+{
+	int ret;
+
+	if (!c) {
+		IIO_ERROR("create_services called with no valid client\n");
+		goto fail;
+	}
+
+	if (!avahi.group) {
+		avahi.group = avahi_entry_group_new(c, __avahi_group_cb, NULL);
+		if (!avahi.group) {
+			IIO_ERROR("avahi_entry_group_new() failed: %s\n",
+					avahi_strerror(avahi_client_errno(c)));
+			goto fail;
+		}
+	}
+
+	if (!avahi_entry_group_is_empty(avahi.group)) {
+		IIO_DEBUG("Avahi group not empty\n");
+		return;
+	}
+
+	ret = avahi_entry_group_add_service(avahi.group,
+			AVAHI_IF_UNSPEC, AVAHI_PROTO_UNSPEC,
+			0, avahi.name, "_iio._tcp", NULL, NULL, IIOD_PORT, NULL);
+	if (ret < 0) {
+		if (ret == AVAHI_ERR_COLLISION) {
+			char *n;
+			n = avahi_alternative_service_name(avahi.name);
+			avahi_free(avahi.name);
+			avahi.name = n;
+			IIO_DEBUG("Service name collision, renaming service to '%s'\n",
+					avahi.name);
+			avahi_entry_group_reset(avahi.group);
+			create_services(c);
+			return;
+		}
+		IIO_ERROR("Failed to add _iio._tcp service: %s\n", avahi_strerror(ret));
+		goto fail;
+	}
+
+	ret = avahi_entry_group_commit(avahi.group);
+	if (ret < 0) {
+		IIO_ERROR("Failed to commit entry group: %s\n", avahi_strerror(ret));
+		goto fail;
+	}
+
+	IIO_INFO("Avahi: Registered '%s' to ZeroConf server %s\n",
+			avahi.name, avahi_client_get_version_string(c));
+
+	return;
+
+fail:
+	avahi_entry_group_reset(avahi.group);
+}
+
+#define IIOD_ON "iiod on "
+
+static void start_avahi_thd(struct thread_pool *pool, void *d)
+{
+
+	struct pollfd pfd[2];
+	int ret = ENOMEM;
+	char label[AVAHI_LABEL_MAX];
+	char host[AVAHI_LABEL_MAX - sizeof(IIOD_ON)];
+	struct timespec ts;
+	ts.tv_nsec = 0;
+	ts.tv_sec = 1;
+
+	pfd[1].fd = thread_pool_get_poll_fd(pool);
+	pfd[1].events = POLLIN;
+	pfd[1].revents = 0;
+
+	while(true) {
+		if (pfd[1].revents & POLLIN) /* STOP event */
+			break;
+
+		ret = gethostname(host, sizeof(host));
+		IIO_ERROR("host %s\n", host);
+		if (ret || !strncmp(host, "none", sizeof("none") - 1))
+			goto again;
+
+		iio_snprintf(label, sizeof(label), "%s%s", IIOD_ON, host);
+
+		if (!avahi.name)
+			avahi.name = avahi_strdup(label);
+		if (!avahi.name)
+			break;
+
+		if (!avahi.poll)
+			avahi.poll = avahi_threaded_poll_new();
+		if (!avahi.poll) {
+			goto again;
+		}
+
+		if (!avahi.client)
+			avahi.client = client_new();
+		if (avahi.client)
+			break;
+again:
+		IIO_INFO("Avahi didn't start, try again later\n");
+		nanosleep(&ts, NULL);
+		ts.tv_sec++;
+		/* If it hasn't started in 10 times over 60 seconds,
+		 * it is not going to, so stop
+		 */
+		if (ts.tv_sec >= 11)
+			break;
+	}
+
+	if (avahi.client && avahi.poll) {
+		avahi_threaded_poll_start(avahi.poll);
+		IIO_INFO("Avahi: Started.\n");
+	} else  {
+		shutdown_avahi();
+		IIO_INFO("Avahi: Failed to start.\n");
+	}
+}
+
+void start_avahi(struct thread_pool *pool)
+{
+	int ret;
+	char err_str[1024];
+
+	IIO_INFO("Attempting to start Avahi\n");
+
+	avahi.poll = NULL;
+	avahi.client = NULL;
+	avahi.group = NULL;
+	avahi.name = NULL;
+
+	/* In case dbus, or avahi deamon are not started, we create a thread
+	 * that tries a few times to attach, if it can't within the first
+	 * minute, it gives up.
+	 */
+	ret = thread_pool_add_thread(pool, start_avahi_thd, NULL, "avahi_thd");
+	if (ret) {
+		iio_strerror(ret, err_str, sizeof(err_str));
+		IIO_ERROR("Failed to create new Avahi thread: %s\n",
+				err_str);
+	}
+}
+
+void stop_avahi(void)
+{
+	shutdown_avahi();
+	IIO_INFO("Avahi: Stopped\n");
+}

iiod/dns-sd.h

@@ -0,0 +1,17 @@
+/* SPDX-license-identifier: LGPL-v2-or-later */
+/*
+ * libiio - Library for interfacing industrial I/O (IIO) devices
+ *
+ * Copyright (C) 2021 Analog Devices, Inc.
+ * Author: Paul Cercueil <[email protected]>
+ */
+
+#ifndef __IIOD_DNS_SD_H
+#define __IIOD_DNS_SD_H
+
+struct thread_pool;
+
+void start_avahi(struct thread_pool *pool);
+void stop_avahi(void);
+
+#endif /* __IIOD_DNS_SD_H */