Resolve hosts by DNS name in separate threads so we can cancel them

getaddrinfo(3) may block a long time so proper termination of the daemon may
block if DNS servers are not reachable.

getaddrinfo(3) is an optional cancellation point in posix threads so it
might still block a shutdown but at least on Android (with the signal based
pthread_cancel implementation) it works, on Linux starter will kill charon
anyway after a while.

src/libcharon/daemon.c

@@ -84,7 +84,8 @@ static void destroy(private_daemon_t *this)
 {
 	/* terminate all idle threads */
 	lib->processor->set_threads(lib->processor, 0);
-
+	/* make sure nobody waits for a DNS query */
+	lib->hosts->flush(lib->hosts);
 	/* close all IKE_SAs */
 	if (this->public.ike_sa_manager)
 	{

src/libstrongswan/Android.mk

@@ -3,8 +3,8 @@ include $(CLEAR_VARS)
 
 # copy-n-paste from Makefile.am
 LOCAL_SRC_FILES := \
-library.c chunk.c debug.c enum.c settings.c printf_hook.c asn1/asn1.c \
-asn1/asn1_parser.c asn1/oid.c bio/bio_reader.c bio/bio_writer.c \
+library.c chunk.c debug.c enum.c host_resolver.c settings.c printf_hook.c \
+asn1/asn1.c asn1/asn1_parser.c asn1/oid.c bio/bio_reader.c bio/bio_writer.c \
 crypto/crypters/crypter.c crypto/hashers/hasher.c crypto/pkcs7.c crypto/pkcs9.c \
 crypto/proposal/proposal_keywords.c crypto/proposal/proposal_keywords_static.c \
 crypto/prfs/prf.c crypto/prfs/mac_prf.c \

src/libstrongswan/Makefile.am

@@ -1,8 +1,8 @@
 ipseclib_LTLIBRARIES = libstrongswan.la
 
 libstrongswan_la_SOURCES = \
-library.c chunk.c debug.c enum.c settings.c printf_hook.c asn1/asn1.c \
-asn1/asn1_parser.c asn1/oid.c bio/bio_reader.c bio/bio_writer.c \
+library.c chunk.c debug.c enum.c host_resolver.c settings.c printf_hook.c \
+asn1/asn1.c asn1/asn1_parser.c asn1/oid.c bio/bio_reader.c bio/bio_writer.c \
 crypto/crypters/crypter.c crypto/hashers/hasher.c crypto/pkcs7.c crypto/pkcs9.c \
 crypto/proposal/proposal_keywords.c crypto/proposal/proposal_keywords_static.c \
 crypto/prfs/prf.c crypto/prfs/mac_prf.c \
@@ -31,7 +31,7 @@ utils/optionsfrom.c utils/capabilities.c utils/backtrace.c utils/tun_device.c
 if USE_DEV_HEADERS
 strongswan_includedir = ${dev_headers}
 nobase_strongswan_include_HEADERS = \
-library.h chunk.h debug.h enum.h settings.h printf_hook.h \
+library.h chunk.h debug.h enum.h host_resolver.h settings.h printf_hook.h \
 asn1/asn1.h asn1/asn1_parser.h asn1/oid.h bio/bio_reader.h bio/bio_writer.h \
 crypto/crypters/crypter.h crypto/hashers/hasher.h crypto/mac.h \
 crypto/pkcs7.h crypto/pkcs9.h crypto/proposal/proposal_keywords.h \

src/libstrongswan/host_resolver.c

@@ -0,0 +1,289 @@
+/*
+ * Copyright (C) 2012 Tobias Brunner
+ * Hochschule fuer Technik Rapperswil
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * for more details.
+ */
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netdb.h>
+
+#include "host_resolver.h"
+
+#include <debug.h>
+#include <processing/jobs/callback_job.h>
+#include <threading/condvar.h>
+#include <threading/mutex.h>
+#include <threading/thread.h>
+#include <utils/hashtable.h>
+#include <utils/linked_list.h>
+
+typedef struct private_host_resolver_t private_host_resolver_t;
+
+/**
+ * Private data of host_resolver_t
+ */
+struct private_host_resolver_t {
+
+	/**
+	 * Public interface
+	 */
+	host_resolver_t public;
+
+	/**
+	 * Hashtable to check for queued queries, query_t*
+	 */
+	hashtable_t *queries;
+
+	/**
+	 * Queue for queries, query_t*
+	 */
+	linked_list_t *queue;
+
+	/**
+	 * Mutex to safely access private data
+	 */
+	mutex_t *mutex;
+
+	/**
+	 * Condvar to signal arrival of new queries
+	 */
+	condvar_t *new_query;
+
+	/**
+	 * Maximum number of resolver threads
+	 */
+	u_int max_threads;
+
+	/**
+	 * Current number of threads
+	 */
+	u_int threads;
+
+	/**
+	 * TRUE if no new queries are accepted
+	 */
+	bool disabled;
+
+};
+
+typedef struct {
+	/** DNS name we are looking for */
+	char *name;
+	/** address family we request */
+	int family;
+	/** Condvar to signal completion of a query */
+	condvar_t *done;
+	/** refcount */
+	refcount_t refcount;
+	/** the result if successful */
+	host_t *result;
+} query_t;
+
+/**
+ * Destroy the given query_t object if refcount is zero
+ */
+static void query_destroy(query_t *this)
+{
+	if (ref_put(&this->refcount))
+	{
+		DESTROY_IF(this->result);
+		this->done->destroy(this->done);
+		free(this->name);
+		free(this);
+	}
+}
+
+/**
+ * Signals all waiting threads and destroys the query
+ */
+static void query_signal_and_destroy(query_t *this)
+{
+	this->done->broadcast(this->done);
+	query_destroy(this);
+}
+
+/**
+ * Hash a queued query
+ */
+static u_int query_hash(query_t *this)
+{
+	return chunk_hash_inc(chunk_create(this->name, strlen(this->name)),
+						  chunk_hash(chunk_from_thing(this->family)));
+}
+
+/**
+ * Compare two queued queries
+ */
+static bool query_equals(query_t *this, query_t *other)
+{
+	return this->family == other->family && streq(this->name, other->name);
+}
+
+/**
+ * Main function of resolver threads
+ */
+static job_requeue_t resolve_hosts(private_host_resolver_t *this)
+{
+	struct addrinfo hints, *result;
+	query_t *query;
+	int error;
+	bool old;
+
+	this->mutex->lock(this->mutex);
+	while (this->queue->remove_first(this->queue, (void**)&query) != SUCCESS)
+	{
+		thread_cleanup_push((thread_cleanup_t)this->mutex->unlock, this->mutex);
+		old = thread_cancelability(TRUE);
+		this->new_query->wait(this->new_query, this->mutex);
+		thread_cancelability(old);
+		thread_cleanup_pop(FALSE);
+	}
+	this->mutex->unlock(this->mutex);
+
+	memset(&hints, 0, sizeof(hints));
+	hints.ai_family = query->family;
+
+	thread_cleanup_push((thread_cleanup_t)query_signal_and_destroy, query);
+	old = thread_cancelability(TRUE);
+	error = getaddrinfo(query->name, NULL, &hints, &result);
+	thread_cancelability(old);
+	thread_cleanup_pop(FALSE);
+
+	this->mutex->lock(this->mutex);
+	if (error != 0)
+	{
+		DBG1(DBG_LIB, "resolving '%s' failed: %s", query->name,
+			 gai_strerror(error));
+	}
+	else
+	{	/* result is a linked list, but we use only the first address */
+		query->result = host_create_from_sockaddr(result->ai_addr);
+		freeaddrinfo(result);
+	}
+	this->queries->remove(this->queries, query);
+	query->done->broadcast(query->done);
+	this->mutex->unlock(this->mutex);
+	query_destroy(query);
+	return JOB_REQUEUE_DIRECT;
+}
+
+METHOD(host_resolver_t, resolve, host_t*,
+	private_host_resolver_t *this, char *name, int family)
+{
+	query_t *query, lookup = {
+		.name = name,
+		.family = family,
+	};
+	host_t *result;
+
+	if (streq(name, "%any") || streq(name, "0.0.0.0"))
+	{
+		return host_create_any(family ? family : AF_INET);
+	}
+	if (streq(name, "%any6") || streq(name, "::"))
+	{
+		return host_create_any(family ? family : AF_INET6);
+	}
+	if (family == AF_INET && strchr(name, ':'))
+	{	/* do not try to convert v6 addresses for v4 family */
+		return NULL;
+	}
+	this->mutex->lock(this->mutex);
+	if (this->disabled)
+	{
+		this->mutex->unlock(this->mutex);
+		return NULL;
+	}
+	query = this->queries->get(this->queries, &lookup);
+	if (!query)
+	{
+		INIT(query,
+			.name = strdup(name),
+			.family = family,
+			.done = condvar_create(CONDVAR_TYPE_DEFAULT),
+			.refcount = 1,
+		);
+		this->queries->put(this->queries, query, query);
+		this->queue->insert_last(this->queue, query);
+		this->new_query->signal(this->new_query);
+	}
+	ref_get(&query->refcount);
+	if (this->threads < this->max_threads)
+	{
+		this->threads++;
+		lib->processor->queue_job(lib->processor,
+			(job_t*)callback_job_create_with_prio(
+				(callback_job_cb_t)resolve_hosts, this,	NULL,
+				(callback_job_cancel_t)return_false, JOB_PRIO_CRITICAL));
+	}
+	query->done->wait(query->done, this->mutex);
+	this->mutex->unlock(this->mutex);
+
+	result = query->result ? query->result->clone(query->result) : NULL;
+	query_destroy(query);
+	return result;
+}
+
+METHOD(host_resolver_t, flush, void,
+	private_host_resolver_t *this)
+{
+	enumerator_t *enumerator;
+	query_t *query;
+
+	this->mutex->lock(this->mutex);
+	enumerator = this->queries->create_enumerator(this->queries);
+	while (enumerator->enumerate(enumerator, &query, NULL))
+	{	/* use the hashtable here as we also want to signal dequeued queries */
+		this->queries->remove_at(this->queries, enumerator);
+		query->done->broadcast(query->done);
+	}
+	enumerator->destroy(enumerator);
+	this->queue->destroy_function(this->queue, (void*)query_destroy);
+	this->queue = linked_list_create();
+	this->disabled = TRUE;
+	this->mutex->unlock(this->mutex);
+}
+
+METHOD(host_resolver_t, destroy, void,
+	private_host_resolver_t *this)
+{
+	this->queue->destroy_function(this->queue, (void*)query_signal_and_destroy);
+	this->queries->destroy(this->queries);
+	this->new_query->destroy(this->new_query);
+	this->mutex->destroy(this->mutex);
+	free(this);
+}
+
+/*
+ * Described in header
+ */
+host_resolver_t *host_resolver_create(u_int max_threads)
+{
+	private_host_resolver_t *this;
+
+	INIT(this,
+		.public = {
+			.resolve = _resolve,
+			.flush = _flush,
+			.destroy = _destroy,
+		},
+		.queries = hashtable_create((hashtable_hash_t)query_hash,
+									(hashtable_equals_t)query_equals, 8),
+		.queue = linked_list_create(),
+		.mutex = mutex_create(MUTEX_TYPE_DEFAULT),
+		.new_query = condvar_create(CONDVAR_TYPE_DEFAULT),
+		.max_threads = max_threads,
+	);
+
+	return &this->public;
+}

src/libstrongswan/host_resolver.h

@@ -0,0 +1,62 @@
+/*
+ * Copyright (C) 2012 Tobias Brunner
+ * Hochschule fuer Technik Rapperswil
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * for more details.
+ */
+
+/**
+ * @defgroup host_resolver host_resolver
+ * @{ @ingroup libstrongswan
+ */
+
+#ifndef HOST_RESOLVER_H_
+#define HOST_RESOLVER_H_
+
+#include "utils/host.h"
+
+typedef struct host_resolver_t host_resolver_t;
+
+/**
+ * Resolve hosts by DNS name but do so in a separate thread (calling
+ * getaddrinfo(3) directly might block indefinitely, or at least a very long
+ * time if no DNS servers are reachable).
+ */
+struct host_resolver_t {
+
+	/**
+	 * Resolve host from the given DNS name.
+	 *
+	 * @param name		name to lookup
+	 * @param family	requested address family
+	 * @return			resolved host or NULL if failed or canceled
+	 */
+	host_t *(*resolve)(host_resolver_t *this, char *name, int family);
+
+	/**
+	 * Flush the queue of queries. No new queries will be accepted afterwards.
+	 */
+	void (*flush)(host_resolver_t *this);
+
+	/**
+	 * Destroy a host_resolver_t.
+	 */
+	void (*destroy)(host_resolver_t *this);
+};
+
+/**
+ * Create a host_resolver_t instance.
+ *
+ * @param max_threads	maximum number of resolver threads to use
+ */
+host_resolver_t *host_resolver_create(u_int max_threads);
+
+#endif /** HOST_RESOLVER_H_ @}*/

src/libstrongswan/library.c

@@ -27,6 +27,7 @@
 #include <selectors/traffic_selector.h>
 
 #define CHECKSUM_LIBRARY IPSEC_LIB_DIR"/libchecksum.so"
+#define HOST_RESOLVER_MAX_THREADS 2
 
 typedef struct private_library_t private_library_t;
 
@@ -68,6 +69,7 @@ void library_deinit()
 	this->public.scheduler->destroy(this->public.scheduler);
 	this->public.processor->destroy(this->public.processor);
 	this->public.plugins->destroy(this->public.plugins);
+	this->public.hosts->destroy(this->public.hosts);
 	this->public.settings->destroy(this->public.settings);
 	this->public.credmgr->destroy(this->public.credmgr);
 	this->public.creds->destroy(this->public.creds);
@@ -182,6 +184,7 @@ bool library_init(char *settings)
 
 	this->objects = hashtable_create((hashtable_hash_t)hash,
 									 (hashtable_equals_t)equals, 4);
+	this->public.hosts = host_resolver_create(HOST_RESOLVER_MAX_THREADS);
 	this->public.settings = settings_create(settings);
 	this->public.proposal = proposal_keywords_create();
 	this->public.crypto = crypto_factory_create();

src/libstrongswan/library.h

@@ -77,6 +77,7 @@
 #include "printf_hook.h"
 #include "utils.h"
 #include "chunk.h"
+#include "host_resolver.h"
 #include "settings.h"
 #include "integrity_checker.h"
 #include "processing/processor.h"
@@ -170,6 +171,11 @@ struct library_t {
 	 */
 	scheduler_t *scheduler;
 
+	/**
+	 * resolve hosts by DNS name
+	 */
+	host_resolver_t *hosts;
+
 	/**
 	 * various settings loaded from settings file
 	 */

src/libstrongswan/utils/host.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2006-2009 Tobias Brunner
+ * Copyright (C) 2006-2012 Tobias Brunner
  * Copyright (C) 2006 Daniel Roethlisberger
  * Copyright (C) 2005-2006 Martin Willi
  * Copyright (C) 2005 Jan Hutter
@@ -16,14 +16,10 @@
  * for more details.
  */
 
-#define _GNU_SOURCE
-#include <sys/socket.h>
-#include <netdb.h>
-#include <string.h>
-
 #include "host.h"
 
 #include <debug.h>
+#include <library.h>
 
 #define IPV4_LEN	 4
 #define IPV6_LEN	16
@@ -450,48 +446,14 @@ host_t *host_create_from_sockaddr(sockaddr_t *sockaddr)
  */
 host_t *host_create_from_dns(char *string, int af, u_int16_t port)
 {
-	private_host_t *this;
-	struct addrinfo hints, *result;
-	int error;
+	host_t *this;
 
-	if (streq(string, "%any"))
-	{
-		return host_create_any_port(af ? af : AF_INET, port);
-	}
-	if (streq(string, "%any6"))
-	{
-		return host_create_any_port(af ? af : AF_INET6, port);
-	}
-	if (af == AF_INET && strchr(string, ':'))
-	{	/* do not try to convert v6 addresses for v4 family */
-		return NULL;
-	}
-
-	memset(&hints, 0, sizeof(hints));
-	hints.ai_family = af;
-	error = getaddrinfo(string, NULL, &hints, &result);
-	if (error != 0)
-	{
-		DBG1(DBG_LIB, "resolving '%s' failed: %s", string, gai_strerror(error));
-		return NULL;
-	}
-	/* result is a linked list, but we use only the first address */
-	this = (private_host_t*)host_create_from_sockaddr(result->ai_addr);
-	freeaddrinfo(result);
+	this = lib->hosts->resolve(lib->hosts, string, af);
 	if (this)
 	{
-		switch (this->address.sa_family)
-		{
-			case AF_INET:
-				this->address4.sin_port = htons(port);
-				break;
-			case AF_INET6:
-				this->address6.sin6_port = htons(port);
-				break;
-		}
-		return &this->public;
+		this->set_port(this, port);
 	}
-	return NULL;
+	return this;
 }
 
 /*