Merge branch 'variadic-enumerators'

This adds several changes to enumerator_t and linked_list_t to improve
portability.  In particular to Apple's ARM64 iOS platform, whose calling
convention for variadic and regular functions are different.  This means
that assigning a non-variadic function to a variadic function pointer,
as we did with our enumerator_t::enumerate() implementations and several
callbacks, will result in crashes as the called function will access the
arguments differently than the caller provided them.

To avoid this issue the enumerator_t interface is now fully variadic.
A new mandatory method is added, venumerate(), that takes a va_list with
the arguments provided while enumerating.  enumerate() is replaced with
a generic implementation that prepares a va_list and calls the
enumerator's venumerate() implementation.  As this allows passing the
arguments of one enumerator to another it avoids the five pointer hack
used by enumerator_create_nested() and enumerator_create_cleaner().
To simplify the implementation of venumerate() a helper macro is provided
that assigns values from a given va_list to local variables.

The signature of the callback passed to enumerator_create_filter() has
also changed significantly.  It's now required to enumerate over the
original enumerator in the callback as this avoids the previous in/out
pointer hack. The arguments to the outer enumerator are provided in a
va_list.

Similar changes to avoid such five pointer hacks affect the signatures
of the callbacks for linked_list_t's invoke_function() and find_first()
methods.  For the latter the return type also changed from status_t to
bool, which is important as SUCCESS is defined as 0, so checks for ==
SUCCESS will now fail.

44 files changed, 738 insertions, 503 deletions

diff --git a/src/libcharon/plugins/android_dns/android_dns_handler.c b/src/libcharon/plugins/android_dns/android_dns_handler.c
index 160a145d3..68bbaecb2 100644
--- a/src/libcharon/plugins/android_dns/android_dns_handler.c
+++ b/src/libcharon/plugins/android_dns/android_dns_handler.c
@@ -182,12 +182,15 @@ METHOD(attribute_handler_t, release, void,
 }
 
 METHOD(enumerator_t, enumerate_dns, bool,
-	enumerator_t *this, configuration_attribute_type_t *type, chunk_t *data)
+	enumerator_t *this, va_list args)
 {
+	configuration_attribute_type_t *type;
+	chunk_t *data;
+
+	VA_ARGS_VGET(args, type, data);
 	*type = INTERNAL_IP4_DNS;
 	*data = chunk_empty;
-	/* stop enumeration */
-	this->enumerate = (void*)return_false;
+	this->venumerate = return_false;
 	return TRUE;
 }
 
@@ -198,7 +201,8 @@ METHOD(attribute_handler_t, create_attribute_enumerator, enumerator_t *,
 	enumerator_t *enumerator;
 
 	INIT(enumerator,
-		.enumerate = (void*)_enumerate_dns,
+		.enumerate = enumerator_enumerate_default,
+		.venumerate = _enumerate_dns,
 		.destroy = (void*)free,
 	);
 	return enumerator;
diff --git a/src/libcharon/plugins/attr/attr_provider.c b/src/libcharon/plugins/attr/attr_provider.c
index f4c143641..3310f79fd 100644
--- a/src/libcharon/plugins/attr/attr_provider.c
+++ b/src/libcharon/plugins/attr/attr_provider.c
@@ -75,17 +75,23 @@ typedef struct {
 	ike_version_t ike;
 } enumerator_data_t;
 
-/**
- * convert enumerator value from attribute_entry
- */
-static bool attr_enum_filter(enumerator_data_t *data, attribute_entry_t **in,
-			configuration_attribute_type_t *type, void* none, chunk_t *value)
+CALLBACK(attr_enum_filter, bool,
+	enumerator_data_t *data, enumerator_t *orig, va_list args)
 {
-	if ((*in)->ike == IKE_ANY || (*in)->ike == data->ike)
+	configuration_attribute_type_t *type;
+	attribute_entry_t *entry;
+	chunk_t *value;
+
+	VA_ARGS_VGET(args, type, value);
+
+	while (orig->enumerate(orig, &entry))
 	{
-		*type = (*in)->type;
-		*value = (*in)->value;
-		return TRUE;
+		if (entry->ike == IKE_ANY || entry->ike == data->ike)
+		{
+			*type = entry->type;
+			*value = entry->value;
+			return TRUE;
+		}
 	}
 	return FALSE;
 }
@@ -112,7 +118,7 @@ METHOD(attribute_provider_t, create_attribute_enumerator, enumerator_t*,
 		this->lock->read_lock(this->lock);
 		return enumerator_create_filter(
 				this->attributes->create_enumerator(this->attributes),
-				(void*)attr_enum_filter, data, attr_enum_destroy);
+				attr_enum_filter, data, attr_enum_destroy);
 	}
 	return enumerator_create_empty();
 }
diff --git a/src/libcharon/plugins/bypass_lan/bypass_lan_listener.c b/src/libcharon/plugins/bypass_lan/bypass_lan_listener.c
index e690028f2..644cff029 100644
--- a/src/libcharon/plugins/bypass_lan/bypass_lan_listener.c
+++ b/src/libcharon/plugins/bypass_lan/bypass_lan_listener.c
@@ -110,15 +110,12 @@ static bool policy_equals(bypass_policy_t *a, bypass_policy_t *b)
  */
 static bool consider_interface(private_bypass_lan_listener_t *this, char *iface)
 {
-	status_t expected;
-
 	if (!iface || !this->ifaces_filter)
 	{
 		return TRUE;
 	}
-	expected = this->ifaces_exclude ? NOT_FOUND : SUCCESS;
-	return this->ifaces_filter->find_first(this->ifaces_filter, (void*)streq,
-										   NULL, iface) == expected;
+	return this->ifaces_filter->find_first(this->ifaces_filter,
+					linked_list_match_str, NULL, iface) != this->ifaces_exclude;
 }
 
 /**
diff --git a/src/libcharon/plugins/dhcp/dhcp_provider.c b/src/libcharon/plugins/dhcp/dhcp_provider.c
index f0681b1da..50ffbab9d 100644
--- a/src/libcharon/plugins/dhcp/dhcp_provider.c
+++ b/src/libcharon/plugins/dhcp/dhcp_provider.c
@@ -151,8 +151,7 @@ METHOD(attribute_provider_t, create_attribute_enumerator, enumerator_t*,
 	identification_t *id;
 	host_t *vip;
 
-	if (pools->find_first(pools, (linked_list_match_t)streq,
-						  NULL, "dhcp") != SUCCESS)
+	if (!pools->find_first(pools, linked_list_match_str, NULL, "dhcp"))
 	{
 		return NULL;
 	}
diff --git a/src/libcharon/plugins/dhcp/dhcp_socket.c b/src/libcharon/plugins/dhcp/dhcp_socket.c
index 807c68274..42f8f1ef9 100644
--- a/src/libcharon/plugins/dhcp/dhcp_socket.c
+++ b/src/libcharon/plugins/dhcp/dhcp_socket.c
@@ -382,8 +382,7 @@ METHOD(dhcp_socket_t, enroll, dhcp_transaction_t*,
 	while (try <= DHCP_TRIES && discover(this, transaction))
 	{
 		if (!this->condvar->timed_wait(this->condvar, this->mutex, 1000 * try) &&
-			this->request->find_first(this->request, NULL,
-									  (void**)&transaction) == SUCCESS)
+			this->request->find_first(this->request, NULL, (void**)&transaction))
 		{
 			break;
 		}
diff --git a/src/libcharon/plugins/dhcp/dhcp_transaction.c b/src/libcharon/plugins/dhcp/dhcp_transaction.c
index 3ee88a698..87711799c 100644
--- a/src/libcharon/plugins/dhcp/dhcp_transaction.c
+++ b/src/libcharon/plugins/dhcp/dhcp_transaction.c
@@ -114,16 +114,22 @@ METHOD(dhcp_transaction_t, add_attribute, void,
 	this->attributes->insert_last(this->attributes, entry);
 }
 
-/**
- * Filter function to map entries to type/data
- */
-static bool attribute_filter(void *null, attribute_entry_t **entry,
-							 configuration_attribute_type_t *type,
-							 void **dummy, chunk_t *data)
+CALLBACK(attribute_filter, bool,
+	void *null, enumerator_t *orig, va_list args)
 {
-	*type = (*entry)->type;
-	*data = (*entry)->data;
-	return TRUE;
+	configuration_attribute_type_t *type;
+	attribute_entry_t *entry;
+	chunk_t *data;
+
+	VA_ARGS_VGET(args, type, data);
+
+	if (orig->enumerate(orig, &entry))
+	{
+		*type = entry->type;
+		*data = entry->data;
+		return TRUE;
+	}
+	return FALSE;
 }
 
 METHOD(dhcp_transaction_t, create_attribute_enumerator, enumerator_t*,
@@ -131,7 +137,7 @@ METHOD(dhcp_transaction_t, create_attribute_enumerator, enumerator_t*,
 {
 	return enumerator_create_filter(
 						this->attributes->create_enumerator(this->attributes),
-						(void*)attribute_filter, NULL, NULL);
+						attribute_filter, NULL, NULL);
 }
 
 /**
diff --git a/src/libcharon/plugins/dnscert/dnscert_cred.c b/src/libcharon/plugins/dnscert/dnscert_cred.c
index d32794c99..533bd5be4 100644
--- a/src/libcharon/plugins/dnscert/dnscert_cred.c
+++ b/src/libcharon/plugins/dnscert/dnscert_cred.c
@@ -75,12 +75,15 @@ typedef struct {
 } cert_enumerator_t;
 
 METHOD(enumerator_t, cert_enumerator_enumerate, bool,
-	cert_enumerator_t *this, certificate_t **cert)
+	cert_enumerator_t *this, va_list args)
 {
+	certificate_t **cert;
 	dnscert_t *cur_crt;
 	rr_t *cur_rr;
 	chunk_t certificate;
 
+	VA_ARGS_VGET(args, cert);
+
 	/* Get the next supported CERT using the inner enumerator. */
 	while (this->inner->enumerate(this->inner, &cur_rr))
 	{
@@ -175,7 +178,8 @@ METHOD(credential_set_t, create_cert_enumerator, enumerator_t*,
 
 	INIT(e,
 		.public = {
-			.enumerate = (void*)_cert_enumerator_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _cert_enumerator_enumerate,
 			.destroy = _cert_enumerator_destroy,
 		},
 		.inner = response->get_rr_set(response)->create_rr_enumerator(
diff --git a/src/libcharon/plugins/eap_dynamic/eap_dynamic.c b/src/libcharon/plugins/eap_dynamic/eap_dynamic.c
index 83ccd3a8a..204fb317d 100644
--- a/src/libcharon/plugins/eap_dynamic/eap_dynamic.c
+++ b/src/libcharon/plugins/eap_dynamic/eap_dynamic.c
@@ -69,6 +69,15 @@ static bool entry_matches(eap_vendor_type_t *item, eap_vendor_type_t *other)
 	return item->type == other->type && item->vendor == other->vendor;
 }
 
+CALLBACK(entry_matches_cb, bool,
+	eap_vendor_type_t *item, va_list args)
+{
+	eap_vendor_type_t *other;
+
+	VA_ARGS_VGET(args, other);
+	return entry_matches(item, other);
+}
+
 /**
  * Load the given EAP method
  */
@@ -121,8 +130,7 @@ static void select_method(private_eap_dynamic_t *this)
 	{
 		if (inner)
 		{
-			if (inner->find_first(inner, (void*)entry_matches,
-								  NULL, entry) != SUCCESS)
+			if (!inner->find_first(inner, entry_matches_cb, NULL, entry))
 			{
 				if (entry->vendor)
 				{
diff --git a/src/libcharon/plugins/eap_radius/eap_radius_provider.c b/src/libcharon/plugins/eap_radius/eap_radius_provider.c
index 9a87ad38d..58bbc2edd 100644
--- a/src/libcharon/plugins/eap_radius/eap_radius_provider.c
+++ b/src/libcharon/plugins/eap_radius/eap_radius_provider.c
@@ -404,11 +404,13 @@ typedef struct {
 	attr_t *current;
 } attribute_enumerator_t;
 
-
 METHOD(enumerator_t, attribute_enumerate, bool,
-	attribute_enumerator_t *this, configuration_attribute_type_t *type,
-	chunk_t *data)
+	attribute_enumerator_t *this, va_list args)
 {
+	configuration_attribute_type_t *type;
+	chunk_t *data;
+
+	VA_ARGS_VGET(args, type, data);
 	if (this->current)
 	{
 		destroy_attr(this->current);
@@ -446,7 +448,8 @@ METHOD(attribute_provider_t, create_attribute_enumerator, enumerator_t*,
 
 	INIT(enumerator,
 		.public = {
-			.enumerate = (void*)_attribute_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _attribute_enumerate,
 			.destroy = _attribute_destroy,
 		},
 		.list = linked_list_create(),
diff --git a/src/libcharon/plugins/eap_sim_file/eap_sim_file_triplets.c b/src/libcharon/plugins/eap_sim_file/eap_sim_file_triplets.c
index ec1686910..e11e0e5ea 100644
--- a/src/libcharon/plugins/eap_sim_file/eap_sim_file_triplets.c
+++ b/src/libcharon/plugins/eap_sim_file/eap_sim_file_triplets.c
@@ -79,10 +79,8 @@ typedef struct {
 	private_eap_sim_file_triplets_t *this;
 } triplet_enumerator_t;
 
-/**
- * destroy a triplet enumerator
- */
-static void enumerator_destroy(triplet_enumerator_t *e)
+METHOD(enumerator_t, enumerator_destroy, void,
+	triplet_enumerator_t *e)
 {
 	if (e->current)
 	{
@@ -97,13 +95,14 @@ static void enumerator_destroy(triplet_enumerator_t *e)
 	free(e);
 }
 
-/**
- * enumerate through triplets
- */
-static bool enumerator_enumerate(triplet_enumerator_t *e, identification_t **imsi,
-								 char **rand, char **sres, char **kc)
+METHOD(enumerator_t, enumerator_enumerate, bool,
+	triplet_enumerator_t *e, va_list args)
 {
+	identification_t **imsi;
 	triplet_t *triplet;
+	char **rand, **sres, **kc;
+
+	VA_ARGS_VGET(args, imsi, rand, sres, kc);
 
 	if (e->inner->enumerate(e->inner, &triplet))
 	{
@@ -124,12 +123,15 @@ METHOD(eap_sim_file_triplets_t, create_enumerator, enumerator_t*,
 	triplet_enumerator_t *enumerator = malloc_thing(triplet_enumerator_t);
 
 	this->mutex->lock(this->mutex);
-	enumerator->public.enumerate = (void*)enumerator_enumerate;
-	enumerator->public.destroy = (void*)enumerator_destroy;
-	enumerator->inner = this->triplets->create_enumerator(this->triplets);
-	enumerator->current = NULL;
-	enumerator->this = this;
-
+	INIT(enumerator,
+		.public = {
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _enumerator_enumerate,
+			.destroy = _enumerator_destroy,
+		},
+		.inner = this->triplets->create_enumerator(this->triplets),
+		.this = this,
+	);
 	return &enumerator->public;
 }
 
diff --git a/src/libcharon/plugins/forecast/forecast_listener.c b/src/libcharon/plugins/forecast/forecast_listener.c
index 2024c2682..4585731de 100644
--- a/src/libcharon/plugins/forecast/forecast_listener.c
+++ b/src/libcharon/plugins/forecast/forecast_listener.c
@@ -613,17 +613,23 @@ METHOD(listener_t, ike_update, bool,
 	return TRUE;
 }
 
-/**
- * Filter to map entries to ts/mark
- */
-static bool ts_filter(entry_t *entry, traffic_selector_t **ts,
-					  traffic_selector_t **out, void *dummy, uint32_t *mark,
-					  void *dummy2, bool *reinject)
+CALLBACK(ts_filter, bool,
+	entry_t *entry, enumerator_t *orig, va_list args)
 {
-	*out = *ts;
-	*mark = entry->mark;
-	*reinject = entry->reinject;
-	return TRUE;
+	traffic_selector_t *ts, **out;
+	uint32_t *mark;
+	bool *reinject;
+
+	VA_ARGS_VGET(args, out, mark, reinject);
+
+	if (orig->enumerate(orig, &ts))
+	{
+		*out = ts;
+		*mark = entry->mark;
+		*reinject = entry->reinject;
+		return TRUE;
+	}
+	return FALSE;
 }
 
 /**
@@ -632,7 +638,7 @@ static bool ts_filter(entry_t *entry, traffic_selector_t **ts,
 static enumerator_t* create_inner_local(entry_t *entry, rwlock_t *lock)
 {
 	return enumerator_create_filter(array_create_enumerator(entry->lts),
-									(void*)ts_filter, entry, NULL);
+									ts_filter, entry, NULL);
 }
 
 /**
@@ -641,7 +647,7 @@ static enumerator_t* create_inner_local(entry_t *entry, rwlock_t *lock)
 static enumerator_t* create_inner_remote(entry_t *entry, rwlock_t *lock)
 {
 	return enumerator_create_filter(array_create_enumerator(entry->rts),
-									(void*)ts_filter, entry, NULL);
+									ts_filter, entry, NULL);
 }
 
 METHOD(forecast_listener_t, create_enumerator, enumerator_t*,
diff --git a/src/libcharon/plugins/ha/ha_message.c b/src/libcharon/plugins/ha/ha_message.c
index 42dfaf0e2..5f73b7156 100644
--- a/src/libcharon/plugins/ha/ha_message.c
+++ b/src/libcharon/plugins/ha/ha_message.c
@@ -331,10 +331,12 @@ typedef struct {
 } attribute_enumerator_t;
 
 METHOD(enumerator_t, attribute_enumerate, bool,
-	attribute_enumerator_t *this, ha_message_attribute_t *attr_out,
-	ha_message_value_t *value)
+	attribute_enumerator_t *this, va_list args)
 {
-	ha_message_attribute_t attr;
+	ha_message_attribute_t attr, *attr_out;
+	ha_message_value_t *value;
+
+	VA_ARGS_VGET(args, attr_out, value);
 
 	if (this->cleanup)
 	{
@@ -602,7 +604,8 @@ METHOD(ha_message_t, create_attribute_enumerator, enumerator_t*,
 
 	INIT(e,
 		.public = {
-			.enumerate = (void*)_attribute_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _attribute_enumerate,
 			.destroy = _enum_destroy,
 		},
 		.buf = chunk_skip(this->buf, 2),
diff --git a/src/libcharon/plugins/ha/ha_tunnel.c b/src/libcharon/plugins/ha/ha_tunnel.c
index a0e514614..1a6108ed9 100644
--- a/src/libcharon/plugins/ha/ha_tunnel.c
+++ b/src/libcharon/plugins/ha/ha_tunnel.c
@@ -111,8 +111,12 @@ typedef struct {
 } shared_enum_t;
 
 METHOD(enumerator_t, shared_enumerate, bool,
-	shared_enum_t *this, shared_key_t **key, id_match_t *me, id_match_t *other)
+	shared_enum_t *this, va_list args)
 {
+	shared_key_t **key;
+	id_match_t *me, *other;
+
+	VA_ARGS_VGET(args, key, me, other);
 	if (this->key)
 	{
 		if (me)
@@ -151,7 +155,8 @@ METHOD(ha_creds_t, create_shared_enumerator, enumerator_t*,
 
 	INIT(enumerator,
 		.public = {
-			.enumerate = (void*)_shared_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _shared_enumerate,
 			.destroy = (void*)free,
 		},
 		.key = this->key,
diff --git a/src/libcharon/plugins/ipseckey/ipseckey_cred.c b/src/libcharon/plugins/ipseckey/ipseckey_cred.c
index ff50d8a17..b3ac2b328 100644
--- a/src/libcharon/plugins/ipseckey/ipseckey_cred.c
+++ b/src/libcharon/plugins/ipseckey/ipseckey_cred.c
@@ -62,13 +62,16 @@ typedef struct {
 } cert_enumerator_t;
 
 METHOD(enumerator_t, cert_enumerator_enumerate, bool,
-	cert_enumerator_t *this, certificate_t **cert)
+	cert_enumerator_t *this, va_list args)
 {
+	certificate_t **cert;
 	ipseckey_t *cur_ipseckey;
 	public_key_t *public;
 	rr_t *cur_rr;
 	chunk_t key;
 
+	VA_ARGS_VGET(args, cert);
+
 	/* Get the next supported IPSECKEY using the inner enumerator. */
 	while (this->inner->enumerate(this->inner, &cur_rr))
 	{
@@ -211,7 +214,8 @@ METHOD(credential_set_t, create_cert_enumerator, enumerator_t*,
 
 	INIT(e,
 		.public = {
-			.enumerate = (void*)_cert_enumerator_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _cert_enumerator_enumerate,
 			.destroy = _cert_enumerator_destroy,
 		},
 		.inner = rrset->create_rr_enumerator(rrset),
diff --git a/src/libcharon/plugins/kernel_iph/kernel_iph_net.c b/src/libcharon/plugins/kernel_iph/kernel_iph_net.c
index efeb98045..18a87b707 100644
--- a/src/libcharon/plugins/kernel_iph/kernel_iph_net.c
+++ b/src/libcharon/plugins/kernel_iph/kernel_iph_net.c
@@ -466,9 +466,12 @@ typedef struct {
 } addr_enumerator_t;
 
 METHOD(enumerator_t, addr_enumerate, bool,
-	addr_enumerator_t *this, host_t **host)
+	addr_enumerator_t *this, va_list args)
 {
 	iface_t *entry;
+	host_t **host;
+
+	VA_ARGS_VGET(args, host);
 
 	while (TRUE)
 	{
@@ -523,7 +526,8 @@ METHOD(kernel_net_t, create_address_enumerator, enumerator_t*,
 
 	INIT(enumerator,
 		.public = {
-			.enumerate = (void*)_addr_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _addr_enumerate,
 			.destroy = _addr_destroy,
 		},
 		.which = which,
diff --git a/src/libcharon/plugins/kernel_libipsec/kernel_libipsec_ipsec.c b/src/libcharon/plugins/kernel_libipsec/kernel_libipsec_ipsec.c
index 77e37e249..d4832e233 100644
--- a/src/libcharon/plugins/kernel_libipsec/kernel_libipsec_ipsec.c
+++ b/src/libcharon/plugins/kernel_libipsec/kernel_libipsec_ipsec.c
@@ -84,12 +84,12 @@ static void exclude_route_destroy(exclude_route_t *this)
 	free(this);
 }
 
-/**
- * Find an exclude route entry by destination address
- */
-static bool exclude_route_match(exclude_route_t *current,
-								host_t *dst)
+CALLBACK(exclude_route_match, bool,
+	exclude_route_t *current, va_list args)
 {
+	host_t *dst;
+
+	VA_ARGS_VGET(args, dst);
 	return dst->ip_equals(dst, current->dst);
 }
 
@@ -204,12 +204,12 @@ static void policy_entry_destroy(policy_entry_t *this)
 	free(this);
 }
 
-/**
- * Compare two policy_entry_t objects
- */
-static inline bool policy_entry_equals(policy_entry_t *a,
-									   policy_entry_t *b)
+CALLBACK(policy_entry_equals, bool,
+	policy_entry_t *a, va_list args)
 {
+	policy_entry_t *b;
+
+	VA_ARGS_VGET(args, b);
 	return a->direction == b->direction &&
 		   a->src.proto == b->src.proto &&
 		   a->dst.proto == b->dst.proto &&
@@ -297,9 +297,8 @@ static void add_exclude_route(private_kernel_libipsec_ipsec_t *this,
 	exclude_route_t *exclude;
 	host_t *gtw;
 
-	if (this->excludes->find_first(this->excludes,
-								  (linked_list_match_t)exclude_route_match,
-								  (void**)&exclude, dst) == SUCCESS)
+	if (this->excludes->find_first(this->excludes, exclude_route_match,
+								  (void**)&exclude, dst))
 	{
 		route->exclude = exclude;
 		exclude->refs++;
@@ -524,9 +523,8 @@ METHOD(kernel_ipsec_t, add_policy, status_t,
 	policy = create_policy_entry(id->src_ts, id->dst_ts, id->dir);
 
 	this->mutex->lock(this->mutex);
-	if (this->policies->find_first(this->policies,
-								  (linked_list_match_t)policy_entry_equals,
-								  (void**)&found, policy) == SUCCESS)
+	if (this->policies->find_first(this->policies, policy_entry_equals,
+								  (void**)&found, policy))
 	{
 		policy_entry_destroy(policy);
 		policy = found;
@@ -567,9 +565,8 @@ METHOD(kernel_ipsec_t, del_policy, status_t,
 	policy = create_policy_entry(id->src_ts, id->dst_ts, id->dir);
 
 	this->mutex->lock(this->mutex);
-	if (this->policies->find_first(this->policies,
-								  (linked_list_match_t)policy_entry_equals,
-								  (void**)&found, policy) != SUCCESS)
+	if (!this->policies->find_first(this->policies, policy_entry_equals,
+									(void**)&found, policy))
 	{
 		policy_entry_destroy(policy);
 		this->mutex->unlock(this->mutex);
diff --git a/src/libcharon/plugins/kernel_netlink/kernel_netlink_ipsec.c b/src/libcharon/plugins/kernel_netlink/kernel_netlink_ipsec.c
index da05de304..c411b829d 100644
--- a/src/libcharon/plugins/kernel_netlink/kernel_netlink_ipsec.c
+++ b/src/libcharon/plugins/kernel_netlink/kernel_netlink_ipsec.c
@@ -542,10 +542,10 @@ static policy_sa_t *policy_sa_create(private_kernel_netlink_ipsec_t *this,
 /**
  * Destroy a policy_sa(_in)_t object
  */
-static void policy_sa_destroy(policy_sa_t *policy, policy_dir_t *dir,
+static void policy_sa_destroy(policy_sa_t *policy, policy_dir_t dir,
 							  private_kernel_netlink_ipsec_t *this)
 {
-	if (*dir == POLICY_OUT)
+	if (dir == POLICY_OUT)
 	{
 		policy_sa_out_t *out = (policy_sa_out_t*)policy;
 		out->src_ts->destroy(out->src_ts);
@@ -555,6 +555,16 @@ static void policy_sa_destroy(policy_sa_t *policy, policy_dir_t *dir,
 	free(policy);
 }
 
+CALLBACK(policy_sa_destroy_cb, void,
+	policy_sa_t *policy, va_list args)
+{
+	private_kernel_netlink_ipsec_t *this;
+	policy_dir_t dir;
+
+	VA_ARGS_VGET(args, dir, this);
+	policy_sa_destroy(policy, dir, this);
+}
+
 typedef struct policy_entry_t policy_entry_t;
 
 /**
@@ -599,9 +609,8 @@ static void policy_entry_destroy(private_kernel_netlink_ipsec_t *this,
 	}
 	if (policy->used_by)
 	{
-		policy->used_by->invoke_function(policy->used_by,
-										(linked_list_invoke_t)policy_sa_destroy,
-										 &policy->direction, this);
+		policy->used_by->invoke_function(policy->used_by, policy_sa_destroy_cb,
+										 policy->direction, this);
 		policy->used_by->destroy(policy->used_by);
 	}
 	free(policy);
@@ -2768,7 +2777,7 @@ METHOD(kernel_ipsec_t, del_policy, status_t,
 			ipsec_sa_equals(mapping->sa, &assigned_sa))
 		{
 			current->used_by->remove_at(current->used_by, enumerator);
-			policy_sa_destroy(mapping, &id->dir, this);
+			policy_sa_destroy(mapping, id->dir, this);
 			break;
 		}
 		if (is_installed)
diff --git a/src/libcharon/plugins/kernel_netlink/kernel_netlink_net.c b/src/libcharon/plugins/kernel_netlink/kernel_netlink_net.c
index 2dc76d941..0dd3e30cb 100644
--- a/src/libcharon/plugins/kernel_netlink/kernel_netlink_net.c
+++ b/src/libcharon/plugins/kernel_netlink/kernel_netlink_net.c
@@ -163,19 +163,21 @@ static void iface_entry_destroy(iface_entry_t *this)
 	free(this);
 }
 
-/**
- * find an interface entry by index
- */
-static bool iface_entry_by_index(iface_entry_t *this, int *ifindex)
+CALLBACK(iface_entry_by_index, bool,
+	iface_entry_t *this, va_list args)
 {
-	return this->ifindex == *ifindex;
+	int ifindex;
+
+	VA_ARGS_VGET(args, ifindex);
+	return this->ifindex == ifindex;
 }
 
-/**
- * find an interface entry by name
- */
-static bool iface_entry_by_name(iface_entry_t *this, char *ifname)
+CALLBACK(iface_entry_by_name, bool,
+	iface_entry_t *this, va_list args)
 {
+	char *ifname;
+
+	VA_ARGS_VGET(args, ifname);
 	return streq(this->ifname, ifname);
 }
 
@@ -1112,8 +1114,8 @@ static bool is_interface_up_and_usable(private_kernel_netlink_net_t *this,
 {
 	iface_entry_t *iface;
 
-	if (this->ifaces->find_first(this->ifaces, (void*)iface_entry_by_index,
-								 (void**)&iface, &index) == SUCCESS)
+	if (this->ifaces->find_first(this->ifaces, iface_entry_by_index,
+								 (void**)&iface, index))
 	{
 		return iface_entry_up_and_usable(iface);
 	}
@@ -1125,9 +1127,13 @@ static bool is_interface_up_and_usable(private_kernel_netlink_net_t *this,
  *
  * this->lock must be locked when calling this function
  */
-static void addr_entry_unregister(addr_entry_t *addr, iface_entry_t *iface,
-								  private_kernel_netlink_net_t *this)
+CALLBACK(addr_entry_unregister, void,
+	addr_entry_t *addr, va_list args)
 {
+	private_kernel_netlink_net_t *this;
+	iface_entry_t *iface;
+
+	VA_ARGS_VGET(args, iface, this);
 	if (addr->refcount)
 	{
 		addr_map_entry_remove(this->vips, addr, iface);
@@ -1171,9 +1177,8 @@ static void process_link(private_kernel_netlink_net_t *this,
 	{
 		case RTM_NEWLINK:
 		{
-			if (this->ifaces->find_first(this->ifaces,
-									(void*)iface_entry_by_index, (void**)&entry,
-									&msg->ifi_index) != SUCCESS)
+			if (!this->ifaces->find_first(this->ifaces, iface_entry_by_index,
+										 (void**)&entry, msg->ifi_index))
 			{
 				INIT(entry,
 					.ifindex = msg->ifi_index,
@@ -1217,7 +1222,7 @@ static void process_link(private_kernel_netlink_net_t *this,
 					 * another interface? */
 					this->ifaces->remove_at(this->ifaces, enumerator);
 					current->addrs->invoke_function(current->addrs,
-								(void*)addr_entry_unregister, current, this);
+										addr_entry_unregister, current, this);
 					iface_entry_destroy(current);
 					break;
 				}
@@ -1288,8 +1293,8 @@ static void process_addr(private_kernel_netlink_net_t *this,
 	}
 
 	this->lock->write_lock(this->lock);
-	if (this->ifaces->find_first(this->ifaces, (void*)iface_entry_by_index,
-								 (void**)&iface, &msg->ifa_index) == SUCCESS)
+	if (this->ifaces->find_first(this->ifaces, iface_entry_by_index,
+								 (void**)&iface, msg->ifa_index))
 	{
 		addr_map_entry_t *entry, lookup = {
 			.ip = host,
@@ -1518,35 +1523,39 @@ typedef struct {
 	kernel_address_type_t which;
 } address_enumerator_t;
 
-/**
- * cleanup function for address enumerator
- */
-static void address_enumerator_destroy(address_enumerator_t *data)
+CALLBACK(address_enumerator_destroy, void,
+	address_enumerator_t *data)
 {
 	data->this->lock->unlock(data->this->lock);
 	free(data);
 }
 
-/**
- * filter for addresses
- */
-static bool filter_addresses(address_enumerator_t *data,
-							 addr_entry_t** in, host_t** out)
+CALLBACK(filter_addresses, bool,
+	address_enumerator_t *data, enumerator_t *orig, va_list args)
 {
-	if (!(data->which & ADDR_TYPE_VIRTUAL) && (*in)->refcount)
-	{	/* skip virtual interfaces added by us */
-		return FALSE;
-	}
-	if (!(data->which & ADDR_TYPE_REGULAR) && !(*in)->refcount)
-	{	/* address is regular, but not requested */
-		return FALSE;
-	}
-	if ((*in)->scope >= RT_SCOPE_LINK)
-	{	/* skip addresses with a unusable scope */
-		return FALSE;
+	addr_entry_t *addr;
+	host_t **out;
+
+	VA_ARGS_VGET(args, out);
+
+	while (orig->enumerate(orig, &addr))
+	{
+		if (!(data->which & ADDR_TYPE_VIRTUAL) && addr->refcount)
+		{	/* skip virtual interfaces added by us */
+			continue;
+		}
+		if (!(data->which & ADDR_TYPE_REGULAR) && !addr->refcount)
+		{	/* address is regular, but not requested */
+			continue;
+		}
+		if (addr->scope >= RT_SCOPE_LINK)
+		{	/* skip addresses with a unusable scope */
+			continue;
+		}
+		*out = addr->ip;
+		return TRUE;
 	}
-	*out = (*in)->ip;
-	return TRUE;
+	return FALSE;
 }
 
 /**
@@ -1556,30 +1565,35 @@ static enumerator_t *create_iface_enumerator(iface_entry_t *iface,
 											 address_enumerator_t *data)
 {
 	return enumerator_create_filter(
-				iface->addrs->create_enumerator(iface->addrs),
-				(void*)filter_addresses, data, NULL);
+						iface->addrs->create_enumerator(iface->addrs),
+						filter_addresses, data, NULL);
 }
 
-/**
- * filter for interfaces
- */
-static bool filter_interfaces(address_enumerator_t *data, iface_entry_t** in,
-							  iface_entry_t** out)
+CALLBACK(filter_interfaces, bool,
+	address_enumerator_t *data, enumerator_t *orig, va_list args)
 {
-	if (!(data->which & ADDR_TYPE_IGNORED) && !(*in)->usable)
-	{	/* skip interfaces excluded by config */
-		return FALSE;
-	}
-	if (!(data->which & ADDR_TYPE_LOOPBACK) && ((*in)->flags & IFF_LOOPBACK))
-	{	/* ignore loopback devices */
-		return FALSE;
-	}
-	if (!(data->which & ADDR_TYPE_DOWN) && !((*in)->flags & IFF_UP))
-	{	/* skip interfaces not up */
-		return FALSE;
+	iface_entry_t *iface, **out;
+
+	VA_ARGS_VGET(args, out);
+
+	while (orig->enumerate(orig, &iface))
+	{
+		if (!(data->which & ADDR_TYPE_IGNORED) && !iface->usable)
+		{	/* skip interfaces excluded by config */
+			continue;
+		}
+		if (!(data->which & ADDR_TYPE_LOOPBACK) && (iface->flags & IFF_LOOPBACK))
+		{	/* ignore loopback devices */
+			continue;
+		}
+		if (!(data->which & ADDR_TYPE_DOWN) && !(iface->flags & IFF_UP))
+		{	/* skip interfaces not up */
+			continue;
+		}
+		*out = iface;
+		return TRUE;
 	}
-	*out = *in;
-	return TRUE;
+	return FALSE;
 }
 
 METHOD(kernel_net_t, create_address_enumerator, enumerator_t*,
@@ -1596,9 +1610,9 @@ METHOD(kernel_net_t, create_address_enumerator, enumerator_t*,
 	return enumerator_create_nested(
 				enumerator_create_filter(
 					this->ifaces->create_enumerator(this->ifaces),
-					(void*)filter_interfaces, data, NULL),
+					filter_interfaces, data, NULL),
 				(void*)create_iface_enumerator, data,
-				(void*)address_enumerator_destroy);
+				address_enumerator_destroy);
 }
 
 METHOD(kernel_net_t, get_interface_name, bool,
@@ -1661,8 +1675,8 @@ static int get_interface_index(private_kernel_netlink_net_t *this, char* name)
 	DBG2(DBG_KNL, "getting iface index for %s", name);
 
 	this->lock->read_lock(this->lock);
-	if (this->ifaces->find_first(this->ifaces, (void*)iface_entry_by_name,
-								(void**)&iface, name) == SUCCESS)
+	if (this->ifaces->find_first(this->ifaces, iface_entry_by_name,
+								(void**)&iface, name))
 	{
 		ifindex = iface->ifindex;
 	}
@@ -1687,8 +1701,8 @@ static char *get_interface_name_by_index(private_kernel_netlink_net_t *this,
 	DBG2(DBG_KNL, "getting iface name for index %d", index);
 
 	this->lock->read_lock(this->lock);
-	if (this->ifaces->find_first(this->ifaces, (void*)iface_entry_by_index,
-								(void**)&iface, &index) == SUCCESS)
+	if (this->ifaces->find_first(this->ifaces, iface_entry_by_index,
+								(void**)&iface, index))
 	{
 		name = strdup(iface->ifname);
 	}
@@ -1928,7 +1942,7 @@ static host_t *get_route(private_kernel_netlink_net_t *this, host_t *dest,
 
 				table = (uintptr_t)route->table;
 				if (this->rt_exclude->find_first(this->rt_exclude, NULL,
-												 (void**)&table) == SUCCESS)
+												 (void**)&table))
 				{	/* route is from an excluded routing table */
 					continue;
 				}
@@ -2165,8 +2179,14 @@ METHOD(enumerator_t, destroy_subnet_enumerator, void,
 }
 
 METHOD(enumerator_t, enumerate_subnets, bool,
-	subnet_enumerator_t *this, host_t **net, uint8_t *mask, char **ifname)
+	subnet_enumerator_t *this, va_list args)
 {
+	host_t **net;
+	uint8_t *mask;
+	char **ifname;
+
+	VA_ARGS_VGET(args, net, mask, ifname);
+
 	if (!this->current)
 	{
 		this->current = this->msg;
@@ -2270,7 +2290,8 @@ METHOD(kernel_net_t, create_local_subnet_enumerator, enumerator_t*,
 
 	INIT(enumerator,
 		.public = {
-			.enumerate = (void*)_enumerate_subnets,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _enumerate_subnets,
 			.destroy = _destroy_subnet_enumerator,
 		},
 		.private = this,
@@ -2380,11 +2401,11 @@ METHOD(kernel_net_t, add_ip, status_t,
 	}
 	/* try to find the target interface, either by config or via src ip */
 	if (!this->install_virtual_ip_on ||
-		 this->ifaces->find_first(this->ifaces, (void*)iface_entry_by_name,
-						(void**)&iface, this->install_virtual_ip_on) != SUCCESS)
+		!this->ifaces->find_first(this->ifaces, iface_entry_by_name,
+								 (void**)&iface, this->install_virtual_ip_on))
 	{
-		if (this->ifaces->find_first(this->ifaces, (void*)iface_entry_by_name,
-									 (void**)&iface, iface_name) != SUCCESS)
+		if (!this->ifaces->find_first(this->ifaces, iface_entry_by_name,
+									 (void**)&iface, iface_name))
 		{	/* if we don't find the requested interface we just use the first */
 			this->ifaces->get_first(this->ifaces, (void**)&iface);
 		}
diff --git a/src/libcharon/plugins/kernel_pfkey/kernel_pfkey_ipsec.c b/src/libcharon/plugins/kernel_pfkey/kernel_pfkey_ipsec.c
index fd427ebbb..fd1adb2ae 100644
--- a/src/libcharon/plugins/kernel_pfkey/kernel_pfkey_ipsec.c
+++ b/src/libcharon/plugins/kernel_pfkey/kernel_pfkey_ipsec.c
@@ -464,10 +464,10 @@ static policy_sa_t *policy_sa_create(private_kernel_pfkey_ipsec_t *this,
 /**
  * Destroy a policy_sa(_in)_t object
  */
-static void policy_sa_destroy(policy_sa_t *policy, policy_dir_t *dir,
+static void policy_sa_destroy(policy_sa_t *policy, policy_dir_t dir,
 							  private_kernel_pfkey_ipsec_t *this)
 {
-	if (*dir == POLICY_OUT)
+	if (dir == POLICY_OUT)
 	{
 		policy_sa_out_t *out = (policy_sa_out_t*)policy;
 		out->src_ts->destroy(out->src_ts);
@@ -477,6 +477,16 @@ static void policy_sa_destroy(policy_sa_t *policy, policy_dir_t *dir,
 	free(policy);
 }
 
+CALLBACK(policy_sa_destroy_cb, void,
+	policy_sa_t *policy, va_list args)
+{
+	private_kernel_pfkey_ipsec_t *this;
+	policy_dir_t dir;
+
+	VA_ARGS_VGET(args, dir, this);
+	policy_sa_destroy(policy, dir, this);
+}
+
 typedef struct policy_entry_t policy_entry_t;
 
 /**
@@ -557,9 +567,8 @@ static void policy_entry_destroy(policy_entry_t *policy,
 	}
 	if (policy->used_by)
 	{
-		policy->used_by->invoke_function(policy->used_by,
-										(linked_list_invoke_t)policy_sa_destroy,
-										 &policy->direction, this);
+		policy->used_by->invoke_function(policy->used_by, policy_sa_destroy_cb,
+										 policy->direction, this);
 		policy->used_by->destroy(policy->used_by);
 	}
 	DESTROY_IF(policy->src.net);
@@ -567,12 +576,21 @@ static void policy_entry_destroy(policy_entry_t *policy,
 	free(policy);
 }
 
-/**
- * compares two policy_entry_t
- */
-static inline bool policy_entry_equals(policy_entry_t *current,
-									   policy_entry_t *policy)
+CALLBACK(policy_entry_destroy_cb, void,
+	policy_entry_t *policy, va_list args)
 {
+	private_kernel_pfkey_ipsec_t *this;
+
+	VA_ARGS_VGET(args, this);
+	policy_entry_destroy(policy, this);
+}
+
+CALLBACK(policy_entry_equals, bool,
+	policy_entry_t *current, va_list args)
+{
+	policy_entry_t *policy;
+
+	VA_ARGS_VGET(args, policy);
 	return current->direction == policy->direction &&
 		   current->src.proto == policy->src.proto &&
 		   current->dst.proto == policy->dst.proto &&
@@ -582,13 +600,13 @@ static inline bool policy_entry_equals(policy_entry_t *current,
 		   current->dst.net->equals(current->dst.net, policy->dst.net);
 }
 
-/**
- * compare the given kernel index with that of a policy
- */
-static inline bool policy_entry_match_byindex(policy_entry_t *current,
-											  uint32_t *index)
+CALLBACK(policy_entry_match_byindex, bool,
+	policy_entry_t *current, va_list args)
 {
-	return current->index == *index;
+	uint32_t index;
+
+	VA_ARGS_VGET(args, index);
+	return current->index == index;
 }
 
 /**
@@ -1261,9 +1279,8 @@ static void process_acquire(private_kernel_pfkey_ipsec_t *this,
 
 	index = response.x_policy->sadb_x_policy_id;
 	this->mutex->lock(this->mutex);
-	if (this->policies->find_first(this->policies,
-								(linked_list_match_t)policy_entry_match_byindex,
-								(void**)&policy, &index) == SUCCESS &&
+	if (this->policies->find_first(this->policies, policy_entry_match_byindex,
+								  (void**)&policy, index) &&
 		policy->used_by->get_first(policy->used_by, (void**)&sa) == SUCCESS)
 	{
 		reqid = sa->sa->cfg.reqid;
@@ -2554,8 +2571,7 @@ static status_t add_policy_internal(private_kernel_pfkey_ipsec_t *this,
 
 	/* we try to find the policy again and update the kernel index */
 	this->mutex->lock(this->mutex);
-	if (this->policies->find_first(this->policies, NULL,
-								  (void**)&policy) != SUCCESS)
+	if (!this->policies->find_first(this->policies, NULL, (void**)&policy))
 	{
 		DBG2(DBG_KNL, "unable to update index, the policy is already gone, "
 					  "ignoring");
@@ -2606,9 +2622,8 @@ METHOD(kernel_ipsec_t, add_policy, status_t,
 
 	/* find a matching policy */
 	this->mutex->lock(this->mutex);
-	if (this->policies->find_first(this->policies,
-								  (linked_list_match_t)policy_entry_equals,
-								  (void**)&found, policy) == SUCCESS)
+	if (this->policies->find_first(this->policies, policy_entry_equals,
+								   (void**)&found, policy))
 	{	/* use existing policy */
 		DBG2(DBG_KNL, "policy %R === %R %N already exists, increasing "
 			 "refcount", id->src_ts, id->dst_ts, policy_dir_names, id->dir);
@@ -2701,9 +2716,8 @@ METHOD(kernel_ipsec_t, query_policy, status_t,
 
 	/* find a matching policy */
 	this->mutex->lock(this->mutex);
-	if (this->policies->find_first(this->policies,
-								  (linked_list_match_t)policy_entry_equals,
-								  (void**)&found, policy) != SUCCESS)
+	if (!this->policies->find_first(this->policies, policy_entry_equals,
+									(void**)&found, policy))
 	{
 		DBG1(DBG_KNL, "querying policy %R === %R %N failed, not found",
 			 id->src_ts, id->dst_ts, policy_dir_names, id->dir);
@@ -2814,9 +2828,8 @@ METHOD(kernel_ipsec_t, del_policy, status_t,
 
 	/* find a matching policy */
 	this->mutex->lock(this->mutex);
-	if (this->policies->find_first(this->policies,
-								  (linked_list_match_t)policy_entry_equals,
-								  (void**)&found, policy) != SUCCESS)
+	if (!this->policies->find_first(this->policies, policy_entry_equals,
+									(void**)&found, policy))
 	{
 		DBG1(DBG_KNL, "deleting policy %R === %R %N failed, not found",
 			 id->src_ts, id->dst_ts, policy_dir_names, id->dir);
@@ -2860,7 +2873,7 @@ METHOD(kernel_ipsec_t, del_policy, status_t,
 	if (policy->used_by->get_count(policy->used_by) > 0)
 	{	/* policy is used by more SAs, keep in kernel */
 		DBG2(DBG_KNL, "policy still used by another CHILD_SA, not removed");
-		policy_sa_destroy(mapping, &id->dir, this);
+		policy_sa_destroy(mapping, id->dir, this);
 
 		if (!is_installed)
 		{	/* no need to update as the policy was not installed for this SA */
@@ -2915,7 +2928,7 @@ METHOD(kernel_ipsec_t, del_policy, status_t,
 	}
 
 	this->policies->remove(this->policies, found, NULL);
-	policy_sa_destroy(mapping, &id->dir, this);
+	policy_sa_destroy(mapping, id->dir, this);
 	policy_entry_destroy(policy, this);
 	this->mutex->unlock(this->mutex);
 
@@ -3088,8 +3101,7 @@ METHOD(kernel_ipsec_t, destroy, void,
 		lib->watcher->remove(lib->watcher, this->socket_events);
 		close(this->socket_events);
 	}
-	this->policies->invoke_function(this->policies,
-								   (linked_list_invoke_t)policy_entry_destroy,
+	this->policies->invoke_function(this->policies, policy_entry_destroy_cb,
 									this);
 	this->policies->destroy(this->policies);
 	this->excludes->destroy(this->excludes);
diff --git a/src/libcharon/plugins/kernel_pfroute/kernel_pfroute_net.c b/src/libcharon/plugins/kernel_pfroute/kernel_pfroute_net.c
index efcf1c2a7..6d06ee179 100644
--- a/src/libcharon/plugins/kernel_pfroute/kernel_pfroute_net.c
+++ b/src/libcharon/plugins/kernel_pfroute/kernel_pfroute_net.c
@@ -601,9 +601,12 @@ typedef struct {
 } rt_enumerator_t;
 
 METHOD(enumerator_t, rt_enumerate, bool,
-	rt_enumerator_t *this, int *xtype, struct sockaddr **addr)
+	rt_enumerator_t *this, va_list args)
 {
-	int i, type;
+	struct sockaddr **addr;
+	int i, type, *xtype;
+
+	VA_ARGS_VGET(args, xtype, addr);
 
 	if (this->remaining < sizeof(this->addr->sa_len) ||
 		this->remaining < this->addr->sa_len)
@@ -637,7 +640,8 @@ static enumerator_t *create_rt_enumerator(int types, int remaining,
 
 	INIT(this,
 		.public = {
-			.enumerate = (void*)_rt_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _rt_enumerate,
 			.destroy = (void*)free,
 		},
 		.types = types,
@@ -1050,41 +1054,45 @@ typedef struct {
 	kernel_address_type_t which;
 } address_enumerator_t;
 
-/**
- * cleanup function for address enumerator
- */
-static void address_enumerator_destroy(address_enumerator_t *data)
+CALLBACK(address_enumerator_destroy, void,
+	address_enumerator_t *data)
 {
 	data->this->lock->unlock(data->this->lock);
 	free(data);
 }
 
-/**
- * filter for addresses
- */
-static bool filter_addresses(address_enumerator_t *data,
-							 addr_entry_t** in, host_t** out)
+CALLBACK(filter_addresses, bool,
+	address_enumerator_t *data, enumerator_t *orig, va_list args)
 {
-	host_t *ip;
-	if (!(data->which & ADDR_TYPE_VIRTUAL) && (*in)->virtual)
-	{   /* skip virtual interfaces added by us */
-		return FALSE;
-	}
-	if (!(data->which & ADDR_TYPE_REGULAR) && !(*in)->virtual)
-	{	/* address is regular, but not requested */
-		return FALSE;
-	}
-	ip = (*in)->ip;
-	if (ip->get_family(ip) == AF_INET6)
+	addr_entry_t *addr;
+	host_t *ip, **out;
+	struct sockaddr_in6 *sin6;
+
+	VA_ARGS_VGET(args, out);
+
+	while (orig->enumerate(orig, &addr))
 	{
-		struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)ip->get_sockaddr(ip);
-		if (IN6_IS_ADDR_LINKLOCAL(&sin6->sin6_addr))
-		{   /* skip addresses with a unusable scope */
-			return FALSE;
+		if (!(data->which & ADDR_TYPE_VIRTUAL) && addr->virtual)
+		{   /* skip virtual interfaces added by us */
+			continue;
 		}
+		if (!(data->which & ADDR_TYPE_REGULAR) && !addr->virtual)
+		{	/* address is regular, but not requested */
+			continue;
+		}
+		ip = addr->ip;
+		if (ip->get_family(ip) == AF_INET6)
+		{
+			sin6 = (struct sockaddr_in6 *)ip->get_sockaddr(ip);
+			if (IN6_IS_ADDR_LINKLOCAL(&sin6->sin6_addr))
+			{   /* skip addresses with a unusable scope */
+				continue;
+			}
+		}
+		*out = ip;
+		return TRUE;
 	}
-	*out = ip;
-	return TRUE;
+	return FALSE;
 }
 
 /**
@@ -1094,29 +1102,34 @@ static enumerator_t *create_iface_enumerator(iface_entry_t *iface,
 											 address_enumerator_t *data)
 {
 	return enumerator_create_filter(iface->addrs->create_enumerator(iface->addrs),
-									(void*)filter_addresses, data, NULL);
+									filter_addresses, data, NULL);
 }
 
-/**
- * filter for interfaces
- */
-static bool filter_interfaces(address_enumerator_t *data, iface_entry_t** in,
-							  iface_entry_t** out)
+CALLBACK(filter_interfaces, bool,
+	address_enumerator_t *data, enumerator_t *orig, va_list args)
 {
-	if (!(data->which & ADDR_TYPE_IGNORED) && !(*in)->usable)
-	{	/* skip interfaces excluded by config */
-		return FALSE;
-	}
-	if (!(data->which & ADDR_TYPE_LOOPBACK) && ((*in)->flags & IFF_LOOPBACK))
-	{	/* ignore loopback devices */
-		return FALSE;
-	}
-	if (!(data->which & ADDR_TYPE_DOWN) && !((*in)->flags & IFF_UP))
-	{	/* skip interfaces not up */
-		return FALSE;
+	iface_entry_t *iface, **out;
+
+	VA_ARGS_VGET(args, out);
+
+	while (orig->enumerate(orig, &iface))
+	{
+		if (!(data->which & ADDR_TYPE_IGNORED) && !iface->usable)
+		{	/* skip interfaces excluded by config */
+			continue;
+		}
+		if (!(data->which & ADDR_TYPE_LOOPBACK) && (iface->flags & IFF_LOOPBACK))
+		{	/* ignore loopback devices */
+			continue;
+		}
+		if (!(data->which & ADDR_TYPE_DOWN) && !(iface->flags & IFF_UP))
+		{	/* skip interfaces not up */
+			continue;
+		}
+		*out = iface;
+		return TRUE;
 	}
-	*out = *in;
-	return TRUE;
+	return FALSE;
 }
 
 METHOD(kernel_net_t, create_address_enumerator, enumerator_t*,
@@ -1133,9 +1146,9 @@ METHOD(kernel_net_t, create_address_enumerator, enumerator_t*,
 	return enumerator_create_nested(
 				enumerator_create_filter(
 					this->ifaces->create_enumerator(this->ifaces),
-					(void*)filter_interfaces, data, NULL),
+					filter_interfaces, data, NULL),
 				(void*)create_iface_enumerator, data,
-				(void*)address_enumerator_destroy);
+				address_enumerator_destroy);
 }
 
 METHOD(kernel_net_t, get_features, kernel_feature_t,
@@ -1789,13 +1802,18 @@ METHOD(enumerator_t, destroy_subnet_enumerator, void,
 }
 
 METHOD(enumerator_t, enumerate_subnets, bool,
-	subnet_enumerator_t *this, host_t **net, uint8_t *mask, char **ifname)
+	subnet_enumerator_t *this, va_list args)
 {
 	enumerator_t *enumerator;
+	host_t **net;
 	struct rt_msghdr *rtm;
 	struct sockaddr *addr;
+	uint8_t *mask;
+	char **ifname;
 	int type;
 
+	VA_ARGS_VGET(args, net, mask, ifname);
+
 	if (!this->current)
 	{
 		this->current = this->buf;
@@ -1888,7 +1906,8 @@ METHOD(kernel_net_t, create_local_subnet_enumerator, enumerator_t*,
 
 	INIT(enumerator,
 		.public = {
-			.enumerate = (void*)_enumerate_subnets,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _enumerate_subnets,
 			.destroy = _destroy_subnet_enumerator,
 		},
 		.buf = buf,
diff --git a/src/libcharon/plugins/load_tester/load_tester_creds.c b/src/libcharon/plugins/load_tester/load_tester_creds.c
index 2f482962a..2cedd130e 100644
--- a/src/libcharon/plugins/load_tester/load_tester_creds.c
+++ b/src/libcharon/plugins/load_tester/load_tester_creds.c
@@ -395,22 +395,28 @@ METHOD(credential_set_t, create_cert_enumerator, enumerator_t*,
 	return NULL;
 }
 
-/**
- * Filter function for shared keys, returning ID matches
- */
-static bool shared_filter(void *null, shared_key_t **in, shared_key_t **out,
-				void **un1, id_match_t *me, void **un2, id_match_t *other)
+CALLBACK(shared_filter, bool,
+	void *null, enumerator_t *orig, va_list args)
 {
-	*out = *in;
-	if (me)
-	{
-		*me = ID_MATCH_ANY;
-	}
-	if (other)
+	shared_key_t *key, **out;
+	id_match_t *me, *other;
+
+	VA_ARGS_VGET(args, out, me, other);
+
+	if (orig->enumerate(orig, &key))
 	{
-		*other = ID_MATCH_ANY;
+		*out = key;
+		if (me)
+		{
+			*me = ID_MATCH_ANY;
+		}
+		if (other)
+		{
+			*other = ID_MATCH_ANY;
+		}
+		return TRUE;
 	}
-	return TRUE;
+	return FALSE;
 }
 
 METHOD(credential_set_t, create_shared_enumerator, enumerator_t*,
@@ -431,7 +437,7 @@ METHOD(credential_set_t, create_shared_enumerator, enumerator_t*,
 			return NULL;
 	}
 	return enumerator_create_filter(enumerator_create_single(shared, NULL),
-									(void*)shared_filter, NULL, NULL);
+									shared_filter, NULL, NULL);
 }
 
 METHOD(load_tester_creds_t, destroy, void,
diff --git a/src/libcharon/plugins/medcli/medcli_config.c b/src/libcharon/plugins/medcli/medcli_config.c
index 78159c845..f34990176 100644
--- a/src/libcharon/plugins/medcli/medcli_config.c
+++ b/src/libcharon/plugins/medcli/medcli_config.c
@@ -223,10 +223,11 @@ typedef struct {
 } peer_enumerator_t;
 
 METHOD(enumerator_t, peer_enumerator_enumerate, bool,
-	peer_enumerator_t *this, peer_cfg_t **cfg)
+	peer_enumerator_t *this, va_list args)
 {
 	char *name, *local_net, *remote_net;
 	chunk_t me, other;
+	peer_cfg_t **cfg;
 	child_cfg_t *child_cfg;
 	auth_cfg_t *auth;
 	peer_cfg_create_t peer = {
@@ -249,6 +250,8 @@ METHOD(enumerator_t, peer_enumerator_enumerate, bool,
 		.mode = MODE_TUNNEL,
 	};
 
+	VA_ARGS_VGET(args, cfg);
+
 	DESTROY_IF(this->current);
 	if (!this->inner->enumerate(this->inner, &name, &me, &other,
 								&local_net, &remote_net))
@@ -295,7 +298,8 @@ METHOD(backend_t, create_peer_cfg_enumerator, enumerator_t*,
 
 	INIT(e,
 		.public = {
-			.enumerate = (void*)_peer_enumerator_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _peer_enumerator_enumerate,
 			.destroy = _peer_enumerator_destroy,
 		},
 		.ike = this->ike,
diff --git a/src/libcharon/plugins/medcli/medcli_creds.c b/src/libcharon/plugins/medcli/medcli_creds.c
index 677229b9f..528fc004d 100644
--- a/src/libcharon/plugins/medcli/medcli_creds.c
+++ b/src/libcharon/plugins/medcli/medcli_creds.c
@@ -50,10 +50,13 @@ typedef struct {
 } private_enumerator_t;
 
 METHOD(enumerator_t, private_enumerator_enumerate, bool,
-	private_enumerator_t *this, private_key_t **key)
+	private_enumerator_t *this, va_list args)
 {
+	private_key_t **key;
 	chunk_t chunk;
 
+	VA_ARGS_VGET(args, key);
+
 	DESTROY_IF(this->current);
 	while (this->inner->enumerate(this->inner, &chunk))
 	{
@@ -92,7 +95,8 @@ METHOD(credential_set_t, create_private_enumerator, enumerator_t*,
 
 	INIT(e,
 		.public = {
-			.enumerate = (void*)_private_enumerator_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _private_enumerator_enumerate,
 			.destroy = _private_enumerator_destroy,
 		},
 	);
@@ -123,11 +127,14 @@ typedef struct {
 } cert_enumerator_t;
 
 METHOD(enumerator_t, cert_enumerator_enumerate, bool,
-	cert_enumerator_t *this, certificate_t **cert)
+	cert_enumerator_t *this, va_list args)
 {
+	certificate_t **cert;
 	public_key_t *public;
 	chunk_t chunk;
 
+	VA_ARGS_VGET(args, cert);
+
 	DESTROY_IF(this->current);
 	while (this->inner->enumerate(this->inner, &chunk))
 	{
@@ -180,7 +187,8 @@ METHOD(credential_set_t, create_cert_enumerator, enumerator_t*,
 
 	INIT(e,
 		.public = {
-			.enumerate = (void*)_cert_enumerator_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _cert_enumerator_enumerate,
 			.destroy = _cert_enumerator_destroy,
 		},
 		.type = key,
diff --git a/src/libcharon/plugins/medsrv/medsrv_creds.c b/src/libcharon/plugins/medsrv/medsrv_creds.c
index 0d99c4f77..16d4bd7f3 100644
--- a/src/libcharon/plugins/medsrv/medsrv_creds.c
+++ b/src/libcharon/plugins/medsrv/medsrv_creds.c
@@ -52,12 +52,14 @@ typedef struct {
 } cert_enumerator_t;
 
 METHOD(enumerator_t, cert_enumerator_enumerate, bool,
-	cert_enumerator_t *this, certificate_t **cert)
+	cert_enumerator_t *this, va_list args)
 {
-	certificate_t *trusted;
+	certificate_t *trusted, **cert;
 	public_key_t *public;
 	chunk_t chunk;
 
+	VA_ARGS_VGET(args, cert);
+
 	DESTROY_IF(this->current);
 	while (this->inner->enumerate(this->inner, &chunk))
 	{
@@ -110,7 +112,8 @@ METHOD(credential_set_t, create_cert_enumerator, enumerator_t*,
 
 	INIT(e,
 		.public = {
-			.enumerate = (void*)_cert_enumerator_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _cert_enumerator_enumerate,
 			.destroy = _cert_enumerator_destroy,
 		},
 		.type = key,
diff --git a/src/libcharon/plugins/osx_attr/osx_attr_handler.c b/src/libcharon/plugins/osx_attr/osx_attr_handler.c
index 6baf76d35..e7a627b93 100644
--- a/src/libcharon/plugins/osx_attr/osx_attr_handler.c
+++ b/src/libcharon/plugins/osx_attr/osx_attr_handler.c
@@ -218,12 +218,15 @@ METHOD(attribute_handler_t, release, void,
 }
 
 METHOD(enumerator_t, enumerate_dns, bool,
-	enumerator_t *this, configuration_attribute_type_t *type, chunk_t *data)
+	enumerator_t *this, va_list args)
 {
+	configuration_attribute_type_t *type;
+	chunk_t *data;
+
+	VA_ARGS_VGET(args, type, data);
 	*type = INTERNAL_IP4_DNS;
 	*data = chunk_empty;
-	/* stop enumeration */
-	this->enumerate = (void*)return_false;
+	this->venumerate = (void*)return_false;
 	return TRUE;
 }
 
@@ -234,7 +237,8 @@ METHOD(attribute_handler_t, create_attribute_enumerator, enumerator_t *,
 	enumerator_t *enumerator;
 
 	INIT(enumerator,
-		.enumerate = (void*)_enumerate_dns,
+		.enumerate = enumerator_enumerate_default,
+		.venumerate = _enumerate_dns,
 		.destroy = (void*)free,
 	);
 	return enumerator;
diff --git a/src/libcharon/plugins/p_cscf/p_cscf_handler.c b/src/libcharon/plugins/p_cscf/p_cscf_handler.c
index 76633845e..cdf266054 100644
--- a/src/libcharon/plugins/p_cscf/p_cscf_handler.c
+++ b/src/libcharon/plugins/p_cscf/p_cscf_handler.c
@@ -83,9 +83,12 @@ typedef struct {
 } attr_enumerator_t;
 
 METHOD(enumerator_t, enumerate_attrs, bool,
-	attr_enumerator_t *this, configuration_attribute_type_t *type,
-	chunk_t *data)
+	attr_enumerator_t *this, va_list args)
 {
+	configuration_attribute_type_t *type;
+	chunk_t *data;
+
+	VA_ARGS_VGET(args, type, data);
 	if (this->request_ipv4)
 	{
 		*type = P_CSCF_IP4_ADDRESS;
@@ -103,12 +106,13 @@ METHOD(enumerator_t, enumerate_attrs, bool,
 	return FALSE;
 }
 
-/**
- * Check if the given host has a matching address family
- */
-static bool is_family(host_t *host, int *family)
+CALLBACK(is_family, bool,
+	host_t *host, va_list args)
 {
-	return host->get_family(host) == *family;
+	int family;
+
+	VA_ARGS_VGET(args, family);
+	return host->get_family(host) == family;
 }
 
 /**
@@ -116,7 +120,7 @@ static bool is_family(host_t *host, int *family)
  */
 static bool has_host_family(linked_list_t *list, int family)
 {
-	return list->find_first(list, (void*)is_family, NULL, &family) == SUCCESS;
+	return list->find_first(list, is_family, NULL, family);
 }
 
 METHOD(attribute_handler_t, create_attribute_enumerator, enumerator_t *,
@@ -132,7 +136,8 @@ METHOD(attribute_handler_t, create_attribute_enumerator, enumerator_t *,
 
 	INIT(enumerator,
 		.public = {
-			.enumerate = (void*)_enumerate_attrs,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _enumerate_attrs,
 			.destroy = (void*)free,
 		},
 	);
diff --git a/src/libcharon/plugins/resolve/resolve_handler.c b/src/libcharon/plugins/resolve/resolve_handler.c
index 9077b51d4..05b865464 100644
--- a/src/libcharon/plugins/resolve/resolve_handler.c
+++ b/src/libcharon/plugins/resolve/resolve_handler.c
@@ -391,10 +391,13 @@ typedef struct {
 	bool v6;
 } attribute_enumerator_t;
 
-static bool attribute_enumerate(attribute_enumerator_t *this,
-								configuration_attribute_type_t *type,
-								chunk_t *data)
+METHOD(enumerator_t, attribute_enumerate, bool,
+	attribute_enumerator_t *this, va_list args)
 {
+	configuration_attribute_type_t *type;
+	chunk_t *data;
+
+	VA_ARGS_VGET(args, type, data);
 	if (this->v4)
 	{
 		*type = INTERNAL_IP4_DNS;
@@ -443,7 +446,8 @@ METHOD(attribute_handler_t, create_attribute_enumerator, enumerator_t*,
 
 	INIT(enumerator,
 		.public = {
-			.enumerate = (void*)attribute_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _attribute_enumerate,
 			.destroy = (void*)free,
 		},
 		.v4 = has_host_family(vips, AF_INET),
diff --git a/src/libcharon/plugins/sql/sql_config.c b/src/libcharon/plugins/sql/sql_config.c
index cf7c3b814..55e818122 100644
--- a/src/libcharon/plugins/sql/sql_config.c
+++ b/src/libcharon/plugins/sql/sql_config.c
@@ -504,11 +504,12 @@ typedef struct {
 	ike_cfg_t *current;
 } ike_enumerator_t;
 
-/**
- * Implementation of ike_enumerator_t.public.enumerate
- */
-static bool ike_enumerator_enumerate(ike_enumerator_t *this, ike_cfg_t **cfg)
+METHOD(enumerator_t, ike_enumerator_enumerate, bool,
+	ike_enumerator_t *this, va_list args)
 {
+	ike_cfg_t **cfg;
+
+	VA_ARGS_VGET(args, cfg);
 	DESTROY_IF(this->current);
 	this->current = build_ike_cfg(this->this, this->inner, this->me, this->other);
 	if (this->current)
@@ -519,10 +520,8 @@ static bool ike_enumerator_enumerate(ike_enumerator_t *this, ike_cfg_t **cfg)
 	return FALSE;
 }
 
-/**
- * Implementation of ike_enumerator_t.public.destroy
- */
-static void ike_enumerator_destroy(ike_enumerator_t *this)
+METHOD(enumerator_t, ike_enumerator_destroy, void,
+	ike_enumerator_t *this)
 {
 	DESTROY_IF(this->current);
 	this->inner->destroy(this->inner);
@@ -532,19 +531,22 @@ static void ike_enumerator_destroy(ike_enumerator_t *this)
 METHOD(backend_t, create_ike_cfg_enumerator, enumerator_t*,
 	private_sql_config_t *this, host_t *me, host_t *other)
 {
-	ike_enumerator_t *e = malloc_thing(ike_enumerator_t);
-
-	e->this = this;
-	e->me = me;
-	e->other = other;
-	e->current = NULL;
-	e->public.enumerate = (void*)ike_enumerator_enumerate;
-	e->public.destroy = (void*)ike_enumerator_destroy;
+	ike_enumerator_t *e;
 
+	INIT(e,
+		.public = {
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _ike_enumerator_enumerate,
+			.destroy = _ike_enumerator_destroy,
+		},
+		.this = this,
+		.me = me,
+		.other = other,
+	);
 	e->inner = this->db->query(this->db,
-			"SELECT id, certreq, force_encap, local, remote "
-			"FROM ike_configs",
-			DB_INT, DB_INT, DB_INT, DB_TEXT, DB_TEXT);
+							   "SELECT id, certreq, force_encap, local, remote "
+							   "FROM ike_configs",
+							   DB_INT, DB_INT, DB_INT, DB_TEXT, DB_TEXT);
 	if (!e->inner)
 	{
 		free(e);
@@ -569,11 +571,12 @@ typedef struct {
 	peer_cfg_t *current;
 } peer_enumerator_t;
 
-/**
- * Implementation of peer_enumerator_t.public.enumerate
- */
-static bool peer_enumerator_enumerate(peer_enumerator_t *this, peer_cfg_t **cfg)
+METHOD(enumerator_t, peer_enumerator_enumerate, bool,
+	peer_enumerator_t *this, va_list args)
 {
+	peer_cfg_t **cfg;
+
+	VA_ARGS_VGET(args, cfg);
 	DESTROY_IF(this->current);
 	this->current = build_peer_cfg(this->this, this->inner, this->me, this->other);
 	if (this->current)
@@ -584,10 +587,8 @@ static bool peer_enumerator_enumerate(peer_enumerator_t *this, peer_cfg_t **cfg)
 	return FALSE;
 }
 
-/**
- * Implementation of peer_enumerator_t.public.destroy
- */
-static void peer_enumerator_destroy(peer_enumerator_t *this)
+METHOD(enumerator_t, peer_enumerator_destroy, void,
+	peer_enumerator_t *this)
 {
 	DESTROY_IF(this->current);
 	this->inner->destroy(this->inner);
@@ -599,12 +600,16 @@ METHOD(backend_t, create_peer_cfg_enumerator, enumerator_t*,
 {
 	peer_enumerator_t *e = malloc_thing(peer_enumerator_t);
 
-	e->this = this;
-	e->me = me;
-	e->other = other;
-	e->current = NULL;
-	e->public.enumerate = (void*)peer_enumerator_enumerate;
-	e->public.destroy = (void*)peer_enumerator_destroy;
+	INIT(e,
+		.public = {
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _peer_enumerator_enumerate,
+			.destroy = _peer_enumerator_destroy,
+		},
+		.this = this,
+		.me = me,
+		.other = other,
+	);
 
 	/* TODO: only get configs whose IDs match exactly or contain wildcards */
 	e->inner = this->db->query(this->db,
diff --git a/src/libcharon/plugins/sql/sql_cred.c b/src/libcharon/plugins/sql/sql_cred.c
index 117eec921..3317de6c8 100644
--- a/src/libcharon/plugins/sql/sql_cred.c
+++ b/src/libcharon/plugins/sql/sql_cred.c
@@ -52,11 +52,14 @@ typedef struct {
 } private_enumerator_t;
 
 METHOD(enumerator_t, private_enumerator_enumerate, bool,
-	   private_enumerator_t *this, private_key_t **key)
+	   private_enumerator_t *this, va_list args)
 {
+	private_key_t **key;
 	chunk_t blob;
 	int type;
 
+	VA_ARGS_VGET(args, key);
+
 	DESTROY_IF(this->current);
 	while (this->inner->enumerate(this->inner, &type, &blob))
 	{
@@ -88,7 +91,8 @@ METHOD(credential_set_t, create_private_enumerator, enumerator_t*,
 
 	INIT(e,
 		.public = {
-			.enumerate = (void*)_private_enumerator_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _private_enumerator_enumerate,
 			.destroy = _private_enumerator_destroy,
 		},
 	);
@@ -132,11 +136,14 @@ typedef struct {
 } cert_enumerator_t;
 
 METHOD(enumerator_t, cert_enumerator_enumerate, bool,
-	   cert_enumerator_t *this, certificate_t **cert)
+	   cert_enumerator_t *this, va_list args)
 {
+	certificate_t **cert;
 	chunk_t blob;
 	int type;
 
+	VA_ARGS_VGET(args, cert);
+
 	DESTROY_IF(this->current);
 	while (this->inner->enumerate(this->inner, &type, &blob))
 	{
@@ -169,7 +176,8 @@ METHOD(credential_set_t, create_cert_enumerator, enumerator_t*,
 
 	INIT(e,
 		.public = {
-			.enumerate = (void*)_cert_enumerator_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _cert_enumerator_enumerate,
 			.destroy = _cert_enumerator_destroy,
 		},
 	);
@@ -221,12 +229,15 @@ typedef struct {
 } shared_enumerator_t;
 
 METHOD(enumerator_t, shared_enumerator_enumerate, bool,
-	   shared_enumerator_t *this, shared_key_t **shared,
-	   id_match_t *me, id_match_t *other)
+	   shared_enumerator_t *this, va_list args)
 {
+	shared_key_t **shared;
+	id_match_t *me, *other;
 	chunk_t blob;
 	int type;
 
+	VA_ARGS_VGET(args, shared, me, other);
+
 	DESTROY_IF(this->current);
 	while (this->inner->enumerate(this->inner, &type, &blob))
 	{
@@ -265,7 +276,8 @@ METHOD(credential_set_t, create_shared_enumerator, enumerator_t*,
 
 	INIT(e,
 		.public = {
-			.enumerate = (void*)_shared_enumerator_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _shared_enumerator_enumerate,
 			.destroy = _shared_enumerator_destroy,
 		},
 		.me = me,
@@ -340,9 +352,11 @@ typedef enum {
 } cdp_type_t;
 
 METHOD(enumerator_t, cdp_enumerator_enumerate, bool,
-	   cdp_enumerator_t *this, char **uri)
+	   cdp_enumerator_t *this, va_list args)
 {
-	char *text;
+	char *text, **uri;
+
+	VA_ARGS_VGET(args, uri);
 
 	free(this->current);
 	while (this->inner->enumerate(this->inner, &text))
@@ -384,7 +398,8 @@ METHOD(credential_set_t, create_cdp_enumerator, enumerator_t*,
 	}
 	INIT(e,
 		.public = {
-			.enumerate = (void*)_cdp_enumerator_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _cdp_enumerator_enumerate,
 			.destroy = _cdp_enumerator_destroy,
 		},
 	);
diff --git a/src/libcharon/plugins/stroke/stroke_attribute.c b/src/libcharon/plugins/stroke/stroke_attribute.c
index cd1b4d093..7835031c2 100644
--- a/src/libcharon/plugins/stroke/stroke_attribute.c
+++ b/src/libcharon/plugins/stroke/stroke_attribute.c
@@ -178,28 +178,32 @@ METHOD(attribute_provider_t, release_address, bool,
 	return found;
 }
 
-/**
- * Filter function to convert host to DNS configuration attributes
- */
-static bool attr_filter(void *lock, host_t **in,
-						configuration_attribute_type_t *type,
-						void *dummy, chunk_t *data)
+CALLBACK(attr_filter, bool,
+	void *lock, enumerator_t *orig, va_list args)
 {
-	host_t *host = *in;
+	configuration_attribute_type_t *type;
+	chunk_t *data;
+	host_t *host;
 
-	switch (host->get_family(host))
+	VA_ARGS_VGET(args, type, data);
+
+	while (orig->enumerate(orig, &host))
 	{
-		case AF_INET:
-			*type = INTERNAL_IP4_DNS;
-			break;
-		case AF_INET6:
-			*type = INTERNAL_IP6_DNS;
-			break;
-		default:
-			return FALSE;
+		switch (host->get_family(host))
+		{
+			case AF_INET:
+				*type = INTERNAL_IP4_DNS;
+				break;
+			case AF_INET6:
+				*type = INTERNAL_IP6_DNS;
+				break;
+			default:
+				continue;
+		}
+		*data = host->get_address(host);
+		return TRUE;
 	}
-	*data = host->get_address(host);
-	return TRUE;
+	return FALSE;
 }
 
 METHOD(attribute_provider_t, create_attribute_enumerator, enumerator_t*,
@@ -223,7 +227,7 @@ METHOD(attribute_provider_t, create_attribute_enumerator, enumerator_t*,
 				enumerator->destroy(enumerator);
 				return enumerator_create_filter(
 									attr->dns->create_enumerator(attr->dns),
-									(void*)attr_filter, this->lock,
+									attr_filter, this->lock,
 									(void*)this->lock->unlock);
 			}
 		}
@@ -338,24 +342,28 @@ METHOD(stroke_attribute_t, del_dns, void,
 	this->lock->unlock(this->lock);
 }
 
-/**
- * Pool enumerator filter function, converts pool_t to name, size, ...
- */
-static bool pool_filter(void *lock, mem_pool_t **poolp, const char **name,
-						void *d1, u_int *size, void *d2, u_int *online,
-						void *d3, u_int *offline)
+CALLBACK(pool_filter, bool,
+	void *lock, enumerator_t *orig, va_list args)
 {
-	mem_pool_t *pool = *poolp;
+	mem_pool_t *pool;
+	const char **name;
+	u_int *size, *online, *offline;
 
-	if (pool->get_size(pool) == 0)
+	VA_ARGS_VGET(args, name, size, online, offline);
+
+	while (orig->enumerate(orig, &pool))
 	{
-		return FALSE;
+		if (pool->get_size(pool) == 0)
+		{
+			continue;
+		}
+		*name = pool->get_name(pool);
+		*size = pool->get_size(pool);
+		*online = pool->get_online(pool);
+		*offline = pool->get_offline(pool);
+		return TRUE;
 	}
-	*name = pool->get_name(pool);
-	*size = pool->get_size(pool);
-	*online = pool->get_online(pool);
-	*offline = pool->get_offline(pool);
-	return TRUE;
+	return FALSE;
 }
 
 METHOD(stroke_attribute_t, create_pool_enumerator, enumerator_t*,
@@ -363,7 +371,7 @@ METHOD(stroke_attribute_t, create_pool_enumerator, enumerator_t*,
 {
 	this->lock->read_lock(this->lock);
 	return enumerator_create_filter(this->pools->create_enumerator(this->pools),
-									(void*)pool_filter,
+									pool_filter,
 									this->lock, (void*)this->lock->unlock);
 }
 
diff --git a/src/libcharon/plugins/stroke/stroke_ca.c b/src/libcharon/plugins/stroke/stroke_ca.c
index 13ed41e0e..4593e9bdc 100644
--- a/src/libcharon/plugins/stroke/stroke_ca.c
+++ b/src/libcharon/plugins/stroke/stroke_ca.c
@@ -171,26 +171,30 @@ typedef struct {
 	identification_t *id;
 } cert_data_t;
 
-/**
- * destroy cert_data
- */
-static void cert_data_destroy(cert_data_t *data)
+CALLBACK(cert_data_destroy, void,
+	cert_data_t *data)
 {
 	data->this->lock->unlock(data->this->lock);
 	free(data);
 }
 
-/**
- * filter function for certs enumerator
- */
-static bool certs_filter(cert_data_t *data, ca_cert_t **in,
-						 certificate_t **out)
+CALLBACK(certs_filter, bool,
+	cert_data_t *data, enumerator_t *orig, va_list args)
 {
+	ca_cert_t *cacert;
 	public_key_t *public;
-	certificate_t *cert = (*in)->cert;
+	certificate_t **out;
+
+	VA_ARGS_VGET(args, out);
 
-	if (data->cert == CERT_ANY || data->cert == cert->get_type(cert))
+	while (orig->enumerate(orig, &cacert))
 	{
+		certificate_t *cert = cacert->cert;
+
+		if (data->cert != CERT_ANY && data->cert != cert->get_type(cert))
+		{
+			continue;
+		}
 		public = cert->get_public_key(cert);
 		if (public)
 		{
@@ -208,9 +212,9 @@ static bool certs_filter(cert_data_t *data, ca_cert_t **in,
 		}
 		else if (data->key != KEY_ANY)
 		{
-			return FALSE;
+			continue;
 		}
-		if (data->id == NULL || cert->has_subject(cert, data->id))
+		if (!data->id || cert->has_subject(cert, data->id))
 		{
 			*out = cert;
 			return TRUE;
@@ -235,8 +239,8 @@ METHOD(credential_set_t, create_cert_enumerator, enumerator_t*,
 
 	this->lock->read_lock(this->lock);
 	enumerator = this->certs->create_enumerator(this->certs);
-	return enumerator_create_filter(enumerator, (void*)certs_filter, data,
-									(void*)cert_data_destroy);
+	return enumerator_create_filter(enumerator, certs_filter, data,
+									cert_data_destroy);
 }
 
 /**
@@ -354,11 +358,12 @@ METHOD(credential_set_t, create_cdp_enumerator, enumerator_t*,
 			data, (void*)cdp_data_destroy);
 }
 
-/**
- * Compare the given certificate to the ca_cert_t items in the list
- */
-static bool match_cert(ca_cert_t *item, certificate_t *cert)
+CALLBACK(match_cert, bool,
+	ca_cert_t *item, va_list args)
 {
+	certificate_t *cert;
+
+	VA_ARGS_VGET(args, cert);
 	return cert->equals(cert, item->cert);
 }
 
@@ -405,8 +410,7 @@ static certificate_t *add_cert_internal(private_stroke_ca_t *this,
 {
 	ca_cert_t *found;
 
-	if (this->certs->find_first(this->certs, (linked_list_match_t)match_cert,
-								(void**)&found, cert) == SUCCESS)
+	if (this->certs->find_first(this->certs, match_cert, (void**)&found, cert))
 	{
 		cert->destroy(cert);
 		cert = found->cert->get_ref(found->cert);
@@ -511,8 +515,7 @@ METHOD(stroke_ca_t, get_cert_ref, certificate_t*,
 	ca_cert_t *found;
 
 	this->lock->read_lock(this->lock);
-	if (this->certs->find_first(this->certs, (linked_list_match_t)match_cert,
-								(void**)&found, cert) == SUCCESS)
+	if (this->certs->find_first(this->certs, match_cert, (void**)&found, cert))
 	{
 		cert->destroy(cert);
 		cert = found->cert->get_ref(found->cert);
diff --git a/src/libcharon/plugins/stroke/stroke_config.c b/src/libcharon/plugins/stroke/stroke_config.c
index d47787d72..00f74831c 100644
--- a/src/libcharon/plugins/stroke/stroke_config.c
+++ b/src/libcharon/plugins/stroke/stroke_config.c
@@ -68,13 +68,20 @@ METHOD(backend_t, create_peer_cfg_enumerator, enumerator_t*,
 									 (void*)this->mutex->unlock, this->mutex);
 }
 
-/**
- * filter function for ike configs
- */
-static bool ike_filter(void *data, peer_cfg_t **in, ike_cfg_t **out)
+CALLBACK(ike_filter, bool,
+	void *data, enumerator_t *orig, va_list args)
 {
-	*out = (*in)->get_ike_cfg(*in);
-	return TRUE;
+	peer_cfg_t *cfg;
+	ike_cfg_t **out;
+
+	VA_ARGS_VGET(args, out);
+
+	if (orig->enumerate(orig, &cfg))
+	{
+		*out = cfg->get_ike_cfg(cfg);
+		return TRUE;
+	}
+	return FALSE;
 }
 
 METHOD(backend_t, create_ike_cfg_enumerator, enumerator_t*,
@@ -82,7 +89,7 @@ METHOD(backend_t, create_ike_cfg_enumerator, enumerator_t*,
 {
 	this->mutex->lock(this->mutex);
 	return enumerator_create_filter(this->list->create_enumerator(this->list),
-									(void*)ike_filter, this->mutex,
+									ike_filter, this->mutex,
 									(void*)this->mutex->unlock);
 }
 
diff --git a/src/libcharon/plugins/stroke/stroke_handler.c b/src/libcharon/plugins/stroke/stroke_handler.c
index d0cc9afab..19d5a62a1 100644
--- a/src/libcharon/plugins/stroke/stroke_handler.c
+++ b/src/libcharon/plugins/stroke/stroke_handler.c
@@ -62,35 +62,39 @@ static void attributes_destroy(attributes_t *this)
 	free(this);
 }
 
-/**
- * Filter function to convert host to DNS configuration attributes
- */
-static bool attr_filter(void *lock, host_t **in,
-						configuration_attribute_type_t *type,
-						void *dummy, chunk_t *data)
+CALLBACK(attr_filter, bool,
+	void *lock, enumerator_t *orig, va_list args)
 {
-	host_t *host = *in;
+	configuration_attribute_type_t *type;
+	chunk_t *data;
+	host_t *host;
 
-	switch (host->get_family(host))
-	{
-		case AF_INET:
-			*type = INTERNAL_IP4_DNS;
-			break;
-		case AF_INET6:
-			*type = INTERNAL_IP6_DNS;
-			break;
-		default:
-			return FALSE;
-	}
-	if (host->is_anyaddr(host))
-	{
-		*data = chunk_empty;
-	}
-	else
+	VA_ARGS_VGET(args, type, data);
+
+	while (orig->enumerate(orig, &host))
 	{
-		*data = host->get_address(host);
+		switch (host->get_family(host))
+		{
+			case AF_INET:
+				*type = INTERNAL_IP4_DNS;
+				break;
+			case AF_INET6:
+				*type = INTERNAL_IP6_DNS;
+				break;
+			default:
+				continue;
+		}
+		if (host->is_anyaddr(host))
+		{
+			*data = chunk_empty;
+		}
+		else
+		{
+			*data = host->get_address(host);
+		}
+		return TRUE;
 	}
-	return TRUE;
+	return FALSE;
 }
 
 METHOD(attribute_handler_t, create_attribute_enumerator, enumerator_t*,
@@ -114,7 +118,7 @@ METHOD(attribute_handler_t, create_attribute_enumerator, enumerator_t*,
 				enumerator->destroy(enumerator);
 				return enumerator_create_filter(
 									attr->dns->create_enumerator(attr->dns),
-									(void*)attr_filter, this->lock,
+									attr_filter, this->lock,
 									(void*)this->lock->unlock);
 			}
 		}
diff --git a/src/libcharon/plugins/stroke/stroke_list.c b/src/libcharon/plugins/stroke/stroke_list.c
index a33316658..22992599d 100644
--- a/src/libcharon/plugins/stroke/stroke_list.c
+++ b/src/libcharon/plugins/stroke/stroke_list.c
@@ -958,8 +958,7 @@ static void list_plugins(FILE *out)
 				{
 					case FEATURE_PROVIDE:
 						fp = &features[i];
-						loaded = list->find_first(list, NULL,
-												  (void**)&fp) == SUCCESS;
+						loaded = list->find_first(list, NULL, (void**)&fp);
 						fprintf(out, "    %s%s\n",
 								str, loaded ? "" : " (not loaded)");
 						break;
diff --git a/src/libcharon/plugins/uci/uci_config.c b/src/libcharon/plugins/uci/uci_config.c
index e0578fe9b..dcd4ae348 100644
--- a/src/libcharon/plugins/uci/uci_config.c
+++ b/src/libcharon/plugins/uci/uci_config.c
@@ -118,11 +118,12 @@ static u_int create_rekey(char *string)
 }
 
 METHOD(enumerator_t, peer_enumerator_enumerate, bool,
-	peer_enumerator_t *this, peer_cfg_t **cfg)
+	peer_enumerator_t *this, va_list args)
 {
 	char *name, *ike_proposal, *esp_proposal, *ike_rekey, *esp_rekey;
 	char *local_id, *local_addr, *local_net;
 	char *remote_id, *remote_addr, *remote_net;
+	peer_cfg_t **cfg;
 	child_cfg_t *child_cfg;
 	ike_cfg_t *ike_cfg;
 	auth_cfg_t *auth;
@@ -145,6 +146,8 @@ METHOD(enumerator_t, peer_enumerator_enumerate, bool,
 		.mode = MODE_TUNNEL,
 	};
 
+	VA_ARGS_VGET(args, cfg);
+
 	/* defaults */
 	name = "unnamed";
 	local_id = NULL;
@@ -212,7 +215,8 @@ METHOD(backend_t, create_peer_cfg_enumerator, enumerator_t*,
 
 	INIT(e,
 		.public = {
-			.enumerate = (void*)_peer_enumerator_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _peer_enumerator_enumerate,
 			.destroy = _peer_enumerator_destroy,
 		},
 		.inner = this->parser->create_section_enumerator(this->parser,
@@ -241,10 +245,13 @@ typedef struct {
 } ike_enumerator_t;
 
 METHOD(enumerator_t, ike_enumerator_enumerate, bool,
-	ike_enumerator_t *this, ike_cfg_t **cfg)
+	ike_enumerator_t *this, va_list args)
 {
+	ike_cfg_t **cfg;
 	char *local_addr, *remote_addr, *ike_proposal;
 
+	VA_ARGS_VGET(args, cfg);
+
 	/* defaults */
 	local_addr = "0.0.0.0";
 	remote_addr = "0.0.0.0";
@@ -282,7 +289,8 @@ METHOD(backend_t, create_ike_cfg_enumerator, enumerator_t*,
 
 	INIT(e,
 		.public = {
-			.enumerate = (void*)_ike_enumerator_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _ike_enumerator_enumerate,
 			.destroy = _ike_enumerator_destroy,
 		},
 		.inner = this->parser->create_section_enumerator(this->parser,
diff --git a/src/libcharon/plugins/uci/uci_creds.c b/src/libcharon/plugins/uci/uci_creds.c
index f5d5ace70..404a3e39f 100644
--- a/src/libcharon/plugins/uci/uci_creds.c
+++ b/src/libcharon/plugins/uci/uci_creds.c
@@ -52,12 +52,15 @@ typedef struct {
 } shared_enumerator_t;
 
 METHOD(enumerator_t, shared_enumerator_enumerate, bool,
-	shared_enumerator_t *this, shared_key_t **key, id_match_t *me,
-	id_match_t *other)
+	shared_enumerator_t *this, va_list args)
 {
+	shared_key_t **key;
+	id_match_t *me, *other;
 	char *local_id, *remote_id, *psk;
 	identification_t *local, *remote;
 
+	VA_ARGS_VGET(args, key, me, other);
+
 	while (TRUE)
 	{
 		/* defaults */
@@ -126,7 +129,8 @@ METHOD(credential_set_t, create_shared_enumerator, enumerator_t*,
 
 	INIT(e,
 		.public = {
-			.enumerate = (void*)_shared_enumerator_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _shared_enumerator_enumerate,
 			.destroy = _shared_enumerator_destroy,
 		},
 		.me = me,
diff --git a/src/libcharon/plugins/uci/uci_parser.c b/src/libcharon/plugins/uci/uci_parser.c
index 2429e9e44..e847dd393 100644
--- a/src/libcharon/plugins/uci/uci_parser.c
+++ b/src/libcharon/plugins/uci/uci_parser.c
@@ -58,11 +58,10 @@ typedef struct {
 } section_enumerator_t;
 
 METHOD(enumerator_t, section_enumerator_enumerate, bool,
-	section_enumerator_t *this, ...)
+	section_enumerator_t *this, va_list args)
 {
 	struct uci_element *element;
 	char **value;
-	va_list args;
 	int i;
 
 	if (&this->current->list == this->list)
@@ -70,8 +69,6 @@ METHOD(enumerator_t, section_enumerator_enumerate, bool,
 		return FALSE;
 	}
 
-	va_start(args, this);
-
 	value = va_arg(args, char**);
 	if (value)
 	{
@@ -96,7 +93,6 @@ METHOD(enumerator_t, section_enumerator_enumerate, bool,
 			*value = uci_to_option(element)->value;
 		}
 	}
-	va_end(args);
 
 	this->current = list_to_element(this->current->list.next);
 	return TRUE;
@@ -124,7 +120,13 @@ METHOD(uci_parser_t, create_section_enumerator, enumerator_t*,
 		i++;
 	}
 	va_end(args);
-	e = malloc(sizeof(section_enumerator_t) + sizeof(char*) * i);
+	INIT_EXTRA(e, sizeof(char*) * i,
+		.public = {
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _section_enumerator_enumerate,
+			.destroy = _section_enumerator_destroy,
+		},
+	);
 	i = 0;
 	va_start(args, this);
 	do
@@ -134,9 +136,6 @@ METHOD(uci_parser_t, create_section_enumerator, enumerator_t*,
 	while (e->keywords[i++]);
 	va_end(args);
 
-	e->public.enumerate = (void*)_section_enumerator_enumerate;
-	e->public.destroy = _section_enumerator_destroy;
-
 	/* load uci context */
 	e->ctx = uci_alloc_context();
 	if (uci_load(e->ctx, this->package, &e->package) != UCI_OK)
diff --git a/src/libcharon/plugins/unity/unity_handler.c b/src/libcharon/plugins/unity/unity_handler.c
index 25e0756b7..4a1478c6d 100644
--- a/src/libcharon/plugins/unity/unity_handler.c
+++ b/src/libcharon/plugins/unity/unity_handler.c
@@ -368,9 +368,12 @@ typedef struct {
 } attribute_enumerator_t;
 
 METHOD(enumerator_t, enumerate_attributes, bool,
-	attribute_enumerator_t *this, configuration_attribute_type_t *type,
-	chunk_t *data)
+	attribute_enumerator_t *this, va_list args)
 {
+	configuration_attribute_type_t *type;
+	chunk_t *data;
+
+	VA_ARGS_VGET(args, type, data);
 	if (this->i < countof(attributes))
 	{
 		*type = attributes[this->i++];
@@ -393,7 +396,8 @@ METHOD(attribute_handler_t, create_attribute_enumerator, enumerator_t *,
 	}
 	INIT(enumerator,
 		.public = {
-			.enumerate = (void*)_enumerate_attributes,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _enumerate_attributes,
 			.destroy = (void*)free,
 		},
 	);
@@ -407,24 +411,27 @@ typedef struct {
 	ike_sa_id_t *id;
 } include_filter_t;
 
-/**
- * Include enumerator filter function
- */
-static bool include_filter(include_filter_t *data,
-						   entry_t **entry, traffic_selector_t **ts)
+CALLBACK(include_filter, bool,
+	include_filter_t *data, enumerator_t *orig, va_list args)
 {
-	if (data->id->equals(data->id, (*entry)->id))
+	entry_t *entry;
+	traffic_selector_t **ts;
+
+	VA_ARGS_VGET(args, ts);
+
+	while (orig->enumerate(orig, &entry))
 	{
-		*ts = (*entry)->ts;
-		return TRUE;
+		if (data->id->equals(data->id, entry->id))
+		{
+			*ts = entry->ts;
+			return TRUE;
+		}
 	}
 	return FALSE;
 }
 
-/**
- * Destroy include filter data, unlock mutex
- */
-static void destroy_filter(include_filter_t *data)
+CALLBACK(destroy_filter, void,
+	include_filter_t *data)
 {
 	data->mutex->unlock(data->mutex);
 	free(data);
@@ -442,7 +449,7 @@ METHOD(unity_handler_t, create_include_enumerator, enumerator_t*,
 	data->mutex->lock(data->mutex);
 	return enumerator_create_filter(
 					this->include->create_enumerator(this->include),
-					(void*)include_filter, data, (void*)destroy_filter);
+					include_filter, data, destroy_filter);
 }
 
 METHOD(unity_handler_t, destroy, void,
diff --git a/src/libcharon/plugins/unity/unity_provider.c b/src/libcharon/plugins/unity/unity_provider.c
index 07f5f9b61..b6a55648e 100644
--- a/src/libcharon/plugins/unity/unity_provider.c
+++ b/src/libcharon/plugins/unity/unity_provider.c
@@ -77,12 +77,15 @@ static void append_ts(bio_writer_t *writer, traffic_selector_t *ts)
 }
 
 METHOD(enumerator_t, attribute_enumerate, bool,
-	attribute_enumerator_t *this, configuration_attribute_type_t *type,
-	chunk_t *attr)
+	attribute_enumerator_t *this, va_list args)
 {
+	configuration_attribute_type_t *type;
+	chunk_t *attr;
 	traffic_selector_t *ts;
 	bio_writer_t *writer;
 
+	VA_ARGS_VGET(args, type, attr);
+
 	if (this->list->get_count(this->list) == 0)
 	{
 		return FALSE;
@@ -183,7 +186,8 @@ METHOD(attribute_provider_t, create_attribute_enumerator, enumerator_t*,
 
 	INIT(attr_enum,
 		.public = {
-			.enumerate = (void*)_attribute_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _attribute_enumerate,
 			.destroy = _attribute_destroy,
 		},
 		.list = list,
diff --git a/src/libcharon/plugins/vici/suites/test_message.c b/src/libcharon/plugins/vici/suites/test_message.c
index 045e34fff..73bba239b 100644
--- a/src/libcharon/plugins/vici/suites/test_message.c
+++ b/src/libcharon/plugins/vici/suites/test_message.c
@@ -122,9 +122,14 @@ typedef struct {
 	endecode_test_t *next;
 } endecode_enum_t;
 
-static bool endecode_enumerate(endecode_enum_t *this, vici_type_t *type,
-							   char **name, chunk_t *data)
+METHOD(enumerator_t, endecode_enumerate, bool,
+	endecode_enum_t *this, va_list args)
 {
+	vici_type_t *type;
+	chunk_t *data;
+	char **name;
+
+	VA_ARGS_VGET(args, type, name, data);
 	if (this->next)
 	{
 		*type = this->next->type;
@@ -149,7 +154,8 @@ static enumerator_t *endecode_create_enumerator(endecode_test_t *test)
 
 	INIT(enumerator,
 		.public = {
-			.enumerate = (void*)endecode_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _endecode_enumerate,
 			.destroy = (void*)free,
 		},
 		.next = test,
diff --git a/src/libcharon/plugins/vici/vici_attribute.c b/src/libcharon/plugins/vici/vici_attribute.c
index 4e1fa9708..ab765fa14 100644
--- a/src/libcharon/plugins/vici/vici_attribute.c
+++ b/src/libcharon/plugins/vici/vici_attribute.c
@@ -184,16 +184,22 @@ METHOD(attribute_provider_t, release_address, bool,
 	return found;
 }
 
-/**
- * Filter mapping attribute_t to enumerated type/value arguments
- */
-static bool attr_filter(void *data, attribute_t **attr,
-						configuration_attribute_type_t *type,
-						void *in, chunk_t *value)
+CALLBACK(attr_filter, bool,
+	void *data, enumerator_t *orig, va_list args)
 {
-	*type = (*attr)->type;
-	*value = (*attr)->value;
-	return TRUE;
+	attribute_t *attr;
+	configuration_attribute_type_t *type;
+	chunk_t *value;
+
+	VA_ARGS_VGET(args, type, value);
+
+	if (orig->enumerate(orig, &attr))
+	{
+		*type = attr->type;
+		*value = attr->value;
+		return TRUE;
+	}
+	return FALSE;
 }
 
 /**
@@ -203,7 +209,7 @@ CALLBACK(create_nested, enumerator_t*,
 	pool_t *pool, void *this)
 {
 	return enumerator_create_filter(array_create_enumerator(pool->attrs),
-									(void*)attr_filter, NULL, NULL);
+									attr_filter, NULL, NULL);
 }
 
 /**
diff --git a/src/libcharon/plugins/vici/vici_config.c b/src/libcharon/plugins/vici/vici_config.c
index 3af67df94..0c355e3a0 100644
--- a/src/libcharon/plugins/vici/vici_config.c
+++ b/src/libcharon/plugins/vici/vici_config.c
@@ -141,13 +141,20 @@ METHOD(backend_t, create_peer_cfg_enumerator, enumerator_t*,
 									 (void*)this->lock->unlock, this->lock);
 }
 
-/**
- * Enumerator filter function for ike configs
- */
-static bool ike_filter(void *data, peer_cfg_t **in, ike_cfg_t **out)
+CALLBACK(ike_filter, bool,
+	void *data, enumerator_t *orig, va_list args)
 {
-	*out = (*in)->get_ike_cfg(*in);
-	return TRUE;
+	peer_cfg_t *cfg;
+	ike_cfg_t **out;
+
+	VA_ARGS_VGET(args, out);
+
+	if (orig->enumerate(orig, &cfg))
+	{
+		*out = cfg->get_ike_cfg(cfg);
+		return TRUE;
+	}
+	return FALSE;
 }
 
 METHOD(backend_t, create_ike_cfg_enumerator, enumerator_t*,
@@ -155,7 +162,7 @@ METHOD(backend_t, create_ike_cfg_enumerator, enumerator_t*,
 {
 	this->lock->read_lock(this->lock);
 	return enumerator_create_filter(this->conns->create_enumerator(this->conns),
-									(void*)ike_filter, this->lock,
+									ike_filter, this->lock,
 									(void*)this->lock->unlock);
 }
 
diff --git a/src/libcharon/plugins/vici/vici_message.c b/src/libcharon/plugins/vici/vici_message.c
index 58b896773..91d344994 100644
--- a/src/libcharon/plugins/vici/vici_message.c
+++ b/src/libcharon/plugins/vici/vici_message.c
@@ -135,11 +135,16 @@ typedef struct {
 } parse_enumerator_t;
 
 METHOD(enumerator_t, parse_enumerate, bool,
-	parse_enumerator_t *this, vici_type_t *out, char **name, chunk_t *value)
+	parse_enumerator_t *this, va_list args)
 {
+	vici_type_t *out;
+	chunk_t *value;
+	char **name;
 	uint8_t type;
 	chunk_t data;
 
+	VA_ARGS_VGET(args, out, name, value);
+
 	if (!this->reader->remaining(this->reader) ||
 		!this->reader->read_uint8(this->reader, &type))
 	{
@@ -218,7 +223,8 @@ METHOD(vici_message_t, create_enumerator, enumerator_t*,
 
 	INIT(enumerator,
 		.public = {
-			.enumerate = (void*)_parse_enumerate,
+			.enumerate = enumerator_enumerate_default,
+			.venumerate = _parse_enumerate,
 			.destroy = _parse_destroy,
 		},
 		.reader = bio_reader_create(this->encoding),
diff --git a/src/libcharon/plugins/whitelist/whitelist_listener.c b/src/libcharon/plugins/whitelist/whitelist_listener.c
index 7e5b2f4e0..136554674 100644
--- a/src/libcharon/plugins/whitelist/whitelist_listener.c
+++ b/src/libcharon/plugins/whitelist/whitelist_listener.c
@@ -119,14 +119,19 @@ METHOD(whitelist_listener_t, remove_, void,
 	DESTROY_IF(id);
 }
 
-/**
- * Enumerator filter, from hashtable (key, value) to single identity
- */
-static bool whitelist_filter(rwlock_t *lock, identification_t **key,
-							 identification_t **id, identification_t **value)
+CALLBACK(whitelist_filter, bool,
+	rwlock_t *lock, enumerator_t *orig, va_list args)
 {
-	*id = *value;
-	return TRUE;
+	identification_t *key, *value, **out;
+
+	VA_ARGS_VGET(args, out);
+
+	if (orig->enumerate(orig, &key, &value))
+	{
+		*out = value;
+		return TRUE;
+	}
+	return FALSE;
 }
 
 METHOD(whitelist_listener_t, create_enumerator, enumerator_t*,
@@ -134,7 +139,7 @@ METHOD(whitelist_listener_t, create_enumerator, enumerator_t*,
 {
 	this->lock->read_lock(this->lock);
 	return enumerator_create_filter(this->ids->create_enumerator(this->ids),
-									(void*)whitelist_filter, this->lock,
+									whitelist_filter, this->lock,
 									(void*)this->lock->unlock);
 }