tree-wide: return NULL from freeing functions

I started working on this because I wanted to change how
DEFINE_TRIVIAL_CLEANUP_FUNC is defined. Even independently of that change, it's
nice to make make things more consistent and predictable.

src/network/netdev/l2tp-tunnel.c

@@ -39,18 +39,16 @@ static const char* const l2tp_local_address_type_table[_NETDEV_L2TP_LOCAL_ADDRES
 
 DEFINE_PRIVATE_STRING_TABLE_LOOKUP_FROM_STRING(l2tp_local_address_type, L2tpLocalAddressType);
 
-static void l2tp_session_free(L2tpSession *s) {
+static L2tpSession* l2tp_session_free(L2tpSession *s) {
         if (!s)
-                return;
+                return NULL;
 
         if (s->tunnel && s->section)
                 ordered_hashmap_remove(s->tunnel->sessions_by_section, s->section);
 
         network_config_section_free(s->section);
-
         free(s->name);
-
-        free(s);
+        return mfree(s);
 }
 
 DEFINE_NETWORK_SECTION_FUNCTIONS(L2tpSession, l2tp_session_free);

src/network/netdev/macsec.c

@@ -35,9 +35,9 @@ static void security_association_init(SecurityAssociation *sa) {
         sa->use_for_encoding = -1;
 }
 
-static void macsec_receive_association_free(ReceiveAssociation *c) {
+static ReceiveAssociation* macsec_receive_association_free(ReceiveAssociation *c) {
         if (!c)
-                return;
+                return NULL;
 
         if (c->macsec && c->section)
                 ordered_hashmap_remove(c->macsec->receive_associations_by_section, c->section);
@@ -45,7 +45,7 @@ static void macsec_receive_association_free(ReceiveAssociation *c) {
         network_config_section_free(c->section);
         security_association_clear(&c->sa);
 
-        free(c);
+        return mfree(c);
 }
 
 DEFINE_NETWORK_SECTION_FUNCTIONS(ReceiveAssociation, macsec_receive_association_free);
@@ -90,9 +90,9 @@ static int macsec_receive_association_new_static(MACsec *s, const char *filename
         return 0;
 }
 
-static void macsec_receive_channel_free(ReceiveChannel *c) {
+static ReceiveChannel* macsec_receive_channel_free(ReceiveChannel *c) {
         if (!c)
-                return;
+                return NULL;
 
         if (c->macsec) {
                 if (c->sci.as_uint64 > 0)
@@ -104,7 +104,7 @@ static void macsec_receive_channel_free(ReceiveChannel *c) {
 
         network_config_section_free(c->section);
 
-        free(c);
+        return mfree(c);
 }
 
 DEFINE_NETWORK_SECTION_FUNCTIONS(ReceiveChannel, macsec_receive_channel_free);
@@ -162,9 +162,9 @@ static int macsec_receive_channel_new_static(MACsec *s, const char *filename, un
         return 0;
 }
 
-static void macsec_transmit_association_free(TransmitAssociation *a) {
+static TransmitAssociation* macsec_transmit_association_free(TransmitAssociation *a) {
         if (!a)
-                return;
+                return NULL;
 
         if (a->macsec && a->section)
                 ordered_hashmap_remove(a->macsec->transmit_associations_by_section, a->section);
@@ -172,7 +172,7 @@ static void macsec_transmit_association_free(TransmitAssociation *a) {
         network_config_section_free(a->section);
         security_association_clear(&a->sa);
 
-        free(a);
+        return mfree(a);
 }
 
 DEFINE_NETWORK_SECTION_FUNCTIONS(TransmitAssociation, macsec_transmit_association_free);

src/network/netdev/wireguard.c

@@ -26,11 +26,11 @@
 
 static void resolve_endpoints(NetDev *netdev);
 
-static void wireguard_peer_free(WireguardPeer *peer) {
+static WireguardPeer* wireguard_peer_free(WireguardPeer *peer) {
         WireguardIPmask *mask;
 
         if (!peer)
-                return;
+                return NULL;
 
         if (peer->wireguard) {
                 LIST_REMOVE(peers, peer->wireguard->peers, peer);
@@ -54,7 +54,7 @@ static void wireguard_peer_free(WireguardPeer *peer) {
         free(peer->preshared_key_file);
         explicit_bzero_safe(peer->preshared_key, WG_KEY_LEN);
 
-        free(peer);
+        return mfree(peer);
 }
 
 DEFINE_NETWORK_SECTION_FUNCTIONS(WireguardPeer, wireguard_peer_free);