network: drop sections contain invalid settings in network_verify()

If e.g., an [Address] section has an invalid setting, then
previously assigned settings in the section is freed, and
only later settings are stored. That may cause partially broken
section stored in Network object.

This makes if an invalid setting is found, then set 'invalid' flag
instead of freeing it. And invalid sections are dropped later by
network_verify().

src/network/networkd-util.h

@@ -17,6 +17,7 @@ typedef enum AddressFamilyBoolean {
 
 typedef struct NetworkConfigSection {
         unsigned line;
+        bool invalid;
         char filename[];
 } NetworkConfigSection;
 
@@ -32,3 +33,24 @@ int network_config_section_new(const char *filename, unsigned line, NetworkConfi
 void network_config_section_free(NetworkConfigSection *network);
 DEFINE_TRIVIAL_CLEANUP_FUNC(NetworkConfigSection*, network_config_section_free);
 extern const struct hash_ops network_config_hash_ops;
+
+static inline bool section_is_invalid(NetworkConfigSection *section) {
+        /* If this retuns false, then it does _not_ mean the section is valid. */
+
+        if (!section)
+                return false;
+
+        return section->invalid;
+}
+
+#define DEFINE_NETWORK_SECTION_FUNCTIONS(type, free_func)               \
+        static inline void free_func##_or_set_invalid(type *p) {        \
+                assert(p);                                              \
+                                                                        \
+                if (p->section)                                         \
+                        p->section->invalid = true;                     \
+                else                                                    \
+                        free_func(p);                                   \
+        }                                                               \
+        DEFINE_TRIVIAL_CLEANUP_FUNC(type*, free_func);                  \
+        DEFINE_TRIVIAL_CLEANUP_FUNC(type*, free_func##_or_set_invalid);