homed: port to notify_recv() + convert to PidRef (#36557)

Just some refactoring/modernization

src/basic/pidref.c

@@ -457,12 +457,36 @@ bool pidref_is_automatic(const PidRef *pidref) {
         return pidref && pid_is_automatic(pidref->pid);
 }
 
-static void pidref_hash_func(const PidRef *pidref, struct siphash *state) {
+void pidref_hash_func(const PidRef *pidref, struct siphash *state) {
         siphash24_compress_typesafe(pidref->pid, state);
 }
 
-static int pidref_compare_func(const PidRef *a, const PidRef *b) {
-        return CMP(a->pid, b->pid);
+int pidref_compare_func(const PidRef *a, const PidRef *b) {
+        int r;
+
+        assert(a);
+        assert(b);
+
+        r = CMP(pidref_is_set(a), pidref_is_set(b));
+        if (r != 0)
+                return r;
+
+        r = CMP(pidref_is_automatic(a), pidref_is_automatic(b));
+        if (r != 0)
+                return r;
+
+        r = CMP(pidref_is_remote(a), pidref_is_remote(b));
+        if (r != 0)
+                return r;
+
+        r = CMP(a->pid, b->pid);
+        if (r != 0)
+                return r;
+
+        if (a->fd_id != 0 && b->fd_id != 0)
+                return CMP(a->fd_id, b->fd_id);
+
+        return 0;
 }
 
 DEFINE_HASH_OPS(pidref_hash_ops, PidRef, pidref_hash_func, pidref_compare_func);

src/basic/pidref.h

@@ -108,5 +108,9 @@ int pidref_verify(const PidRef *pidref);
 
 #define TAKE_PIDREF(p) TAKE_GENERIC((p), PidRef, PIDREF_NULL)
 
+struct siphash;
+void pidref_hash_func(const PidRef *pidref, struct siphash *state);
+int pidref_compare_func(const PidRef *a, const PidRef *b);
+
 extern const struct hash_ops pidref_hash_ops;
 extern const struct hash_ops pidref_hash_ops_free; /* Has destructor call for pidref_free(), i.e. expects heap allocated PidRef as keys */