Convert finit to use libev and fix so plugin ctors runs on dlopen().

Lots of cleanup and simplification of the main code in this commit.
Most notably libev has been added to take care of the main loop and
monitor services. Still TODO is migrating to use the libev signal
handling.

Convert initctl.c:listen_initctl() to a plugin instead.  This also
meant introducing a new form of I/O plugin to finit, also handled
by libev.

Load plugins *after* we've setup the base filesystem (BASEFS) in case
plugins reside on a filesystem not reachable before "mount -a" has run.
This also has the side effect of lining up nicely with the first level
plugin hooks.

If a plugin wants to hook up with a loded service we connect them by
their respective numeric IDs in plugin_register().  I.e., the service
monitor checks if a service has a registered callback, which in turn
decides if a service should be started, stopped or reloaded.

Rip out old EeePC distribution defines from finit.h, none of it really
applies anymore.  If you need distribution specific settings this is
the place to put them.

Make hookpoint names (#defines) clearer: after BASEFS, after networking,
after all setup, etc.

Use #inlude_next <signal.h> in signal.h to include system header file!

Simplify service monitor: move essential code to svc.c and rip out
the TIPC dependency. Write your own service.so plugin, or wait for
a more complete example of how to extend service monitoring using
the primitives in svc.c

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

plugin.h

@@ -21,13 +21,17 @@
  * THE SOFTWARE.
  */
 
-#ifndef PLUGIN_H_
-#define PLUGIN_H_
+#ifndef FINIT_PLUGIN_H_
+#define FINIT_PLUGIN_H_
 
+#include <ev.h>
 #include <sys/queue.h>		/* BSD sys/queue.h API */
 
-#define PLUGIN_INIT(x) void x(void) __attribute__ ((constructor));
-#define PLUGIN_EXIT(x) void x(void) __attribute__ ((destructor));
+#define PLUGIN_IO_READ  EV_READ
+#define PLUGIN_IO_WRITE EV_READ
+
+#define PLUGIN_INIT(x) static void __attribute__ ((constructor)) x(void)
+#define PLUGIN_EXIT(x) static void __attribute__ ((destructor))  x(void)
 
 #define PLUGIN_ITERATOR(x)  LIST_FOREACH(x, &plugins, link)
 
@@ -35,45 +39,78 @@
  * Predefined hook points for easier plugin debugging 
  */
 typedef enum {
-	HOOK_POST_LOAD = 0,
-	HOOK_PRE_SETUP,
-	HOOK_POST_SIGSETUP,
-	HOOK_POST_NETWORK,
-	HOOK_PRE_RUNLOOP,
+	HOOK_BASEFS_UP = 0,
+	HOOK_NETWORK_UP,
+	HOOK_SYSTEM_UP,
 	HOOK_SHUTDOWN,
 	HOOK_MAX_NUM
 } hook_point_t;
 
+/**
+ * plugin_t - Finit &plugin_t object
+ * @link: BSD sys/queue.h linked list node
+ * @name: Plugin name, or identifier to match against a &svc_t object
+ * @svc:  Service callback for a loaded &svc_t object
+ * @hook: Hook callback definitions
+ * @io:   I/O hook callback
+ *
+ * To setup an &svc_t object callback for a service monitor the @name
+ * must match the @svc_t @cmd exactly for them to "pair".
+ *
+ * A &plugin_t object may contain a service callback, several hooks
+ * and/or an I/O callback as well. This way all critical extensions
+ * to finit can fit in one single plugin, if needed.
+ *
+ * The "dynamic events" discussed in the svc callback is for external
+ * service plugins to implement.  However, it can be anything that 
+ * can cause a service to need to SIGHUP at runtime.  E.g., acquiring
+ * a DHCP lease, or an interface going UP/DOWN.
+ *
+ * It is up to the external service plugin to track these events and
+ * relay them to each @dynamic service plugins' callback.  I.e., to
+ * all those with the dynamic flag set.
+ */
 typedef struct plugin {
 	/* BSD sys/queue.h linked list node. */
 	LIST_ENTRY(plugin) link;
 
-	/* Optional plugin name, defaults to plugin path if unset. */
-	const char *name;
+	/* Plugin name, defaults to plugin path if unset.
+	 * NOTE: Must be same as @cmd for service plugins! */
+	char *name;
 
 	/* Service callback to be called once per lap of runloop. */
-	struct {
-		void *arg;	/* Optional argument to callback func. */
-		void (*cb) (void *);
+	struct plugin_svc {
+		/* Private */
+		int    id;       /* Service ID# to match this service plugin against, set on installation. */
+		/* Public */
+		void  *arg;	 /* Optional argument to callback func, set by plugin. */
+		int    dynamic;	 /* Reload (SIGHUP) on dynamic event?  Set by plugin. */
+		int    private;  /* For callbacks to use freely, possibly to store "states", set by plugin. */
+		int  (*cb)(void *arg, int event);
 	} svc;
 
 	/* List of hook callbacks. */
 	struct {
-		void *arg;     /* Optional argument to callback func. */
-		void (*cb) (void *);
+		void  *arg;      /* Optional argument to callback func. */
+		void (*cb)(void *arg);
 	} hook[HOOK_MAX_NUM];
+
+	/* I/O Plugin */
+	struct {
+		int    fd, flags; /* 1:READ, 2:WRITE */
+		void  *arg;
+		void (*cb)(void *arg, int fd, int events);
+	} io;
 } plugin_t;
 
+/* Used by svc.h */
+typedef struct plugin_svc plugin_svc_t;
+
 /* Public plugin API */
 int plugin_register   (plugin_t *plugin);
 int plugin_unregister (plugin_t *plugin);
 
-/* Private daemon API */
-void run_hooks        (hook_point_t no);
-void run_services     (void);
-int  load_plugins     (char *path);
-
-#endif	/* PLUGIN_H_ */
+#endif	/* FINIT_PLUGIN_H_ */
 
 /**
  * Local Variables: