Keep a separate state tree for file descriptors inserted into epoll t…

…o avoid conflicts between EVFILT_READ and EVFILT_WRITE Closes mheily#29 Closes mheily#59

There's more work required, but at least this fixes the outstanding issues.

Known limitations:
- Need to verify correct behaviour of EV_DISPATCH when both filters are registered for events.  This now needs to be implemented internally by libkqueue instead of relying on EPOLLET, as EPOLLET applies to both EPOLLIN and EPOLLOUT.

- If the number of events we are to return does not have sufficient space for at least two entries when polling an FD registered for both read and write events, the write event will be lost.  We can fix this by implementing a linked list of pending events we return before calling the platform's wait function. Will probably copy the dlist implementation from FreeRADIUS across, as it's been well tested, and is a header only implementation like the current rbtree. A dlist is needed to store entries for EVFILT_PROC anyway, which is the next filter that needs major attention.

src/common/kevent.c

@@ -177,12 +177,12 @@ kevent_copyin_one(struct kqueue *kq, const struct kevent *src)
         rv = knote_delete(filt, kn);
         dbg_printf("knote_delete returned %d", rv);
     } else if (src->flags & EV_DISABLE) {
-        kn->kev.flags |= EV_DISABLE;
         rv = filt->kn_disable(filt, kn);
+        if (rv == 0) kn->kev.flags |= EV_DISABLE;
         dbg_printf("kn_disable returned %d", rv);
     } else if (src->flags & EV_ENABLE) {
-        kn->kev.flags &= ~EV_DISABLE;
         rv = filt->kn_enable(filt, kn);
+        if (rv == 0) kn->kev.flags &= ~EV_DISABLE;
         dbg_printf("kn_enable returned %d", rv);
     } else if (src->flags & EV_ADD || src->flags == 0 || src->flags & EV_RECEIPT) {
         kn->kev.udata = src->udata;

src/common/private.h

@@ -139,7 +139,7 @@ struct knote {
  *
  */
 struct filter {
-    short           kf_id;               //!< EVFILT_* facility this filter provides.
+    short           kf_id;						//!< EVFILT_* facility this filter provides.
 
     /* filter operations */
 
@@ -151,20 +151,19 @@ struct filter {
 
 
     int            (*kn_create)(struct filter *, struct knote *);
-    int            (*kn_modify)(struct filter *, struct knote *,
-                            const struct kevent *);
+    int            (*kn_modify)(struct filter *, struct knote *, const struct kevent *);
     int            (*kn_delete)(struct filter *, struct knote *);
     int            (*kn_enable)(struct filter *, struct knote *);
     int            (*kn_disable)(struct filter *, struct knote *);
 
-    struct eventfd kf_efd;             /* Used by user.c */
+    struct eventfd kf_efd;						//!< Used by user.c
 
     //MOVE TO POSIX?
-    int           kf_pfd;                   /* fd to poll(2) for readiness */
-    int           kf_wfd;                   /* fd to write when an event occurs */
+    int           kf_pfd;						//!< fd to poll(2) for readiness
+    int           kf_wfd;						//!< fd to write when an event occurs
     //----?
 
-    struct evfilt_data *kf_data;        /* filter-specific data */
+    struct evfilt_data *kf_data;				//!< filter-specific data */
     RB_HEAD(knt, knote) kf_knote;
     pthread_rwlock_t    kf_knote_mtx;
     struct kqueue      *kf_kqueue;
@@ -182,10 +181,10 @@ struct filter {
  * in receiving notifications for.
  */
 struct kqueue {
-    int             kq_id;                    //!< File descriptor used to identify this kqueue.
-    struct filter   kq_filt[EVFILT_SYSCOUNT]; //!< Filters supported by the kqueue.  Each
-                                              ///< kqueue maintains one filter state structure
-                                              ///< per filter type.
+    int             kq_id;                   	//!< File descriptor used to identify this kqueue.
+    struct filter   kq_filt[EVFILT_SYSCOUNT];	//!< Filters supported by the kqueue.  Each
+                    							///< kqueue maintains one filter state structure
+                                            	///< per filter type.
     fd_set          kq_fds, kq_rfds;
     int             kq_nfds;
     tracing_mutex_t kq_mtx;