Disable historydb inserts if there are no listeners with filtering enabled.

Reduces memory use, since we don't need to store the last positions
of all active stations.

src/accept.c

@@ -1447,6 +1447,7 @@ void accept_thread(void *asdf)
 			acceptpl = hmalloc(poll_n * sizeof(*acceptpl));
 			
 			n = 0;
+			int has_filtered_listeners_now = 0;
 			for (l = listen_list; (l); l = l->next) {
 				/* The accept thread does not poll() UDP sockets for core peers.
 				 * Worker 0 takes care of that, and processes the incoming packets.
@@ -1464,6 +1465,9 @@ void accept_thread(void *asdf)
 					fd = l->fd;
 				}
 				
+				if ((l->filter_s) || (l->client_flags & CLFLAGS_USERFILTEROK))
+					has_filtered_listeners_now = 1;
+				
 				hlog(LOG_DEBUG, "... %d: fd %d (%s)", n, fd, l->addr_s);
 				acceptpfd[n].fd = fd;
 				acceptpfd[n].events = POLLIN|POLLPRI|POLLERR|POLLHUP;
@@ -1471,6 +1475,9 @@ void accept_thread(void *asdf)
 				n++;
 			}
 			hlog(LOG_INFO, "Accept thread ready.");
+			historydb_enabled = has_filtered_listeners_now;
+			if (!historydb_enabled)
+				hlog(LOG_INFO, "Disabled historydb, listeners do not have filtering enabled.");
 			
 			/* stop the dupechecking and uplink threads while adjusting
 			 * the amount of workers... they walk the worker list, and

src/dupecheck.c

@@ -40,6 +40,8 @@ int dupecheck_running;
 pthread_t dupecheck_th;
 long dupecheck_cellgauge;
 
+int historydb_enabled;  /* historydb inserts enabled only if filtering available */
+
 int pbuf_global_count;
 int pbuf_global_dupe_count;
 
@@ -649,10 +651,15 @@ static int dupecheck_drain_worker(struct worker_t *w,
 		pbnext = pb->next; // it may get modified below..
 		
 		if (rc == 0) {
-			// put non-duplicate packet in history database
-			// and let filter module do it's thing
-			historydb_insert(pb);
-			filter_postprocess_dupefilter(pb);
+			/* put non-duplicate packet in history database
+			 * and let filter module do it's thing, if historydb
+			 * is enabled (disabled if no filtered listeners
+			 * configured, for memory savings)
+			 */
+			if (historydb_enabled) {
+				historydb_insert(pb);
+				filter_postprocess_dupefilter(pb);
+			}
 	
 			// Not duplicate
 			**pb_out_prevp = pb;

src/dupecheck.h

@@ -41,6 +41,7 @@ extern long long dupecheck_dupecount; /* statistics counter */
 extern long long dupecheck_dupetypes[DTYPE_MAX+1];
 extern long      dupecheck_cellgauge; /* statistics gauge   */
 
+extern int historydb_enabled;
 extern int dupecheck_eventfd;
 
 extern int  outgoing_lag_report(struct worker_t *self, int*lag, int*dupelag);