s4: add samba server tevent trace helper stuff

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14248

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>

source4/samba/server_util.c

@@ -0,0 +1,94 @@
+/*
+   Unix SMB/CIFS implementation.
+
+   Utility routines
+
+   Copyright (C) 2020 Ralph Boehme <slow@samba.org>
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "includes.h"
+#include "lib/tevent/tevent.h"
+#include "lib/util/unix_privs.h"
+#include "server_util.h"
+
+struct samba_tevent_trace_state {
+	size_t events;
+	time_t last_logsize_check;
+};
+
+struct samba_tevent_trace_state *create_samba_tevent_trace_state(
+	TALLOC_CTX *mem_ctx)
+{
+	return talloc_zero(mem_ctx, struct samba_tevent_trace_state);
+}
+
+void samba_tevent_trace_callback(enum tevent_trace_point point,
+				 void *private_data)
+{
+	struct samba_tevent_trace_state *state =
+		talloc_get_type_abort(private_data,
+				      struct samba_tevent_trace_state);
+	time_t now = time(NULL);
+	bool do_check_logs = false;
+	void *priv = NULL;
+
+	switch (point) {
+	case TEVENT_TRACE_BEFORE_WAIT:
+		break;
+	default:
+		return;
+	}
+
+	state->events++;
+
+	/*
+	 * Throttling by some random numbers. smbd uses a similar logic
+	 * checking every 50 SMB requests. Assuming 4 events per request
+	 * we get to the number of 200.
+	 */
+	if ((state->events % 200) == 0) {
+		do_check_logs = true;
+	}
+	/*
+	 * Throttling by some delay, choosing 29 to avoid lockstep with
+	 * the default tevent tickle timer.
+	 */
+	if ((state->last_logsize_check + 29) < now) {
+		do_check_logs = true;
+	}
+
+	if (!do_check_logs) {
+		return;
+	}
+
+	/*
+	 * need_to_check_log_size() checks both the number of messages
+	 * that have been logged and if the logging backend is actually
+	 * going to file. We want to bypass the "number of messages"
+	 * check, so we have to call force_check_log_size() before.
+	 */
+	force_check_log_size();
+	if (!need_to_check_log_size()) {
+		return;
+	}
+
+	priv = root_privileges();
+	check_log_size();
+	TALLOC_FREE(priv);
+
+	state->last_logsize_check = now;
+	return;
+}

source4/samba/server_util.h

@@ -0,0 +1,33 @@
+/*
+   Unix SMB/CIFS implementation.
+
+   Utility routines
+
+   Copyright (C) 2020 Ralph Boehme <slow@samba.org>
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef SAMBA_SERVER_UTIL_H
+#define SAMBA_SERVER_UTIL_H
+
+struct samba_tevent_trace_state;
+
+struct samba_tevent_trace_state *create_samba_tevent_trace_state(
+	TALLOC_CTX *mem_ctx);
+
+void samba_tevent_trace_callback(enum tevent_trace_point point,
+				 void *private_data);
+
+#endif

source4/samba/wscript_build

@@ -17,6 +17,10 @@ bld.SAMBA_LIBRARY('process_model',
                   enabled=bld.AD_DC_BUILD_IS_ENABLED()
                   )
 
+bld.SAMBA_SUBSYSTEM('samba_server_util',
+	            source='server_util.c',
+                    deps='samba-util')
+
 bld.SAMBA_BINARY('samba',
 	source='server.c',
 	subsystem_name='service',