Add simulation tests

Use clknetsim to run multiple chronyd instances with simulated clocks
and network. It allows fast and reproducible testing, without real
network.

Included are several tests of performance in different clock/network
conditions, chronyd options, NTP authentication, chronyc, and past bug
fixes.

test/simulation/201-freqaccumulation

@@ -0,0 +1,35 @@
+#!/bin/bash
+
+. test.common
+
+# Test fix in commit 60d0fa299307076143da94d36deb7b908fa9bdb7
+
+test_start "frequency accumulation"
+
+time_offset=100.0
+jitter=1e-6
+base_delay=1e-6
+wander=0.0
+
+limit=200
+time_max_limit=1e-5
+freq_max_limit=1e-7
+time_rms_limit=1e-5
+freq_rms_limit=1e-7
+min_sync_time=120
+max_sync_time=140
+
+client_server_options="minpoll 6 maxpoll 6"
+client_conf="driftfile tmp/drift
+makestep 1 1"
+
+for freq_offset in -5e-2 -5e-4 5e-4 5e-2; do
+	for drift in -1e+4 -1e+2 1e+2 1e+4; do
+		echo "$drift 100000" > tmp/drift
+		run_test || test_fail
+		check_chronyd_exit || test_fail
+		check_sync || test_fail
+	done
+done
+
+test_pass