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/105-ntpauth

@@ -0,0 +1,33 @@
+#!/bin/bash
+
+. test.common
+
+test_start "NTP authentication"
+
+server_conf="keyfile tmp/keys"
+client_conf="keyfile tmp/keys"
+
+cat > tmp/keys <<-EOF
+1 $(tr -c -d 'a-zA-Z0-9' < /dev/urandom 2> /dev/null | head -c 24)
+2 ASCII:$(tr -c -d 'a-zA-Z0-9' < /dev/urandom 2> /dev/null | head -c 24)
+3 MD5 ASCII:$(tr -c -d 'a-zA-Z' < /dev/urandom 2> /dev/null | head -c 24)
+4 MD5 HEX:$(tr -c -d '0-9A-F' < /dev/urandom 2> /dev/null | head -c 32)
+EOF
+
+for key in 1 2 3 4; do
+	client_server_options="key $key"
+	run_test || test_fail
+	check_chronyd_exit || test_fail
+	check_source_selection || test_fail
+	check_packet_interval || test_fail
+	check_sync || test_fail
+done
+
+server_conf=""
+
+run_test || test_fail
+check_chronyd_exit || test_fail
+# This check must fail as server doesn't know the key
+check_sync && test_fail
+
+test_pass