Added system test for stale-refresh-time

This test works as follow:
- Query for data.example rrset.
- Sleep until its TTL expires (2 secs).
- Disable authoritative server.
- Query for data.example again.
- Since server is down, answer come from stale cache, which has
  a configured stale-answer-ttl of 3 seconds.
- Enable authoritative server.
- Query for data.example again
- Since last query before activating authoritative server failed, and
  since 'stale-refresh-time' seconds hasn't elapsed yet, answer should
  come from stale cache and not from the authoritative server.

bin/tests/system/serve-stale/tests.sh

@@ -471,10 +471,6 @@ grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
 status=$((status+ret))
 
-# keep track of time so we can access these rrset later,
-# when we expect them to become ancient.
-t1=`$PERL -e 'print time()'`
-
 n=$((n+1))
 echo_i "prime cache othertype.example (low max-stale-ttl) ($n)"
 ret=0
@@ -502,6 +498,10 @@ grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
 status=$((status+ret))
 
+# keep track of time so we can access these rrset later,
+# when we expect them to become ancient.
+t1=`$PERL -e 'print time()'`
+
 n=$((n+1))
 echo_i "verify prime cache statistics (low max-stale-ttl) ($n)"
 ret=0
@@ -656,6 +656,100 @@ grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
 status=$((status+ret))
 
+# Test stale-refresh-time when serve-stale is enabled via rndc.
+# Steps for testing stale-refresh-time option (default).
+# 1. Prime cache data.example txt
+# 2. Disable responses from authoritative server.
+# 3. Sleep for TTL duration so rrset TTL expires (2 sec)
+# 4. Query data.example
+# 5. Check if response come from stale rrset (3 sec TTL)
+# 6. Enable responses from authoritative server.
+# 7. Query data.example
+# 8. Check if response come from stale rrset, since the query
+#    is within stale-refresh-time window.
+n=$((n+1))
+echo_i "flush cache, enable responses from authoritative server ($n)"
+ret=0
+$RNDCCMD 10.53.0.1 flushtree example > rndc.out.test$n.1 2>&1 || ret=1
+$DIG -p ${PORT} @10.53.0.2 txt enable  > dig.out.test$n
+grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
+grep "TXT.\"1\"" dig.out.test$n > /dev/null || ret=1
+if [ $ret != 0 ]; then echo_i "failed"; fi
+status=$((status+ret))
+
+n=$((n+1))
+echo_i "check 'rndc serve-stale status' ($n)"
+ret=0
+$RNDCCMD 10.53.0.1 serve-stale status > rndc.out.test$n 2>&1 || ret=1
+grep '_default: on (rndc) (stale-answer-ttl=3 max-stale-ttl=20)' rndc.out.test$n > /dev/null || ret=1
+if [ $ret != 0 ]; then echo_i "failed"; fi
+status=$((status+ret))
+
+# Step 1.
+n=$((n+1))
+echo_i "prime cache data.example (stale-refresh-time rndc) ($n)"
+ret=0
+$DIG -p ${PORT} @10.53.0.1 data.example TXT > dig.out.test$n
+grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
+grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
+grep "data\.example\..*2.*IN.*TXT.*A text record with a 2 second ttl" dig.out.test$n > /dev/null || ret=1
+if [ $ret != 0 ]; then echo_i "failed"; fi
+status=$((status+ret))
+
+# Step 2.
+n=$((n+1))
+echo_i "disable responses from authoritative server ($n)"
+ret=0
+$DIG -p ${PORT} @10.53.0.2 txt disable  > dig.out.test$n
+grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
+grep "TXT.\"0\"" dig.out.test$n > /dev/null || ret=1
+if [ $ret != 0 ]; then echo_i "failed"; fi
+status=$((status+ret))
+
+# Step 3.
+sleep 2
+
+# Step 4.
+n=$((n+1))
+echo_i "sending query for test ($n)"
+$DIG -p ${PORT} @10.53.0.1 data.example TXT > dig.out.test$n
+
+# Step 5.
+echo_i "check stale data.example (stale-refresh-time rndc) ($n)"
+ret=0
+grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
+grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
+grep "data\.example\..*3.*IN.*TXT.*A text record with a 2 second ttl" dig.out.test$n > /dev/null || ret=1
+if [ $ret != 0 ]; then echo_i "failed"; fi
+status=$((status+ret))
+
+# Step 6.
+n=$((n+1))
+echo_i "enable responses from authoritative server ($n)"
+ret=0
+$DIG -p ${PORT} @10.53.0.2 txt enable > dig.out.test$n
+grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
+grep "TXT.\"1\"" dig.out.test$n > /dev/null || ret=1
+if [ $ret != 0 ]; then echo_i "failed"; fi
+status=$((status+ret))
+
+# Step 7.
+echo_i "sending query for test $((n+1))"
+$DIG -p ${PORT} @10.53.0.1 data.example TXT > dig.out.test$((n+1)) &
+
+# ensure the file has been written before proceeding
+waitfile dig.out.test$((n+1))
+
+# Step 8.
+n=$((n+1))
+echo_i "check stale data.example comes from cache (stale-refresh-time rndc) ($n)"
+ret=0
+grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
+grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
+grep "data\.example\..*3.*IN.*TXT.*A text record with a 2 second ttl" dig.out.test$n > /dev/null || ret=1
+if [ $ret != 0 ]; then echo_i "failed"; fi
+status=$((status+ret))
+
 #
 # Now test server with no serve-stale options set.
 #