get_dns_stats: Expose total cache size and cached text entries

It wasn't possible from script land to determine the total size
of the cache table held by the DNS_Mgr. Add the total and also
also the TEXT entries count.

scripts/base/init-bare.zeek

@@ -757,6 +757,8 @@ type DNSStats: record {
 	pending:          count; ##< Current pending queries.
 	cached_hosts:     count; ##< Number of cached hosts.
 	cached_addresses: count; ##< Number of cached addresses.
+	cached_texts:     count; ##< Number of cached text entries.
+	cached_total:     count; ##< Total number of cached entries.
 };
 
 ## Statistics about number of gaps in TCP connections.

src/DNS_Mgr.cc

@@ -1485,6 +1485,7 @@ void DNS_Mgr::GetStats(Stats* stats)
 	stats->cached_hosts = 0;
 	stats->cached_addresses = 0;
 	stats->cached_texts = 0;
+	stats->cached_total = all_mappings.size();
 
 	for ( const auto& [key, mapping] : all_mappings )
 		{

src/DNS_Mgr.h

@@ -209,6 +209,7 @@ public:
 		unsigned long cached_hosts;
 		unsigned long cached_addresses;
 		unsigned long cached_texts;
+		unsigned long cached_total;
 		};
 
 	/**

src/stats.bif

@@ -259,6 +259,8 @@ function get_dns_stats%(%): DNSStats
 	r->Assign(n++, static_cast<uint64_t>(dstats.pending));
 	r->Assign(n++, static_cast<uint64_t>(dstats.cached_hosts));
 	r->Assign(n++, static_cast<uint64_t>(dstats.cached_addresses));
+	r->Assign(n++, static_cast<uint64_t>(dstats.cached_texts));
+	r->Assign(n++, static_cast<uint64_t>(dstats.cached_total));
 
 	return r;
 	%}

testing/btest/Baseline/bifs.get_dns_stats/out

@@ -0,0 +1,2 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+[requests=0, successful=0, failed=0, pending=0, cached_hosts=0, cached_addresses=0, cached_texts=0, cached_total=0]

testing/btest/bifs/get_dns_stats.test

@@ -0,0 +1,8 @@
+# @TEST-DOC: With FAKE_DNS mode caching is disabled, so testing is difficult, invoke the bif once at least.
+# @TEST-EXEC: zeek -b %INPUT >out
+# @TEST-EXEC: btest-diff out
+
+event zeek_init()
+	{
+	print get_dns_stats();
+	}