DNS: Retain stale entries in HostCache and return when requested

net/dns/host_cache_unittest.cc

Index: net/dns/host_cache_unittest.cc
diff --git a/net/dns/host_cache_unittest.cc b/net/dns/host_cache_unittest.cc
index 838fedcfaa893ada8757235aa050ac135c3e2f54..c34627b1696a82a88e6aab1bc0a61e7c75758844 100644
--- a/net/dns/host_cache_unittest.cc
+++ b/net/dns/host_cache_unittest.cc
@@ -42,7 +42,7 @@ TEST(HostCacheTest, Basic) {
   EXPECT_FALSE(cache.Lookup(key1, now));
   cache.Set(key1, entry, now, kTTL);
   EXPECT_TRUE(cache.Lookup(key1, now));
-  EXPECT_TRUE(cache.Lookup(key1, now)->error == entry.error);
+  EXPECT_TRUE(cache.Lookup(key1, now)->error() == entry.error());
 
   EXPECT_EQ(1U, cache.size());
 
@@ -253,9 +253,9 @@ TEST(HostCacheTest, HostResolverFlagsArePartOfKey) {
 }
 
 TEST(HostCacheTest, NoCache) {
-  // Disable caching.
   const base::TimeDelta kTTL = base::TimeDelta::FromSeconds(10);
 
+  // Disable caching.
   HostCache cache(0);
   EXPECT_TRUE(cache.caching_is_disabled());
 
@@ -296,6 +296,105 @@ TEST(HostCacheTest, Clear) {
   EXPECT_EQ(0u, cache.size());
 }
 
+// Try to add too many entries to cache; it should evict the one with the oldest
+// expiration time.
+TEST(HostCacheTest, Evict) {
+  HostCache cache(2);
+
+  base::TimeTicks now;
+
+  HostCache::Key key1 = Key("foobar.com");
+  HostCache::Key key2 = Key("foobar2.com");
+  HostCache::Key key3 = Key("foobar3.com");
+  HostCache::Entry entry = HostCache::Entry(OK, AddressList());
+
+  EXPECT_EQ(0u, cache.size());
+  EXPECT_FALSE(cache.Lookup(key1, now));
+  EXPECT_FALSE(cache.Lookup(key2, now));
+  EXPECT_FALSE(cache.Lookup(key3, now));
+
+  // |key1| expires in 10 seconds, but |key2| in just 5.
+  cache.Set(key1, entry, now, base::TimeDelta::FromSeconds(10));
+  cache.Set(key2, entry, now, base::TimeDelta::FromSeconds(5));
+  EXPECT_EQ(2u, cache.size());
+  EXPECT_TRUE(cache.Lookup(key1, now));
+  EXPECT_TRUE(cache.Lookup(key2, now));
+  EXPECT_FALSE(cache.Lookup(key3, now));
+
+  // |key2| should be chosen for eviction, since it expires sooner.
+  cache.Set(key3, entry, now, base::TimeDelta::FromSeconds(10));
+  EXPECT_EQ(2u, cache.size());
+  EXPECT_TRUE(cache.Lookup(key1, now));
+  EXPECT_FALSE(cache.Lookup(key2, now));
+  EXPECT_TRUE(cache.Lookup(key3, now));
+}
+
+// Try to retrieve stale entries from the cache. They should be returned by
+// |LookupStale()| but not |Lookup()|, with correct |EntryStaleness| data.
+TEST(HostCacheTest, Stale) {
+  const base::TimeDelta kTTL = base::TimeDelta::FromSeconds(10);
+
+  HostCache cache(kMaxCacheEntries);
+
+  // Start at t=0.
+  base::TimeTicks now;
+  HostCache::EntryStaleness stale;
+
+  HostCache::Key key = Key("foobar.com");
+  HostCache::Entry entry = HostCache::Entry(OK, AddressList());
+
+  EXPECT_EQ(0U, cache.size());
+
+  // Add an entry for "foobar.com" at t=0.
+  EXPECT_FALSE(cache.Lookup(key, now));
+  EXPECT_FALSE(cache.LookupStale(key, now, &stale));
+  cache.Set(key, entry, now, kTTL);
+  EXPECT_TRUE(cache.Lookup(key, now));
+  EXPECT_TRUE(cache.LookupStale(key, now, &stale));
+  EXPECT_FALSE(stale.is_stale());
+  EXPECT_EQ(0, stale.stale_hits);
+
+  EXPECT_EQ(1U, cache.size());
+
+  // Advance to t=5.
+  now += base::TimeDelta::FromSeconds(5);
+
+  EXPECT_TRUE(cache.Lookup(key, now));
+  EXPECT_TRUE(cache.LookupStale(key, now, &stale));
+  EXPECT_FALSE(stale.is_stale());
+  EXPECT_EQ(0, stale.stale_hits);
+
+  // Advance to t=15.
+  now += base::TimeDelta::FromSeconds(10);
+
+  EXPECT_FALSE(cache.Lookup(key, now));
+  EXPECT_TRUE(cache.LookupStale(key, now, &stale));
+  EXPECT_TRUE(stale.is_stale());
+  EXPECT_EQ(base::TimeDelta::FromSeconds(5), stale.expired_by);
+  EXPECT_EQ(0, stale.network_changes);
+  EXPECT_EQ(1, stale.stale_hits);
+
+  // Advance to t=20.
+  now += base::TimeDelta::FromSeconds(5);
+
+  EXPECT_FALSE(cache.Lookup(key, now));
+  EXPECT_TRUE(cache.LookupStale(key, now, &stale));
+  EXPECT_TRUE(stale.is_stale());
+  EXPECT_EQ(base::TimeDelta::FromSeconds(10), stale.expired_by);
+  EXPECT_EQ(0, stale.network_changes);
+  EXPECT_EQ(2, stale.stale_hits);
+
+  // Simulate network change.
+  cache.OnNetworkChange();
+
+  EXPECT_FALSE(cache.Lookup(key, now));
+  EXPECT_TRUE(cache.LookupStale(key, now, &stale));
+  EXPECT_TRUE(stale.is_stale());
+  EXPECT_EQ(base::TimeDelta::FromSeconds(10), stale.expired_by);
+  EXPECT_EQ(1, stale.network_changes);
+  EXPECT_EQ(3, stale.stale_hits);
+}
+
 // Tests the less than and equal operators for HostCache::Key work.
 TEST(HostCacheTest, KeyComparators) {
   struct {