Fix DnsTlsSocket fast shutdown pathp9.0

Previously, DnsTlsSocket's destructor told the loop thread to
perform a clean shutdown by closing an IPC file descriptor.
However, the IPC file descriptor is now an eventfd, which does
not alert the listening thread when it is closed.

This change uses the eventfd counter's sign bit as an indication
that the destructor is requesting an immediate close.

Test: Includes regression test.
Bug: 123212403
Bug: 124058672
Bug: 122856181
Change-Id: I6edc26bf504cbfbba7d055b1f8e52ac70e02c6e0
Merged-In: I6edc26bf504cbfbba7d055b1f8e52ac70e02c6e0
(cherry picked from commit 83eccadc7e9d0ee0f75aab980cfdc2159c4c98a2)

1 files changed, 41 insertions, 0 deletions

diff --git a/tests/dns_tls_test.cpp b/tests/dns_tls_test.cpp
index bb5bfe56..b7fb3a45 100644
--- a/tests/dns_tls_test.cpp
+++ b/tests/dns_tls_test.cpp
@@ -28,6 +28,8 @@
 #include "dns/IDnsTlsSocketFactory.h"
 #include "dns/IDnsTlsSocketObserver.h"
 
+#include "dns_responder/dns_tls_frontend.h"
+
 #include <chrono>
 #include <arpa/inet.h>
 #include <android-base/macros.h>
@@ -871,5 +873,44 @@ TEST(QueryMapTest, FillHole) {
     EXPECT_FALSE(map.recordQuery(makeSlice(QUERY)));
 }
 
+class StubObserver : public IDnsTlsSocketObserver {
+  public:
+    bool closed = false;
+    void onResponse(std::vector<uint8_t>) override {}
+
+    void onClosed() override { closed = true; }
+};
+
+TEST(DnsTlsSocketTest, SlowDestructor) {
+    constexpr char tls_addr[] = "127.0.0.3";
+    constexpr char tls_port[] = "8530";  // High-numbered port so root isn't required.
+    // This test doesn't perform any queries, so the backend address can be invalid.
+    constexpr char backend_addr[] = "192.0.2.1";
+    constexpr char backend_port[] = "1";
+
+    test::DnsTlsFrontend tls(tls_addr, tls_port, backend_addr, backend_port);
+    ASSERT_TRUE(tls.startServer());
+
+    DnsTlsServer server;
+    parseServer(tls_addr, 8530, &server.ss);
+
+    StubObserver observer;
+    ASSERT_FALSE(observer.closed);
+    DnsTlsSessionCache cache;
+    auto socket = std::make_unique<DnsTlsSocket>(server, MARK, &observer, &cache);
+    ASSERT_TRUE(socket->initialize());
+
+    // Test: Time the socket destructor.  This should be fast.
+    auto before = std::chrono::steady_clock::now();
+    socket.reset();
+    auto after = std::chrono::steady_clock::now();
+    auto delay = after - before;
+    ALOGV("Shutdown took %lld ns", delay / std::chrono::nanoseconds{1});
+    EXPECT_TRUE(observer.closed);
+    // Shutdown should complete in milliseconds, but if the shutdown signal is lost
+    // it will wait for the timeout, which is expected to take 20seconds.
+    EXPECT_LT(delay, std::chrono::seconds{5});
+}
+
 } // end of namespace net
 } // end of namespace android