Merge "Revert "Test for thread creation failed"" am: a60f48b6

    EXPECT_EQ(1U, GetNumQueries(dns, host_name));

}

// Run a large number of DNS queries through asynchronous API to create

// thousands of threads in resolver to simulate the failure of thread creation

// when memory per process is exhausted. (The current critical value is about

// 84xx threads.)

TEST_F(ResolverTest, Async_OutOfMemory) {

    constexpr char host_name[] = "howdy.example.com.";

    constexpr size_t AMOUNT_OF_UIDS = 40;

    constexpr size_t MAX_QUERIES_PER_UID = 256;

    constexpr size_t NUM_OF_QUERIES = AMOUNT_OF_UIDS * MAX_QUERIES_PER_UID;

    test::DNSResponder dns;

    StartDns(dns, {{host_name, ns_type::ns_t_a, "1.2.3.4"}});

    ASSERT_TRUE(mDnsClient.SetResolversForNetwork());

    dns.setDeferredResp(true);

    std::vector<int> fds;

    fds.reserve(NUM_OF_QUERIES);

    bool send_query = true;

    for (size_t i = 0; i < AMOUNT_OF_UIDS && send_query; i++) {

        ScopedChangeUID scopedChangeUID(TEST_UID - i);

        for (size_t j = 0; j < MAX_QUERIES_PER_UID; j++) {

            int fd = resNetworkQuery(TEST_NETID, "howdy.example.com", ns_c_in, ns_t_a, 0);

            if (fd >= 0) {

                fds.emplace_back(fd);

            } else {

                send_query = false;

                break;

            }

        }

    }

    dns.setDeferredResp(false);

    EXPECT_EQ(NUM_OF_QUERIES, fds.size());

    // TODO: AIBinder_DeathRecipient_new does not work (b/172178636), which

    // should be fixed. Fortunately, netd crash is still detectable at the point

    // of DumpResolverService() in TearDown(), where accesses mDnsClient. Also,

    // the fds size will be less than NUM_OF_QUERIES in that case.

    uint8_t buf[MAXPACKET];

    int rcode;

    for (auto fd : fds) {

        memset(buf, 0, MAXPACKET);

        getAsyncResponse(fd, &rcode, buf, MAXPACKET);

        // The results of each DNS query are not examined, since they won't all

        // succeed or all fail. Here we only focus on netd is crashed or not.

    }

}

// This test checks that the resolver should not generate the request containing OPT RR when using

// cleartext DNS. If we query the DNS server not supporting EDNS0 and it reponds with

// FORMERR_ON_EDNS, we will fallback to no EDNS0 and try again. If the server does no response, we