adb: support forwarding TCP port 0.

This CL adds support to forward or reverse TCP port 0 to allow the
system to automatically select an open port. The resolved port number
will be printed to stdout:
  $ adb forward tcp:0 tcp:8000
  12345
  $ adb reverse tcp:0 tcp:9000
  23456
This allows testing to be more robust by not hardcoding TCP ports which
may already be in use.

Forwarding port 0 is a host-only change and will work with any device,
but reversing port 0 requires the device to be updated with a new adbd
binary.

This CL also does a little bit of cleanup such as moving the alistener
class out of adb.h, and adds some error checking and additional tests.

Bug: 28051746
Test: python -m unittest discover
Test: adb_test
Test: `adb forward` and `adb reverse` with tcp:0
Change-Id: Icaa87346685b403ab5da7f0e6aa186aa091da572
diff --git a/adb_listeners_test.cpp b/adb_listeners_test.cpp
new file mode 100644
index 0000000..b697769
--- /dev/null
+++ b/adb_listeners_test.cpp
@@ -0,0 +1,166 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "adb_listeners.h"
+
+#include <gtest/gtest.h>
+
+#include <android-base/stringprintf.h>
+#include <android-base/strings.h>
+
+#include "fdevent.h"
+#include "sysdeps.h"
+#include "transport.h"
+
+// Returns true if the given listener is present in format_listeners(). Empty parameters will
+// be ignored.
+static bool listener_is_installed(const std::string& serial, const std::string& source,
+                                  const std::string& dest) {
+    // format_listeners() gives lines of "<serial> <source> <dest>\n".
+    for (const std::string& line : android::base::Split(format_listeners(), "\n")) {
+        std::vector<std::string> info = android::base::Split(line, " ");
+        if (info.size() == 3 &&
+                (serial.empty() || info[0] == serial) &&
+                (source.empty() || info[1] == source) &&
+                (dest.empty() || info[2] == dest)) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+class AdbListenersTest : public ::testing::Test {
+  public:
+    void SetUp() override {
+        // We don't need an fdevent loop, but adding/removing listeners must be done from the
+        // fdevent thread if one exists. Since previously run tests may have created an fdevent
+        // thread, we need to reset to prevent the thread check.
+        fdevent_reset();
+    }
+
+    void TearDown() override {
+        // Clean up any listeners that may have been installed.
+        remove_all_listeners();
+
+        // Make sure we didn't leave any dangling events.
+        ASSERT_EQ(0u, fdevent_installed_count());
+    }
+
+  protected:
+    atransport transport_;
+};
+
+TEST_F(AdbListenersTest, test_install_listener) {
+    std::string error;
+
+    ASSERT_EQ(INSTALL_STATUS_OK,
+              install_listener("tcp:9000", "tcp:9000", &transport_, false, nullptr, &error));
+    ASSERT_TRUE(error.empty());
+
+    ASSERT_TRUE(listener_is_installed("", "tcp:9000", "tcp:9000"));
+}
+
+TEST_F(AdbListenersTest, test_install_listener_rebind) {
+    std::string error;
+
+    ASSERT_EQ(INSTALL_STATUS_OK,
+              install_listener("tcp:9000", "tcp:9000", &transport_, false, nullptr, &error));
+    ASSERT_TRUE(error.empty());
+
+    ASSERT_EQ(INSTALL_STATUS_OK,
+              install_listener("tcp:9000", "tcp:9001", &transport_, false, nullptr, &error));
+    ASSERT_TRUE(error.empty());
+
+    ASSERT_TRUE(listener_is_installed("", "tcp:9000", "tcp:9001"));
+}
+
+TEST_F(AdbListenersTest, test_install_listener_no_rebind) {
+    std::string error;
+
+    ASSERT_EQ(INSTALL_STATUS_OK,
+              install_listener("tcp:9000", "tcp:9000", &transport_, true, nullptr, &error));
+    ASSERT_TRUE(error.empty());
+
+    ASSERT_EQ(INSTALL_STATUS_CANNOT_REBIND,
+              install_listener("tcp:9000", "tcp:9001", &transport_, true, nullptr, &error));
+    ASSERT_FALSE(error.empty());
+
+    ASSERT_TRUE(listener_is_installed("", "tcp:9000", "tcp:9000"));
+}
+
+TEST_F(AdbListenersTest, test_install_listener_tcp_port_0) {
+    int port = 0;
+    std::string error;
+
+    ASSERT_EQ(INSTALL_STATUS_OK,
+              install_listener("tcp:0", "tcp:9000", &transport_, true, &port, &error));
+    ASSERT_TRUE(error.empty());
+
+    ASSERT_TRUE(listener_is_installed("", android::base::StringPrintf("tcp:%d", port), "tcp:9000"));
+}
+
+TEST_F(AdbListenersTest, test_remove_listener) {
+    std::string error;
+
+    ASSERT_EQ(INSTALL_STATUS_OK,
+              install_listener("tcp:9000", "tcp:9000", &transport_, false, nullptr, &error));
+    ASSERT_TRUE(error.empty());
+
+    ASSERT_EQ(INSTALL_STATUS_OK, remove_listener("tcp:9000", &transport_));
+    ASSERT_TRUE(format_listeners().empty());
+}
+
+TEST_F(AdbListenersTest, test_remove_nonexistent_listener) {
+    std::string error;
+
+    ASSERT_EQ(INSTALL_STATUS_OK,
+              install_listener("tcp:9000", "tcp:9000", &transport_, false, nullptr, &error));
+    ASSERT_TRUE(error.empty());
+
+    ASSERT_EQ(INSTALL_STATUS_LISTENER_NOT_FOUND, remove_listener("tcp:1", &transport_));
+    ASSERT_TRUE(listener_is_installed("", "tcp:9000", "tcp:9000"));
+}
+
+TEST_F(AdbListenersTest, test_remove_all_listeners) {
+    std::string error;
+
+    ASSERT_EQ(INSTALL_STATUS_OK,
+              install_listener("tcp:9000", "tcp:9000", &transport_, false, nullptr, &error));
+    ASSERT_TRUE(error.empty());
+
+    ASSERT_EQ(INSTALL_STATUS_OK,
+              install_listener("tcp:9001", "tcp:9001", &transport_, false, nullptr, &error));
+    ASSERT_TRUE(error.empty());
+
+    remove_all_listeners();
+    ASSERT_TRUE(format_listeners().empty());
+}
+
+TEST_F(AdbListenersTest, test_transport_disconnect) {
+    std::string error;
+
+    ASSERT_EQ(INSTALL_STATUS_OK,
+              install_listener("tcp:9000", "tcp:9000", &transport_, false, nullptr, &error));
+    ASSERT_TRUE(error.empty());
+
+    ASSERT_EQ(INSTALL_STATUS_OK,
+              install_listener("tcp:9001", "tcp:9001", &transport_, false, nullptr, &error));
+    ASSERT_TRUE(error.empty());
+
+    transport_.RunDisconnects();
+    ASSERT_TRUE(format_listeners().empty());
+}