Refactor listener subsystem (smartsocket)

The special marker "*smartsocket* is used in multiple locations in the
code. This CL unifies usage of the string and creates a convenient
method to identify smartsocket listeners.

Test: NA
Change-Id: I9ea193caf220a8b044f50932d6dfdd2dfc200390

3 files changed, 14 insertions, 10 deletions

diff --git a/adb_listeners.cpp b/adb_listeners.cpp
index 6f7f3438..c24016fb 100644
--- a/adb_listeners.cpp
+++ b/adb_listeners.cpp
@@ -33,15 +33,18 @@
 #include "transport.h"
 
 // A listener is an entity which binds to a local port and, upon receiving a connection on that
-// port, creates an asocket to connect the new local connection to a specific remote service.
+// port, creates an asocket to connect the new local connection to a specific remote service. They
+// are mostly used to implement forward and reverse-forward.
 //
-// TODO: some listeners read from the new connection to determine what exact service to connect to
-// on the far side.
+// Some listeners, called "smartsockets" read from the new connection to determine what exact
+// service to connect to on the far side. This is implemented with a different fdevent handler.
 class alistener {
   public:
     alistener(const std::string& _local_name, const std::string& _connect_to);
     ~alistener();
 
+    bool isSmartSocket() { return connect_to == kSmartSocketConnectTo; }
+
     fdevent* fde = nullptr;
     int fd = -1;
 
@@ -127,8 +130,7 @@ std::string format_listeners() EXCLUDES(listener_list_mutex) {
     std::lock_guard<std::mutex> lock(listener_list_mutex);
     std::string result;
     for (auto& l : listener_list) {
-        // Ignore special listeners like those for *smartsocket*
-        if (l->connect_to[0] == '*') {
+        if (l->isSmartSocket()) {
             continue;
         }
         //  <device-serial> " " <local-name> " " <remote-name> "\n"
@@ -170,7 +172,7 @@ void remove_all_listeners() EXCLUDES(listener_list_mutex) {
 void enable_server_sockets() EXCLUDES(listener_list_mutex) {
     std::lock_guard<std::mutex> lock(listener_list_mutex);
     for (auto& l : listener_list) {
-        if (l->connect_to == "*smartsocket*") {
+        if (l->isSmartSocket()) {
             fdevent_set(l->fde, FDE_READ);
         }
     }
@@ -179,7 +181,7 @@ void enable_server_sockets() EXCLUDES(listener_list_mutex) {
 void close_smartsockets() EXCLUDES(listener_list_mutex) {
     std::lock_guard<std::mutex> lock(listener_list_mutex);
     auto pred = [](const std::unique_ptr<alistener>& listener) {
-        return listener->connect_to == "*smartsocket*";
+        return listener->isSmartSocket();
     };
     listener_list.remove_if(pred);
 }
@@ -192,7 +194,7 @@ InstallStatus install_listener(const std::string& local_name, const char* connec
     for (auto& l : listener_list) {
         if (local_name == l->local_name) {
             // Can't repurpose a smartsocket.
-            if (l->connect_to[0] == '*') {
+            if (l->isSmartSocket()) {
                 *error = "cannot repurpose smartsocket";
                 return INSTALL_STATUS_INTERNAL_ERROR;
             }
@@ -230,7 +232,7 @@ InstallStatus install_listener(const std::string& local_name, const char* connec
     }
 
     close_on_exec(listener->fd);
-    if (listener->connect_to == "*smartsocket*") {
+    if (listener->isSmartSocket()) {
 #if ADB_HOST
         listener->fde = fdevent_create(listener->fd, ss_listener_event_func, listener.get());
 #else
diff --git a/adb_listeners.h b/adb_listeners.h
index 0aa774a7..7fd46f02 100644
--- a/adb_listeners.h
+++ b/adb_listeners.h
@@ -22,6 +22,8 @@
 
 #include <android-base/macros.h>
 
+inline constexpr const char* kSmartSocketConnectTo = "*smartsocket*";
+
 // error/status codes for install_listener.
 enum InstallStatus {
   INSTALL_STATUS_OK = 0,
diff --git a/client/main.cpp b/client/main.cpp
index 27e7badd..818d305a 100644
--- a/client/main.cpp
+++ b/client/main.cpp
@@ -157,7 +157,7 @@ int adb_server_main(int is_daemon, const std::string& socket_spec, const char* o
     // If we told a previous adb server to quit because of version mismatch, we can get to this
     // point before it's finished exiting. Retry for a while to give it some time. Don't actually
     // accept any connections until adb_wait_for_device_initialization finishes below.
-    while (install_listener(socket_spec, "*smartsocket*", nullptr, INSTALL_LISTENER_DISABLED,
+    while (install_listener(socket_spec, kSmartSocketConnectTo, nullptr, INSTALL_LISTENER_DISABLED,
                             nullptr, &error) != INSTALL_STATUS_OK) {
         if (std::chrono::steady_clock::now() - start > 0.5s) {
             LOG(FATAL) << "could not install *smartsocket* listener: " << error;