snapuserd: Use gflags for arguments.

This is in preparation for expanding the command-line features of
snapuserd.

Bug: N/A
Test: builds
Change-Id: Id33c4f190dc0f99cd436f0e9a6b1d6ee92e245e4

fs_mgr/libsnapshot/Android.bp

@@ -423,10 +423,11 @@ cc_defaults {
         "libbase",
         "libbrotli",
         "libcutils_sockets",
-        "liblog",
         "libdm",
-        "libz",
+        "libgflags",
+        "liblog",
         "libsnapshot_cow",
+        "libz",
     ],
 }
 

fs_mgr/libsnapshot/cow_snapuserd_test.cpp

@@ -169,7 +169,7 @@ void CowSnapuserdTest::StartSnapuserdDaemon() {
     ASSERT_GE(pid, 0);
     if (pid == 0) {
         std::string arg0 = "/system/bin/snapuserd";
-        std::string arg1 = kSnapuserdSocketTest;
+        std::string arg1 = "-socket="s + kSnapuserdSocketTest;
         char* const argv[] = {arg0.data(), arg1.data(), nullptr};
         ASSERT_GE(execv(arg0.c_str(), argv), 0);
     } else {

fs_mgr/libsnapshot/snapuserd_daemon.cpp

@@ -17,19 +17,21 @@
 #include "snapuserd_daemon.h"
 
 #include <android-base/logging.h>
+#include <gflags/gflags.h>
 #include <libsnapshot/snapuserd_client.h>
 
 #include "snapuserd_server.h"
 
+DEFINE_string(socket, android::snapshot::kSnapuserdSocket, "Named socket or socket path.");
+
 namespace android {
 namespace snapshot {
 
-bool Daemon::StartServer(const std::string& socketname) {
-    if (!server_.Start(socketname)) {
+void Daemon::StartServer() {
+    if (!server_.Start(FLAGS_socket)) {
         LOG(ERROR) << "Snapuserd daemon failed to start...";
         exit(EXIT_FAILURE);
     }
-    return true;
 }
 
 void Daemon::MaskAllSignalsExceptIntAndTerm() {
@@ -99,11 +101,9 @@ int main([[maybe_unused]] int argc, char** argv) {
 
     android::snapshot::Daemon& daemon = android::snapshot::Daemon::Instance();
 
-    std::string socket = android::snapshot::kSnapuserdSocket;
-    if (argc >= 2) {
-        socket = argv[1];
-    }
-    daemon.StartServer(socket);
+    gflags::ParseCommandLineFlags(&argc, &argv, false);
+
+    daemon.StartServer();
     daemon.Run();
 
     return 0;

fs_mgr/libsnapshot/snapuserd_daemon.h

@@ -32,7 +32,7 @@ class Daemon {
         return instance;
     }
 
-    bool StartServer(const std::string& socketname);
+    void StartServer();
     void Run();
     void Interrupt();