From b0828a3dfe8d6d00a6b6819c9fcf149039d7c8d2 Mon Sep 17 00:00:00 2001
From: Martin Michelsen <fuzziqersoftware+g@gmail.com>
Date: Thu, 21 Apr 2022 15:54:44 -0700
Subject: [PATCH] add set-block-function-calls proxy command

---
 src/CommandFormats.hh | 10 +++++++---
 src/ProxyCommands.cc  | 22 +++++++++++++++++++++-
 src/ProxyServer.cc    |  1 +
 src/ProxyServer.hh    |  1 +
 src/ServerShell.cc    | 13 +++++++++++++
 5 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/src/CommandFormats.hh b/src/CommandFormats.hh
index c930bc14..7a810086 100644
--- a/src/CommandFormats.hh
+++ b/src/CommandFormats.hh
@@ -878,14 +878,18 @@ struct S_QuestMenuEntry_BB_A2_A4 {
 // For example: 2022:03:30: 15:36:42.000
 // Client will respond with a 99 command.
 
-// B2 (S->C): Write memory
+// B2 (S->C): Execute code
 // GC v1.0 and v1.1 only.
 // Format unknown.
 // Client will respond with a B3 command.
 
-// B3 (C->S): Write memory response
+// B3 (C->S): Execute code response
 // GC v1.0 and v1.1 only.
-// Format unknown.
+
+struct C_ExecuteCodeResponse_GC_B3 {
+  le_uint32_t return_value;
+  le_uint32_t unused;
+};
 
 // B4: Invalid command
 // B5: Invalid command
diff --git a/src/ProxyCommands.cc b/src/ProxyCommands.cc
index 92e2535c..5f011a97 100644
--- a/src/ProxyCommands.cc
+++ b/src/ProxyCommands.cc
@@ -306,6 +306,26 @@ static bool process_server_88(shared_ptr<ServerState>,
   return true;
 }
 
+static bool process_server_gc_B2(shared_ptr<ServerState>,
+    ProxyServer::LinkedSession& session, uint16_t, uint32_t flag, string& data) {
+  if (session.save_files) {
+    string output_filename = string_printf("code.bin.%" PRId64, now());
+    save_file(output_filename, data);
+    session.log(INFO, "Wrote code from server to file %s", output_filename.c_str());
+  }
+
+  if (session.function_call_return_value >= 0) {
+    session.log(INFO, "Blocking function call from server");
+    C_ExecuteCodeResponse_GC_B3 cmd;
+    cmd.return_value = session.function_call_return_value;
+    cmd.unused = 0;
+    session.send_to_end(true, 0xB3, flag, &cmd, sizeof(cmd));
+    return false;
+  } else {
+    return true;
+  }
+}
+
 template <typename CmdT>
 static bool process_server_C4(shared_ptr<ServerState>,
     ProxyServer::LinkedSession& session, uint16_t, uint32_t flag, string& data) {
@@ -792,7 +812,7 @@ static process_command_t gc_server_handlers[0x100] = {
   /* 80 */ defh, process_server_81<SC_SimpleMail_GC_81>, defh, defh, defh, defh, defh, defh, process_server_88, defh, defh, defh, defh, defh, defh, defh,
   /* 90 */ defh, defh, defh, defh, defh, defh, defh, defh, defh, defh, process_server_gc_9A, defh, defh, defh, defh, defh,
   /* A0 */ defh, defh, defh, defh, defh, defh, process_server_44_A6<S_OpenFile_PC_GC_44_A6>, process_server_13_A7, defh, defh, defh, defh, defh, defh, defh, defh,
-  /* B0 */ defh, defh, defh, defh, defh, defh, defh, defh, process_server_gc_B8, defh, defh, defh, defh, defh, defh, defh,
+  /* B0 */ defh, defh, process_server_gc_B2, defh, defh, defh, defh, defh, process_server_gc_B8, defh, defh, defh, defh, defh, defh, defh,
   /* C0 */ defh, defh, defh, defh, process_server_C4<S_ChoiceSearchResultEntry_GC_C4>, defh, defh, defh, defh, process_server_60_62_6C_6D_C9_CB, defh, process_server_60_62_6C_6D_C9_CB, defh, defh, defh, defh,
   /* D0 */ defh, defh, defh, defh, defh, process_server_gc_1A_D5, defh, defh, defh, defh, defh, defh, defh, defh, defh, defh,
   /* E0 */ defh, defh, defh, defh, process_server_gc_E4, defh, defh, defh, defh, defh, defh, defh, defh, defh, defh, defh,
diff --git a/src/ProxyServer.cc b/src/ProxyServer.cc
index aa0d517c..fdf5b187 100644
--- a/src/ProxyServer.cc
+++ b/src/ProxyServer.cc
@@ -374,6 +374,7 @@ ProxyServer::LinkedSession::LinkedSession(
     enable_chat_filter(true),
     enable_switch_assist(false),
     save_files(false),
+    function_call_return_value(-1),
     override_section_id(-1),
     override_lobby_event(-1),
     override_lobby_number(-1),
diff --git a/src/ProxyServer.hh b/src/ProxyServer.hh
index 2a968e87..36712da8 100644
--- a/src/ProxyServer.hh
+++ b/src/ProxyServer.hh
@@ -58,6 +58,7 @@ public:
     bool enable_chat_filter;
     bool enable_switch_assist;
     bool save_files;
+    int64_t function_call_return_value; // -1 = don't block function calls
     G_SwitchStateChanged_6x05 last_switch_enabled_command;
     int16_t override_section_id;
     int16_t override_lobby_event;
diff --git a/src/ServerShell.cc b/src/ServerShell.cc
index f8a4791a..62bcb6eb 100644
--- a/src/ServerShell.cc
+++ b/src/ServerShell.cc
@@ -141,6 +141,11 @@ Proxy commands (these will only work when exactly one client is connected):\n\
     on, any file that the remote server sends to the client will be saved to\n\
     the current directory. This includes data like quests, Episode 3 card\n\
     definitions, and GBA games.\n\
+  set-block-function-calls [return-value]\n\
+    Enable blocking of function calls from the server. When enabled, the proxy\n\
+    responds as if the function was called (with the given return value), but\n\
+    does not send the code to the client. To stop blocking function calls, omit\n\
+    the return value.\n\
 ");
 
 
@@ -372,6 +377,14 @@ Proxy commands (these will only work when exactly one client is connected):\n\
     auto session = this->get_proxy_session();
     set_boolean(&session->save_files, command_args);
 
+  } else if (command_name == "set-block-function-calls") {
+    auto session = this->get_proxy_session();
+    if (command_args.empty()) {
+      session->function_call_return_value = -1;
+    } else {
+      session->function_call_return_value = stoul(command_args);
+    }
+
   } else {
     throw invalid_argument("unknown command; try \'help\'");
   }