[kadet.89]

Function detour

CBaseServer::ForwardPacketsFromMasterServerUp dater(void)

PHP Code:

DETOUR_DECL_MEMBER0(DetourForwardPacketsFromMasterServerUpdater, int)
{
    int r = DETOUR_MEMBER_CALL(DetourForwardPacketsFromMasterServerUpdater)();
    return r;
} 


I want to rewrite this function. I have a pseudoсode:

PHP Code:

int __cdecl CBaseServer::ForwardPacketsFromMasterServerUpdater(int a1)
{
  int result; // eax@1
  int v2; // esi@1
  int v3; // ST2C_4@3
  __int16 v4; // ST28_2@3
  int buf; // [sp+3Ch] [bp-402Ch]@3
  int v6; // [sp+403Ch] [bp-2Ch]@3
  int v7; // [sp+4048h] [bp-20h]@3
  __int16 v8; // [sp+404Eh] [bp-1Ah]@3

  result = Steam3Server();
  v2 = *(_DWORD *)result;
  if ( *(_DWORD *)result )
  {
    while ( 1 )
    {
      result = (*(int (__cdecl **)(int, int *, signed int, int *, __int16 *))(*(_DWORD *)v2 + 152))(
                 v2,
                 &buf,
                 16384,
                 &v7,
                 &v8);
      if ( result <= 0 )
        break;
      v3 = result;
      v4 = v8;
      netadr_s::SetIP(&v6, v7);
      netadr_s::SetPort(&v6, v4);
      netadr_s::SetType(&v6, 3);
      NET_SendPacket(0, *(_DWORD *)(a1 + 8), (int)&v6, (int)&buf, v3, 0, 0);
    }
  }
  return result;
} 


How can I get access to result, v6, a1 from Detour ? It is necessary to make calls: netadr_s::SetIP(&v6, v7) ....
And how can I get the address of the function ForwardPacketsFromMasterServerUpdater in DETOUR_DECL_MEMBER0() {..} ?

[donrevan]

What do you want to accomplish? There are maybe other ways to do this more easily.

Anyway, let's see what I can do

The function basicly looks for pending packets it needs to send. In this process are 2 calls involved.
The first is GetNextOutgoingPacket to get the next packet it needs and NET_SendPacket to send it.

You can see that this calls GetNextOutgoingPacket because it's doing:

ASM:
call dword ptr [eax+98h]

pseudocode:
result = (*(int (__cdecl **)(int, int *, signed int, int *, __int16 *))(*(_DWORD *)v2 + 152))(
                 v2,
                 &buf,
                 16384,
                 &v7,
                 &v8); //152 == 0x98

which means call function at vtable index 38. Thanks to OSW we've this. Count the virtual functions and you'll know that 38 is our match.
You want to change result, v6 and a1.
a1 is CBaseServer, v6 clearly is the netadr struct and result is the packet length.

I don't know if this is a really good idea because the function is called alot but you can hook NET_SendPacket and check if the return address == ForwardPacketsFromMasterServerUpdater and modify the params if so.

[kadet.89]

Thanks for the reply. I solved the problem in another way. I replaced the address of the called function NET_SendPacket with the address of mine function.