To implement the SO_KEEPALIVE socket option into dllmain.c in the ReactOS repository, you'll need to make adjustments in the WSPGetSockOpt and WSPSetSockOpt functions, as they are responsible for handling socket options.

Here’s how to implement and integrate SO_KEEPALIVE functionality:

Steps to Implement SO_KEEPALIVE

1. Update WSPGetSockOpt:

   • Add a case for SO_KEEPALIVE under the SOL_SOCKET level.
   • Retrieve the value from Socket->SharedData to determine whether the keepalive option is enabled or not.

2. Update WSPSetSockOpt:

   • Add a case for SO_KEEPALIVE under the SOL_SOCKET level.
   • Update the Socket->SharedData structure to enable or disable the keepalive option based on the input value.

3. Ensure Helper Functionality:

   • The helper DLL (HelperData) may handle certain options directly. For SO_KEEPALIVE, ensure that the helper DLL supports this option.

4. Testing:

   • Test the changes with various sockets to verify that enabling/disabling the keepalive option works as expected.

Code Changes

Below are the code snippets to incorporate SO_KEEPALIVE into the WSPGetSockOpt and WSPSetSockOpt functions.

Modify WSPGetSockOpt

Add the following case under case SOL_SOCKET in the WSPGetSockOpt function:

case SO_KEEPALIVE:
    BoolBuffer = (Socket->SharedData->KeepAlive != 0);
    Buffer = &BoolBuffer;
    BufferSize = sizeof(BOOL);
    break;

Modify WSPSetSockOpt

Add the following case under case SOL_SOCKET in the WSPSetSockOpt function:

case SO_KEEPALIVE:
    if (optlen < sizeof(BOOL))
    {
        if (lpErrno) *lpErrno = WSAEFAULT;
        return SOCKET_ERROR;
    }
    Socket->SharedData->KeepAlive = (*optval != 0) ? 1 : 0;
    return NO_ERROR;

Modify PSOCKET_SHARED_INFO (if necessary)

Ensure that the PSOCKET_SHARED_INFO structure (likely Socket->SharedData) has a field for KeepAlive. If it doesn’t exist, add it:

BOOLEAN KeepAlive;

Initialize this field properly wherever Socket->SharedData is allocated or reset.

Integration Points

• Initialization: Ensure that the KeepAlive field is initialized to FALSE (or 0) when the socket is created.

• Helper DLL: If the helper DLL handles the SO_KEEPALIVE option directly, delegate the handling to the helper via WSHSetSocketInformation and WSHGetSocketInformation.

• Documentation: Update any documentation or inline comments to reflect the addition of SO_KEEPALIVE support.

Example Test Case

1. Create a socket using WSPSocket.
2. Use WSPSetSockOpt to enable SO_KEEPALIVE.
3. Verify the option using WSPGetSockOpt.
4. Monitor TCP keepalive packets (using tools like Wireshark) to confirm functionality.

These changes will enable SO_KEEPALIVE functionality for sockets in the ReactOS networking stack.