# Build Instructions for Windows

## Quick Start Guide

Follow these steps to build and run the DNS Packet Filter on Windows.

## Prerequisites

1. **Windows 10/11** (64-bit)
2. **Visual Studio 2019 or later** with C++ development tools
   - Or **MinGW-w64** with GCC 8.0+
3. **CMake 3.15 or later**
   - Download from: https://cmake.org/download/

## Step 1: Setup WinDivert Library

**IMPORTANT**: You need to download WinDivert on a Windows machine.

1. Download WinDivert 2.2:
   ```
   https://github.com/basil00/WinDivert/releases/download/v2.2.2/WinDivert-2.2.2-A.zip
   ```

2. Extract the ZIP file

3. Copy the required files:

   **From `WinDivert-2.2.2-A/include/`:**
   ```
   Copy: windivert.h
   To:   external/WinDivert/include/windivert.h
   ```

   **From `WinDivert-2.2.2-A/x64/`:**
   ```
   Copy: WinDivert.dll
   To:   external/WinDivert/lib/WinDivert.dll

   Copy: WinDivert64.sys
   To:   external/WinDivert/lib/WinDivert64.sys

   Copy: WinDivert.lib
   To:   external/WinDivert/lib/WinDivert.lib
   ```

4. Verify the directory structure:
   ```
   external/WinDivert/
   ├── include/
   │   └── windivert.h
   └── lib/
       ├── WinDivert.dll
       ├── WinDivert64.sys
       └── WinDivert.lib
   ```

## Step 2: Build with CMake

### Option A: Using Visual Studio

1. Open Command Prompt or PowerShell

2. Navigate to the project directory:
   ```cmd
   cd C:\path\to\windows-filter
   ```

3. Create build directory:
   ```cmd
   mkdir build
   cd build
   ```

4. Generate Visual Studio project files:
   ```cmd
   cmake .. -G "Visual Studio 17 2022"
   ```

   For Visual Studio 2019, use:
   ```cmd
   cmake .. -G "Visual Studio 16 2019"
   ```

5. Build the project:
   ```cmd
   cmake --build . --config Release
   ```

6. Output files will be in `build/Release/`

### Option B: Using Visual Studio IDE

1. Generate project files:
   ```cmd
   mkdir build
   cd build
   cmake .. -G "Visual Studio 17 2022"
   ```

2. Open `build/DNSPacketFilter.sln` in Visual Studio

3. Set build configuration to **Release**

4. Build → Build Solution (or press F7)

5. Output files will be in `build/Release/`

### Option C: Using MinGW

1. Ensure MinGW-w64 is in your PATH

2. Create build directory:
   ```cmd
   mkdir build
   cd build
   ```

3. Generate Makefiles:
   ```cmd
   cmake .. -G "MinGW Makefiles" -DCMAKE_BUILD_TYPE=Release
   ```

4. Build:
   ```cmd
   mingw32-make
   ```

5. Output files will be in `build/`

## Step 3: Verify Build Output

After successful build, check that these files exist in the output directory:

```
build/Release/  (or build/ for MinGW)
├── dns_filter.exe
├── WinDivert.dll
├── WinDivert64.sys
└── config/
    └── rules.json
```

## Step 4: Run the Application

**IMPORTANT**: Must run as Administrator!

1. Open Command Prompt **as Administrator**:
   - Press Windows Key
   - Type "cmd"
   - Right-click "Command Prompt"
   - Select "Run as administrator"

2. Navigate to the build output directory:
   ```cmd
   cd C:\path\to\windows-filter\build\Release
   ```

3. Run the application:
   ```cmd
   dns_filter.exe
   ```

4. You should see:
   ```
   ==================================================
       Windows DNS Packet Filter
       Powered by WinDivert
   ==================================================

   Configuration file: config/rules.json

   Loaded X filtering rules
   ...
   DNS Packet Filter is now active!
   ```

5. Press `Ctrl+C` to stop

## Troubleshooting

### CMake Configuration Errors

**Error: "Could not find WinDivert.lib"**

Solution:
- Verify WinDivert files are in `external/WinDivert/lib/`
- Re-run Step 1 to copy the files correctly

**Error: "CMake version too old"**

Solution:
- Download latest CMake from https://cmake.org/download/
- Or use `choco install cmake` (if you have Chocolatey)

### Build Errors

**Error: "windivert.h: No such file or directory"**

Solution:
- Verify `external/WinDivert/include/windivert.h` exists
- Re-run Step 1 to copy the header file

**Error: "C++17 support required"**

Solution:
- Update Visual Studio to 2017 or later
- Or update MinGW to GCC 8.0 or later

### Runtime Errors

**Error: "Access denied"**

Solution:
- Run as Administrator (see Step 4)

**Error: "WinDivert driver not found"**

Solution:
- Ensure `WinDivert64.sys` is in the same directory as `dns_filter.exe`
- Check antivirus didn't quarantine the file

**Error: "Failed to load configuration"**

Solution:
- Verify `config/rules.json` exists in the same directory
- Check JSON syntax is valid

## Testing the Build

1. Start the filter (as Administrator)

2. Open another Command Prompt and test DNS queries:
   ```cmd
   nslookup example.com
   nslookup google.com
   ```

3. Check the log file:
   ```cmd
   type dns_filter.log
   ```

4. You should see DNS queries being logged

## Development Workflow

For development and testing:

1. Make code changes in `src/` or `include/`

2. Rebuild:
   ```cmd
   cd build
   cmake --build . --config Release
   ```

3. Test the changes:
   ```cmd
   cd Release
   dns_filter.exe
   ```

## Clean Build

To perform a clean build:

```cmd
# Remove build directory
rmdir /s /q build

# Create new build
mkdir build
cd build
cmake .. -G "Visual Studio 17 2022"
cmake --build . --config Release
```

## Advanced: Cross-Compilation

To build from Linux/macOS for Windows:

1. Install MinGW cross-compiler

2. Configure CMake with toolchain:
   ```bash
   cmake .. -DCMAKE_TOOLCHAIN_FILE=mingw-w64-toolchain.cmake
   ```

3. Build:
   ```bash
   make
   ```

Note: You still need to copy WinDivert files on the target Windows machine.

## Next Steps

After successful build:

1. Read [README.md](README.md) for usage instructions
2. Edit `config/rules.json` to customize filtering rules
3. Review logs in `dns_filter.log`

## Getting Help

If you encounter issues:

1. Check the [Troubleshooting](#troubleshooting) section above
2. Verify all prerequisites are installed correctly
3. Ensure WinDivert files are copied correctly
4. Check build output for specific error messages

---

Happy filtering!