Fix Windows build: add conditional headers for sys/socket.h

- Add #ifdef _WIN32 to use winsock2.h/ws2tcpip.h instead of sys/socket.h
- Update build.sh to support both Linux and Windows/MSYS2
- Auto-detect platform and configure accordingly (--host=x86_64-w64-mingw32 for Windows)
- All 22 tests pass on Linux

build.sh

@@ -0,0 +1,112 @@
+#!/bin/bash
+# Build script for uTun (supports both Linux and Windows/MSYS2)
+# Usage: ./build.sh [options]
+# Options:
+#   -h, --help      Show this help
+#   --clean         Clean before build
+#   -j[N]           Build with N parallel jobs (default: 4)
+
+set -e  # Exit on error
+
+# Detect platform
+if [[ "$OSTYPE" == "msys" ]] || [[ "$OSTYPE" == "cygwin" ]] || [[ -n "$MSYSTEM" ]]; then
+    IS_WINDOWS=1
+    echo "Detected Windows/MSYS2 environment"
+else
+    IS_WINDOWS=0
+    echo "Detected Linux environment"
+fi
+
+# Parse arguments
+CLEAN=0
+JOBS="-j4"
+MAKE_ARGS=""
+
+while [[ $# -gt 0 ]]; do
+    case $1 in
+        -h|--help)
+            echo "Usage: ./build.sh [options]"
+            echo "Options:"
+            echo "  -h, --help      Show this help"
+            echo "  --clean         Clean before build"
+            echo "  -j[N]           Build with N parallel jobs (default: 4)"
+            exit 0
+            ;;
+        --clean)
+            CLEAN=1
+            shift
+            ;;
+        -j*)
+            JOBS="$1"
+            shift
+            ;;
+        *)
+            MAKE_ARGS="$MAKE_ARGS $1"
+            shift
+            ;;
+    esac
+done
+
+# Check required tools
+if ! command -v gcc &> /dev/null; then
+    echo "Error: gcc not found."
+    if [ "$IS_WINDOWS" -eq 1 ]; then
+        echo "Please install: pacman -S mingw-w64-ucrt-x86_64-toolchain"
+    else
+        echo "Please install build-essential or gcc"
+    fi
+    exit 1
+fi
+
+# Clean if requested
+if [ "$CLEAN" -eq 1 ]; then
+    echo "Cleaning build..."
+    make clean 2>/dev/null || true
+    rm -f config.status config.h
+fi
+
+# Check if configure script exists
+if [ ! -f ./configure ]; then
+    echo "Configure script not found. Generating..."
+    if ! command -v autoreconf &> /dev/null; then
+        echo "Error: autoreconf not found."
+        if [ "$IS_WINDOWS" -eq 1 ]; then
+            echo "Install autotools: pacman -S autoconf automake libtool"
+        else
+            echo "Install autotools: apt-get install autoconf automake libtool"
+        fi
+        exit 1
+    fi
+    autoreconf -fiv
+fi
+
+# Run configure if needed
+if [ ! -f config.status ] || [ config.status -ot configure ]; then
+    echo "Configuring build..."
+    if [ "$IS_WINDOWS" -eq 1 ]; then
+        # Windows: configure for mingw
+        ./configure --prefix=/usr/local --host=x86_64-w64-mingw32 2>&1 | tee configure.log
+    else
+        # Linux: standard configure
+        ./configure --prefix=/usr/local 2>&1 | tee configure.log
+    fi
+else
+    echo "Using existing configuration."
+fi
+
+# Build
+echo "Compiling with $JOBS..."
+if [ "$IS_WINDOWS" -eq 1 ]; then
+    make $JOBS $MAKE_ARGS 2>&1 | tee build_win.log
+else
+    make $JOBS $MAKE_ARGS 2>&1 | tee build_linux.log
+fi
+
+echo ""
+echo "Build completed successfully!"
+if [ "$IS_WINDOWS" -eq 1 ]; then
+    echo "Binary: src/utun.exe"
+    echo "Make sure wintun.dll is in the same directory as utun.exe"
+else
+    echo "Binary: src/utun"
+fi

lib/debug_config.h

@@ -6,7 +6,12 @@
 #ifndef DEBUG_CONFIG_H
 #define DEBUG_CONFIG_H
 
-#include <sys/socket.h>   // struct sockaddr_storage
+#ifdef _WIN32
+    #include <winsock2.h>
+    #include <ws2tcpip.h>
+#else
+    #include <sys/socket.h>   // struct sockaddr_storage
+#endif
 #include <stddef.h>       // size_t
 #include <stdint.h>
 #include <stddef.h>