# SPDX-License-Identifier: MIT
#
# Makefile for eBPF Port Knocking Programs
# Supports both Linux (using libbpf) and Windows eBPF (using eBPF for Windows)
#

# Detect platform
ifeq ($(OS),Windows_NT)
    PLATFORM := windows
    EBPF_SDK_DIR := C:/Users/vagrant/Downloads/ebpf-for-windows
else
    UNAME_S := $(shell uname -s)
    ifeq ($(UNAME_S),Linux)
        PLATFORM := linux
        EBPF_SDK_DIR := /home/tlh/VMs/ebpf-for-windows
    else
        $(error Unsupported platform: $(UNAME_S))
    endif
endif

# Directories
SRC_DIR := .
OUT_DIR := out
INCLUDE_DIR := include

# Toolchain
CLANG := clang

# Output files
BPF_OBJ_LINUX := $(OUT_DIR)/port_knock_linux.o
BPF_OBJ_WINDOWS := $(OUT_DIR)/port_knock.o

# Compiler flags
COMMON_FLAGS := -Wall -Wextra -Wno-unused-value -O2 -g

# Linux-specific flags
LINUX_CFLAGS := -D__TARGET_ARCH_x86 -D__LINUX_BPF__ $(COMMON_FLAGS)
LINUX_INCLUDES := -I/usr/include/bpf -I/usr/include -I$(INCLUDE_DIR)

# Windows-specific flags
# Point to eBPF for Windows SDK headers
WINDOWS_CFLAGS := -D_WIN32 $(COMMON_FLAGS)
WINDOWS_INCLUDES := -I$(INCLUDE_DIR) -I$(EBPF_SDK_DIR)/include -I$(EBPF_SDK_DIR)/tests/include

.PHONY: all clean build-linux build-windows make-windows help

# Default target - show help
all: help

# Linux build
build-linux: $(BPF_OBJ_LINUX)

make-windows: $(BPF_OBJ_WINDOWS)

$(OUT_DIR):
	mkdir -p $(OUT_DIR)

$(BPF_OBJ_LINUX): $(SRC_DIR)/port_knock.c $(INCLUDE_DIR)/common.h | $(OUT_DIR)
	@echo "=== Building eBPF for Linux ==="
	$(CLANG) $(LINUX_CFLAGS) $(LINUX_INCLUDES) \
		-target bpf \
		-D__BPF_TRACING__ \
		-c $< -o $@
	@echo "Built: $@"
	@echo "  Sections: $$(bpftool prog show $$@ 2>/dev/null || echo '  (use bpftool to inspect)')"

# Windows build (using eBPF for Windows)
build-windows: $(BPF_OBJ_WINDOWS)

$(BPF_OBJ_WINDOWS): $(SRC_DIR)/port_knock.c $(INCLUDE_DIR)/common.h | $(OUT_DIR)
	@echo "=== Building eBPF for Windows ==="
	$(CLANG) $(WINDOWS_CFLAGS) $(WINDOWS_INCLUDES) \
		-target bpf \
		-c $< -o $@
	@echo "Built: $@"

# Verify program
verify: $(BPF_OBJ_LINUX)
	@echo "=== Verifying eBPF program ==="
	@bpftool prog show $(BPF_OBJ_LINUX) 2>/dev/null || echo "Use bpftool to verify"

# Show sections
show-sections: $(BPF_OBJ_LINUX)
	@bpftool prog show $(BPF_OBJ_LINUX)

# Show disassembly
show-disasm: $(BPF_OBJ_LINUX)
	@bpftool prog disasm $(BPF_OBJ_LINUX)

# Clean
clean:
	rm -rf $(OUT_DIR)

# Help
help:
	@echo "eBPF Port Knocking Program - Build System"
	@echo ""
	@echo "Targets:"
	@echo "  build-linux     Build for Linux eBPF (using libbpf/aya)"
	@echo "  build-windows   Build for Windows eBPF (using eBPF for Windows)"
	@echo "  verify          Verify the compiled program"
	@echo "  show-sections   Show eBPF program sections"
	@echo "  show-disasm     Show disassembly of the program"
	@echo "  clean           Remove build artifacts"
	@echo ""
	@echo "Usage:"
	@echo "  Linux:   make build-linux"
	@echo "  Windows: make build-windows"
	@echo ""
	@echo "Prerequisites:"
	@echo "  Linux:   clang, libbpf, bpftool"
	@echo "  Windows: clang, eBPF for Windows SDK (at Z:/ebpf-for-windows)"