Function LoadWinPCAP

pcap/pcap_windows.go:162–253

LoadWinPCAP attempts to dynamically load the wpcap DLL and resolve necessary functions

()

// LoadWinPCAP attempts to dynamically load the wpcap DLL and resolve necessary functions
func LoadWinPCAP() error {
	if pcapLoaded {
		return nil
	}

	kernel32, err := syscall.LoadLibrary("kernel32.dll")
	if err != nil {
		return fmt.Errorf("couldn't load kernel32.dll")
	}
	defer syscall.FreeLibrary(kernel32)

	initDllPath(kernel32)

	if haveSearch, _ := syscall.GetProcAddress(kernel32, "AddDllDirectory"); haveSearch != 0 {
		// if AddDllDirectory is present, we can use LOAD_LIBRARY_* stuff with LoadLibraryEx to avoid wpcap.dll hijacking
		// see: https://msdn.microsoft.com/en-us/library/ff919712%28VS.85%29.aspx
		const LOAD_LIBRARY_SEARCH_USER_DIRS = 0x00000400
		const LOAD_LIBRARY_SEARCH_SYSTEM32 = 0x00000800
		wpcapHandle, err = windows.LoadLibraryEx("wpcap.dll", 0, LOAD_LIBRARY_SEARCH_USER_DIRS|LOAD_LIBRARY_SEARCH_SYSTEM32)
		if err != nil {
			return fmt.Errorf("couldn't load wpcap.dll")
		}
	} else {
		// otherwise fall back to load it with the unsafe search cause by SetDllDirectory
		wpcapHandle, err = windows.LoadLibrary("wpcap.dll")
		if err != nil {
			return fmt.Errorf("couldn't load wpcap.dll")
		}
	}
	initLoadedDllPath(kernel32)
	msvcrtHandle, err = syscall.LoadLibrary("msvcrt.dll")
	if err != nil {
		return fmt.Errorf("couldn't load msvcrt.dll")
	}
	callocPtr, err = syscall.GetProcAddress(msvcrtHandle, "calloc")
	if err != nil {
		return fmt.Errorf("couldn't get calloc function")
	}

	pcapStrerrorPtr = mustLoad("pcap_strerror")
	pcapStatustostrPtr = mightLoad("pcap_statustostr") // not available on winpcap
	pcapOpenLivePtr = mustLoad("pcap_open_live")
	pcapOpenOfflinePtr = mustLoad("pcap_open_offline")
	pcapClosePtr = mustLoad("pcap_close")
	pcapGeterrPtr = mustLoad("pcap_geterr")
	pcapStatsPtr = mustLoad("pcap_stats")
	pcapCompilePtr = mustLoad("pcap_compile")
	pcapFreecodePtr = mustLoad("pcap_freecode")
	pcapLookupnetPtr = mustLoad("pcap_lookupnet")
	pcapOfflineFilterPtr = mustLoad("pcap_offline_filter")
	pcapSetfilterPtr = mustLoad("pcap_setfilter")
	pcapListDatalinksPtr = mustLoad("pcap_list_datalinks")
	pcapFreeDatalinksPtr = mustLoad("pcap_free_datalinks")
	pcapDatalinkValToNamePtr = mustLoad("pcap_datalink_val_to_name")
	pcapDatalinkValToDescriptionPtr = mustLoad("pcap_datalink_val_to_description")
	pcapOpenDeadPtr = mustLoad("pcap_open_dead")
	pcapNextExPtr = mustLoad("pcap_next_ex")
	pcapDatalinkPtr = mustLoad("pcap_datalink")