add flag to specify alternative filepath to secret

For the hyp client to be able to support multiple servers, each with their own secret, this capability is requried.

hyp/cmd/knock.go

@@ -31,8 +31,14 @@ Example usage:
 	`,
 	Args: cobra.ExactArgs(1),
 	Run: func(cmd *cobra.Command, args []string) {
+
 		// load secret and generate ports using secret and current time
-		secretBytes, err := os.ReadFile("hyp.secret")
+		secretFilePath, err := cmd.Flags().GetString("secret")
+		if err != nil {
+			panic(fmt.Errorf("failed to parse command flag 'secret': %w", err))
+		}
+
+		secretBytes, err := os.ReadFile(secretFilePath)
 		if err != nil {
 			log.Fatalf("failed to read file 'hyp.secret': %v", err)
 		}
@@ -56,4 +62,6 @@ Example usage:
 
 func init() {
 	rootCmd.AddCommand(knockCmd)
+
+	knockCmd.PersistentFlags().String("secret", "hyp.secret", "Path to the file containing the hyp secret.")
 }

hypd/server/packet.go

@@ -36,7 +36,7 @@ var (
 	sharedSecret   string             // base32 encoded shared secret used for totp
 )
 
-// packetServer is the main function when operating in server mode
+// PacketServer is the main function when operating in server mode
 // it sets up the pcap on the capture device and starts a goroutine
 // to rotate the knock sequence
 func PacketServer(captureDevice string) error {
@@ -50,7 +50,7 @@ func PacketServer(captureDevice string) error {
 	knockSequences = []KnockSequence{}
 
 	// Open pcap handle on device
-	handle, err := pcap.OpenLive(captureDevice, 1600, true, pcap.BlockForever)
+	handle, err := pcap.OpenLive(captureDevice, 126, true, pcap.BlockForever)
 	if err != nil {
 		return fmt.Errorf("failed to open pcap on capture device: %w", err)
 	}