Fix slow exchanges on linux by adding polling and other improvements (#14)

* add prints to investigate slowness

* add loop sleep for blocking Stack

* add connection close http attribute and detect end of HTML page

* add timeout to bridge read

* examples/xnet: add ntp timestamp to prints and show output in readme

* add polling to http tap interface

* more digits in ntp format

* prevent crashes on non-8 timestamp

internet/pcap/capture.go

@@ -671,6 +671,7 @@ const (
 	// FieldClassBinaryText represents long stretches of binary data such as BOOTP DHCPv4 field.
 	FieldClassBinaryText // binary-text
 	FieldClassOperation  // op
+	FieldClassTimestamp  // timestamp
 )
 
 const octet = 8
@@ -1058,25 +1059,25 @@ var baseNTPFields = [...]FrameField{
 	},
 	{
 		Name:           "Reference Time",
-		Class:          FieldClassText,
+		Class:          FieldClassTimestamp,
 		FrameBitOffset: 16 * octet,
 		BitLength:      8 * octet,
 	},
 	{
 		Name:           "Origin Time",
-		Class:          FieldClassText,
+		Class:          FieldClassTimestamp,
 		FrameBitOffset: 24 * octet,
 		BitLength:      8 * octet,
 	},
 	{
 		Name:           "Receive Time",
-		Class:          FieldClassText,
+		Class:          FieldClassTimestamp,
 		FrameBitOffset: 32 * octet,
 		BitLength:      8 * octet,
 	},
 	{
 		Name:           "Transit Time",
-		Class:          FieldClassText,
+		Class:          FieldClassTimestamp,
 		FrameBitOffset: 40 * octet,
 		BitLength:      8 * octet,
 	},