waterutil: doc.go: added packet format diagrams

waterutil/doc.go

@@ -26,26 +26,26 @@ TAP - MAC Frame:
   +-----------------------------------------------------------------------------
 
 TUN - IPv4 Packet:
-  +-----------------------------------------------------------------------------------------------------------------+
-  | Offsets | Octet |           0           |           1           |           2           |           3           |
-  |  Octet  |  Bit  |00|01|02|03|04|05|06|07|08|09|10|11|12|13|14|15|16|17|18|19|20|21|22|23|24|25|26|27|28|29|30|31|
-  +-----------------------------------------------------------------------------------------------------------------+
-  |    0    |   0   |  Version  |    IHL    |      DSCP       | ECN |                 Total  Length                 |
-  +-----------------------------------------------------------------------------------------------------------------+
-  |    4    |  32   |                Identification                 | Flags  |           Fragment Offset            |
-  +-----------------------------------------------------------------------------------------------------------------+
-  |    8    |  64   |     Time To Live      |       Protocol        |                Header Checksum                |
-  +-----------------------------------------------------------------------------------------------------------------+
-  |   12    |  96   |                                       Source IP Address                                       |
-  +-----------------------------------------------------------------------------------------------------------------+
-  |   16    |  128  |                                    Destination IP Address                                     |
-  +-----------------------------------------------------------------------------------------------------------------+
-  |   20    |  160  |                                     Options (if IHL > 5)                                      |
-  +-----------------------------------------------------------------------------------------------------------------+
-  |   24    |  192  |                                                                                               |
-  |   30    |  224  |                                            Payload                                            |
-  |   ...   |  ...  |                                                                                               |
-  +-----------------------------------------------------------------------------------------------------------------+
+  +---------------------------------------------------------------------------------------------------------------+
+  |       | Octet |           0           |           1           |           2           |           3           |
+  | Octet |  Bit  |00|01|02|03|04|05|06|07|08|09|10|11|12|13|14|15|16|17|18|19|20|21|22|23|24|25|26|27|28|29|30|31|
+  +---------------------------------------------------------------------------------------------------------------+
+  |   0   |   0   |  Version  |    IHL    |      DSCP       | ECN |                 Total  Length                 |
+  +---------------------------------------------------------------------------------------------------------------+
+  |   4   |  32   |                Identification                 | Flags  |           Fragment Offset            |
+  +---------------------------------------------------------------------------------------------------------------+
+  |   8   |  64   |     Time To Live      |       Protocol        |                Header Checksum                |
+  +---------------------------------------------------------------------------------------------------------------+
+  |  12   |  96   |                                       Source IP Address                                       |
+  +---------------------------------------------------------------------------------------------------------------+
+  |  16   |  128  |                                    Destination IP Address                                     |
+  +---------------------------------------------------------------------------------------------------------------+
+  |  20   |  160  |                                     Options (if IHL > 5)                                      |
+  +---------------------------------------------------------------------------------------------------------------+
+  |  24   |  192  |                                                                                               |
+  |  30   |  224  |                                            Payload                                            |
+  |  ...  |  ...  |                                                                                               |
+  +---------------------------------------------------------------------------------------------------------------+
 
 */
 package waterutil