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== A Simple ASCII Header Generator for Network Protocols ==

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Written by:

Luis MartinGarcia.

-> E-Mail: luis.mgarc@gmail.com

-> WWWW: http://www.luismg.com

-> GitHub: https://github.com/luismartingarcia

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TABLE OF CONTENTS

0x01 Introduction............................................................. 0x02 Downloading Protocol...................................................... 0x03 Installing Protocol...................................................... 0x04 Running Protocol......................................................... |_ 0x04.1 Displaying Existing Protocols...................................... |_ 0x04.2 Displaying Custom Protocols........................................ | |_ 0x04.2.1 Field Lists................................................. | |_ 0x04.2.2 Options..................................................... |_ 0x04.3 Command-line Options............................................... 0x05 Examples................................................................. 0x06 Contact, Support and Bug Reporting.......................................

0x01 - INTRODUCTION

Protocol is a simple command-line tool that serves two purposes:

• Provide a simple way for engineers to have a look at standard network protocol headers, directly from the command-line, without having to google for the relevant RFC or for ugly header image diagrams.

• Provide a way for researchers and engineers to quickly generate ASCII RFC-like header diagrams for their own custom protocols.

0x02 - DOWNLOADING PROTOCOL

The latest version of protocol is available via GitHub. It can be downloaded directly from the following website clicking on the button "Download ZIP".

https://github.com/luismartingarcia/protocol

Alternatively, the code can be checked out using GIT, running the following command:

git clone https://github.com/luismartingarcia/protocol.git

If prompted for a username and password, don't enter any, just hit Enter.

Documentation and extra information is always available through the following site:

http://www.luismg.com/protocol

0x03 - INSTALLING PROTOCOL

Protocol can be installed by running the included setup.py script as follows:

setup.py install

Note that in order to install Protocol, root or administrative privileges are required. On GNU/Linux systems, it can be installed as follows:

sudo ./setup.py install

0x04 - RUNNING PROTOCOL

Once installed, Protocol can be run from the command line. The syntax is the following:

protocol <EXISTING_PROTOCOL_NAME(S)>

or

protocol <CUSTOM_PROTOCOL_SPECIFICATION(S)>

The following subsections describe each approach.

0x04.1 Displaying Existing Protocols

The first approach lets users print ASCII headers for existing network protocols. In particular, the following protocols are available.

"ethernet"            : Ethernet
"8021q"               : IEEE 802.1q
"dot1q"               : IEEE 802.1q
"tcp"                 : Transmission Control Protocol (TCP)
"udp"                 : User Datagram Protocol (TCP)
"ip"                  : Internet Protocol (IP), version 4.
"ipv6"                : Internet Protocol (IP), version 6.
"icmp"                : Internet Control Message Protocol (ICMP)
"icmp-destination":   : ICMP Destination Unreachable
"icmp-time"           : ICMP Time Exceeded
"icmp-parameter"      : ICMP Parameter Problem
"icmp-source"         : ICMP Source Quench
"icmp-redirect"       : ICMP Redirect
"icmp-echo"           : ICMP Echo Request/Reply
"icmp-timestamp"      : ICMP Timestamp Request/Reply
"icmp-information"    : ICMP Information Request/Reply
"icmpv6"              : Internet Control Message Protocol for IPv6 (ICMPv6)
"icmpv6-destination"  : ICMPv6 Destination Unreachable
"icmpv6-big"          : ICMPv6 Packet Too Big
"icmpv6-time"         : ICMPv6 Time Exceeded
"icmpv6-parameter"    : ICMPv6 Parameter Problem
"icmpv6-echo"         : ICMPv6 Echo Request/Reply
"icmpv6-rsol"         : ICMPv6 Router Solicitation
"icmpv6-radv"         : ICMPv6 Router Advertisement
"icmpv6-nsol"         : ICMPv6 Neighbor Solicitation
"icmpv6-nadv"         : ICMPv6 Neighbor Advertisement
"icmpv6-redirect"     : ICMPv6 Redirect

One or more of the protocols listed above can be printed. Here are a few examples:

protocol tcp
protocol dot1q
protocol tcp udp
protocol ipv6 icmpv6 icmpv6-redirect

Note that protocol names don't need to be fully specified, as long as there is no ambiguity. For example 'protocol et' is equivalent to 'protocol ethernet'. Whenever there is ambiguity (e.g. 'protocol icmpv6-r', a list of possible options will be displayed.

$ protocol icmpv6-r
Ambiguous protocol specifier 'icmpv6-r'. Did you mean any of these?
  icmpv6-radv
  icmpv6-redirect
  icmpv6-rsol

0x04.1 Displaying Custom Protocols

Apart from already existing protocols, Protocol can represent any arbitrary protocol headers. In order to do that, instead of specifying the name of an existing protocol, a custom protocol specification may be supplied. Such specification must follow a simple but specific syntax:

"<LIST_OF_FIELDS>[?OPTIONS]"

Where [LIST_OF_FIELDS] is a comma-separated list of protocol field names and lengths (expressed in bits), and [?OPTIONS] is an optional part that allows users to specify format modifiers for the ASCII header. Note that if any of the field names contains spaces, the protocol specification must be enclosed in double quotes.

0x04.2.1 Field Lists

The most important part of a protocol specification are field lists. This
is just a comma-separated list of name:length tuples, where name represents
the text that describes the protocol field and can contain any character,
except for '?' and length is an integer greater than zero, representing the
number of bits the field takes in the header. Here are a few examples:

Type:8,Code:8,Checksum:16,Message Body:64
Source Port:16,Destination Port:16,Length:16,Checksum:16

Note that there is no whitespace after the commas. This is a restriction
that must be respected.

Also, note that field lengths don't need to align to the length of the
line. If a particular field is too long, Protocol will just wrap it to the
next line. Here are some examples:

$ protocol "Source:16,TTL:8,Reserved:40"
 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|             Source            |      TTL      |               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               +
|                            Reserved                           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


$ protocol "Source:16,Reserved:40,TTL:8"
 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|             Source            |                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               +-+-+-+-+-+-+-+-+
|                    Reserved                   |      TTL      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

$ protocol "Reserved:32,Target Address:128"
 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                            Reserved                           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
+                                                               +
|                                                               |
+                         Target Address                        +
|                                                               |
+                                                               +
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

0x04.2.2 Options

Once the list of fields has been specified, users may optionally pass
formatting options to control the way the ASCII header is generated.
Options are supplied as a comma-separated list of label=value elements.
The first one is preceded by the '?' sign, which lets Protocol figure out
where the field list ends and where the list of options begins. The options
currently available are the following:

bits=<n>       : Number of bits per line. By default it's 32, same as IETF.
                 This is useful for protocols that don't align perfectly to
                 32-bit words, like Ethernet.
numbers=<Y/N>  : Instructs protocol to print or avoid printing the bit
                 counts on top of the header.
evenchar=<c>   : Instructs protocol to use the supplied character, instead
                 of the default "-" as the character in even positions of
                 the horizontal lines.
oddchar=<c>    : Same as evenchar but for characters in odd positions of the
                 horizontal lines. By default it takes the value '+'
startchar=<c>  : Instructs protocol to use the supplied character instead
                 of the default "+" for the first position of a horizontal
                 line.
endchar=<c>    : Same as startchar but for the character in the last
                 position of the horizontal lines.
sepchar=<c>    : Instructs protocol to use the supplied character instead
                 of the default "|" for the field separator character.

The following diagram shows the character modifiers described above.

   Bit counts                                                     sepchar(|)
     ^   ^                                                              |
     |   |                                                              |
     |   |                                                              |
     0   |               1                   2                   3      |
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |
    |             Source            |      TTL      |    Reserved   | <-+
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ^              ^ ^ ^              ^ ^ ^                         ^
    |              | | |              | | |                         |
 startchar(+)     evenchar( -)       oddchar(+)                endchar(+)

    |<------------------------------------------------------------->|
                               bits(32)

0x04.3 Command-line Options

Apart from per-protocol format specifiers, Protocol can also be configured
using command-line parameter. The following list provides a description of
each option available.

Usage: protocol {<protocol> or <spec>} [OPTIONS]
PARAMETERS:
 <protocol>          : Name of an existing protocol
 <spec>              : Field by field specification of non-existing protocol
OPTIONS:
 -b, --bits <n>      : Number of bits per line
 -f, --file          : Read specs from a text file
 -h, --help          : Displays this help information
 -n, --no-numbers    : Do not print bit numbers on top of the header
 -V, --version       : Displays current version
 --evenchar  <char>  : Character for the even positions of horizontal lines
 --oddchar   <char>  : Character for the odd positions of horizontal lines
 --startchar <char>  : Character that starts horizontal lines
 --endchar   <char>  : Character that ends horizontal lines
 --sepchar   <char>  : Character that separates protocol fields

0x05 - EXAMPLES

This section presents additional examples on how to run protocol.

$ protocol tcp
 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|          Source Port          |        Destination Port       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                        Sequence Number                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                     Acknowledgment Number                     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Offset|  Res. |     Flags     |             Window            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|            Checksum           |         Urgent Pointer        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                    Options                    |    Padding    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


$ protocol "Source Port:16,Destination Port:16,Sequence Number:32,\
  Acknowledgment Number:32,Offset:4,Res.:4,Flags:8,Window:16,Checksum:16,\
  Urgent Pointer:16,Options:24,Padding:8"
 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|          Source Port          |        Destination Port       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                        Sequence Number                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                     Acknowledgment Number                     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Offset|  Res. |     Flags     |             Window            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|            Checksum           |         Urgent Pointer        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                    Options                    |    Padding    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


$ protocol "Field4:4,Field4:4,Field8:8,Field16:16,Field32:32,Field64:64?\
  bits=16,numbers=y,startchar=*,endchar=*,evenchar=-,oddchar=-,sepchar=|"
 0                   1
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
*-------------------------------*
| Field4| Field4|     Field8    |
*-------------------------------*
|            Field16            |
*-------------------------------*
|                               |
*            Field32            *
|                               |
*-------------------------------*
|                               |
*                               *
|                               |
*            Field64            *
|                               |
*                               *
|                               |
*-------------------------------*


$ protocol ip --bits 16
 0                   1
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version|  IHL  |Type of Service|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|          Total Length         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|         Identification        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Flags|     Fragment Offset     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Time to Live |    Protocol   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|        Header Checksum        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                               |
+         Source Address        +
|                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                               |
+      Destination Address      +
|                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|            Options            |
+               +-+-+-+-+-+-+-+-+
|               |    Padding    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


$ protocol udp --oddchar "-" --startchar "-" --endchar "-"
 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-----------------------------------------------------------------
|          Source Port          |        Destination Port       |
-----------------------------------------------------------------
|             Length            |            Checksum           |
-----------------------------------------------------------------


$ protocol ipv6 --no-numbers
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Traffic Class |               Flow Label              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|         Payload Length        |  Next Header  |   Hop Limit   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
+                                                               +
|                                                               |
+                         Source Address                        +
|                                                               |
+                                                               +
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
+                                                               +
|                                                               |
+                       Destination Address                     +
|                                                               |
+                                                               +
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


$ protocol udp icmp
 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|          Source Port          |        Destination Port       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|             Length            |            Checksum           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Type     |      Code     |            Checksum           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
+                          Message Body                         +
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

0x06 - CONTACT, SUPPORT AND BUG REPORTING

For any questions, bug reports, bug fixes, feature requests, code contributions, etc, please contact me using the e-mail address displayed on the header of this file. Please note that Protocol's support is just like IP transport: best-effort. I will do my best to deal with your enquiries but no guarantees. Special support packages are available for those willing to send me real $ via Paypal ;-)