How to automatically prefill command on the Linux bash

Linux Bash is one of the most famous Linux shells. It offers a great number of features like for example spawning and controlling process, redirecting streams, supporting scripts and a flexible way to control you editing line.

Problem

How to automatically pre-populate a command on the shell after prompt.

Solution description

The shell has tree default streams: stdout, stdin and stderr. By manipulating the stdin of the process we can simulate typing a command.

Reference implementation

The original script can be found here: https://github.com/rtomaszewski/experiments/blob/master/type-command.c

Demonstration

• Compile first the program

gcc -o type-command type-command.c

• Run for the firs time

# ./type-command
type-command: the variable TYPE_CMD_ENABLED is not set, set it to 'no' to surpress this message; set the TYPE_CMD_TYPE for the command to type

Example: export TYPE_CMD_ENABLED=yes; export TYPE_CMD_TYPE=date

• Export the variable to controls if the program should try to type a command or not

# export TYPE_CMD_ENABLED=yes
# ./type-command
#

• Specify the command that you wish to be typed

# export TYPE_CMD_ENABLED=yes; export TYPE_CMD_TYPE=date
# ./type-command
# date
Sun Mar 30 19:27:55 UTC 2014>

References

http://stackoverflow.com/questions/10866005/bash-how-to-prefill-command-line-input
http://stackoverflow.com/questions/11198603/inject-keystroke-to-different-process-using-bash
http://unix.stackexchange.com/questions/48103/construct-a-command-by-putting-a-string-into-a-tty

http://fossies.org/linux/misc/old/console-tools-0.3.3.tar.gz%3at/console-tools-0.3.3/vttools/writevt.c

http://man7.org/linux/man-pages/man4/tty_ioctl.4.html
http://man7.org/linux/man-pages/man3/tcflush.3.html
http://www.tldp.org/LDP/lpg/node143.html

How to create a sequence of replace commands to change your file

Use existing plugin: RegReplace

We could write a custom plugin using the Sublime API or try to use a plugin that promises to offer this functionality already: https://github.com/facelessuser/RegReplace

Demonstration

We have a following structured but not consistently formatted data that we would like to adjust so it is easier toread and work with.

To reformat the text we can use the above plugin and define a series of regex that match and modify text.

• Installed RegReplace plugin.
• Create a reg_replace.sublime-settings in your Sublime2\Data\Packages\User\ directory and define the regex commands we want to use.

{
    "replacements": {
        // add teh .<digit> when is missing
        "ig_order_add_dot_digit": {
            "find": "([0-9][0-9]) at",
            "replace": "\\1.0 at"
//            "greedy": true,
//            "case": false
        },
        "ig_order_add_dot_digit2": {
            "find": "([0-9][0-9]) *- ",
            "replace": "\\1.0 - ",
            "greedy": true
        },
        "ig_order_fix_spaces": {
            "find": "/(201[0-9]) *",
            "replace": "/\\1 "
        },
        "ig_order_fix_spaces2": {
            "find": "-   -    -  ",
            "replace": "-    -    -     "
        },
        "ig_order_change_android_str": {
            "find": "AndroidApp",
            "replace": "AndrAp"
        },
        "ig_order_remove_str": {
            "find": "/s ",
            "replace": " ",
            "greedy": true
        },
        "ig_order_fix_header": {
            "find": "(Date) *(Time) *(Activity) *(Market) *(Period) *(Channel) *(Currency) *(Size) *(Level) *(Stop) *(Type) *(Limit) *(Result)",
            "replace": "Date        Time    Activity Market                                               Period              Channel Cur Size Level  Stop Type Limit Result",
            "greedy": true
        },



        "ig_transactions_fix_header": {
            "find": "(Type) *(Date) *(Ref) *(Market) *(Period) *(Opening) *(Ccy) *(Size) *(Closing) *(P/L)",
            "replace": "Type    Date        Ref         Market                                                  Period            Opening Ccy Size    Closing P/L",
            "greedy": true
        },
       "ig_transactions_add_dot_digit": {
            "find": "([0-9][0-9]) +£",
            "replace": "\\1.0 £"
        },
        "ig_transactions_add_dot_digit2": {
            "find": "(£ +.*\\..* +)([0-9]+) +",
            "replace": "\\1\\2.0 "
        },
        "ig_transactions_fix_plus_minus_sign": {
            "find": "([0-9]+\\.[0-9]+ +[0-9]+\\.[0-9]+ +)([0-9]+\\.[0-9]+)",
            "replace": "\\1 \\2"
        }

    }
}

• Define the final  regex command to run and associate a a keyboard short in Default (Windows).sublime-keymap file

[
{ 
    {
        "keys": ["alt+ctrl+t"],
        "command": "reg_replace",
        "args": {"replacements": [
                                    // orders
                                    "ig_order_add_dot_digit",
                                    "ig_order_add_dot_digit2",
                                    "ig_order_fix_spaces",
                                    "ig_order_fix_spaces2",
                                    "ig_order_change_android_str",
                                    "ig_order_remove_str",
                                    "ig_order_fix_header",

                                    // transactions
                                    "ig_transactions_fix_header",
                                    "ig_transactions_add_dot_digit",
                                    "ig_transactions_add_dot_digit2",
                                    "ig_transactions_fix_plus_minus_sign"


                                ],  "find_only": true}
    }
]

• When you activate the regex chain command it will first show what part of the file are going to be changed

• Accept the "yes" option at the bottom and reformat the file

How to write a plugin for Sublime editor

Below is a list of links for Sublime API and Sublime commands if you want to write a custom plugins.

Sublime API

https://www.sublimetext.com/docs/api-reference
https://www.sublimetext.com/docs/2/api_reference.html

Commands

http://sublimetext.info/docs/en/core/commands.html
http://www.sublimetext.com/docs/commands

Debug best practices

Once you follow the steps below everything you do in the editor will be logged on the console.

• Open Sublime console: Ctrl+~
• Enable verbose and debug within the editor

sublime.log_commands(True)
sublime.log_input(True)

• Example commands to try on the console 

view.run_command("goto_line", {"line": 7})
view.window().run_command("show_minimap", {"key": True})

Interface redundancy on the host with TCP Multipath

TCP and UDP protocols are used exchange data between hosts. They have been used for a decade or longer and are very well documented how they work.

Everyone knows the problem that when you lost your active link on the server all your TCP sessions are going to die as well. Let's say your server has 2 active interfaces. There is no way to move/migrate a TCP session to use another active interface (by default). The other link can't be used automatically as a fail back mechanism.

There are couple of reasons behind why it isn't to works, the simplest one is that the new link used a different IP address. Even if the Linux kernel would start using the new interface and start sending IP/TCP packets sourced with the new IP address these packets wouldn't be recognized on the remote site. The remote site expect tcp segments from one and only one IP source.

Problem

How to provide a link level redundancy on the server to keep a TCP session alive even if one interface experience an error.

Analysis and solution Demonstration

The problem could be see as a more generic issue: how to implement multihoming or link redundancy. There are couple of working solution out there. The simplest example:

• Link bonding(link aggregation) on the server; requires support and proper configuration on the switch and the server

We will look at another one: TCP Multipath. What is cool about this is that it is transparent to your application. It visualizes a session and provide a single TCP session to the application that can benefit from built-in multipath redundancy on the kernel level.

References

http://multipath-tcp.org/
Decoupled from IP, TCP is at last able to support multihomed hosts
https://devcentral.f5.com/articles/multipath-tcp-mptcp
https://devcentral.f5.com/articles/the-evolution-of-tcp

How to build a high performance network appliance like routers using commodity hardware and off the shelf components

You can assemble a server from off the shelf components that will be able to sent and receive traffic in multi Gigabit speed. Here is an example of an 10Gps net card from Intel.

But can we turn this server into a high performance network appliance? Do we still need a dedicated hardware like for example ASIC, FPGA, low latency RAM and TCAM RAM in network devise so they can efficiently switch and forward packets with maximum wire speed.

Router hardware design plan

Looking at this presentation from 2012 https://ripe64.ripe.net/presentations/18-ripe-64-router-architecture-challenges.pdf you would think that yes. These would be the obvious reasons (screenshots taken from the presentation):

Network processing unit (NPU) and new hardware design

The key points listed above still hold. But the next generation network appliances will be rather build with a help of a multicore generic NPU using the power of parallel processing than expensive and purposely design ASIC. With the right software (OS - often Linux, drivers, firmware, SDK, and API libraries) you will be able to turn a conventional x86 server with a modern PCIe data bus into a high performance, low latency and high speed network appliance.

Netronome Network Cards Accelerate SDN and NFV Designs
100Gps FlowNIC-6xxx network card
Hardware reference designs for FlowProcessor NPU chips

How to do URL based load balancing on F5

There are many load balancers out there. Some of them offer a great flexibility to control the traffic by allowing a user to upload a custom script that implement the load balancing algorithm to solve a particular problem.

Problem

How to do HTTP URL based load balancing on F5.

Solution and demonstration

This is an iRule script that inspects the HTTP GET URL string to decided where to load balance it: https://github.com/rtomaszewski/f5/blob/master/lb-based-on-url.tcl.

Create default pool

Create VIP

Create custom pools

Testing

To verify that our iRule is working properly we can enable debugging by changing the iRule variable DEBUG to 1.

Next we can simulate traffic

curl -v http://vip/
curl -v http://vip/url1
curl -v http://vip/url2
curl -v http://vip/url3

And watch the logs on the lb.

tail -f /var/log/ltm

Mar  2 15:49:37 local/tmm1 info tmm1[5232]: Rule rule-url-lb-vip-80 <HTTP_REQUEST>: '11.22.33.44': HTTP::uri eq /
Mar  2 15:49:37 local/tmm1 info tmm1[5232]: Rule rule-url-lb-vip-80 <HTTP_REQUEST>: '11.22.33.44': sent traffic to pool pool-vip-80
Mar  2 15:49:37 local/tmm info tmm[5231]: Rule rule-url-lb-vip-80 <HTTP_REQUEST>: '11.22.33.44': HTTP::uri eq /url1
Mar  2 15:49:37 local/tmm info tmm[5231]: Rule rule-url-lb-vip-80 <HTTP_REQUEST>: '11.22.33.44': sent traffic to pool pool-vip-80-url1
Mar  2 15:49:37 local/tmm1 info tmm1[5232]: Rule rule-url-lb-vip-80 <HTTP_REQUEST>: '11.22.33.44': HTTP::uri eq /url2
Mar  2 15:49:37 local/tmm1 info tmm1[5232]: Rule rule-url-lb-vip-80 <HTTP_REQUEST>: '11.22.33.44': sent traffic to pool pool-vip-80-url2
Mar  2 15:49:37 local/tmm1 info tmm1[5232]: Rule rule-url-lb-vip-80 <HTTP_REQUEST>: '11.22.33.44': HTTP::uri eq /url3
Mar  2 15:49:37 local/tmm1 info tmm1[5232]: Rule rule-url-lb-vip-80 <HTTP_REQUEST>: '11.22.33.44': sent traffic to pool pool-vip-80-url3

Reference

https://devcentral.f5.com/wiki/iRules.HomePage.ashx

Dirty trick how to analysis ASA performance based on interface overruns and underruns

There are number of firewall vendors on the market you can chose from (other links to Gartner magic quadrant for firewalls here and here). Every vendor has a product line ranging from the low to high end firewalls. An example product list for Cisco ASA can be seen here: http://www.cisco.com/c/en/us/products/security/asa-5500-series-next-generation-firewalls/models-comparison.html#~tab-b

Problem

I can see in my firewalls interface stats underruns and overrruns and the counters increase.

Solution

This is rather a dirty trick and your monitoring system should be able to graph the interface stats. But if you are in a position like me where you have no visibility to interface statistics like you could have in Zenoss, Cacti, Zabbix or other monitoring system you may need to manually check this...

• We need to first start collecting data so we can look at it later.

Run at least one a day the command and save in a file 1.txt, 2.txt, etc.

sh clock
sh int

• After some time you should have a collection of files 

$ ls -1 *.txt
1.txt
2.txt
3.txt
4.1.txt
4.2.txt
5.1.txt
6.1.txt
8.txt

An example outpout form the file can be seen here: https://github.com/rtomaszewski/experiments/blob/master/asa-interfaces-example.txt

• Download the script asa-interfaces.sh and run it 

bash asa-interfaces.sh

Base on the files you collected it will generate stats for every interface (time stamp is in the last column). Example output:

Interface GigabitEthernet0/0 "outside", is up, line protocol is up
        31 input errors, 0 CRC, 0 frame, 31 overrun, 0 ignored, 0 abort 07:48:45.631 cst Wed Feb 12 2014
        31 input errors, 0 CRC, 0 frame, 31 overrun, 0 ignored, 0 abort 05:38:08.573 cst Thu Feb 13 2014
        31 input errors, 0 CRC, 0 frame, 31 overrun, 0 ignored, 0 abort 03:37:26.853 cst Fri Feb 14 2014
        94 input errors, 0 CRC, 0 frame, 94 overrun, 0 ignored, 0 abort 03:52:52.523 cst Wed Feb 19 2014
        94 input errors, 0 CRC, 0 frame, 94 overrun, 0 ignored, 0 abort 10:03:08.799 cst Wed Feb 19 2014
        94 input errors, 0 CRC, 0 frame, 94 overrun, 0 ignored, 0 abort 06:11:22.244 cst Thu Feb 20 2014
        104 input errors, 0 CRC, 0 frame, 104 overrun, 0 ignored, 0 abort 08:35:21.315 cst Sun Feb 23 2014
        104 input errors, 0 CRC, 0 frame, 104 overrun, 0 ignored, 0 abort 08:22:57.704 cst Mon Feb 24 2014
Interface GigabitEthernet0/1 "dmz", is up, line protocol is up
        719 input errors, 0 CRC, 0 frame, 719 overrun, 0 ignored, 0 abort 07:48:45.631 cst Wed Feb 12 2014
        719 input errors, 0 CRC, 0 frame, 719 overrun, 0 ignored, 0 abort 05:38:08.573 cst Thu Feb 13 2014
        734 input errors, 0 CRC, 0 frame, 734 overrun, 0 ignored, 0 abort 03:37:26.853 cst Fri Feb 14 2014
        1502 input errors, 0 CRC, 0 frame, 1502 overrun, 0 ignored, 0 abort 03:52:52.523 cst Wed Feb 19 2014
        1794 input errors, 0 CRC, 0 frame, 1794 overrun, 0 ignored, 0 abort 10:03:08.799 cst Wed Feb 19 2014
        1881 input errors, 0 CRC, 0 frame, 1881 overrun, 0 ignored, 0 abort 06:11:22.244 cst Thu Feb 20 2014
        1921 input errors, 0 CRC, 0 frame, 1921 overrun, 0 ignored, 0 abort 08:35:21.315 cst Sun Feb 23 2014
        1971 input errors, 0 CRC, 0 frame, 1971 overrun, 0 ignored, 0 abort 08:22:57.704 cst Mon Feb 24 2014
Interface GigabitEthernet0/2 "myapp1", is up, line protocol is up
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 07:48:45.631 cst Wed Feb 12 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 05:38:08.573 cst Thu Feb 13 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 03:37:26.853 cst Fri Feb 14 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 03:52:52.523 cst Wed Feb 19 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 10:03:08.799 cst Wed Feb 19 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 06:11:22.244 cst Thu Feb 20 2014
        1 input errors, 0 CRC, 0 frame, 1 overrun, 0 ignored, 0 abort 08:35:21.315 cst Sun Feb 23 2014
        1 input errors, 0 CRC, 0 frame, 1 overrun, 0 ignored, 0 abort 08:22:57.704 cst Mon Feb 24 2014
Interface GigabitEthernet0/3 "state-failover", is up, line protocol is up
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 07:48:45.631 cst Wed Feb 12 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 05:38:08.573 cst Thu Feb 13 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 03:37:26.853 cst Fri Feb 14 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 03:52:52.523 cst Wed Feb 19 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 10:03:08.799 cst Wed Feb 19 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 06:11:22.244 cst Thu Feb 20 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 08:35:21.315 cst Sun Feb 23 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 08:22:57.704 cst Mon Feb 24 2014
Interface Management0/0 "lan-failover", is up, line protocol is up
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 07:48:45.631 cst Wed Feb 12 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 05:38:08.573 cst Thu Feb 13 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 03:37:26.853 cst Fri Feb 14 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 03:52:52.523 cst Wed Feb 19 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 10:03:08.799 cst Wed Feb 19 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 06:11:22.244 cst Thu Feb 20 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 08:35:21.315 cst Sun Feb 23 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 08:22:57.704 cst Mon Feb 24 2014
Interface GigabitEthernet1/0 "inside", is up, line protocol is up
        364 input errors, 0 CRC, 0 frame, 364 overrun, 0 ignored, 0 abort 07:48:45.631 cst Wed Feb 12 2014
        382 input errors, 0 CRC, 0 frame, 382 overrun, 0 ignored, 0 abort 05:38:08.573 cst Thu Feb 13 2014
        392 input errors, 0 CRC, 0 frame, 392 overrun, 0 ignored, 0 abort 03:37:26.853 cst Fri Feb 14 2014
        444 input errors, 0 CRC, 0 frame, 444 overrun, 0 ignored, 0 abort 03:52:52.523 cst Wed Feb 19 2014
        444 input errors, 0 CRC, 0 frame, 444 overrun, 0 ignored, 0 abort 10:03:08.799 cst Wed Feb 19 2014
        468 input errors, 0 CRC, 0 frame, 468 overrun, 0 ignored, 0 abort 06:11:22.244 cst Thu Feb 20 2014
        707 input errors, 0 CRC, 0 frame, 707 overrun, 0 ignored, 0 abort 08:35:21.315 cst Sun Feb 23 2014
        756 input errors, 0 CRC, 0 frame, 756 overrun, 0 ignored, 0 abort 08:22:57.704 cst Mon Feb 24 2014
Interface GigabitEthernet1/1 "app2", is up, line protocol is up
        640 input errors, 0 CRC, 0 frame, 640 overrun, 0 ignored, 0 abort 07:48:45.631 cst Wed Feb 12 2014
        658 input errors, 0 CRC, 0 frame, 658 overrun, 0 ignored, 0 abort 05:38:08.573 cst Thu Feb 13 2014
        683 input errors, 0 CRC, 0 frame, 683 overrun, 0 ignored, 0 abort 03:37:26.853 cst Fri Feb 14 2014
        797 input errors, 0 CRC, 0 frame, 797 overrun, 0 ignored, 0 abort 03:52:52.523 cst Wed Feb 19 2014
        811 input errors, 0 CRC, 0 frame, 811 overrun, 0 ignored, 0 abort 10:03:08.799 cst Wed Feb 19 2014
        863 input errors, 0 CRC, 0 frame, 863 overrun, 0 ignored, 0 abort 06:11:22.244 cst Thu Feb 20 2014
        984 input errors, 0 CRC, 0 frame, 984 overrun, 0 ignored, 0 abort 08:35:21.315 cst Sun Feb 23 2014
        1052 input errors, 0 CRC, 0 frame, 1052 overrun, 0 ignored, 0 abort 08:22:57.704 cst Mon Feb 24 2014
Interface GigabitEthernet1/2 "", is administratively down, line protocol is down
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 07:48:45.631 cst Wed Feb 12 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 05:38:08.573 cst Thu Feb 13 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 03:37:26.853 cst Fri Feb 14 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 03:52:52.523 cst Wed Feb 19 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 10:03:08.799 cst Wed Feb 19 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 06:11:22.244 cst Thu Feb 20 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 08:35:21.315 cst Sun Feb 23 2014
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 08:22:57.704 cst Mon Feb 24 2014



Interface GigabitEthernet0/0 "outside", is up, line protocol is up
        646983182 packets output, 473597063148 bytes, 0 underruns 07:48:45.631 cst Wed Feb 12 2014
        700155558 packets output, 509814505730 bytes, 0 underruns 05:38:08.573 cst Thu Feb 13 2014
        753341661 packets output, 546026853810 bytes, 0 underruns 03:37:26.853 cst Fri Feb 14 2014
        1025937535 packets output, 734304301602 bytes, 0 underruns 03:52:52.523 cst Wed Feb 19 2014
        1054530605 packets output, 761409276094 bytes, 0 underruns 10:03:08.799 cst Wed Feb 19 2014
        1105491616 packets output, 798565630885 bytes, 0 underruns 06:11:22.244 cst Thu Feb 20 2014
        1264871240 packets output, 907739984962 bytes, 0 underruns 08:35:21.315 cst Sun Feb 23 2014
        1315876113 packets output, 943680519398 bytes, 0 underruns 08:22:57.704 cst Mon Feb 24 2014
Interface GigabitEthernet0/1 "dmz", is up, line protocol is up
        985243431 packets output, 309823858329 bytes, 459 underruns 07:48:45.631 cst Wed Feb 12 2014
        1070533450 packets output, 336205856058 bytes, 459 underruns 05:38:08.573 cst Thu Feb 13 2014
        1159894277 packets output, 366047579951 bytes, 483 underruns 03:37:26.853 cst Fri Feb 14 2014
        1596471490 packets output, 500836893219 bytes, 483 underruns 03:52:52.523 cst Wed Feb 19 2014
        1635530484 packets output, 511489408071 bytes, 483 underruns 10:03:08.799 cst Wed Feb 19 2014
        1722164227 packets output, 536769375853 bytes, 483 underruns 06:11:22.244 cst Thu Feb 20 2014
        2032554621 packets output, 636075162304 bytes, 2831 underruns 08:35:21.315 cst Sun Feb 23 2014
        2174454722 packets output, 688313076839 bytes, 2831 underruns 08:22:57.704 cst Mon Feb 24 2014
Interface GigabitEthernet0/2 "myapp1", is up, line protocol is up
        1968362 packets output, 524301440 bytes, 0 underruns 07:48:45.631 cst Wed Feb 12 2014
        1987058 packets output, 526612914 bytes, 0 underruns 05:38:08.573 cst Thu Feb 13 2014
        2005883 packets output, 528940672 bytes, 0 underruns 03:37:26.853 cst Fri Feb 14 2014
        4036852 packets output, 3167775775 bytes, 2831 underruns 03:52:52.523 cst Wed Feb 19 2014
        13676338 packets output, 15853359823 bytes, 2831 underruns 10:03:08.799 cst Wed Feb 19 2014
        23861856 packets output, 16649050850 bytes, 3052 underruns 06:11:22.244 cst Thu Feb 20 2014
        66743830 packets output, 20187731129 bytes, 5941 underruns 08:35:21.315 cst Sun Feb 23 2014
        80290600 packets output, 21286340673 bytes, 6860 underruns 08:22:57.704 cst Mon Feb 24 2014
Interface GigabitEthernet0/3 "state-failover", is up, line protocol is up
        16582048 packets output, 17699836232 bytes, 0 underruns 07:48:45.631 cst Wed Feb 12 2014
        17971640 packets output, 19234649922 bytes, 0 underruns 05:38:08.573 cst Thu Feb 13 2014
        19380417 packets output, 20791969660 bytes, 0 underruns 03:37:26.853 cst Fri Feb 14 2014
        26970739 packets output, 29162172960 bytes, 0 underruns 03:52:52.523 cst Wed Feb 19 2014
        27259841 packets output, 29471830004 bytes, 0 underruns 10:03:08.799 cst Wed Feb 19 2014
        29612954 packets output, 32141440890 bytes, 0 underruns 06:11:22.244 cst Thu Feb 20 2014
        39077736 packets output, 42912691094 bytes, 0 underruns 08:35:21.315 cst Sun Feb 23 2014
        42074827 packets output, 46322035220 bytes, 0 underruns 08:22:57.704 cst Mon Feb 24 2014
Interface Management0/0 "lan-failover", is up, line protocol is up
        1863787 packets output, 265441230 bytes, 0 underruns 07:48:45.631 cst Wed Feb 12 2014
        1977505 packets output, 281732398 bytes, 0 underruns 05:38:08.573 cst Thu Feb 13 2014
        2091970 packets output, 298145244 bytes, 0 underruns 03:37:26.853 cst Fri Feb 14 2014
        2718733 packets output, 387975068 bytes, 0 underruns 03:52:52.523 cst Wed Feb 19 2014
        2750523 packets output, 392530668 bytes, 0 underruns 10:03:08.799 cst Wed Feb 19 2014
        2855417 packets output, 407567752 bytes, 0 underruns 06:11:22.244 cst Thu Feb 20 2014
        3242848 packets output, 463113612 bytes, 0 underruns 08:35:21.315 cst Sun Feb 23 2014
        3366749 packets output, 480878922 bytes, 0 underruns 08:22:57.704 cst Mon Feb 24 2014
Interface GigabitEthernet1/0 "inside", is up, line protocol is up
        229534738 packets output, 55157234973 bytes, 0 underruns 07:48:45.631 cst Wed Feb 12 2014
        249682890 packets output, 59948227086 bytes, 0 underruns 05:38:08.573 cst Thu Feb 13 2014
        272763726 packets output, 66350185657 bytes, 0 underruns 03:37:26.853 cst Fri Feb 14 2014
        378020447 packets output, 91307448807 bytes, 0 underruns 03:52:52.523 cst Wed Feb 19 2014
        384704374 packets output, 93165635304 bytes, 0 underruns 10:03:08.799 cst Wed Feb 19 2014
        402556578 packets output, 97469565455 bytes, 0 underruns 06:11:22.244 cst Thu Feb 20 2014
        492798902 packets output, 119550853698 bytes, 0 underruns 08:35:21.315 cst Sun Feb 23 2014
        564346002 packets output, 137603523999 bytes, 0 underruns 08:22:57.704 cst Mon Feb 24 2014
Interface GigabitEthernet1/1 "app2", is up, line protocol is up
        142287604 packets output, 56966204294 bytes, 0 underruns 07:48:45.631 cst Wed Feb 12 2014
        154809474 packets output, 62049309926 bytes, 0 underruns 05:38:08.573 cst Thu Feb 13 2014
        167733332 packets output, 67152657884 bytes, 0 underruns 03:37:26.853 cst Fri Feb 14 2014
        231962627 packets output, 93689642614 bytes, 0 underruns 03:52:52.523 cst Wed Feb 19 2014
        235640974 packets output, 95384548398 bytes, 0 underruns 10:03:08.799 cst Wed Feb 19 2014
        249769631 packets output, 103735197461 bytes, 0 underruns 06:11:22.244 cst Thu Feb 20 2014
        290301462 packets output, 119748550482 bytes, 0 underruns 08:35:21.315 cst Sun Feb 23 2014
        303003248 packets output, 125098088305 bytes, 0 underruns 08:22:57.704 cst Mon Feb 24 2014
Interface GigabitEthernet1/2 "", is administratively down, line protocol is down
        0 packets output, 0 bytes, 0 underruns 07:48:45.631 cst Wed Feb 12 2014
        0 packets output, 0 bytes, 0 underruns 05:38:08.573 cst Thu Feb 13 2014
        0 packets output, 0 bytes, 0 underruns 03:37:26.853 cst Fri Feb 14 2014
        0 packets output, 0 bytes, 0 underruns 03:52:52.523 cst Wed Feb 19 2014
        0 packets output, 0 bytes, 0 underruns 10:03:08.799 cst Wed Feb 19 2014
        0 packets output, 0 bytes, 0 underruns 06:11:22.244 cst Thu Feb 20 2014
        0 packets output, 0 bytes, 0 underruns 08:35:21.315 cst Sun Feb 23 2014
        0 packets output, 0 bytes, 0 underruns 08:22:57.704 cst Mon Feb 24 2014

Once you have the data in-front of you can easily see how the stats were changing over time, over longer period of time like a week.

In my case we suspected that the Firewall hit the capacity limit but further investigation confirmed that the device is doing well and no upgrade is necessary.

References

http://www.gossamer-threads.com/lists/cisco/nsp/152428
http://ccna2ccnp.blogspot.co.uk/2012/12/ciscoasa-oversubcription-maximizing.html
http://www.cisco.com/en/US/docs/internetworking/troubleshooting/guide/tr1904.html
http://en.wikipedia.org/wiki/Buffer_underrun
http://www.cisco.com/c/en/us/support/docs/security/asa-5500-x-series-next-generation-firewalls/115985-asa-overrun-product-tech-note-00.html