[sFlow] Use sflowtool to parse sFlow datagram

In order to test and understand sFlow more in details, I prepare the following environment below. Switch 1 and 2 are emulated using Open vSwitch. In the previous sFlow article, there is a sFlow setting on Open vSwitch. Please check it out.

            192.168.12.201           10.3.207.244           192.168.12.202
            +------------+        +-----------------+       +------------+
            |  PC1       |        | sFlow Collector |       |  PC2       |
            |            |        |                 |       |            |
            |            |        |                 |       |            |
            +-----+------+        +---^--------^----+       +-----+------+
                  |                   |        |                  |
                  |                   |        |                  |
                  |                   ^ sFlow  ^                  |
                  +---------+         | Data   |       +----------+
                            |         ^        ^       |
                            |         |        |       |
                            |         ^        ^       |
                            |         |        |       |
                   +--------+---------++      ++-------++---------+
                   |    Switch 1       |      |   Switch 2        |
                   | 10.3.207.142      +------+ 10.3.207.143      |
                   +-------------------+      +-------------------+

sFlowtool is an open source toolkit for us to leverage the functionality of parsing sFlow datagram. In my environment, when I ping PC2 from PC1, then Switch 1 and 2 will send sFlow Counter and Flow Sample datagram to the sFlow collector. Now, I will use sFlowtool to parse  the information that it gets.

> ./sflowtool
Counter Sample:startDatagram =================================
datagramSourceIP 0.0.0.0
datagramSize 144
unixSecondsUTC 1359534209
datagramVersion 5
agentSubId 0
agent 10.3.207.142
packetSequenceNo 403
sysUpTime 947000
samplesInPacket 1
startSample ----------------------
sampleType_tag 0:2
sampleType COUNTERSSAMPLE
sampleSequenceNo 95
sourceId 0:4
counterBlock_tag 0:1
ifIndex 4
networkType 6
ifSpeed 1000000000
ifDirection 1
ifStatus 3
ifInOctets 126361
ifInUcastPkts 1072
ifInMulticastPkts 0
ifInBroadcastPkts 4294967295
ifInDiscards 0
ifInErrors 0
ifInUnknownProtos 4294967295
ifOutOctets 137350
ifOutUcastPkts 1135
ifOutMulticastPkts 4294967295
ifOutBroadcastPkts 4294967295
ifOutDiscards 0
ifOutErrors 0
ifPromiscuousMode 0
endSample   ----------------------
endDatagram   =================================
startDatagram =================================
datagramSourceIP 0.0.0.0
datagramSize 144
unixSecondsUTC 1359534210
datagramVersion 5
agentSubId 0
agent 10.3.207.244
packetSequenceNo 404
sysUpTime 948000
samplesInPacket 1
startSample ----------------------
sampleType_tag 0:2
sampleType COUNTERSSAMPLE
sampleSequenceNo 95
sourceId 0:5
counterBlock_tag 0:1
ifIndex 5
networkType 6
ifSpeed 100000000
ifDirection 2
ifStatus 1
ifInOctets 0
ifInUcastPkts 0
ifInMulticastPkts 0
ifInBroadcastPkts 4294967295
ifInDiscards 0
ifInErrors 0
ifInUnknownProtos 4294967295
ifOutOctets 0
ifOutUcastPkts 0
ifOutMulticastPkts 4294967295
ifOutBroadcastPkts 4294967295
ifOutDiscards 0
ifOutErrors 0
ifPromiscuousMode 0
endSample   ----------------------
endDatagram   =================================

Flow Sample:startDatagram =================================
datagramSourceIP 10.3.207.244
datagramSize 216
unixSecondsUTC 1359597631
datagramVersion 5
agentSubId 0
agent 10.3.207.142
packetSequenceNo 941
sysUpTime 2174000
samplesInPacket 1
startSample ----------------------
sampleType_tag 0:1
sampleType FLOWSAMPLE
sampleSequenceNo 72
sourceId 0:4
meanSkipCount 64
samplePool 4010
dropEvents 0
inputPort 4
outputPort 3
flowBlock_tag 0:1001
extendedType SWITCH
in_vlan 0
in_priority 0
out_vlan 0
out_priority 0
flowBlock_tag 0:1
flowSampleType HEADER
headerProtocol 1
sampledPacketSize 102
strippedBytes 4
headerLen 98
headerBytes 00-AB-77-E3-4B-00-00-AB-71-13-2D-00-08-00-45-00-00-54-00-00-40-00-40-01-9F-C5-C0-A8-0C-CA-C0-A8-0C-C9-08-00-C4-0E-55-06-08-57-28-96-AD-FD-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
dstMAC 00ab77e34b00
srcMAC 00ab71132d00
IPSize 84
ip.tot_len 84
srcIP 192.168.12.202
dstIP 192.168.12.201
IPProtocol 1
IPTOS 0
IPTTL 64
ICMPType 8
ICMPCode 0
endSample   ----------------------
endDatagram   =================================

If you use this, then you will get another format of data:
> ./sflowtool -l
Counter Sample:
CNTR,10.3.207.142,3,6,1000000000,1,3,112616,955,1,4294967295,0,0,4294967295,123043,1012,4294967295,4294967295,0,0,0

Flow Sample:
FLOW,10.3.207.142,4,3,00ab71132d00,00ab77e34b00,0x0800,0,0,192.168.12.202,192.168.12.201,1,0x00,64,0,0,0x00,102,84,64

[C++ STL] Containers

We all know that using data structure well is very important in programming, because it affects the performance, data accuracy, maintenance no matter what kind of the program you write. In C language, we have to provide our data structure by ourselves or by searching for related library and grab it to use. But, if possible ( I mean if your program is able to use g++ compiler and the environment ), you can consider to just use Containers (C++ STL) in your program. It is useful and powerful. For more information, here is the official web site : http://www.cplusplus.com/reference/stl/

Container class templates

Sequence containers:

vector Vector (class template )

deque Double ended queue (class template )

list List (class template )

Container adaptors:

stack LIFO stack (class template )

queue FIFO queue (class template )

priority_queue Priority queue (class template )

Associative containers:

set Set (class template )

multiset Multiple-key set (class template )

map Map (class template )

multimap Multiple-key map (class template )

bitset Bitset (class template)

[Library] The useful libraries for C

Needless to say, C is powerful. But, if you use Java or Python, you will reconize that C lakes a bunch of Libraries(APIs) or a framework for C programmer to do job quicker. Sometimes you have to look for some C libraries to meet your requirement, and then you can avoid from carving the same wheels again and again. This document will record the useful libraries for C language and I will continue to add the new one on it. For those who are a great C programmer, if you know a good library for C, please also let me know that. Thanks in advance.

OGDF - Open Graph Drawing Framework
http://www.ogdf.net/ogdf.php

Curl Lib
the multiprotocol file transfer library
http://curl.haxx.se/libcurl/

mongoose
The lightweight web server in C
http://code.google.com/p/mongoose/

SimCList – A C library for Lists
http://mij.oltrelinux.com/devel/simclist/

JSON Library
http://www.digip.org/jansson/

The libevent API provides a mechanism to execute a callback function when a specific event occurs on a file descriptor or after a timeout has been reached. Furthermore, libevent also support callbacks due to signals or regular timeouts
http://libevent.org/

libev - a high performance full-featured event loop written in C
It is similar with libevent, but is more efficiently
http://doc.dvgu.ru/devel/ev.html

The Better String Library
http://bstring.sourceforge.net/

Unit Test Frameworks
https://github.com/imb/fctx

Exception Handling for C
http://code.google.com/p/exceptions4c/

SSL Library
https://polarssl.org/ssl-library

libssh2 is a client-side C library implementing the SSH2 protocol
http://www.libssh2.org/

MD5
http://256.com/sources/md5/

CIDR Library ( Need to verify )
http://www.over-yonder.net/~fullermd/projects/libcidr 

NETCONF library in C
https://code.google.com/p/libnetconf/

SQLite is a software library that implements a self-contained, serverless, zero-configuration, transactional SQL database engine.
http://www.sqlite.org/

[SDN] The news about Juniper to build its own software-defined networking stack

Software Defined Networking is becoming hotter and hotter topic from last year. Properly networking guys will talk about Software-defined Networking (SDN) everywhere this year. The event that VMware bought Nicira became a catalyst for some related Network Vendors to think about what the strategy and tactic they should have and deal with this wave of SDN. It let me think of this song ( Blondie – The Tide Is High )
  The tide is high but I'm holding on ...
   I'm gonna be your number one ...
   ...

In sum, SDN is important and key to survive this time in the networking world. Here is an example about that Juniper takes an action to provide their SDN approach. I excerpt some paragraph as follows:


Quota from the news:
http://www.theregister.co.uk/2013/01/16/juniper_sdn_strategy/

Juniper's approach to SDN, explained Muglia, will break the monolithic software stack inside of switches and routers – for campuses, branches, and service providers and not just for data centers – into four different planes: management, services, control, and forwarding.

This software will run on a virtualization layer called JunosV App Engine – which sounds a lot like a KVM hypervisor container for an x86 server, but Juniper did not say. This virtualization software will ship later in the first quarter of this year.

Central to that SDN stack is Contrail, a startup that was just getting ready to uncloak last month with its SDN wares when Juniper swept in with $176m in cash and snapped it up. Contrail was founded by a team of networking and software platform experts from Google, Juniper, Cisco, and Aruba Networks, and significantly had former Juniper CTO and chief architect Kireeti Kompella as its CTO. Now Kompella is back at Juniper, and is central to its SDN strategy.

[Signal] The examples of using alarm() and sigaction()

In the following URL, it provides a good explanation about signal and signal handling.
https://www.sharcnet.ca/help/index.php/Signal_Handling_and_Checkpointing

Handling signal is a important job when we want to write a great code.
There are several signal functions that we could use often in programming. I will give some examples of how to use alarm() and sigaction() functions as below.
P.S: the URL link is the orginal source code which is from.


The follwing two examples are about how to use alarm() and ualarm().
http://jyhshin.pixnet.net/blog/post/27749178-linux-%E8%A8%88%E6%99%82%E5%99%A8-alarm-signal-%281%29

/* Example of using alarm() */ #include <unistd.h> #include <stdio.h> #include <signal.h> int main(int argc, char *argv[]) { sigset_t block; sigemptyset(&block); sigaddset(&block, SIGALRM); sigprocmask(SIG_BLOCK, &block, NULL); while (1) { alarm(2); printf("%d\n", time(NULL)); sigwaitinfo(&block, NULL); } return 0; }

/* Example of using ualarm() */ #define _XOPEN_SOURCE 500 #include <unistd.h> #include <stdio.h> #include <signal.h> int main(int argc, char *argv[]) { sigset_t block; sigemptyset(&block); sigaddset(&block, SIGALRM); sigprocmask(SIG_BLOCK, &block, NULL); ualarm(500000, 500000); while (1) { printf("%d\n", time(NULL)); sigwaitinfo(&block, NULL); } return 0; }

Actually, sigaction() is widely used in handling signal, for instance, SIGINT (interrupt), SIGCHLD, and so on. Here are the examples to show the usage of sigaction with SIGINT.
http://www.linuxprogrammingblog.com/code-examples/sigaction

/* Example of using sigaction() to setup a signal handler with 3 arguments * including siginfo_t. */ #include <stdio.h> #include <unistd.h> #include <signal.h> #include <string.h> static void hdl (int sig, siginfo_t *siginfo, void *context) { printf ("Sending PID: %ld, UID: %ld\n", (long)siginfo->si_pid, (long)siginfo->si_uid); } int main (int argc, char *argv[]) { struct sigaction act; memset (&act, '\0', sizeof(act)); /* Use the sa_sigaction field because the handles has two additional parameters */ act.sa_sigaction = &hdl; /* The SA_SIGINFO flag tells sigaction() to use the sa_sigaction field, not sa_handler. */ act.sa_flags = SA_SIGINFO; if (sigaction(SIGINT, &act, NULL) < 0) { perror ("sigaction error"); return 1; } while (1) sleep (10); return 0; }

http://fanqiang.chinaunix.net/a4/b2/20010508/113528_b.html

/* Example of using sigaction() to setup a signal handler * with setting sa_handler */ #include <stdio.h> #include <unistd.h> #include <signal.h> #include <string.h> #include <errno.h> #define PROMPT "Do you want to terminate the process?" char *prompt=PROMPT; void ctrl_c_oper(int signo) { write(STDERR_FILENO,prompt,strlen(prompt)); } int main() { struct sigaction act; act.sa_handler=ctrl_c_oper; sigemptyset(&act.sa_mask); act.sa_flags=0; if(sigaction(SIGINT,&act,NULL)<0) { fprintf(stderr,"Install Signal Action Error:%s\n\a",strerror(errno)); exit(1); } while(1); }

[ZeroMQ] The example of ZeroMQ via C#

Recently I found these two articles that give a very good introduction of ZeroMQ and an useful use case for synchronized PUB-SUB pattern. Although it uses C# as its programming language instead of C, but I still think we can learn some important concept from these.And also, these articles provide very good images to illustrate the communication patterns.

http://www.codeproject.com/Articles/488207/ZeroMQ-via-Csharp-Introduction

• There are several communication patterns described

http://www.codeproject.com/Articles/514959/ZeroMQ-via-Csharp-Multi-part-messages-JSON-and-Syn

• Multi-part messages
• Synchronized Pub-Sub pattern using PUB-SUB + REQ-REP

[SWIG] How to add C function in Python by using SWIG

Here is a simple example to use SWIG to automatically wrap C function and generate a wrapper and build a shared library for python.

/*** File : example.c ***/
#include 
<time.h>
double My_variable = 3.0;
int fact(int n) {
if (n <= 1) return 1;
else return n*fact(n-1);
}
int my_mod(int x, int y) {
return (x%y);
}
char *get_time()
{
time_t ltime;
time(&ltime);
return ctime(&ltime);
}
/*************************/

/*** example.i ***/
%module example
%{
/* Put header files here or function declarations like below */
extern double My_variable;
extern int fact(int n);
extern int my_mod(int x, int y);
extern char *get_time();
%}
extern double My_variable;
extern int fact(int n);
extern int my_mod(int x, int y);
extern char *get_time();
/******************/

Another example:

/* File : example.c */

double  My_variable  = 3.0;

/* Compute factorial of n */
int fact(int n) {
  if (n <= 1)
    return 1;
  else
    return n*fact(n-1);
}

/* Compute n mod m */
int my_mod(int n, int m) {
  return(n % m);
}

/* File : example.i */
%module example
%{
/* Put headers and other declarations here */
extern double My_variable;
extern int    fact(int);
extern int    my_mod(int n, int m);
%}

extern double My_variable;
extern int    fact(int);
extern int    my_mod(int n, int m);

What if you have some pointer arguments in C ? How to deal with it in Python? 

For example:void add(double a, double b, double *result) {
 *result = a + b;
}
Please refer to this document. It will give you the nametype mapping in SWIG.http://www.swig.org/Doc1.3/Arguments.html







[Trema] The L2 isolation mechanism in sliceable switch

If someone has ever seen the documents about sliceable switch as below, he/she will feel headache or sick because of a lot of contents and description.
https://github.com/trema/apps/wiki/sliceable_switch_tutorial
https://github.com/trema/apps/wiki/sliceable_switch_features

Now, I will give a flow control chart of slice function which is summarized from the source code ( slice.c ). That can give you a clear image about L2 isolation mechanism in sliceable switch, specially in Slice function. Check it out as the following chart:

 So, broadly speaking, the slice function will check mac binding first, then port_mac binding, and finally port binding. Meanwhile, some configurations will affect the result, for instance, "restrict hosts on port" enabled will force the slice function to check port_mac binding, otherwise, it won't do that.
Based on this flow chart, you can compare with the test cases in https://github.com/trema/apps/wiki/sliceable_switch_features