Danny's tech notebook | 丹尼技術手札

Monday, January 21, 2013

[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.

Tuesday, January 8, 2013

[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);
} 

Friday, December 28, 2012

[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

Thursday, December 13, 2012

[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

Wednesday, December 12, 2012

[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

Monday, December 10, 2012

[MongoDB] Install MongoDB and try a simple example of mongodb_c_driver

MongoDB Installation
http://docs.mongodb.org/manual/tutorial/install-mongodb-on-debian-or-ubuntu-linux/
or
https://www.digitalocean.com/community/articles/how-to-install-mongodb-on-ubuntu-12-04
For instance in my environment:
> sudo apt-key adv --keyserver keyserver.ubuntu.com --recv 7F0CEB10
> sudo echo "deb http://downloads-distro.mongodb.org/repo/ubuntu-upstart dist 10gen" | tee -a /etc/apt/sources.list.d/10gen.list
> sudo apt-get -y update
> sudo apt-get -y install mongodb-10gen

Try command on MongoDB
>mongo
MongoDB shell version: 2.2.2
connecting to: test

> show dbs
db    (empty)
local    (empty)
test    0.203125GB

> use test
switched to db test

> show collections
foo
system.indexes

### Insert new data ###
> db.foo.save({a:1})
> doc = {
... "name" : "kristina",
... "contact info" : {
... "twitter" : "@kchodorow",
... "email" : "kristina@10gen.com"
... },
... "friends" : 400232,
... "pic" : BinData(...)
... "member since" : new Date()}> db.foo.insert(doc)
> db.foo.save({a:2})
> db.foo.save({a:3})

### Find the data ###
> db.foo.find()
{ "_id" : ObjectId("50c592540770027c182d31b9"), "a" : 1 }
{ "_id" : ObjectId("50c59e030770027c182d31ba"), "name" : "kristina", "contact info" : { "twitter" : "@kchodorow", "email" : "kristina@10gen.com" }, "friends" : 400232, "member since" : ISODate("2012-12-10T08:30:50.389Z") }
{ "_id" : ObjectId("50c59e1f0770027c182d31bb"), "a" : 2 }
{ "_id" : ObjectId("50c59e220770027c182d31bc"), "a" : 3 }

> db.foo.findOne()
{ "_id" : ObjectId("50c592540770027c182d31b9"), "a" : 1 }
> db.foo.find({"a":1})
{ "_id" : ObjectId("50c592540770027c182d31b9"), "a" : 1 }
> db.foo.find({"name":"kristina"})
{ "_id" : ObjectId("50c59e030770027c182d31ba"), "name" : "kristina", "contact info" : { "twitter" : "@kchodorow", "email" : "kristina@10gen.com" }, "friends" : 400232, "member since" : ISODate("2012-12-10T08:30:50.389Z") }

Try a simple example of mongodb c driver
For more API info in details, please refer to this: http://api.mongodb.org/c/current/tutorial.htm

> gcc --std=c99 -I/usr/local/include -L/usr/local/lib -o mongodb_test mongodb_test.c -lmongoc
> ./mongodb_test
WARNING: mongo_connect() is deprecated, please use mongo_client()
MONGO_OK:connection succeeded
0

mongodb_test.c (source code)

#include <stdio.h>
#include "mongo.h"

int main() {
  mongo conn[1];
  int status;
  status = mongo_connect( conn, "127.0.0.1", 27017 );

  if( status != MONGO_OK ) {
      switch ( conn->err ) {
        case MONGO_CONN_SUCCESS:    printf( "connection succeeded\n" ); break;
        //case MONGO_CONN_BAD_ARG:    printf( "bad arguments\n" ); return 1;  
        case MONGO_CONN_NO_SOCKET:  printf( "no socket\n" ); return 1;
        case MONGO_CONN_FAIL:       printf( "connection failed\n" ); return 1;
        case MONGO_CONN_NOT_MASTER: printf( "not master\n" ); return 1;
      }
  }else{
      printf( "MONGO_OK:connection succeeded\n%d\n", status );
  }

  mongo_destroy( conn );

  return 0;
}

[Memcached] Install memcached and try libmemcached C API

Install from package
> sudo apt-get install memcached

or Install from source code
We need to have :

libevent downloaded from : http://libevent.org/

> ./configure --prefix=/usr
> make
> sudo make install

memcached downloaded from : http://memcached.org/

> ./configure --prefix=/usr/local
> make
> sudo make install

Check the status of memcached
> sudo service memcached status

Install libmemcached C API from source code

libmemcached C API ownloaded from http://libmemcached.org/libMemcached.html

> ./configure --prefix=/usr
> make
> sudo make install

Give a simple try for libmemcached C API
> gcc -o mem_test2 mem_test2.c -lmemcached -lpthread
> ./mem_test2
Save key:key1 data:"This is c first value" success.
Fetch key:key1 data:This is c first value
Delete Key key1 success.

mem_test2.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <libmemcached/memcached.h>

int main(int argc, char *argv[]) {
    memcached_st *memc;
    memcached_return rc;
    memcached_server_st *servers;
    char value[8191];
    //connect multi server
    memc = memcached_create(NULL);
    servers = memcached_server_list_append(NULL, "localhost", 11211, &rc);
    servers = memcached_server_list_append(servers, "localhost", 11212, &rc);
    rc = memcached_server_push(memc, servers);
    memcached_server_free(servers);
    //Save multi data
    size_t i;
    char *keys[] = {"key1", "key2", "key3"};
    size_t key_length[] = {4, 4, 4};
    char *values[] = {"This is c first value", "This is c second value", "This is c third value"};
    size_t val_length[] = {21, 22, 21};
    for (i = 0; i < 3; i++) {
        rc = memcached_set(memc, keys[i],
                key_length[i], values[i], val_length[i], (time_t) 180,
                (uint32_t) 0);
        if (rc == MEMCACHED_SUCCESS) {
            printf("Save key:%s data:\"%s\" success.\n",
                    keys[i], values[i]);
        }
    }

    //Fetch multi data
    char return_key[MEMCACHED_MAX_KEY];
    size_t return_key_length;
    char *return_value;
    size_t return_value_length;
    uint32_t flags;
    rc = memcached_mget(memc, keys, key_length, 3);
    while ((return_value = memcached_fetch(memc, return_key,
            &return_key_length, &return_value_length, &flags, &rc))) {
        if (rc == MEMCACHED_SUCCESS) {
            printf("Fetch key:%s data:%s\n", return_key, return_value);
        }
    }
    //Delete multi data
    for (i = 0; i < 3; i++) {
        rc = memcached_set(memc, keys[i], key_length[i],
                values[i], val_length[i], (time_t) 180, (uint32_t) 0);
        rc = memcached_delete(memc, keys[i],
                key_length[i], (time_t) 0);
        if (rc == MEMCACHED_SUCCESS) {
            printf("Delete %s success\n", keys[i], values[i]);
        }
    }
    //free
    memcached_free(memc);
    return 0;
}

Wednesday, December 5, 2012

[Presentation] OpenStack 2012 fall summit observation - Quantum/SDN

Taiwan OpenStack User Group (TWOSUG)3rd Meet Up is hold in Dec 5, 2012. I give a presentation in one of session, which is "OpenStack 2012 fall summit observation - Quantum/SDN". The topic is focused on Quantum and SDN and the slide is shared on shlideshare as follows:
http://www.slideshare.net/teyenliu/open-stack-2012-fall-summit-observation-with-quantumsdn-15493510