The usage and implementation principle of ping command in Linux

The general format of the ping command is:
ping [-dfnqrrv][-c send number][-i interval seconds][-i network interface][-l Front load][-p template style][-s packet size][-t survival value [host name or IP address]

Parameter description:
-D uses the So_debug function of the socket.
-F limit detection. Send a large and fast network packet to a machine to see its response.
-N outputs only values.
-Q Displays no information about the delivery packet and displays only the final results.
-R ignores the normal routing table and sends the packet directly to the remote host. It is usually a matter of viewing the network interface on this computer.
-R to record the routing process.
-V details the execution of the instruction.
The-c number stops after sending the specified number of packages.
-I seconds set interval a few seconds to send a network packet to a machine, the default is a second send.
The-I network interface sends out packets using the specified network interface.
-L pre-load setting packets that are sent before the request information is sent.
The-P template style sets the template style that fills the packet.
-S bytes Specifies the number of bytes sent, the default value is 56, plus the 8-byte ICMP header, which is a total of 64ICMP data bytes.
-T survival value sets the size of the Live value TTL.

: Linux ping and ping under Windows slightly different, Linux ping does not automatically terminate, you need to press CTRL + C to terminate or use parameter-C to specify the number of responses required to complete

Linux to test the connectivity of the target host computer command is Ping, which mainly explains two parameters –c and – I

Where the number of –c count, which is the number of ping

-I interval interval, time space between pings

Introduction to the Ping principle

Ping Program Implementation

@ header file Common.h definition, contains header files used in the program and public variables, macros, constants, static variable definitions

#include <sys/socket.h>
#include <sys/time.h>
#include <sys/signal.h>

#include <netdb.h>

#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <netinet/in.h>

#include <unistd.h>

#include <stdlib.h>
#include <string.h>
#include <stdio.h>

#include <ctype.h>

#include <errno.h>

#define Ip_head_len 20
#define Icmp_len 8
#define BUFFER_SIZE 50 * 1024

/*
* Original socket descriptor, as required in signal processor
* is shared with the main program, so it is defined as an external variable (global)
*/
int ip_fd;

/* Process Number * *
int p_id;

/*packet_len is the sum of the IP header and the ICMP header length * *
extern int Packet_len;

/* To end address * *
struct sockaddr_in send_addr;

/* Send Application Buffer * *
Char send_buf[1024];

* * Message Serial number * *
extern int sequence;

/* Host name pointer/*
struct Hostent *host;

/* Identity has received a palindrome */
int flag;

@ Main function MAIN.C definition

#include "Common.h"

Main (int argc, char **argv)
{

/* command is Ping host (host name) |ip_address (IP address) * *
if (argc!= 2)
{
/* Command not correct * *
fprintf (stderr, "usage:ping <HOST|IP_ADDRESS>.N");
Exit (1);
}

/* Create the original socket using ICMP, which can only be generated by root
IP_FD = socket (af_inet, Sock_raw, ipproto_icmp);
if (IP_FD < 0)
{
fprintf (stderr, "raw socket ERROR.N");
Exit (1);
}

/* Change the user ID of the process, Reclaim root permissions, set the current user rights/
Setuid (Getpid ());

Ping (argv[1]);
}

The establishment of the @ping framework ping.c for initializing ping-related information and port information

#include "Common.h"

/*
*handle_alarm used to send IP packets at timed intervals
*/
void handle_alarm (int signo)
{
Send_ip ();

Alarm (1);
}

Ping (char *argv)
{
struct Sigaction Act;

Act.sa_handler = Handle_alarm;
act.sa_flags = 0;
Sigemptyset (&act.sa_mask);
Sigaction (SIGALRM, &act, NULL);
/* Gets the process ID of main, which is used to set the ICMP identifier * *
p_id = Getpid ();

/* Enlarge socket Receive buffer to 50K this is mainly to reduce the possibility of receiving buffer overflow, if accidentally ping a broadcast address or multicast address, will attract a lot of response.
SetSockOpt (IP_FD, Sol_socket, So_rcvbuf, &buffer_size, sizeof (buffer_size));

/* Only address information, do not need to specify port information, because the original socket under the Transport layer * *
send_addr.sin_family = af_inet;

/* Determine whether the host name or IP address * *
if (inet_addr (argv) = = Inaddr_none)
{
/* is the host name * *
if ((host = gethostbyname (argv)) = = NULL)
{
/* Host name Error * *
Perror ("Get host by name Error:unknow host.");
Exit (1);
}
memcpy (&send_addr.sin_addr, host->h_addr, host->h_length);
}
Else
{
/* is the IP address */
Inet_aton (argv, &send_addr.sin_addr);
}

printf ("Ping%s (%s)%d (%d) bytes of Datan", argv,
Inet_ntoa (SEND_ADDR.SIN_ADDR), sizeof (struct timeval),
sizeof (struct timeval) + Ip_head_len + Icmp_len);

Flag = 0;
/* Trigger a SIGALRM signal * *
Raise (SIGALRM);
Recv_ip ();

}

@ Send Message SEND.C, set up ICMP message and package as IP packet, send

#include "Common.h"

int sequence = 0;
int Packet_len = Ip_head_len + Icmp_len;

/*
*SEND_IP is used to send IP packets containing ICMP packets
*/
Send_ip (void)
{
if (sequence!= 0 &&!flag)
{
printf ("Destination Host Unreachablen");
}
int Len;
struct ICMPHDR *icmp_p;

Icmp_p = (struct ICMPHDR *) send_buf;

/* Fill in ICMP message type * *
Icmp_p->type = Icmp_echo;
* * Fill in the ICMP message code/
Icmp_p->code = 0;
/* Fill in the ICMP message identifier * *
(icmp_p->un). echo.id = p_id;
/* Fill in the ICMP message serial number, and increase the ICMP serial number * *
(icmp_p->un). Echo.sequence = sequence + +;

/* Record Sending time * *
Gettimeofday ((struct timeval*) (icmp_p + 1), NULL);

   /*printf ("%dn", sizeof (struct ICMPHDR));
    printf ("Type:%dncode:%dnchecksum:%dnun.echo.id:%dnun.echo.sequence:%dnun.gateway:% dnun.frag.__unused:%d        nun.frag.mtu:%dnn ", Icmp_p->type, icmp_p-> Code, Icmp_p->checksum, (Icmp_p->un). Echo.id, (icmp_p-    >un). Echo.sequence, (icmp_p-> UN). Gateway, (Icmp_p->un) frag.__unused, (Icmp_p->un). Frag.mtu);
    printf ("Type:%dncode:%dnchecksum:%dnun.echo.id:%dnun.echo.sequence:%dnun.gateway:% dnun.frag.__unused:%d    nun.frag.mtu:%dnn ", sizeof (Icmp_p->type), sizeof (Icmp_p->code), sizeof (icmp_p->checksum), sizeof ((icmp_p-        >un). echo.id), sizeof ( Icmp_p->un). echo.sequence), sizeof ((Icmp_p->un). Gateway), sizeof ((Icmp_p->un). frag.__unused),          sizeof ((icmp_p->un). Frag.mtu)); */

/* Message length is equal to IP packet length plus ICMP message length and data length * *
len = sizeof (struct timeval) + Packet_len;

/* Compute the ICMP checksum by using the IP compute method of IP header checksum * *
icmp_p->checksum = 0;
Icmp_p->checksum = Ip_checksum (U_short *) icmp_p, Len);

/* Send IP packet * *
if (SendTo (IP_FD, Send_buf, Len, 0, (struct sockaddr*) &send_addr, sizeof (SEND_ADDR)) < 0)
{
fprintf (stderr, "Send to ERROR.N");
}
}

@ Data Verification CHECK_SUM.C implementation of network data verification work

#include "Common.h"

unsigned short ip_checksum (unsigned short *pcheck, int check_len)
{
int nleft = Check_len;
int sum = 0;
unsigned short *p = Pcheck;
unsigned short result = 0;

while (Nleft > 1)
{
sum = sum + *p + +;
Nleft-= 2;
}

if (Nleft = 1)
{
* (unsigned char *) (&result) = * (unsigned char *) p;
sum + = result;
}

sum = (sum >>) + (sum & 0xFFFF);
sum + = (sum >> 16);

result = SUM;

return result;
}

@ packet receives RECEIVE.C, receives IP message and analyzes, prints related information

#include "Common.h"

/*
*RECV_IP is used to accept IP packets containing ICMP packets
*/
Recv_ip (void)
{
Char recv_buf[1024];
int Len;
int n;

struct IP *ip_p;
struct Timeval *time_now, *time_send;
struct Timeval now;

int Iphead_len;
int Icmp_len;

struct ICMPHDR *icmp_p;

float delay;

while (1)
{
n = recvfrom (ip_fd, Recv_buf, sizeof (RECV_BUF), 0, NULL, NULL);
if (n < 0)
{
if (errno = eintr)
Continue
Else
{
printf ("Recvfrom ERROR.N");
Continue
}

}

Ip_p = (struct ip*) recv_buf;

/* Get IP Header Length * *
Iphead_len = ip_p->ip_hl<<2;
/* Get the ICMP message contained in the IP packet * *
Icmp_p = (struct ICMPHDR *) (recv_buf + Iphead_len);
/* Computes the length of the ICMP message, which equals the length of the received minus the length of the IP header.
Icmp_len = N-iphead_len;

if (Icmp_len < 8)
{
fprintf (stderr, "error ICMP len =%D.N", Icmp_len);
}

//* If the ICMP type is the same, the output is displayed * *
if (Icmp_p->type = = icmp_echoreply)
{
if ((Icmp_p->un). Echo.id!= p_id)
Return
if (Icmp_len < 16)
printf ("Icmplen =%D.N", Icmp_len);

Flag = 1;//said has received a palindrome;

Gettimeofday (&now, NULL);

Time_now = &now;
Time_send = (struct timeval*) (icmp_p + 1);

if ((time_now->tv_usec-= Time_send->tv_usec) < 0)
{
Time_now->tv_sec--;
Time_now->tv_usec + 1000000;
}

Time_now->tv_sec-= time_send->tv_sec;

/* Calculation Delay * *
Delay = time_now->tv_sec * 1000.0 + time_now->tv_usec/1000.0;

/* Print received message related information * *
printf ("%d (%d) bytes from%s:icmp_seq=%d ttl=%d time=%.3fmsn",
Icmp_len, N, Inet_ntoa (SEND_ADDR.SIN_ADDR), (Icmp_p->un). Echo.sequence,
Ip_p->ip_ttl, delay);
}
}
}

@makefile file

#小型ping程序
#用c语言编写
#2008年03月30日

CC = GCC

obj = main.o ping.o send.o receive.o CHECK_SUM.O

ping:$ (obj)
$ (cc) $ (obj)-O Ping

MAIN.O:MAIN.C Common.h ping.c
$ (CC)-C MAIN.C

PING.O:PING.C common.h receive.c SEND.C
$ (CC)-C ping.c

SEND.O:SEND.C Common.h CHECK_SUM.C
$ (CC)-C SEND.C

Receive.o:receive.c Common.h
$ (CC)-C receive.c

CHECK_SUM.O:CHECK_SUM.C Common.h
$ (CC)-C CHECK_SUM.C

Clean
Rm-f $ (obj)

References: "Linux network Programming"
Edited by Lin Yu Guo Lingyun
Published by People's Post and telecommunications press

enters makefile directory
Execute make-f makefile
    make clean can

Program Run Results: (platform Ubuntu)
lwj@lwj-desktop:~/desktop/c/myping$ make-f makefile
gcc-c main.c
gcc-c ping.c
GCC -C SEND.C
gcc-c receive.c
gcc-c check_sum.c
gcc main.o ping.o send.o receive.o check_sum.o-o Ping
lwj@ lwj-desktop:~/desktop/c/myping$ make clean
rm-f main.o ping.o send.o receive.o check_sum.o
lwj@lwj-desktop:~/ desktop/c/myping$ sudo./ping localhost
Password:
ping localhost (127.0.0.1) 8 (+) bytes of data
(a) bytes F Rom 127.0.0.1:icmp_seq=0 ttl=64 time=0.061ms
(a) bytes from 127.0.0.1:icmp_seq=1 ttl=64 time=0.051ms
() b Ytes from 127.0.0.1:icmp_seq=2 ttl=64 time=0.039ms
(a) bytes from 127.0.0.1:icmp_seq=3 ttl=64 time=0.051ms
36 (a) bytes from 127.0.0.1:icmp_seq=4 ttl=64 time=0.050ms
(a) bytes from 127.0.0.1:icmp_seq=5 ttl=64 br> bytes from 127.0.0.1:icmp_seq=6 ttl=64 time=0.051ms
(a) bytes from 127.0.0.1:icmp_seq=7 ttl=64. 053MS

[2]+ Stopped sudo./ping localhost
lwj@lwj-desktop:~/desktop/c/myping$ sudo./ping 10.3.2.206
Ping 10.3.2.206 (10.3.2.206) 8 (+) bytes of data
Bytes from 10.3.2.206:icmp_seq=0 ttl=64 time=0.233ms
Bytes from 10.3.2.206:icmp_seq=1 ttl=64 time=0.063ms
Bytes from 10.3.2.206:icmp_seq=2 ttl=64 time=0.044ms
Bytes from 10.3.2.206:icmp_seq=3 ttl=64 time=0.054ms
Bytes from 10.3.2.206:icmp_seq=4 ttl=64 time=0.044ms
Bytes from 10.3.2.206:icmp_seq=5 ttl=64 time=0.052ms
Bytes from 10.3.2.206:icmp_seq=6 ttl=64 time=0.058ms
Bytes from 10.3.2.206:icmp_seq=7 ttl=64 time=0.055ms
Bytes from 10.3.2.206:icmp_seq=8 ttl=64 time=0.066ms
Bytes from 10.3.2.206:icmp_seq=9 ttl=64 time=0.053ms
Bytes from 10.3.2.206:icmp_seq=10 ttl=64 time=0.053ms
Bytes from 10.3.2.206:icmp_seq=11 ttl=64 time=0.052ms

[3]+ Stopped sudo./ping 10.3.2.206
lwj@lwj-desktop:~/desktop/c/myping$ sudo./ping 10.3.2.205
Ping 10.3.2.205 (10.3.2.205) 8 (+) bytes of data