How do I modify pinger.c to display ICMP response error codes? Source code to modify is below:

//A simple Ping program to ping any address such as google.com in Linux

//run program as : gcc -o ping ping.c

// then : ./ping google.com

//can ping localhost addresses

//see the RAW socket implementation

/*.....Ping Application....*/

/* Note Run under root priveledges */

/* On terminal

$ gcc -o out ping.c

$ sudo su

# ./out 127.0.0.1

OR

# ./out google.com */

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#define PACKET_SIZE 4096

#define MAX_WAIT_TIME 1

#define MAX_NO_PACKETS 3

double rttsum;

double rttavg;

char sendpacket[PACKET_SIZE];

char recvpacket[PACKET_SIZE];

int sockfd, datalen = 56;

int nsend = 0, nreceived = 0;

struct sockaddr_in dest_addr;

pid_t pid;

struct sockaddr_in from;

struct timeval tvrecv;

void statistics(int signo);

unsigned short cal_chksum(unsigned short *addr, int len);

int pack(int pack_no);

void send_packet(void);

void recv_packet(void);

int unpack(char *buf, int len);

void tv_sub(struct timeval *out, struct timeval *in);

void statistics(int signo)

{

printf(" --------------------PING statistics------------------- ");

printf("%d packets transmitted, %d received , %%%d lost ", nsend,

nreceived, (nsend - nreceived) / nsend * 100);

printf("%rttavg=%.3f ms ", rttavg);

close(sockfd);

exit(1);

}

unsigned short cal_chksum(unsigned short *addr, int len)

{

int nleft = len;

int sum = 0;

unsigned short *w = addr;

unsigned short answer = 0;

while (nleft > 1)

{

sum += *w++;

nleft -= 2;

}

if (nleft == 1)

{

*(unsigned char*)(&answer) = *(unsigned char*)w;

sum += answer;

}

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

sum += (sum >> 16);

answer = ~sum;

return answer;

}

int pack(int pack_no)

{

int i, packsize;

struct icmp *icmp;

struct timeval *tval;

icmp = (struct icmp*)sendpacket;

icmp->icmp_type = ICMP_ECHO;

icmp->icmp_code = 0;

icmp->icmp_cksum = 0;

icmp->icmp_seq = pack_no;

icmp->icmp_id = pid;

packsize = 8+datalen;

tval = (struct timeval*)icmp->icmp_data;

gettimeofday(tval, NULL);

icmp->icmp_cksum = cal_chksum((unsigned short*)icmp, packsize);

return packsize;

}

void send_packet()

{

int packetsize;

while (nsend < MAX_NO_PACKETS)

{

nsend++;

packetsize = pack(nsend);

if (sendto(sockfd, sendpacket, packetsize, 0, (struct sockaddr*)

&dest_addr, sizeof(dest_addr)) < 0)

{

perror("sendto error");

continue;

} sleep(1);

}

}

void recv_packet()

{

int n, fromlen;

extern int errno;

signal(SIGALRM, statistics);

fromlen = sizeof(from);

while (nreceived < nsend)

{

alarm(MAX_WAIT_TIME);

if ((n = recvfrom(sockfd, recvpacket, sizeof(recvpacket), 0, (struct

sockaddr*) &from, &fromlen)) < 0)

{

if (errno == EINTR)

continue;

perror("recvfrom error");

continue;

} gettimeofday(&tvrecv, NULL);

if (unpack(recvpacket, n) == - 1)

continue;

nreceived++;

}

}

int unpack(char *buf, int len)

{

int i, iphdrlen;

struct ip *ip;

struct icmp *icmp;

struct timeval *tvsend;

double rtt;

ip = (struct ip*)buf;

iphdrlen = ip->ip_hl << 2;

icmp = (struct icmp*)(buf + iphdrlen);

len -= iphdrlen;

if (len < 8)

{

printf("ICMP packets\'s length is less than 8 ");

return - 1;

}

if ((icmp->icmp_type == ICMP_ECHOREPLY) && (icmp->icmp_id == pid))

{

tvsend = (struct timeval*)icmp->icmp_data;

tv_sub(&tvrecv, tvsend);

rtt = tvrecv.tv_sec * 1000+tvrecv.tv_usec / 1000;

rttsum += rtt;

rttavg = rttsum / 3;

printf("%d byte from %s: icmp_seq=%u ttl=%d rtt=%.3f ms ", len,

inet_ntoa(from.sin_addr), icmp->icmp_seq, ip->ip_ttl, rtt);

// printf("%rttavg=%.3f ms ", rttavg);

}

else

return - 1;

}

main(int argc, char *argv[])

{

struct hostent *host;

struct protoent *protocol;

unsigned long inaddr = 0l;

int waittime = MAX_WAIT_TIME;

int size = 50 * 1024;

if (argc < 2)

{

printf("usage:%s hostname/IP address ", argv[0]);

exit(1);

} if ((protocol = getprotobyname("icmp")) == NULL)

{

perror("getprotobyname");

exit(1);

}

if ((sockfd = socket(AF_INET, SOCK_RAW, protocol->p_proto)) < 0)

{

perror("socket error");

exit(1);

}

setuid(getuid());

setsockopt(sockfd, SOL_SOCKET, SO_RCVBUF, &size, sizeof(size));

bzero(&dest_addr, sizeof(dest_addr));

dest_addr.sin_family = AF_INET;

if (inaddr = inet_addr(argv[1]) == INADDR_NONE)

{

if ((host = gethostbyname(argv[1])) == NULL)

{

perror("gethostbyname error");

exit(1);

}

memcpy((char*) &dest_addr.sin_addr, host->h_addr, host->h_length);

}

else

dest_addr.sin_addr.s_addr = inet_addr(argv[1]);

pid = getpid();

printf("PING %s(%s): %d bytes data in ICMP packets. ", argv[1], inet_ntoa

(dest_addr.sin_addr), datalen);

send_packet();

recv_packet();

statistics(SIGALRM);

return 0;

}

void tv_sub(struct timeval *out, struct timeval *in)

{

if ((out->tv_usec -= in->tv_usec) < 0)

{

--out->tv_sec;

out->tv_usec += 1000000;

} out->tv_sec -= in->tv_sec;

}

/*------------- The End -----------*/