outputTask $2\mathrm{.}2$B: Spoof an ICMP Echo Request. Spoof an ICMP echo request packet on behalf of another

machine $($i$.$e$.,$ using another machine's IP address as its source IP address$).$ This packet should be sent to a

remote machine on the Internet $($the machine must be alive$).$ You should turn on your Wireshark, so if your

spoofing is successful, you can see the echo reply coming back from the remote machine.

Questions. Please answer the following questions.

Question $4.$ Can you set the IP packet length field to an arbitrary value, regardless of how big the

actual packet is$?$

Question $5.$ Using the raw socket programming, do you have to calculate the checksum for the IP

header?

Question $6.$ Why do you need the root privilege to run the programs that use raw sockets? Where

does the program fail if executed without the root privilege? please write the code for icmp echo and answer question the spoofing code #include

#include

#include

#include

#include

#include

#include

$//$ Note: This code is for educational or testing purposes only and should not be used maliciously.

$//$ The IP header's structure

struct ipheader $\{$

unsigned char iph$\_$ihl:$4,$ iph$\_$ver:$4$; $//$ Adjusted the bit fields

unsigned char iph$\_$tos;

unsigned short int iph$\_$len;

unsigned short int iph$\_$ident;

unsigned short int iph$\_$flags$\_$offset; $//$ Changed name and type for flags and offset

unsigned char iph$\_$ttl;

unsigned char iph$\_$protocol;

unsigned short int iph$\_$chksum;

unsigned int iph$\_$sourceip;

unsigned int iph$\_$destip;

$\}$;

$//$ Simple checksum function, might be needed for some headers

unsigned short csum$($unsigned short $*$buf$,$ int nwords$)\{$

unsigned long sum;

for $($sum $=0$; nwords $>0$; nwords$--)$

sum $+=*$buf$++$;

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

sum $+=($sum $>>16)$;

return $($unsigned short$)($~sum$)$;

$\}$

int main$()\{$

int sd;

char buffer$[4096]$;

struct ipheader $*$ip $=($struct ipheader $*)$ buffer;

char $*$data $=$ buffer $+$ sizeof$($struct ipheader$)$; $//$ Pointer to the data portion after the IP header

$//$ Create a raw socket with IP protocol. The IPPROTO$\_$RAW parameter tells the system

sd $=$ socket$($AF$\_$INET, SOCK$\_$RAW, IPPROTO$\_$RAW$)$;

if $($sd $<mtext></mtext><mn>0</mn><mi>)</mi><mtext></mtext><mi>\{</mi>$

perror$("$socket$()$ error"$)$;

exit$(-1)$;

$\}$

$//$ Set the fields in the IP header

ip$->$iph$\_$ver $=4$; $//$ Version $(4$ bits$)$: IPv$4$

ip$->$iph$\_$ihl $=5$; $//$ IHL $(4$ bits$)$: Number of $32-$bit words in header

ip$->$iph$\_$tos $=0$; $//$ Type of service

$//$ Include the length of IP header and message in total length

ip$->$iph$\_$len $=$ htons$($sizeof$($struct ipheader$)+$ strlen$($data$))$;

ip$->$iph$\_$ident $=$ htons$(54321)$; $//$ Identification

ip$->$iph$\_$flags$\_$offset $=$ htons$(0$x$4000)$; $//$ Don't fragment flag, $0$ offset

ip$->$iph$\_$ttl $=255$; $//$ Time to live

ip$->$iph$\_$protocol $=$ IPPROTO$\_$TCP; $//$ Protocol

ip$->$iph$\_$chksum $=0$; $//$ Checksum $($temporarily set to $0)$

$//$ Source IP address, can be spoofed

ip$->$iph$\_$sourceip $=$ inet$\_$addr$("1\mathrm{.}2\mathrm{.}3\mathrm{.}4")$;

$//$ Destination IP address

ip$->$iph$\_$destip $=$ inet$\_$addr$("10\mathrm{.}9\mathrm{.}0\mathrm{.}6")$;

$//$ Copy the message into the buffer after the IP header

strcpy$($data$,$ "Hello"$)$;

$//$ Calculate the IP checksum now that the header is filled out

ip$->$iph$\_$chksum $=$ csum$(($unsigned short $*)$buffer$,$ sizeof$($struct ipheader$))$;

$//$ Inform the kernel that headers are included in the packet

int one $=1$;

const int $*$val $=$ &one;

if $($setsockopt$($sd$,$ IPPROTO$\_$IP$,$ IP$\_$HDRINCL, val, sizeof$($one$))<mtext></mtext><mn>0</mn><mi>)</mi><mtext></mtext><mi>\{</mi>$

perror$("$setsockopt$()$ error"$)$;

exit$(-1)$;

$\}$

$//$ Destination address structure

struct sockaddr$\_$in sin;

sin$.$sin$\_$family $=$ AF$\_$INET;

sin$.$sin$\_$port $=$ htons$(80)$; $//$ Port number if needed

sin$.$sin$\_$addr.s$\_$addr $=$ ip$->$iph$\_$destip;

$//$ Send the packet

if $($sendto$($sd$,$ buffer, ntohs$($ip$->$iph$\_$len$),0,($struct sockaddr $*)$&sin$,$ sizeof$($sin$))<mtext></mtext><mn>0</mn><mi>)</mi><mtext></mtext><mi>\{</mi>$

perror$("$sendto$()$ error"$)$;

exit$(-1)$;

$\}$

close$($sd$)$;

return $0$;

$\}$