ARP Request packet??plz reply soon
From: ANaiveProgrammer (myhotline_at_gmail.com)
Date: 11/24/04
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Date: 23 Nov 2004 15:14:07 -0800
hi there
i have defined the following two structs( Code is attached at the
bottom of this message....) i actually want to send ARP-Request
message to my loopback because im not attached to an Ethernet? Now
what im doing is i have tried to sent my ethernet_frame(See code..) to
my loopback?( Is it a legitimate way to check that ARP-request has
been processed successfully if u r not attached to a LAN, if not then
please tell me how can i check that my ARP-REQUEST has been
successfully processed even if im not attached to a ethernet/LAN?)
Now another problem is that i need to know the correct size of both
the structs i.e. ethernet_frame and arp_request. and when i check that
using sizeof operator then it doesn't show me the correct size.
How will i send a struct over the wire, is the following way correct
write(sockfd,(char *)&ef,sizeof(ef));// ef is theinstance of
ethernet_frame
if above is not correct, thenn who will i send the struct over a
socket?
lastly, i need to be sure about the structs that i have designed i.e.
their structure and datatype and the way i have initialized them in
set_ethernet()
and set_request()..are my initializations correct in these two
functions???
I really appreciate any help, at earliest, as im very new in C under
linux, and this is the first time im programming the link-layer.....
I know this is a long message and will take qutie a bit of ur time.
However i appreciate your effort and time and i hope i will get a
reply soon
Cheers
CODE( in c under RED HAT Linux 8)
--------------------------------
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <string.h>
typedef struct {
//This struct defines Arp--Request.
uint8_t haddr_type;// For Ethernet it is 1
uint8_t proto_type[4];// 0x800
uint8_t hard_len;// 6 Bytes
uint8_t proto_len;// 4 Bytes
uint16_t operation;// 1---> for request
uint8_t sender_hard[6];//Sender Hardware Address
uint8_t sender_proto[4];//Sender protocol Address
uint8_t target_ip[4];// Target IP Address
//Target Hardware Address, to me, is optional so i didn't mention it.
}arp_request;
typedef struct{
uint8_t destip[4];
uint8_t sourceip[4];
uint8_t frametype[3];// 0x806 identifies ARP message
arp_request *req;
} ethernet_frame;
void set_ethernet(ethernet_frame *ef, arp_request *rep1){
//This function set the values of variables defined in ethernet_frame
struct
uint8_t dest[4] = {127,0,0,1};
int k;
for ( k=0; k < 4; k++)
ef->destip[k] = dest[k];
uint8_t source[4] = {144,5,4,1};
for ( k=0; k < 4; k++)
ef->sourceip[k] = source[k];
uint8_t frame[3]={0x8,0x0,0x6};
for( k=0; k<3;k++)
ef->frametype[k] = frame[k];
ef->req = rep1;
}
void set_request(arp_request *req){
//This function set the values of variables defined in arp_request
struct
req->haddr_type = 1;
uint8_t ptype[4] = {0x0,0x8,0x0,0x0};
int k;
for ( k=0; k < 4; k++)
req->proto_type[k] = ptype[k];
req->operation = 1;
uint8_t sendh[6] = {0xff,0xdd,0xcd,0xfa,0x8f,0xff};
for ( k=0; k < 6; k++)
req->sender_hard[k] = sendh[k];
strcpy(req->sender_hard,sendh);
uint8_t senderp[4]={128,0,0,1};
int i;
for (i=0; i < 4; ++i)
req->sender_proto[i] = senderp[i];
uint8_t tip[4] = {127,0,0,1};
int ii;
for ( ii =0; ii < 4; ++ii)
req->target_ip[ii] = tip[ii];
}
int main(){
arp_request request;
set_request(&request);
ethernet_frame ef;
set_ethernet(&ef,&request);
printf("Size of ARP---%d\n",sizeof(request));//It doesnt print
correct size
printf("Size of Ethernet---%d\n",sizeof(ef));//It doesnt print
correct size
int len=0;
set_ethernet(&ef,&request);
int sockfd;
struct sockaddr_in dest;
sockfd = socket(AF_INET,SOCK_STREAM,0);
dest.sin_family = AF_INET;
char type1[4]="0800";
int i;
for( i=0; i < strlen(type1); ++i)
printf("%c",type1[i]);
printf("\n");
dest.sin_addr.s_addr = inet_addr("127.0.0.1");
bind(sockfd,(struct sockaddr*)&dest ,sizeof(struct sockaddr));
printf("Trying to Connect\n");
connect(sockfd,(struct sockaddr*)&dest,sizeof(struct sockaddr));
printf("Connected...\n");
write(sockfd,(char *)&ef,10);
return 0;
}
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