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Special Forums IP Networking multiple arp replies
# 1  
Old 08-28-2005
Question multiple arp replies

Can someone tell me if I tweak the destination field in an arp request for TCP connection to match it with the the mac addresses of different recivers in an ethernet as the packet passes through them in short each one catches the arp request and replies, what would happen I mean will the sender of arp request (reciever for arp reply) try to connect each one.
# 2  
Old 08-29-2005
... Since one packet is only valid on the wire at a time, i wonder how u could achieve what u asked
... maybe you will experience system freeze
# 3  
Old 08-30-2005
May b I'm not clear so let me clear I have built packet socket (PF_PACKET) which catches all the arp packets coming to its interface. Now as I know the ARP packets are broadcasted on the network and when it comes to a particular machine it checks if the destination field (ar_tip & ar_tpa) in the ARP header are meant for it or not now I know the callers IP address and hardware address (ar_sip & ar_spa in request) so I can easily forge the machine the sender requested and send an appropriate ARP reply.

Now my question was if not just one but many machine try to forge like this what would happen.
But I got my answer (google is great!!) that only the first (the fastest) reply is taken.

But I still have a problem,more general , I'm using above said thing in my application but when I'm using recvfrom to get the clients address ( in sockaddr_in structure argument with length in length field ) I'm not able to get it correctly I mean when I'm using inet_ntoa to convert sin_addr structure of got address(in sockaddr_in client) to corresponding IP address the result is not same as I got in ARP header. Even in just a simple UDP packet I'm not able to get the address correctly.
Can u suggest something.

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