A while ago, while simultaneously icmp pinging my isp's dns server and viewing the tcpdump of the interface to which the icmp requests/replies were going out/in from, i realised that my ISP's DNS server drops icmp ping requests, and instead replies with a message visible to tcpdump something along the lines like this: "This server does not allow ping replies." My question is, would there happen to be a jump i could do with netfilter that would enable me to send out such a message for certain types of packets coming in? Thanks. James Stickland, Scarborough Toronto Ontario Canada.
