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ICMP (Internet Control Message Protocol)is a protocol meant to be used as an aid for other protocols, as well as system administrators, to test for connectivity and search for configuration errors in a network. ICMP requests must be quickly answered in order to maintain confidence in their results. Systems also continuously receive ICMP requests, so wrapping them would prove extremely heavy for our resources. In ICMP requests, the information contained in the packet is seldom relevant, so not only processing its information becomes too hard, but it also proves completely useless. If ICMP filters are to be set up for a system, they should do so only at the source/destination level, handling it directly from the kernel.

Gunnar Wolf