(See: ftp://ftp.rfc-editor.org/in-notes/rfc3514.txt)
This fulfills the host requirements for userland support by
way of the setsockopt() IP_EVIL_INTENT message.
There are three sysctl tunables provided to govern system behavior.
net.inet.ip.rfc3514:
Enables support for rfc3514. As this is an
Informational RFC and support is not yet widespread
this option is disabled by default.
net.inet.ip.hear_no_evil
If set the host will discard all received evil packets.
net.inet.ip.speak_no_evil
If set the host will discard all transmitted evil packets.
The IP statistics counter 'ips_evil' (available via 'netstat') provides
information on the number of 'evil' packets recieved.
For reference, the '-E' option to 'ping' has been provided to demonstrate
and test the implementation.
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