should be handled as errors. Historically receive buffer overflows have been
ignored and programs could not tell if they missed messages or messages had
been truncated because of overflows. Since programs historically do not expect
to get receive overflow errors, this behavior is not the default.
This is really really important for programs that use route(4) to keep in sync
with the system. If we loose a message then we need to reload the full system
state, otherwise the behaviour from that point is undefined and can lead
to chasing bogus bug reports.