NetBSD doesn't actually need the same workaround as OpenBSD and Haiku;
on the TCP level, the TCP_KEEPALIVE socket option is recognized.
Without this we saw
13038 19 routinator CALL setsockopt(0x15,0xffff,8,0x7d60bd3d62b4,4)
13038 19 routinator RET setsockopt 0
13038 19 routinator CALL setsockopt(0x15,6,8,0x7d60bd3d62b4,4)
13038 19 routinator RET setsockopt -1 errno 42 Protocol option not available
and '8' in the latter corresponds to the
from <netinet/tcp.h> if I'm not sorely mistaken. Instead we end up
using TCP_KEEPIDLE, which works fine by the looks of it.
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