[tor-relays] Guard flag flapping

[starlight.2015q3 at binnacle.cx]

Ah, forgot to calculate the default TCP
windows for you link speed rather than
mine.

So that's

125000000 bytes/sec ( 1 gigabit / sec )

* 25 milliseconds or 3125000 (for read)

* 40 milliseconds or 5000000 (for write)

   net.core.rmem_max = 16777216
   net.core.wmem_max = 16777216
   net.ipv4.tcp_wmem = 4096  3125000 16777216
   net.ipv4.tcp_rmem = 4096  5000000 16777216

The 25 and 40 milliseconds are
my guess at roughly the faster and 
more middle ping times within the
domestic US Internet.

This just gets each connection started

   net.ipv4.tcp_moderate_rcvbuf = 1
   net.ipv4.tcp_timestamps = 1

cause the IP stack to very quickly
establish precise values for the transmit
and receive TCP windows.