Comment # 18 on bug 986395 from Neil Brown

Thanks, setting max_desync_factor to 0 does make it behave a bit better,
particularly if I "ifdown" and "ifup" after all the settings are in place.

But after the first temporary address becomes deprecated, it doesn't want to
create another one.  It just uses the permanent address.

Very occasionally deprecated address, after it has disappeared, really does
come back.  I was watching closely this time.

When the address stays gone (which it mostly does), the TCP connection seems to
timeout after about 4.5 minutes.  NFS then auto-reconnects and keeps working,
now using the permanent address.

Arg - it happened again.  I'm trying to use "telnet" to an "nc" server to
minimise complexity and watch what is happening, and twice now the temporary
address has become deprecated, disappears from the output of "ip -6 addr" at
which point traffic stops, and then miraculously re-appears about 3 minutes
later and the TCP connection starts working again.

Very hard to work out exactly what is happening when the symptoms keep
changing...