Re: [SLUG] TCP keepalives

[Herbert Xu <herbert@nospam.gondor.apana.org.au>]

Howard Lowndes <lannet@nospam.lannet.com.au> wrote:

> Do these existing connections use the values that existed when the
> connection was established, and any new connections will have the new
> values?

All will use the new values.

> Does the setting of these values activate keepalives, or is there some
> other boolean flag that I need to set in addition?

These settings only come into effect if the IPV4 TCP socket in question had
the KEEPALIVE option set.  But telnetd should set it unless you ran it with
-n.  In any case, do a strace when telnetd starts to see whether KEEPALIVE is
being set.

> What are the implications of changing these values, apart from the
> obvious?  Most long time connections to this server are telnet, imap or
> ssh.

The implication is probably that you're going to be sending a lot of
unnecessary keepalive packets.  It is also possible for some legitimate
connections to get dropped if their connection is poor.

> Am I on the correct track or did I miss a turning somewhere?

It should work without changing any parameters.  Of course, it's easier to
lower the numbers while testing.  But do restore them when you're satisfied
that it's working.
-- 
Debian GNU/Linux 2.1 is out! ( http://www.debian.org/ )
Email:  Herbert Xu ~{PmV>HI~} <herbert@nospam.gondor.apana.org.au>
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