keepalive timer?

David Hopwood <>
Tue Jun 22 20:17:42 CEST 2004


Per Hedeland wrote:
> David Hopwood <> wrote:
>>TCP_KEEPIDLE et al are not Linux-specific; AFAICS they seem to be supported
>>on all BSD-derived TCP stacks (most Unices including OS X, also OpenVMS, but
>>not Win32).
> 
> Interesting - do you have some other example of "most Unices"?
 > The "BSD-derived" would seem to be misleading, since they're not in the
 > latest and greatest FreeBSD (5.2.1), nor can I find them in the online
 > tcp(4) man pages of current OpenBSD or NetBSD.

You're right -- I was confused by the fact that many stacks use internal
variables "tcp_keepidle", etc., but these are not socket options. Taking
this into account, I can only find three Unices that support these options:
Tru64 (Digital/HP/Compaq), MP-RAS (NCR), and Linux.

> I also checked the tcp(7P) man
> page of Solaris 8 and 9, not there either, though I did find an
> apparently undocumented TCP_KEEPALIVE, that might possibly be a
> setsockopt combining SO_KEEPALIVE and Linux TCP_KEEPIDLE, in the include
> files of Solaris 8 (nothing corresponding to TCP_KEEPINTVL/TCP_KEEPCNT
> though).

TCP_KEEPALIVE is defined by the X/Open Transport Interface. At least MAC OS
(Open Transport), OS/390, SCO UnixWare, and AIX also support it.
See <http://nscp.upenn.edu/aix4.3html/libs/commtrf2/Options.htm> or
<http://developer.apple.com/documentation/mac/NetworkingOT/NetworkingWOT-390.html#HEADING390-0>.

-- 
David Hopwood <>




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