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Date:      Sat, 25 Jul 1998 01:47:55 +0200 (MET DST)
From:      Willem Jan  Withagen <wjw@surf.IAE.nl>
To:        mike@smith.net.au (Mike Smith)
Cc:        wjw@IAEhv.nl, dfr@nlsystems.com, hackers@FreeBSD.ORG
Subject:   Re: SYSCTL .......
Message-ID:  <199807242347.BAA23128@surf.IAE.nl>
In-Reply-To: <199807242307.QAA00758@dingo.cdrom.com> from Mike Smith at "Jul 24, 98 04:07:04 pm"

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You ( Mike Smith ) write:
=>  > =>  Last time I was daydreaming about sysctl, I thought that using SYSINIT
=>  > =>  functions to build the tree would be a good idea.  This would have the
=>  > =>  benefit of trivially adding in sysctl variables in kernel modules loaded
=>  > =>  using KLD since it runs SYSINITs in the loaded modules.  To support
=>  > =>  unloading modules, a method of automatically disconnecting variables
=>  > =>  defined by the module is needed. 
=>  > 
=>  > Intresting point. 
=>  > I haven't thought about this point. I considered that once submitted OID's 
=>  > are there for ever. But evaporating LKM's would case some access trouble.
=>  
=>  Correct.  We should incorporate the simple structure reference counting 
=>  implementation that Terry published a little while back (Terry, why is 
=>  this not on your webpage?).
=>  
=>  When registering a node, it should be possible to supply an object 
=>  against which a reference will be taken.  In the case of an LKM, the 
=>  module may not be unloaded without its reference count being zero.

I would consider multiple attempts to create a node redundant, since only
one node will be created. The first invalidation of a node disables the
node, more request to that nature will be again redundant.

=>  Save yourself some grief, and eliminate numeric OIDs.

Why would you say that? if we want to doSNMP we'd need atleast a translation
from namestrings to numberstrings.

=>  > The numeric sequences are more/most important entry for the structure.
=>  > This due to the idea have on SNMP-mib's.
=>  
=>  No, and very bad.  Numeric OIDs should be supported for *legacy* nodes 
=>  only.

At first I find this a little strange,
Tell me more .....

=>  > Given the fact that one of the most common operators on a MIB-tree will be
=>  > get_next, I'm considering adding a UP-relation as well. This will make it
=>  > possible to get back to the one-higher node in the same tree.
=>  
=>  The ability to traverse, and also to best-guess restart a traversal 
=>  from a node that no longer exists, is critical.

Hence my reason not to remove the node, but invalidate it.
The data is no longer there, but the node is.

--WjW
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