On Wed, 2005-10-19 at 10:52 -0700, Yong Chen (yongche) wrote:
> But in ChangeLog, it says:
>
> Fixes:
> - the agent should properly handle requests in the right order.
> (e.g., restrict the agent to processing only one SET at a time)
Yes - that's concerned with the processing of two *different* SET
requests. Not the processing of two varbind assignments in the
*same* SET request.
If an agent receives:
SET oneFish = xxx
SET twoFish = yyy
then it should finish handling the "oneFish" assignment *before*
starting to look at the "twoFish" assignment.
If it receives:
SET redFish = xxx, blueFish = yyy
then it needs to process *both* assignments "at the same time".
> Also the ordering of varbinds in a SET request may have some
> significance because of dependency between the varbinds.
That's why handling SET requests properly is Non-Trivial!
The usual basic technique is to walk through the full
list of assignments, checking them individually and
making any preparations for acting on them.
Then walk through the list again, updating the
individual assignments.
Then walk through the list *again*, checking that
the final state is consistent.
Then walk through the list again, tidying up.
If one assignment ("oldFish") relies on another ("newFish"),
it is *NOT* valid to assume that the varbinds occur in the
most helpful order. The agent *MUST* be able to process
both
SET oldFish = xxx, newFish = yyy
and
SET newFish = yyy, oldFish = xxx
with *exactly* the same results in either case.
> Where can I find doc regarding the simultaneously
> processing SET assignments?
RFC 3416, section 4.2.5
See p22, second para.
> And I've been reading the code, but not finding the "as if
> simultaneously" processing of SETs. Can you please point me
> to the code?
There is no One Single Place where this is handled.
Each MIB will have different requirements for what assignments
rely on other ones, so the "as if simultaneous" code will be
specific to each particular MIB.
For an example, have a look at 'agent/mibgroup/agent/nsLogging'.
This shows one possible approach to ensuring that SEt requests
will be processed correctly, independent of varbind order.
I probably wouldn't write this in quite the same way now, but
it show the basic ideas.
Dave
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