[Xastir-dev] What does "local" mean?

[Curt Mills, WE7U]

On Thu, 16 Jan 2003 BobDonnell at arkalmus.com wrote:

> I'd suggest that setting the ST_DIRECT flag should not be done on the
> basis of having "heard XXX being used as a digipeater" e.g. N7TAP, since
> that too can be aliased.  Something to consider is whether to code to
> disregard any repeats heard of a particular packet - first one heard is
> the only one analyzed.  Flush after a minute.


A separate conversation with Bob, kd7nm:

<we7u> Ah.  Ok, so the rules:  If no asterisk in digi fields and all
of the WIDEn-N/TRACEn-N have n=N, then it's direct.

<kd7nm> If there are zero digipeaters listed, you're OK too.  No
asterisks in the digi field would strongly imply that we need to
check for a first digipeater field being WIDEN-n where N=n - and if
present and N=n, call it direct.  But the thinking of that whole
chain might need to be explained to others.

I'd do:
 1) Any digi fields?
 2) Any asterisks (or 'digipeated' flags, for KISS frames)
 3) Is first digi is a WIDEN-n or TRACEN-n
 4) N=n?

That make sense?

<we7u> Yea, except for the "first digi" part.  Need to check all
digi's for WIDEn-N/TRACEn-N.

<kd7nm> Nope.  Only the first - if that one hasn't been handled,
then it needs to be seen if its direct - if an asterisk was found
for it, we're already done.

<we7u> Ok.  You mean the first WIDEn-N/TRACEn-N then, not the first
digi field.  Could have "gate,relay,gate,relay,WIDE7-7,gate,relay",
but the asterisk doesn't get set until it is decremented to "n-1",
right?

<kd7nm> Yes, they could - but if we found an asterisk anywhere in
the digi list, we're done - it's not direct.  And we only need to
evaluate whether N=n if we're talking about the first digi in the
list - otherwise there will have been an asterisk.

<we7u> Ok.  So there's always an asterisk set on WIDEn-N/TRACEn-N
that have been used up, correct?

<kd7nm> Right - or any earlier digi field that's used up.  If digi
fields have been used up, at a minimum, one asterisk will be
present.  Some TNC firmware provides one asterisk per used digi
field.  You also need to make sure there isn't an asterisk in the
'from' field - or that you don't pay attention to it.

-- 
Curt Mills, WE7U                    hacker_NO_SPAM_ at tc.fluke.com
Senior Methods Engineer/SysAdmin
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