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SubjectRe: SyncPPP IPCP/LCP loop problem and patch
rjd@xyzzy.clara.co.uk writes:

> I've hit a problem with the syncPPP module within Linux.
>
> Under certain conditions (hard to quantify exactly, but try several 8Mbps
> streams hitting a relatively slow, say 200MHz processor) the LCP/IPCP
> negotiation hits the following loop.

[snip]

> My solution in the patch that follows is to detect the flip-flop using a
> counter and then after three occurrences with no genuine IPCP traffic to
> modify behavior on receipt of the LCP conf REQ. After three attempts we
> acknowledge the LCP conf REQ but stay in the opened state rather than
> dropping back and restarting our own LCP negotiation. This is non-RFC1661
> behavior unless you consider it part of the general loop avoidance directive.

Seems to me that when you get the conf-request in opened state, you
should send your conf-request before sending the conf-ack to the
peer's conf-request. I think this would short-circuit the loop (I
could be wrong though, it's getting late).

That behaviour would be in line with the FSM in rfc1661, where the
action for event RCR+ in Opened state is "tld,scr,sca/8", i.e. the one
action involves sending both the conf-request and the conf-ack. It is
debatable to what extent that specifies the order of the messages but
it does list the conf-request first FWIW.

Paul.
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