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List:       ntp-bugs
Subject:    [ntp:bugs] [Bug 2073] New: ntpd spins symmetric passive association
From:       bugzilla-daemon () ntp ! org
Date:       2011-11-28 4:25:25
Message-ID: bug-2073-35 () http ! bugs ! ntp ! org/
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https://bugs.ntp.org/show_bug.cgi?id=2073

             Bug #: 2073
           Summary: ntpd spins symmetric passive association in response
                    to KoD
           Product: ntp
           Version: 4.2.6
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P5
         Component: ntpd
        AssignedTo: hart@ntp.org
        ReportedBy: hart@ntp.org
                CC: bugs@ntp.org
    Classification: Unclassified


While not the topic of this bug (it will likely be the topic of the next filed)
it is relevant that ntp-stable and ntp-dev ntpd send KoD responses with one of
two packet modes.  When the triggering inbound packet was MODE_CLIENT, the KoD
is MODE_SERVER.  For any other triggering packet mode, the KoD is MODE_ACTIVE. 
This is an odd choice but it's out in the wild regardless of future fixes.

While investigating Bug 2069, itself fallout of Bug 2050, I noticed apparent
duplicate associations monitoring the peers billboard even after believing I
had eliminated all ways that broadcastclient ephemeral associations could be
duplicated (taking into account unicast volley and broadcast stages).  Closer
examination of ntpd trace output showed the duplicates were in fact automatic
associations of a different feather, symmetric passive associations spun up in
response to a KoD triggered by a legit mode 4 server response.

I've enhanced the 4.2.7 peers billboard type column in a patch for this issue
to show big "S" for symmetric passive associations, which were showing "u" and
in contrast to symmetric active associations from "peer" directives in
ntp.conf, which show little "s".

I'm also refining the symmetric passive automatic association code to refuse to
spin when the incoming packet shows LEAP_NOTINSYNC (leap=11 in ntpq) as all
KoDs do.

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