ntpdate.c unsafe buffer write - NTP

This is a discussion on ntpdate.c unsafe buffer write - NTP ; Serge Bets wrote: > Hello David, > > On Tuesday, March 18, 2008 at 2:44:12 +0000, David L. Mills wrote: > >> you need to set the minimum average headway/system minimum poll >> interval to 3 in both the server ...

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Thread: ntpdate.c unsafe buffer write

  1. Re: minpoll 3

    Serge Bets wrote:
    > Hello David,
    >
    > On Tuesday, March 18, 2008 at 2:44:12 +0000, David L. Mills wrote:
    >
    >> you need to set the minimum average headway/system minimum poll
    >> interval to 3 in both the server and client; otherwise, the server
    >> will declare a rate violation and toss you a KoD. Use the discard
    >> average 3 command in both the server and client.

    >
    > Thank you: I had no discard command. So now I tried on both the server
    > and the client:
    >
    > | discard average 3
    > | server minpoll 3
    >
    > Still same symptoms: The machines don't discipline their clocks. Until
    > the poll interval ramps to 16 seconds on the client. Forever on the
    > server, whose refclock sticks to minpoll. And ntptime shows time
    > constant 0 for minpoll 3 as well as for minpoll 4.
    >
    >
    > Serge.


    Serge,

    I believe this is not yet in any of the recent tarballs. There has been
    an issue in putting out new tarballs that I expect will be resolved shortly.

    Danny

  2. Re: minpoll 3

    Serge,

    I checked to verify the version claimed for the current snapshot on
    www.ntp.org matches the development version here, but that's no
    guarrantee that some recent stuff since the shot was stamped on 8
    Februrary. Fine tuning of the KoD response as I described in the report
    www.eecis.udel.edu/~mills/upgrade.txt and some other features were added
    since the last snapshot.

    Your description describes exactly what happens if the minimum average
    headway remains at the default 16 s and the client pounds away at 8 s.
    You might peek with the ntpdc sysstats command and vet the counters.
    Verify no error messages at startup; the configuration code might have
    balked when attempting to lower the discard average. Verify with ntpq
    that the poll interval in fact starts out at 3. If the client does
    indeed start out at 3 and the server rate-limits it, use the restrict
    default limited kod command to see if a KoD comes back.

    Dave


    Serge Bets wrote:
    > Hello David,
    >
    > On Tuesday, March 18, 2008 at 2:44:12 +0000, David L. Mills wrote:
    >
    >
    >>you need to set the minimum average headway/system minimum poll
    >>interval to 3 in both the server and client; otherwise, the server
    >>will declare a rate violation and toss you a KoD. Use the discard
    >>average 3 command in both the server and client.

    >
    >
    > Thank you: I had no discard command. So now I tried on both the server
    > and the client:
    >
    > | discard average 3
    > | server minpoll 3
    >
    > Still same symptoms: The machines don't discipline their clocks. Until
    > the poll interval ramps to 16 seconds on the client. Forever on the
    > server, whose refclock sticks to minpoll. And ntptime shows time
    > constant 0 for minpoll 3 as well as for minpoll 4.
    >
    >
    > Serge.


  3. Re: minpoll 3

    Hello David,

    On Sunday, March 23, 2008 at 20:07:33 +0000, David L. Mills wrote:

    > You might peek with the ntpdc sysstats command and vet the counters.
    > Verify no error messages at startup; the configuration code might have
    > balked when attempting to lower the discard average. Verify with ntpq
    > that the poll interval in fact starts out at 3. If the client does
    > indeed start out at 3 and the server rate-limits it, use the restrict
    > default limited kod command to see if a KoD comes back.


    There are no configuration parsing errors: Both "minpoll 3" and
    "average 3" are accepted (while "minpoll 2" or "average nan" shout the
    expected error).

    By default sysstats shows no rate exceeded, with or without "average 3".
    Rate exceeded start to appear when adding restrict limited without
    "average 3".

    With restrict kod on the server, after some time the client logs "no
    servers reachable" and doesn't poll anymore (but the refid stays "DCF",
    no "RATE" or whatever). No problem with "average 3".

    The poll interval indeed starts at 3, and I see a pair of packets in and
    out on the wire every 8-10 seconds.

    Anyway the kernel clock was never disciplined, even with "average 3" and
    no limited/kod restrictions. Thanks Dave, I'll wait for the next
    snapshot and retry.


    Serge.
    --
    Serge point Bets arobase laposte point net

  4. Re: minpoll 3

    Serge,

    Can we table this unil the next snapshot? It certainly works as
    advertised here.

    Dave

    Serge Bets wrote:
    > Hello David,
    >
    > On Sunday, March 23, 2008 at 20:07:33 +0000, David L. Mills wrote:
    >
    >
    >>You might peek with the ntpdc sysstats command and vet the counters.
    >>Verify no error messages at startup; the configuration code might have
    >>balked when attempting to lower the discard average. Verify with ntpq
    >>that the poll interval in fact starts out at 3. If the client does
    >>indeed start out at 3 and the server rate-limits it, use the restrict
    >>default limited kod command to see if a KoD comes back.

    >
    >
    > There are no configuration parsing errors: Both "minpoll 3" and
    > "average 3" are accepted (while "minpoll 2" or "average nan" shout the
    > expected error).
    >
    > By default sysstats shows no rate exceeded, with or without "average 3".
    > Rate exceeded start to appear when adding restrict limited without
    > "average 3".
    >
    > With restrict kod on the server, after some time the client logs "no
    > servers reachable" and doesn't poll anymore (but the refid stays "DCF",
    > no "RATE" or whatever). No problem with "average 3".
    >
    > The poll interval indeed starts at 3, and I see a pair of packets in and
    > out on the wire every 8-10 seconds.
    >
    > Anyway the kernel clock was never disciplined, even with "average 3" and
    > no limited/kod restrictions. Thanks Dave, I'll wait for the next
    > snapshot and retry.
    >
    >
    > Serge.


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