broken trust chain

Mark Andrews marka at isc.org
Wed Jul 29 01:15:24 UTC 2020


A network link that is dropping packets can trigger EDNS failures in versions of
BIND before 9.13.3.  These versions have code to compensate for servers that
fail to respond to EDNS queries or fail to respond to EDNS queries with DO=1
or fail to respond to queries with (particular) EDNS options set. BIND would
fallback to plain DNS queries to workaround these issues, but that broke
DNSSEC when the answers where coming from a signed zone and the packet loss
is due to network issues.

5029.   [func]          Workarounds for servers that misbehave when queried
                        with EDNS have been removed, because these broken
                        servers and the workarounds for their noncompliance
                        cause unnecessary delays, increase code complexity,
                        and prevent deployment of new DNS features. See
                        https://dnsflagday.net for further details. [GL #150]


> On 29 Jul 2020, at 09:10, <Youssef.FassiFihri at inwi.ma> <Youssef.FassiFihri at inwi.ma> wrote:
> 
> Hi All,
> 
> I am using Bind as resolver for end users  .
> 
> At various time, bind logs show "broken trust chain" continuously  , for about 20mn  ~ 30 mn causing an increase of "recursive clients" shown in "rndc status" and a decrease of  "DNS sucess rate KPI" supervised from end users side.  then the error disappear and everything is OK.
> 
> the problem appears on different server at different time.
> 
> What could be the problem?
> 
> Regards, 
> 
> 
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-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742              INTERNET: marka at isc.org



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