Received notify, master unreachable (cached)

Matus UHLAR - fantomas uhlar at
Tue Jun 21 07:16:06 UTC 2011

>> Either the slave tries to reach the master using wrong source IP address
>> ( means it leaves this to system) or the master does not allow
>> traffic from slave (e.g. firewall).

On 17.06.11 21:44, Jarosław Świerczyński wrote:
>Nope, I know for sure that the master becomes reachable from the slave
>because I start it. And some time later the slave itself attempts to
>contact the master again and it succeeds.

Oh, shame on me, I have missed the "(cached)" part in the logfile.

>I had a look at the source code and I believe I found the problem. In
>lib/dns/zone.c the is a cache where unreachable masters are stored.
>Function dns_zonemgr_unreachable() is used to check if a master in
>marked as unreachable, while dns_zonemgr_unrechableadd() - to add
>entries to the cache. In my opinion the problem is that there is no
>mechanism to remove entries from the cache except when they expire.
>BIND should remove an entry for a particular master every time it
>receives any communication from that master, like in
>dns_zone_notifyreceive(). As you pointed out, it doesn't necesarrily
>mean the master is reachable from the slave but it is worth trying to
>respond to the notification, it won't hurt.

I think you may be right, but I'd better put a limit on how often this may 
happen, so the bind won't re-check too often if the master is unreachable.

Matus UHLAR - fantomas, uhlar at ;
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