[asterisk-users] DNS A queries for channel

[samuel]

Hi folks,

I've been using * for quite a few years and everyday it surprises me more.

I was recently analysing some captures with ethereal/wireshark and found out
that * was doing DNS A queries for domain names like
channel.mydomain.comwhere channel is the typical string of the
dstchannel or channel field in
the CDR entries.

Obviously those queries returned with negative answer because it does not
exists such domainname. My question is why is * asking the DNS for the A
entry of the channel? It looks like it does the DNS query upon receiving a
SIP message but none SIP header contains the channel string in the SIP
headers so it must be something internal, maybe some end-point check?
Considering how delicate is * to DNS failures I would like to know whether
this behaviour can be disabled in the config files because it makes * block
easier and charges the DNS server of senseless queries.

I don't know about * internals so it 's far beyond my knowledge following
the reception and treatment of SIP message throughout the sip_channel.c code
so I would really appreciate any hint about this issue.

The capture was done on a 1.4.18 version but I've checked same behaviour
(ngrep port 53) on other 1.4 and 1.2 installations. Does anyone knows if
this has changed in 1.6?

Any help would be really appreciated.

Thanks,
Samuel.
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