gethostbyaddr doing a A query

pappu72_99_at_yahoo.com
Date: 11/17/05 

Date: 17 Nov 2005 06:32:35 -0800

Hello all

I am curious to know the reason for behaviour of gethostbyaddr which i
am mentioning below
I was tracing the packets using tcpdump

19:57:34.470224 IP x1.53399 > x2.domain : 161+ PTR? x3.in-addr.arpa.
(44)
19:57:34.471383 IP x2.domain > x1.53399: 161* 1/3/3 (222)
19:57:34.473371 IP x1.53400 > x1.domain : 162+ A? x3. (39)
19:57:34.474282 IP x2.domain > x1.53400: 162 1/5/5 A[|domain]

x1=server
x2 = DNS server
x3 = client

when client x3 connects to server x1, the server code does a
gethostbyaddr() with clients, x3's address. So we can understand the
PTR query.

But can anyone tell me for what reason does it immediately does a A
query ?

Thanks
Pappan

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