From: Travis H. (travis+ml-postfixsubspacefield.org)
Date: Sat Jan 20 2007 - 23:36:41 CST

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On Wed, Jan 03, 2007 at 09:40:51AM -0500, Victor Duchovni wrote:
> No. Nameservers must and do respond from the IP address to which the
> query was sent.

RFC 1035 section 7.3 disagrees with you:

  Some name servers send their responses from different addresses than
  the one used to receive the query. That is, a resolver cannot rely
  that a response will come from the same address which it sent the
  corresponding query to. This name server bug is typically encountered
  in UNIX systems.

I assume this has to do with the way recv(2) and send(2) were
implemented in the socket API, but my OS states that recv(2) is
normally used only on a connected socket.

Still, it is good that the RFC calls it an error.

For more discussion about interpreting DNS strictly by the RFCs:
http://www.phrack.org/archives/62/p62-0x03_Linenoise.txt

Another interesting piece of trivia is that RFC 768 says that
the source port in a UDP packet is an optional field; that is,
it may be set to an arbitrary value by the implementation, a
fact which may surprise a number of firewall admins.
--
``Unthinking respect for authority is the greatest enemy of truth.''
-- Albert Einstein -><- <URL:http://www.subspacefield.org/~travis/>

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