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LYNX-DEV dns lookups

From: Andy Harper
Subject: LYNX-DEV dns lookups
Date: Mon, 22 Dec 1997 15:10:13 GMT

I discovered the following problem while using LYNX compiled with the socketshr
library for VMS to access a service provided by the british library:

  Despite the name ( resolving to an IP address, lynx fails to
  connect with:
        "unable to access remote host!"

  At first, I thought it was inaccessible but no, I could connect to the port
  using telnet. Further investigations showed that the socketshr package was
  failing to return a valid hostent structure because the DNS could not reverse
  lookup the ip address on a gethostbyname call (note: '' NOT '..addr')

Enquiries to the maintainers of the relevant DNS maintained that it was
incorrect behaviour and that they didn't see the need for a reverse DNS lookup

So, my question to the experts are:
  *  Is it sensible for a system to not have a reverse DNS entry (IE to map ip
     address back to name)? I can't see any security risk posed by having one
     but can see a lot of instances (EG mail) where it would be bad news NOT
     to have one.

  *  What should a gethostbyname call do if, having gotten the IP address from
     the DNS, it fails to retrieve the real name via a reverse lookup in order
     to set the h_name item of the hostent structure?

This is not strictly a lynx question but, as it affects lynx, i thought it
useful to post here for info (and any answers if you have them..)

Thanks for any input.


Andy Harper
Kings College London

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