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How can I get the clients IP address from HTTP headers?

Asked 2009-02-09T10:12:29.697
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I understand it's a standard practice to look at both these variables. Of course they can easily be spoofed. I'm curious how often can you expect these values (especially the HTTP_X_FORWARDED_FOR) to contain genuine information and not just be scrambled or have their values stripped away?

Anyone with the experience or statistics on this stuff?

Is there anything else that can be useful for the task of getting the client's IP address?

http http-headers ip ip-address
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No real answer to your question but:
Generally relying on the clients IP address is in my opinion not a good practice as it is not usable to identify clients in a unique fashion.

Problems on the road are that there are quite a lot scenarios where the IP does not really align to a client:

  • Proxy/Webfilter (mangle almost everything)
  • Anonymizer network (no chance here either)
  • NAT (an internal IP is not very useful for you)
  • ...

I cannot offer any statistics on how many IP addresses are on average reliable but what I can tell you that it is almost impossible to tell if a given IP address is the real clients address.

answered 2009-02-09T10:28:04.137

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