odd fsockopen behavior

[yawnmoth]

Any IP address I try to open with fsockopen on a particular server
seems to use another IP address instead.

eg. I open a socket connection to 192.168.1.1 but the remote_addr that
the other server sees is 192.168.1.255. It's as if, like I said, the
IP address I supply to fsockopen is being replaced with another one.

Anyway, this is breaking a script of mine. I don't think I can really
do a lot in PHP to fix this but is there perhaps some way that I can
detect it? Is there some command line parameter that I can pass to
passthru or something that'll tell me whether or not such a thing is
happening?

Also, how is this even being done? Could a firewall do this? If so,
I'm still not even sure how it'd be done...

[Gordon Burditt]

>Any IP address I try to open with fsockopen on a particular server

seems to use another IP address instead.

eg. I open a socket connection to 192.168.1.1 but the remote_addr that
the other server sees is 192.168.1.255. It's as if, like I said, the
IP address I supply to fsockopen is being replaced with another one.
NAT in a firewall or router?
Using a broadcast address for this is kinda wierd.

Describe your network topology, including all the routers and switches.
Anyway, this is breaking a script of mine. I don't think I can really
do a lot in PHP to fix this but is there perhaps some way that I can
detect it?
If there's NAT in use, you can't detect this just from the
server end. You'd have to ask (and trust) the client end to
give you what *it* thinks the IP address is. But Javascript
is often Turned Off (tm).
Is there some command line parameter that I can pass to
passthru or something that'll tell me whether or not such a thing is
happening?

Also, how is this even being done? Could a firewall do this? If so,
I'm still not even sure how it'd be done...

A firewall with NAT could definitely do this, although it seems its
configuration is a bit wierd.

Gordon L. Burditt

[yawnmoth]

Gordon Burditt wrote:

<snip>
NAT in a firewall or router?
Using a broadcast address for this is kinda wierd.

Describe your network topology, including all the routers and switches. It's remote web hosting on the GoDaddy.com hosting servers. Beyond
that, I don't know...
If there's NAT in use, you can't detect this just from the
server end. You'd have to ask (and trust) the client end to
give you what *it* thinks the IP address is. But Javascript
is often Turned Off (tm).

Wouldn't using a SOCKS proxy or something yield false positives in that
case?

Also, would the gateway computer be the one responsible for the NAT?

[Gordon Burditt]

>> <snip>

NAT in a firewall or router?
Using a broadcast address for this is kinda wierd.

Describe your network topology, including all the routers and switches.It's remote web hosting on the GoDaddy.com hosting servers. Beyond
that, I don't know...

If these servers are available for surfing to the public, and the
addresses you gave are real, there *MUST* be some NAT in there
somewhere, as the addresses are private ones, and the general public
can't route to them.

If there's NAT in use, you can't detect this just from the
server end. You'd have to ask (and trust) the client end to
give you what *it* thinks the IP address is. But Javascript
is often Turned Off (tm).

Wouldn't using a SOCKS proxy or something yield false positives in that
case?

Yes, although it's unclear in my mind whether that would be a FALSE
positive or a TRUE positive.
Also, would the gateway computer be the one responsible for the NAT?

Nobody said the gateway is a computer. It might be a Cisco router,
or a DSL modem/router.

Gordon L. Burditt