[FS#482] Web server listens on all interfaces (Archer MR200)

[LEDE Bugs]

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FS#482 - Web server listens on all interfaces (Archer MR200)
User who did this - Zero (zero)

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Hi. At least I tested it and the httpd works in that address.
About being necessary... The 4G modem (Android) has three interfaces:

bridge0 - 192.168.225.1 - which is the link to the LEDE router.
  (corresponding to usb0 in the LEDE router which in my case has address 192.168.225.143).
rmnet0 - which is the external interface.
rndis0 - which I do not know what is it.

In my case rmnet0 has an address like 10.x.y.z because I have Carrier Grade NAT, but if it were otherwise, it would have a public IP.
If the httpd listens in 0.0.0.0 it would listen also in rmnet0 and I thought it would be visible from outside.
So I thought it was better to restrict the listening interface to enhance security and avoid external access.

But I may be wrong as I do not know the exact behaviour in case of DMZ. I could not test if it was really accesible from outside or not. So I do not know.
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=482#comment1661