Custom nameservers over wifi hotspots with initial web login

Question

I have built a portable router using a raspberry pi. My setup works, unless I connect to a hotspot that requires some kind of web based login.

After some investigation, I think I've tracked it down to a nameserver issue. I am using google's nameservers in my dhcpd.conf file below, this works without issues when i connect to hotspots that dont require an initial web login (home wifi, for example).

/etc/dhcp/dhcpd.conf

ddns-update-style none;
default-lease-time 600;
max-lease-time 7200;
authoritative;
log-facility local7;

subnet 192.168.111.0 netmask 255.255.255.0 {
  range 192.168.111.100 192.168.111.200;
  option broadcast-address 192.168.111.255;
  option routers 192.168.111.1;
  default-lease-time 600;
  max-lease-time 7200;
  option domain-name "local-network";
  option domain-name-servers 8.8.8.8, 8.8.4.4;
}

Removing the option domain-name-servers line makes all clients on wlan1 unable to resolve hostnames.

I am able to find the current hotspot's nameservers inside /etc/resolv.conf

/etc/resolv.conf

nameserver 212.27.40.241
nameserver 212.27.40.240

On my macbook, if I manually enter these nameservers in the network settings area, I am redirected to the hotspot's login page. Once logged in, I can remove these manual entries and it will revert to the name servers provided by my DHCP server.

However, this is not an optimal solution as the connected hotspot on wlan0 will change as I travel and I will have more than one device connected to wlan1.

My goal here is to remove this last step. Is there some way to automate this on the raspberrypi server? Or am I approaching this in the wrong way? Is the best solution to always use the hotspot's default DNS? If so, how do i instruct dhcpd to do so automatically?

Some info about my setup:

• 2 physical wifi adapters
• wlan0 to connect to various hotspots
• wlan1 to create a local network.
• isc-dhcp-server (dhcpd) to distribute IP addresses over wlan1
• hostapd to create a local hotspot
• NAT traversal using iptables

Answer 1

In order for this to work, you need to actually log in to the hotspot using a web interface. There are some scripts that can do this automatically with varying level of success, you may try your luck with e.g. Zeroshell or similar.