Maintaining Connectivity

Here are some tips on maintaining Internet connectivity, no matter the environment.

Behind Wifi Router Requiring Login

Often times you may be in an environment with Wifi that requires you to login though a captive portal, whether that be for free or for a fee. You can try to gain Internet access through this connection without logging in using the following methods.

TCP over ICMP

If ICMP traffic is allowed, you can tunnel through it. It is much less common for ICMP to be allowed. I need to research this more...

TCP over DNS

Often times the devices running the captive portals block all traffic except DNS queries. If they ley DNS queries through, you can tunnel TCP traffic through DNS queries Pros:

• Access in restricted environments

Cons:

• It won't be fast
• It will require that you have a DNS server running somewhere

Recommended software

• iodine (C, multi-platform)
  Iodine lets you tunnel IPv4 data through a DNS server. This can be usable in different situations where internet access is firewalled, but DNS queries are allowed.
  It runs on Linux, Mac OS X, FreeBSD, NetBSD, OpenBSD and Windows and needs a TUN/TAP device. The bandwidth is asymmetrical with limited upstream and up to 1 Mbit/s downstream.
• tcp-over-dns (Java)
  tcp-over-dns contains a special dns server and a special dns client. The client and server work in tandem to provide a TCP (and now UDP too!) tunnel through the standard DNS protocol.