"What is my IP-address?" with Varnish 4+

Ever thought sites like ifconfig.me and similar are too slow from the command line? Here I'll show you how easy it is to setup something similar to those services - except it is extremely fast because of Varnish.

The receiver part:

sub vcl_recv {
  if (req.http.host == "ipv4.is") {
    return …
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