A plug to overwrite the Plug.Conn’s remote_ip based on headers such as X-Forwarded-For.

To use, add the RemoteIp plug to your app’s plug pipeline:

defmodule MyApp do
  use Plug.Builder

  plug RemoteIp
end

There are 2 options that can be passed in:

• :headers - A list of strings naming the req_headers to use when deriving the remote_ip. Order does not matter. Defaults to ~w[forwarded x-forwarded-for x-client-ip x-real-ip].

• :proxies - A list of strings in CIDR notation specifying the IPs of known proxies. Defaults to [].

For example, if you know you are behind proxies in the IP block 1.2.x.x that use the X-Foo, X-Bar, and X-Baz headers, you could say

defmodule MyApp do
  use Plug.Builder

  plug RemoteIp, headers: ~w[x-foo x-bar x-baz], proxies: ~w[1.2.0.0/16]
end

Note that, due to limitations in the inet_cidr library used to parse them, :proxies must be written in full CIDR notation, even if specifying just a single IP. So instead of "127.0.0.1" and "a:b::c:d", you would use "127.0.0.1/32" and "a:b::c:d/128".