Obtaining Client IP address from a WSGI app using Eventlet

I'm currently writing a basic dispatch model server based on the Python Eventlet library (http://eventlet.net/doc/). Having looked at the WSGI docs on Eventlet (http://eventlet.net/doc/modules/wsgi.html), I can see that the eventlet.wsgi.server function logs the x-forwarded-for header in addition to the client IP address.

However, the way to obtain this is to attach a file-like object (the default which is sys.stderr) and then have the server pipe that to that object.

I would like to be able to obtain the client IP from within the application itself (i.e. the function that has start_response and environ as parameters). Indeed, an environ key would be perfect for this. Is there a way to obtain the IP address simply (i.e. through the environ dictionary or similar), without having to resort to redirecting the log object somehow?

Solution

What you want is in the wsgi environ, specifically environ['REMOTE_ADDR'].

However, if there is a proxy involved, then REMOTE_ADDR will be the address of the proxy, and the client address will be included (most likely) in HTTP_X_FORWARDED_FOR.

Here's a function that should do what you want, for most cases (all credit to Sævar):

def get_client_address(environ):
    try:
        return environ['HTTP_X_FORWARDED_FOR'].split(',')[-1].strip()
    except KeyError:
        return environ['REMOTE_ADDR']

You can easily see what is included in the wsgi environ by writing a simple wsgi app and pointing a browser at it, for example:

from eventlet import wsgi
import eventlet

from pprint import pformat

def show_env(env, start_response):
    start_response('200 OK', [('Content-Type', 'text/plain')])
    return ['%s\r\n' % pformat(env)]

wsgi.server(eventlet.listen(('', 8090)), show_env)

And combining the two ...

from eventlet import wsgi
import eventlet

from pprint import pformat

def get_client_address(environ):
    try:
        return environ['HTTP_X_FORWARDED_FOR'].split(',')[-1].strip()
    except KeyError:
        return environ['REMOTE_ADDR']

def show_env(env, start_response):
    start_response('200 OK', [('Content-Type', 'text/plain')])
    return ['%s\r\n\r\nClient Address: %s\r\n' % (pformat(env), get_client_address(env))]

wsgi.server(eventlet.listen(('', 8090)), show_env)