python - Send http request through specific network interface

Question

I have two network interfaces (wifi and ethernet) both with internet access. Let's say my interfaces are eth (ethernet) and wlp2 (wifi). I need specific requests to go through eth interface and others through wpl2.

Something like:

// Through "eth"
request.post(url="http://myapi.com/store_ip", iface="eth")
// Through "wlp2" 
request.post(url="http://myapi.com/log", iface="wlp2")

I'm using requests, but I can use pycurl or urllib if there isn't any way to do it with requests.

How to specify source interface in python requests module? refers to Requests, bind to an ip and it doesn't work.

Answer 1

Here is the solution for?Requests library without monkey-patching anything.

This function will create a Session bound to the given IP address. It is up to you to determine IP address of the desired network interface.

Tested to work with requests==2.23.0.

import requests


def session_for_src_addr(addr: str) -> requests.Session:
    """
    Create `Session` which will bind to the specified local address
    rather than auto-selecting it.
    """
    session = requests.Session()
    for prefix in ('http://', 'https://'):
        session.get_adapter(prefix).init_poolmanager(
            # those are default values from HTTPAdapter's constructor
            connections=requests.adapters.DEFAULT_POOLSIZE,
            maxsize=requests.adapters.DEFAULT_POOLSIZE,
            # This should be a tuple of (address, port). Port 0 means auto-selection.
            source_address=(addr, 0),
        )

    return session


# usage example:
s = session_for_src_addr('192.168.1.12')
s.get('https://httpbin.org/ip')

Be warned though that this approach is identical to curl's --interface option, and won't help in some cases. Depending on your routing configuration, it might happen that even though you bind to the specific IP address, request will go through some other interface. So if this answer does not work for you then first check if curl http://httpbin.org/ip --interface myinterface will work as expected.