Equivalent of `curl --connect-to` in Python Requests library - http

Question

curl has an option connect-to
--connect-to <HOST1:PORT1:HOST2:PORT2>
For a request to the given HOST:PORT pair, connect to CONNECT-TO-HOST:CONNECT-TO-PORT instead. This option is suitable to direct requests at a specific
server, e.g. at a specific cluster node in a cluster of servers. This option is only used to establish the network connection. It does NOT affect the host-
name/port that is used for TLS/SSL (e.g. SNI, certificate verification) or for the application protocols. "host" and "port" may be the empty string, meaning
"any host/port". "connect-to-host" and "connect-to-port" may also be the empty string, meaning "use the request's original host/port".
This option can be used many times to add many connect rules.
What is the equivalent in Python Requests library?

Answer 1

There is no such equivalent but you can patch lower levels to rewrite the remote address when creating the connection.
This works in Python 3:
from unittest.mock import patch
# contextmanager for forcing a connection to a given host, port
def connect_to(host, port):
from urllib3.util.connection import create_connection as orig_create_connection
def _forced_address_connection(address, *args, **kwargs):
forced_address = (host, port)
return orig_create_connection(forced_address, *args, **kwargs)
return patch('urllib3.util.connection.create_connection', _forced_address_connection)
# force connections to 127.0.0.1:8080
with connect_to('127.0.0.1', 8080):
res = requests.get('http://service.example.com/')
Other solutions (patching PoolManager, using custom adapter) were not enough because the URL was rewritten as well (and thus the Host: header). When you use curl --connect-to, nothing is touched at HTTP level.
I also needed to optionally force http connections despite the URL scheme. This is the working augmented version for that:
import contextlib
from unittest.mock import patch
#contextlib.contextmanager
def connect_to(host, port, force_http=False):
from urllib3.connection import HTTPConnection
from urllib3.util.connection import create_connection as orig_create_connection
def _forced_address_connection(address, *args, **kwargs):
forced_address = (host, port)
return orig_create_connection(forced_address, *args, **kwargs)
class ForcedHTTPConnection(HTTPConnection):
def __init__(self, **kwargs):
httpconn_kw = ('host', 'port', 'timeout', 'source_address', 'blocksize')
httpconn_kwargs = dict([(k, kwargs[k]) for k in httpconn_kw if k in kwargs])
super().__init__(**httpconn_kwargs)
patchers = [patch('urllib3.util.connection.create_connection', _forced_address_connection)]
if force_http:
patchers.append(patch('urllib3.connectionpool.HTTPSConnectionPool.ConnectionCls', ForcedHTTPConnection))
for p in patchers:
p.start()
yield
for p in patchers:
p.stop()
# force connections to 127.0.0.1:8080 using http
with connect_to('127.0.0.1', 8080, force_http=True):
res = requests.get('https://service.example.com/')
see also Python 'requests' library - define specific DNS?.