Querying the PCCT in Python

The Platform Communication Channel Table contains information used to send messages in a shared memory buffer between the Operating System and other subsystems on the platform. Typically, the Channel has an interrupt defined that is used to tell the other subsystem that there is new data available.

Recently, I’ve been working with a couple entries that are of a newer type. In addition to the shared memory region and the interrupt values, the PCCT entries for type 3 and type 4 channels also have a series of registers. Where before the PCCT entries were normalized, now they are hierarchical. This makes them a little harder to scan with the human eye to confirm that the proper values have been recorded and read.

To simplify development, I build a simple script.

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Talking to FreeIPA with python-requests

The code that Rich M gave me a while back has bit rotted. At some point, I need to get an updated version, but until then, I can continue to talk to the FreeIPA server using Python and the Requests library. In the future, I can get a session cookie, but for now, python3-request-gssapi will work to authenticate me, provided I have a valid TGT.

I pulled the requests-gssapi library from Koji, as it does not currently ship in any of the RHEL8 repos. Here is the one I installed.


Note that this quick-and-dirty code runs on the IPA server itself. A better approach would be to read the Server name out of /etc/ipa/default.conf.

import requests
from requests_gssapi import HTTPSPNEGOAuth
import socket
hostname = socket.gethostname()
url = "https://%s/ipa/json" % hostname
referer =  "https://%s/ipa" % hostname
body = {"method":"user_find","params":[[""],{}],"id":0}
r = requests.post(url,
                  json = body,
                  headers = {
                    'Content-Type': 'application/json',
                    'Accept': 'applicaton/json',
                    'referer': referer})
if r.status_code  == 200: