socket.RDS_CMSG_RDMA_UPDATE doesn't seem to be real

Bug report

Bug description:

I was recently working through the constants in socket for typeshed. I found that RDS_CMSG_RDMA_UPDATE is not present in linux header files for any version of linux, and the only hits for a google search are python-related. I believe this is a typo for RDS_CMSG_CONG_UPDATE, which is the only RDS_*_UPDATE constant in rds.h: see the header file here

Given that it's been that way for 13 years without anyone noticing, I don't know if it should be fixed or if it should just be removed. Original issue: https://github.com/python/cpython/issues/52025

Original commit: https://github.com/python/cpython/commit/10b8cf4455f48eba93077535e4d03eba2ee4bbfb

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS

CPython の socket モジュールにある定数定義から始め、RDS_CMSG_RDMA_UPDATE と、リンクされている Linux ヘッダーファイル include/uapi/linux/rds.h を比較します。これが RDS_CMSG_CONG_UPDATE の誤記なのか、それとも削除すべきものなのかを確認し、その後、対象プラットフォームで socket 定数が一貫して動作することを検証します。