test_socket fails on systems without certain entries in /etc/services #138216
Description
Bug report
Bug description:
Description
I encountered a failure in test_socket.py on a minimal Linux environment. This issue appears due to the test suit's assumption about system configuration, not a bug in the socket module itself.
Environment
- OS: debian:bookworm-slim(Docker)
- Architecture: x86-64
Error log
======================================================================
ERROR: testGetServBy (test.test_socket.GeneralModuleTests.testGetServBy)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/src/Lib/test/test_socket.py", line 1279, in testGetServBy
raise OSError
OSError
======================================================================
ERROR: testGetaddrinfo (test.test_socket.GeneralModuleTests.testGetaddrinfo)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/src/Lib/test/test_socket.py", line 1676, in testGetaddrinfo
socket.getaddrinfo(HOST, "http")
~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^
File "/src/Lib/socket.py", line 992, in getaddrinfo
for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
socket.gaierror: [Errno -8] Servname not supported for ai_socktypeAnalysis
Though these two functions throw different types of exception, I believe both of them related to the test assume that some services have defined in /etc/services file. However, not all Linux distributions include these entries by default.
This problem stems from that test_socket.py rely on getaddrinfo() and getservbyname() systemcall, which will return services declared in /etc/services. test_socket.py didn't check if the systems has a /etc/services file or declare the services we need(daytime, qotd, domainfor testGetServBy and http for testGetaddrinfo), and the socket module will throw exceptions when the test try to get the information of an 'unknown' service, which fail the test.
Most of the Linux distributions declare common services and their ports in /etc/services, but there's no mandatory standards about which services should be included in /etc/services file. In this case, the test use hardcoding services name that not exist in some distributions and cause the error.
Reproduction
Use Docker
The issue can be reproduced using the following dockerfile.
FROM debian:bookworm-slim
ARG APT_SOURCE=deb.debian.org
RUN sed -i "s|deb.debian.org|${APT_SOURCE}|g" /etc/apt/sources.list.d/debian.sources && \
apt-get update && \
apt-get install -y --no-install-recommends \
git vim pkg-config build-essential gdb lcov \
libbz2-dev libffi-dev libgdbm-dev libgdbm-compat-dev liblzma-dev \
libncurses5-dev libreadline6-dev libsqlite3-dev libssl-dev \
lzma lzma-dev tk-dev uuid-dev zlib1g-dev libzstd-dev libnss3-dev && \
apt-get clean && \
rm -rf /var/lib/apt/lists/*
RUN useradd -m -U dev && \
mkdir /src && chown dev:dev /src
USER dev
WORKDIR /src
CMD ["/bin/bash"]Setup manually
Alternatively, we can modify the /etc/services file to reroduce this issue. Remove or comment out the lines containing daytime, qotd, domain and http or delete the /etc/services file entirely before running the test.
Fixing
I suggest modifying the test to skip if the required services are not available, or to query the /etc/services file for an available service.
I'd be happy to submit a patch if the core team agrees with this fix.
CPython versions tested on:
CPython main branch
Operating systems tested on:
Linux