/usr/lib/x86_64-linux-gnu/dri/swrast_dri.so is in libgl1-mesa-dri 13.0.6-1+b2.
This file is owned by root:root, with mode 0o644.
It is a symlink to /usr/lib/x86_64-linux-gnu/dri/./usr/lib/x86_64-linux-gnu/dri/kms_swrast_dri.so