  In the search of topological superconductors, nailing down the Fermiology of
the normal state is as crucial a prerequisite as unraveling the superconducting
pairing symmetry. In particular, the number of time-reversal-invariant momenta
in the Brillouin zone enclosed by Fermi surfaces is closely linked to the
topological class of time-reversal-invariant systems, and can experimentally be
investigated. We report here a detailed study of de Haas van Alphen quantum
oscillations in single crystals of the topological semimetal CaSn$_{3}$ with
torque magnetometry in high magnetic fields up to 35 T. In conjunction with
density functional theory based calculations, the observed quantum oscillations
frequencies indicate that the Fermi surfaces of CaSn$_{3}$ enclose an odd
number of time-reversal-invariant momenta, satisfying one of the proposed
criteria to realize topological superconductivity. Nonzero Berry phases
extracted from the magnetic oscillations also support the nontrivial
topological nature of CaSn$_{3}$.
