nsmb —
kernel SMB protocol communicator
This virtual device is used by SMBFS filesystem for actual communication with
  SMB servers. It provides the physical transportation, encapsulating the
  networking part of SMBFS. Only SMB over TCP/IP is supported at this moment,
  SMB over NetBIOS is not supported.
For the SMBFS kernel support to work, it's necessary to have both
    this pseudo-device and file-system SMBFS configured into kernel.
This driver first appeared in FreeBSD 4.4. In
  NetBSD, this first appeared in NetBSD
  2.0, together with rest of SMBFS support.
Boris Popov
  <bp@butya.kz>,
  ⟨bp@FreeBSD.org⟩. NetBSD port done by
  Matt Debergalis ⟨deberg@NetBSD.org⟩ and
  Jaromir Dolecek ⟨jdolecek@NetBSD.org⟩.