It collects NFS statistics and number of open connections on port 2049.
The former needs the "nfsd" collector from node-exporter. Unfortunatelly that is not available in our 0.14 package currently.
For the later, we can use the "textfile" collector and have a cronjob that will output to a file that node-exporter will use to export the metrics (like it's done for the intel-microcode monitoring).
Another more time-expensive solution is to improve the "tcpstat" collector with per-port statistics (the information is already available in /proc/net/tcp but it's choosing to export just aggregate statistics).