TCP support in clients and servers

[grarpamp]

Given:
 A research or production network that only supports TCP. Think:
  I2P, Tor, GNUnet, FreeNet, etc.
  Corporate/organizational policies/firewalls, etc.
  Other seemingly odd, broken or interesting special case environments,
   easier tunneling/encapsulation and so on.

Supposing:
 Named(8) seems to bind to TCP and responds when using dig +tcp as
  a client.
 No need for the typical reasons to use UDP; performance, etc.

Questions:
 Does named fully support operating over only TCP as a server?
  zone transfers, resolving names for clients, nsupdate, etc.

 How to configure client resolver libraries to use TCP?
  Things like resolv.conf, host.conf, nsswitch.conf don't seem
  capable of this. Nor do the underlying calls.

 Are not client resolver libraries usually derived from bind?

 What would be needed for both client and server to fully support
  a TCP only mode of operation?

 Is this a planned feature in the future? Any active work?

Notes:
 These seem to support at least some TCP options.
  dig, host, nslookkup
  lwres_freeaddrinfo.3
  lwres_getaddrinfo.3
  lwres_getnameinfo.3
  nsupdate, rndc
  named.conf.5