[PATCH] Add CTDB_REQ_TUNNEL for new protocol

[Martin Schwenke]

Hi Volker,

In case Amitay is completely gone for the evening... he will probably
explain more eloquently...  :-)

On Thu, 5 Oct 2017 12:17:40 +0200, Volker Lendecke via samba-technical
<samba-technical at lists.samba.org> wrote:

> On Thu, Oct 05, 2017 at 03:59:17PM +1100, Amitay Isaacs via samba-technical wrote:
> > This is the last set of preparatory patches required for the refactoring
> > the CTDB daemon code.  With this new components (e.g. cluster manager,
> > database daemon) can design new protocol and use current CTDB daemon as a
> > cluster-wide transport.  This allows us to incrementally carve code out of
> > CTDB daemon.  
> 
> This looks really interesting. Question -- what *is* a tunnel?

Tunnelling provides a new low-level packet type.  A tunnel is then a
bunch of ctdbd processes registering an common tunnel identifier that
allows Unix-domain-socket-connected daemons on different nodes to
communicate with each other. This means the new daemons can have
new, independent protocols and use ctdbd as a transport by wrapping
their packets in tunnel packets.

Later, if we want to, we can re-wire the communication between these
daemons using some other transport (e.g. proxy).  However, for now we
just use ctdbd as the transport because it exists and this
implementation is cheap.  :-)

peace & happiness,
martin