New function: inet_client_addr()...

In stock PostgreSQL, you can get the database name, the username, but
not the address that the client is connecting from (a very, very useful
piece of data).

Function:        inet_client_addr()
Args:        none
Return type:    INET (null on AF_UNIX or some catastrophic failure)
IPv6 safe:    yes

The attached patch includes documentation and the relevant code.  If
there aren't any problems, I think this patch is ready to be committed.

If someone wants a way to return the path of AF_UNIX connections, I
firmly believe that it should live in a similar, but different
function, otherwise PL code (or whatever) will have to tease out
whether it's a local or remote connection.  Not that I think demand is
there for it, but if need be, there should be two more functions
written: unix_client_addr() and just client_addr().  unix_client_addr()
returns TEXT and the path to the socket and client_addr() returns a
TEXT wrapped version of whatever is in MyProcPort->remote_host.  -sc



% psql -h 192.168.102.100 template1
template1=# SELECT inet_client_addr();
  inet_client_addr
------------------
  192.168.102.100
(1 row)

template1=# \q
% echo $PGHOST
tcsh: PGHOST: Undefined variable.
% psql template1
template1=# SELECT inet_client_addr();
  inet_client_addr
------------------

(1 row)

template1=# SELECT inet_client_addr() IS NULL;
  ?column?
----------
  t
(1 row)

template1=# \q
% psql -h 127.0.0.1 template1
template1=# SELECT inet_client_addr() IS NULL;
  ?column?
----------
  f
(1 row)

template1=# SELECT inet_client_addr();
  inet_client_addr
------------------
  127.0.0.1
(1 row)

template1=# \q
% psql -h localhost template1
template1=# SELECT inet_client_addr();
  inet_client_addr
------------------
  ::1
(1 row)

--
Sean Chittenden