correct IP# for NFS kernel upcall to userland daemon

[Rick Macklem]

Hi,

I have been in a recent discussion about what the correct IP address to use for
an upcall from the kernel to the NFS daemon nfsuserd (which maps between
uids<->usernames and gids<->group names).

The code uses UDP for the upcall (I once committed a patch changing that to
an AF_LOCAL socket, but it broke certain sites where the directory the socket
was being created in was NFS mounted).

Currently the code uses a hardwired "127.0.0.1".
Rodney Grimes feels that it would be better to do a name lookup on "localhost"
to get the address to use.

In this case, I am concerned that the daemon will not be able to start up under
conditions where the DNS service isn't yet functional. (This problem can mostly
be avoided by specifying "localhost" in /etc/hosts and configuring the system to
use that file before DNS, but I still don't like having this dependency on DNS for
the daemon starting up.)
Note that the upcall will work for any IP# that refers to the local machine and it
does not need to be the one specified for "localhost" in the DNS.

So, do you think I should do a lookup for "localhost" at daemon startup or use
a hardwired "127.0.0.1/::1"?

Thanks in advance for any comments, rick