Hostname resolution
-------------------
Please read all of this document before making any configuration changes.

This talker code, like all others, does ip -> hostname DNS mapping.
When a connection comes in, the user's socket address is converted into IP
form..then resolved to hostname/alphanumeric form. The usual method is by
using the gethostbyaddr() function. This though has the possiblity of
blocking (or delaying) while the ip is resolved. Either because the route
to the user's DNS server is slow, the user's DNS server is slow, or the IP
doesn't resolve at all. During this delay, the talker can become lagged.

To try and remedy this, 2 features have been implemented.

The first is DNS caching. In this feature, when an ip comes
in, it is checked against a (line-by-line) cache file of IP/hostname
matches. This first cache file is the default cache file. It's manually
edited and contains IP/hostname matches that we KNOW dont resolve well or 
at all. If an IP matches, the hostname or error for that IP is pulled from
the file and saved to the user. This saves the talker from going and
trying to resolve the IP via DNS. If the IP does NOT match, it searches
for the IP in the MAIN cache file. Again, if it's found, the hostname is
pulled from the file to the user. If not, the IP is resolved via DNS
gethostbyaddr(), hostname given to the user, then written to the
END of the cache file. If the cache file is at its size limit, the
IP/hostname match at the TOP of the file is "bumped" and every address
moves up one.
In testing with a 250 line cache file, IPs have matched approximately 60%
of the time, over an uptime of approximately 20 days.
#define's associated with this feature are SITECACHE_FILE,
SITECACHE_FILE_DEF, and SITECACHE_SIZE..found in constants.h. To enable
this feature, set the resolve_names variable to 1 in init_data. See
README.init_data for the location of this variable in init_data


The second feature is DNS lookup by an external resolver program.
In this feature, on talker startup a small daemon (clip-on) is also
started to handle DNS requests. When an ip comes in to the talker, the
pre-mentioned cache-lookups are done. If nothing matches, a request is
constructed and is sent to the clip-on. The clip-on takes the
ip out of the request and proceeds to use non-blocking dns functions and
sockets to resolve the ip. When the clip-on has an answer, it sends it
back to the talker, which processes it into the user.
This has the effect of:
1) taking the load off the talker to do resolving, and making sure it will
never freeze.
2) allow the clip-on to take multiple requests at a time, process them
as-results-come-in, and timeout requests at a set time. The clip-on does
NOT use gethostbyaddr() to resolve, but sockets directly to the local DNS
server, which can be polled without the clip-on freezing itself. 
To enable this feature, set the resolve_names variable to 2 in init_data
(this is the default with the distribution). See README.init_data for the
location of this variable in init_data

These 2 features can also be seperated or combined in use.
For example:
setting resolve_names to 3 will make the talker NOT use any
cache and strictly use the clip-on resolver.
setting resolve_names to 4 will make the talker NOT use any
cache and strictly use gethostbyaddr()
setting resolve_names to 0 will make the talker NOT do any DNS resolution
of any kind.

resolve_names = 2 is recommended. If that does not suit
you, recommendations afterwards fall in this order: 3, 1, 4, 0


-Cygnus
Anthony J. Biacco
ncohafmuta@asteroid-b612.org