Strange as it sounds, it should map to YPERR_DOMAIN instead.
The YP_NODOM protocol error code is generally returned by ypserv when you
ask it for data from a domain that it doesn't support. By contrast,
the YPERR_NODOM error code means 'local domain name not set.'
Consequently, this incorrect mapping leads to yperr_string() generating
a very confusing error message. YPERR_DOMAIN says 'couldn't
bind to a server which serves this domain' which is much closer
to the truth.
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