The getnameinfo implementation requires an address -> name lookup on the
hosts file (ie struct HostsTxt) and the previous implementation used
flags to check whether HostsTxt was sorted according to address or name,
and then re-sorted it if necessary. Now getnameinfo lookup does not
require sorting, it does a simple linear lookup, and so the related code
was simplified
See #172 for discussion.
Added necessary constants (DNS_TYPE_PTR, NI_NUMERICHOST etc.).
Implementation of getnameinfo is similar to getaddrinfo, with internal
functions:
* ResolveDnsReverse: performs rDNS query and parses the PTR record
* ResolveHostsReverse: reads /etc/hosts to map hostname to
address
Earlier, the HOSTS.txt would only need to be sorted at loading time,
because the only kind of lookup was name -> address. Now since address
-> name lookups are also possible, so the HostsTxt struct, the sorting
method (and the related tests) was changed to reflect this.
