The problem was that the 'defdname' field of res_state structure
was not properly initialized in __res_vinit(). This field is used
to store the default domain name, which is normally build from
calling gethostname() (see line 549 of res_init.c).
Unfortunately, in the typical Android case, gethostname() returns
an error (the hostname is configured) and a random stack string is
used later to build the DNS search list (see lines 556+ in res_init.c)
For the sake of illustration, let's say the search list is set to
a random value like 'xWLK'.
The end result is that when trying to result an unknown domain name
(e.g. 'www.ptn'), the query fails then the resolver tries to make a
new query with the DNS search list path(s) appended (e.g. 'www.ptn.xWLK').
The patch simply initializes 'defdname' to an empty string to avoid
this when the net.dns.search system property is not set.
Also contains whitespace/formatting fixes
Merge commit '3773d35eb98e22b5edab4d82fb72bdf86ff80494'
* commit '3773d35eb98e22b5edab4d82fb72bdf86ff80494':
Make the DNS resolver accept domain names with an underscore.
More precisely, this accepts domain labels with an underscore in
the middle (i.e. not at the start or the end of the label). This
is needed to perform complex CNAME chain resolution in certain
VPN networks.
The current solution is to read the net.dns.search property,
and expand the list during the resolve initialization. In the
future, we could implement search list per process.
Update: refine the code accordingly.
Update: remove unnecessary code.
Update: remove the unused variable.
