asyn-ares.c and asyn-thread.c are two separate backends that implement
the same (internal) async resolver API for libcurl to use. Backend is
specified at build time.
The internal resolver API is defined in asyn.h for asynch resolvers.
Fixed indents, coding conventions and white space edits.
Modified the c-ares completion callback function to again NOT read the
conn data when the ares handle is being taken down as then it may have
been freed already.
Move ipv6-functional-probe into a single function that is used from all
places that need to know.
Make the probe function store the result in a static variable so that
subsequent invokes just returns the previous result and won't have to
probe again.
When built IPv6-enabled, we could do Curl_done() with one of the two
resolves having returned already, so when ares_cancel() is called the
resolve callback ends up doing funny things (sometimes resulting in a
segfault) since it would try to actually store the previous resolve even
though we're shutting down the resolve.
This bug was introduced in commit 8ab137b2bc so it hasn't been
included in any public release.
Bug: http://curl.haxx.se/bug/view.cgi?id=3145445
Reported by: Pedro Larroy
The IP version choice was previously only in the UserDefined struct
within the SessionHandle, but since we sometimes alter that option
during a request we need to have it on a per-connection basis.
I also moved more "init conn" code into the allocate_conn() function
which is designed for that purpose more or less.
from hostip.h to setup.h in order to allow proper inclusion in any file.
This represents no functional change at all in which resolver is used,
everything still works as usual, internally and externally there is no
difference in behavior.
(http://curl.haxx.se/bug/view.cgi?id=2891595) which identified how an entry
in the DNS cache would linger too long if the request that added it was in
use that long. He also provided the patch that now makes libcurl capable of
still doing a request while the DNS hash entry may get timed out.
The signalling of that a global DNS cache is wanted is done by setting the
option but the setting of the internal variable that it is in use must not be
done until it finally actually gets used!
NOTE and WARNING: I noticed that you can't actually switch off the global dns
cache with CURLOPT_DNS_USE_GLOBAL_CACHE but you couldn't do that previously
either and the option is very clearly and loudly documented as DO NOTE USE so
I won't bother to fix this bug now.
silly code left from when we switched to let the multi handle "hold" the dns
cache when using the multi interface... Of course this only triggered when a
certain function call returned error at the correct moment.
(http://curl.haxx.se/bug/view.cgi?id=1431750) helped me identify and fix two
different but related bugs:
1) Removing an easy handle from a multi handle before the transfer is done
could leave a connection in the connection cache for that handle that is
in a state that isn't suitable for re-use. A subsequent re-use could then
read from a NULL pointer and segfault.
2) When an easy handle was removed from the multi handle, there could be an
outstanding c-ares DNS name resolve request. When the response arrived,
it caused havoc since the connection struct it "belonged" to could've
been freed already.
Now Curl_done() is called when an easy handle is removed from a multi handle
pre-maturely (that is, before the transfer was complteted). Curl_done() also
makes sure to cancel all (if any) outstanding c-ares requests.
