As of Android 8 (Oreo) access to net.dns# has been removed (https://developer.android.com/about/versions/oreo/android-8.0-changes.html). The reasoning given is that it, "improves privacy on the platform". Currently c-ares uses this to get the list of DNS servers.
Now the only way to access the DNS server list is by using the Connectivity Manager though Java. This adds the necessary JNI code to use the Connectivity Manager and pull the DNS server list. The old way using __system_property_get with net.dns# remains for compatibilty.
Using the Connectivity Manager requires the ACCESS_NETWORK_STATE permission to be set on the app. Existing applications most likely are not setting this and keeping the previous method as a fallback will at the very least ensure those apps don't break on older versions of Android. They will need to add this permission for Android 8 compatibility.
Included in the patch are two initalization functions which are required. The JVM must be registered as well as the Connectivity Manager itself. There is no way to get the Connectivity Manager except though Java. Either being passed down to C directly or by passing in an Android Context which can be used to get the Connectivity Manager. Examples are provided in the documentation.
check for ssize_t to make it possible to use that when receiving the send()
error code. This is necessary to prevent compiler warnings on some systems.
- Made configure create config.h, and all source files now include setup.h that
might include the proper config.h (or a handicrafted alternative).
- Switched to 'ares_socket_t' type for sockets in ares, since Windows don't
use 'int' for that.
- automake-ified and libool-ified c-ares. Now it builds libcares as a shared
lib on most platforms if wanted. (This bloated the size of the release
archive with another 200K!)
- Makefile.am now uses Makefile.inc for the c sources, h headers and man
pages, to make it easier for other makefiles to use the exact same set of
files.
- Adjusted 'maketgz' to use the new automake magic when building distribution
archives.
John Schember
Yang Tse
Daniel Stenberg
Gisle Vanem