[Android] Port getifaddrs implementation from Xamarin.Android (#71943)

In recent Android versions the data returned by getifaddrs is invalid and doesn't allow us to implement System.Net.NetworkInformation.GetAllNetworkInterfaces(). It's possible to reimplement getifaddrs using Netlink and there's already an existing implementation in Xamarin.Android.

Fixes dotnet/android#6973
Ref #62780
Ref #51303

Author: simonrozsival

src/mono/cmake/config.h.in

@@ -517,9 +517,6 @@
 /* Have getifaddrs */
 #cmakedefine HAVE_GETIFADDRS 1
 
-/* Have struct ifaddrs */
-#cmakedefine HAVE_IFADDRS 1
-
 /* Have access */
 #cmakedefine HAVE_ACCESS 1
 

src/native/libs/Common/pal_config.h.in

@@ -11,7 +11,6 @@
 #cmakedefine01 HAVE_F_FULLFSYNC
 #cmakedefine01 HAVE_O_CLOEXEC
 #cmakedefine01 HAVE_GETIFADDRS
-#cmakedefine01 HAVE_IFADDRS
 #cmakedefine01 HAVE_UTSNAME_DOMAINNAME
 #cmakedefine01 HAVE_STAT64
 #cmakedefine01 HAVE_FORK

src/native/libs/System.Native/CMakeLists.txt

@@ -83,6 +83,13 @@ include(${CMAKE_CURRENT_LIST_DIR}/extra_libs.cmake)
 set(NATIVE_LIBS_EXTRA)
 append_extra_system_libs(NATIVE_LIBS_EXTRA)
 
+if (CLR_CMAKE_TARGET_ANDROID)
+    add_compile_options(-Wno-gnu-zero-variadic-macro-arguments)
+
+    list (APPEND NATIVE_LIBS_EXTRA -llog)
+    list (APPEND NATIVE_SOURCES pal_ifaddrs.c)
+endif ()
+
 if (GEN_SHARED_LIB)
     add_library(System.Native
         SHARED