As a general rule, jarjar every static library dependency used in a mainline module into the modules's namespace (especially if it is also used by other modules)
Fully-qualified name of java class needs to be hard-coded into the JNI .so, because JNI_OnLoad does not take any parameters. This means that there needs to be a different .so target for each post-jarjared package, so for each module.
This is the guideline to provide JNI library shared with modules:
provide a common java library in frameworks/libs/net with the Java class (e.g. BpfMap.java).
provide a common native library in frameworks/libs/net with the JNI and provide the native register function with class_name parameter. See register_com_android_net_module_util_BpfMap function in frameworks/libs/net/common/native/bpfmapjni/com_android_net_module_util_BpfMap.cpp as an example.
When you want to use JNI library from frameworks/lib/net:
Each module includes the java library (e.g. net-utils-device-common-bpf) and applies its jarjar rules after build.
Each module creates a native library in their directory, which statically links against the common native library (e.g. libnet_utils_device_common_bpf), and calls the native registered function by hardcoding the post-jarjar class_name.