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Filename Latest commit message Latest commit date
Ken Chen a973c0be7d Add bpf_headers visibility for CtsNativeNetPlatformTestCases 
The CtsNativeNetPlatformTestCases uses BpfUtils.h in bpf_headers.

Bug: 29761778
Bug: 202086915
Test: atest CtsNativeNetPlatformTestCases on signed user build
Change-Id: Ibbb10392a283b88328ae17d9aa54322f50878e76
2022-01-15 02:27:22 +08:00
..
bpf_headers Add bpf_headers visibility for CtsNativeNetPlatformTestCases 2022-01-15 02:27:22 +08:00
bpf_syscall_wrappers Merge "[NETD-TC#12] Fix dependency on libtraffic_controller" 2022-01-14 10:44:52 +00:00
bpfmapjni Move BpfUtils -- add JNI wrapper for libtcutils 2022-01-13 22:24:29 +01:00
ip_checksum Add apex_available and min_sdk_version to libip_checksum 2021-12-28 06:01:57 +00:00
netjniutils Move to renamed NDK symbol AFileDescriptor_getFd 2021-05-12 09:43:35 +01:00
tcutils Move BpfUtils -- move kernelVersion code to its own header 2022-01-13 22:24:29 +01:00
README.md Clarify that JNI libraries used for jarjar'd classes must be statically linked. 2021-12-15 02:28:17 +00:00

README.md

JNI

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. Linkage MUST be static because common functions in the file (e.g., register_com_android_net_module_util_BpfMap) will appear in the library (.so) file, and different versions of the library loaded in the same process by different modules will in general have different versions. It's important that each of these libraries loads the common function from its own library. Static linkage should guarantee this because static linkage resolves symbols at build time, not runtime.