libbpf_android: waitForProgsLoaded

Creating a function for this rather than having people copy/paste a loop
there.

It's very intentional that there is no timeout here. If bpfloader is
down, there is a serious problem, and we shouldn't let code move forward
in a state where it may not have been tested.

Bug: 140330870
Test: boot & use bpf/netd
Change-Id: I358d1fcf77ad5406e294dd57307bc411e2c8ad6a

3 files changed, 13 insertions, 0 deletions

diff --git a/libbpf_android/Android.bp b/libbpf_android/Android.bp
index c369c8c..956fd93 100644
--- a/libbpf_android/Android.bp
+++ b/libbpf_android/Android.bp
@@ -54,6 +54,7 @@ cc_library {
         "libbpf_android_headers"
     ],
     export_header_lib_headers: ["libbpf_android_headers"],
+    export_shared_lib_headers: ["libbpf"],
     local_include_dirs: ["include"],
 
     defaults: ["bpf_defaults"],
diff --git a/libbpf_android/Loader.cpp b/libbpf_android/Loader.cpp
index fb4e36c..021e79f 100644
--- a/libbpf_android/Loader.cpp
+++ b/libbpf_android/Loader.cpp
@@ -36,6 +36,7 @@
 #include <string>
 #include <vector>
 
+#include <android-base/properties.h>
 #include <android-base/strings.h>
 #include <android-base/unique_fd.h>
 
@@ -589,5 +590,11 @@ int loadProg(const char* elfPath) {
     return ret;
 }
 
+void waitForProgsLoaded() {
+    while (!android::base::WaitForProperty("bpf.progs_loaded", "1", std::chrono::seconds(5))) {
+        ALOGW("Waited 5s for bpf.progs_loaded, still waiting...");
+    }
+}
+
 }  // namespace bpf
 }  // namespace android
diff --git a/libbpf_android/include/libbpf_android.h b/libbpf_android/include/libbpf_android.h
index cea707c..0a01c85 100644
--- a/libbpf_android/include/libbpf_android.h
+++ b/libbpf_android/include/libbpf_android.h
@@ -23,8 +23,13 @@
 
 namespace android {
 namespace bpf {
+
 // BPF loader implementation. Loads an eBPF ELF object
 int loadProg(const char* elfpath);
+
+// Wait for bpfloader to load BPF programs.
+void waitForProgsLoaded();
+
 }  // namespace bpf
 }  // namespace android