commit b60599b705913e80d7c18e4ecf3c575c90066655
author Maciej Żenczykowski <maze@google.com> Fri Feb 09 12:30:52 2024 -0800
committer Maciej Żenczykowski <maze@google.com> Fri Feb 09 23:31:17 2024 +0000
tree 521f2569fff8c93cc0a71603078cf1f09eef9141
parent 2b55cd2247509e6d04b72dadf1072556712b5cc7

NetBpfLoad - log Tethering Apex version

(super useful for debugging)

Sample output:
  I NetBpfLoad: NetBpfLoad '/apex/com.android.tethering/bin/netbpfload' starting...
  I NetBpfLoad: NetBpfLoad api:10000/34 kver:6010019 platform:0 mainline:1
  D NetBpfLoad: Found Tethering Apex mounted from blockdev /dev/block/dm-55
  I NetBpfLoad: Tethering APEX version 340090000

Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: Iaf1bc22b02913ea21ff9368abd9933e6ef4017f1

netbpfload/NetBpfLoad.cpp

diff --git a/netbpfload/NetBpfLoad.cpp b/netbpfload/NetBpfLoad.cpp
index c108d92..3c5e4c3 100644
--- a/netbpfload/NetBpfLoad.cpp
+++ b/netbpfload/NetBpfLoad.cpp
@@ -169,9 +169,62 @@
     return 0;
 }
 
+#define APEX_MOUNT_POINT "/apex/com.android.tethering"
 const char * const platformBpfLoader = "/system/bin/bpfloader";
 const char * const platformNetBpfLoad = "/system/bin/netbpfload";
-const char * const apexNetBpfLoad = "/apex/com.android.tethering/bin/netbpfload";
+const char * const apexNetBpfLoad = APEX_MOUNT_POINT "/bin/netbpfload";
+
+int logTetheringApexVersion(void) {
+    char * found_blockdev = NULL;
+    FILE * f = NULL;
+    char buf[4096];
+
+    f = fopen("/proc/mounts", "re");
+    if (!f) return 1;
+
+    // /proc/mounts format: block_device [space] mount_point [space] other stuff... newline
+    while (fgets(buf, sizeof(buf), f)) {
+        char * blockdev = buf;
+        char * space = strchr(blockdev, ' ');
+        if (!space) continue;
+        *space = '\0';
+        char * mntpath = space + 1;
+        space = strchr(mntpath, ' ');
+        if (!space) continue;
+        *space = '\0';
+        if (strcmp(mntpath, APEX_MOUNT_POINT)) continue;
+        found_blockdev = strdup(blockdev);
+        break;
+    }
+    fclose(f);
+    f = NULL;
+
+    if (!found_blockdev) return 2;
+    ALOGD("Found Tethering Apex mounted from blockdev %s", found_blockdev);
+
+    f = fopen("/proc/mounts", "re");
+    if (!f) { free(found_blockdev); return 3; }
+
+    while (fgets(buf, sizeof(buf), f)) {
+        char * blockdev = buf;
+        char * space = strchr(blockdev, ' ');
+        if (!space) continue;
+        *space = '\0';
+        char * mntpath = space + 1;
+        space = strchr(mntpath, ' ');
+        if (!space) continue;
+        *space = '\0';
+        if (strcmp(blockdev, found_blockdev)) continue;
+        if (strncmp(mntpath, APEX_MOUNT_POINT "@", strlen(APEX_MOUNT_POINT "@"))) continue;
+        char * at = strchr(mntpath, '@');
+        if (!at) continue;
+        char * ver = at + 1;
+        ALOGI("Tethering APEX version %s", ver);
+    }
+    fclose(f);
+    free(found_blockdev);
+    return 0;
+}
 
 int main(int argc, char** argv, char * const envp[]) {
     (void)argc;
@@ -205,6 +258,8 @@
         ALOGW("exec '%s' fail: %d[%s]", apexNetBpfLoad, errno, strerror(errno));
     }
 
+    logTetheringApexVersion();
+
     if (isAtLeastT && !android::bpf::isAtLeastKernelVersion(4, 9, 0)) {
         ALOGE("Android T requires kernel 4.9.");
         return 1;