move V+ kernel/arch/bitness checks from BpfHandler to NetBpfLoad

Mainline netbpfload is mandatory on V+, so it matters little
whether we perform the checks in it, or in BpfHandler
(which runs as part of netd startup via libnetd_updatable.so),
and this avoids the need to reimplement isTV() opt-out.

Bug: 333970930
Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I599f2c9d6710f0caa2cd71f0946459d43ddbfc17
diff --git a/netbpfload/NetBpfLoad.cpp b/netbpfload/NetBpfLoad.cpp
index f42e8a5..80df552 100644
--- a/netbpfload/NetBpfLoad.cpp
+++ b/netbpfload/NetBpfLoad.cpp
@@ -286,22 +286,34 @@
         return 1;
     }
 
+    // both S and T require kernel 4.9 (and eBpf support)
     if (isAtLeastT && !isAtLeastKernelVersion(4, 9, 0)) {
         ALOGE("Android T requires kernel 4.9.");
         return 1;
     }
 
+    // U bumps the kernel requirement up to 4.14
     if (isAtLeastU && !isAtLeastKernelVersion(4, 14, 0)) {
         ALOGE("Android U requires kernel 4.14.");
         return 1;
     }
 
+    // V bumps the kernel requirement up to 4.19
+    // see also: //system/netd/tests/kernel_test.cpp TestKernel419
     if (isAtLeastV && !isAtLeastKernelVersion(4, 19, 0)) {
         ALOGE("Android V requires kernel 4.19.");
         return 1;
     }
 
-    if (isAtLeastV && isX86() && !isKernel64Bit()) {
+    // Technically already required by U, but only enforce on V+
+    // see also: //system/netd/tests/kernel_test.cpp TestKernel64Bit
+    if (isAtLeastV && isKernel32Bit() && isAtLeastKernelVersion(5, 16, 0)) {
+        ALOGE("Android V+ platform with 32 bit kernel version >= 5.16.0 is unsupported");
+        if (!isTV()) return 1;
+    }
+
+    // Various known ABI layout issues, particularly wrt. bpf and ipsec/xfrm.
+    if (isAtLeastV && isKernel32Bit() && isX86()) {
         ALOGE("Android V requires X86 kernel to be 64-bit.");
         if (!isTV()) return 1;
     }
@@ -350,6 +362,10 @@
          * Some of these have userspace or kernel workarounds/hacks.
          * Some of them don't...
          * We're going to be removing the hacks.
+         * (for example "ANDROID: xfrm: remove in_compat_syscall() checks").
+         * Note: this check/enforcement only applies to *system* userspace code,
+         * it does not affect unprivileged apps, the 32-on-64 compatibility
+         * problems are AFAIK limited to various CAP_NET_ADMIN protected interfaces.
          *
          * Additionally the 32-bit kernel jit support is poor,
          * and 32-bit userspace on 64-bit kernel bpf ringbuffer compatibility is broken.
diff --git a/netd/BpfHandler.cpp b/netd/BpfHandler.cpp
index 91fec90..925ee50 100644
--- a/netd/BpfHandler.cpp
+++ b/netd/BpfHandler.cpp
@@ -85,31 +85,6 @@
         return Status("U+ platform with kernel version < 4.14.0 is unsupported");
     }
 
-    if (modules::sdklevel::IsAtLeastV()) {
-        // V bumps the kernel requirement up to 4.19
-        // see also: //system/netd/tests/kernel_test.cpp TestKernel419
-        if (!bpf::isAtLeastKernelVersion(4, 19, 0)) {
-            return Status("V+ platform with kernel version < 4.19.0 is unsupported");
-        }
-
-        // Technically already required by U, but only enforce on V+
-        // see also: //system/netd/tests/kernel_test.cpp TestKernel64Bit
-        if (bpf::isKernel32Bit() && bpf::isAtLeastKernelVersion(5, 16, 0)) {
-            return Status("V+ platform with 32 bit kernel, version >= 5.16.0 is unsupported");
-        }
-    }
-
-    // Linux 6.1 is highest version supported by U, starting with V new kernels,
-    // ie. 6.2+ we are dropping various kernel/system userspace 32-on-64 hacks
-    // (for example "ANDROID: xfrm: remove in_compat_syscall() checks").
-    // Note: this check/enforcement only applies to *system* userspace code,
-    // it does not affect unprivileged apps, the 32-on-64 compatibility
-    // problems are AFAIK limited to various CAP_NET_ADMIN protected interfaces.
-    // see also: //system/bpf/bpfloader/BpfLoader.cpp main()
-    if (bpf::isUserspace32bit() && bpf::isAtLeastKernelVersion(6, 2, 0)) {
-        return Status("32 bit userspace with Kernel version >= 6.2.0 is unsupported");
-    }
-
     // U mandates this mount point (though it should also be the case on T)
     if (modules::sdklevel::IsAtLeastU() && !!strcmp(cg2_path, "/sys/fs/cgroup")) {
         return Status("U+ platform with cg2_path != /sys/fs/cgroup is unsupported");