move BPF_CGROUP_INET*_BIND registration into BpfHandler

(in preparation for moving it into netbpfload)

The programs themselves (in bpf_progs/block.c) required a 5.4+ kernel.

We relax this restriction to 4.19+ as we don't have any 5.4 device coverage
(while the pixel 4a 5G / 5 / 5a are all 4.19 devices).

I believe we could relax it further to 4.14+ but Pixel 4/4xl/4a that
would exercise those code paths are EOL and probably have poor to
non existent test coverage, and we cannot do anything for 4.9 T devices
anyway.

Note: on <4.19 kernels (ie. T devices running 4.9/4.14, U running 4.14)
this results in ConnectivityNativeService going from null to initialized
(as the bpf map will exist).

This doesn't hurt as the set/clear port interfaces are only ever
called by vendor code on devices where the kernel doesn't support
the older mechanism.  And even if you call them it will just set/clear
the bits in the bpf bitmap, they just won't actually affect anything.

We could flag the map itself as being 4.19+ as well, but I think
I prefer the no-op map to exist...

Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I1085addd22f4f3b709e1875049633832c5dac836

bpf_progs/block.c

@@ -57,14 +57,18 @@ static inline __always_inline int block_port(struct bpf_sock_addr *ctx) {
     return ALLOW;
 }
 
-DEFINE_BPF_PROG_KVER("bind4/block_port", AID_ROOT, AID_SYSTEM,
-                     bind4_block_port, KVER(5, 4, 0))
+// the program need to be accessible/loadable by netd (from netd updatable plugin)
+#define DEFINE_NETD_RO_BPF_PROG(SECTION_NAME, the_prog, min_kver) \
+    DEFINE_BPF_PROG_EXT(SECTION_NAME, AID_ROOT, AID_ROOT, the_prog, min_kver, KVER_INF,  \
+                        BPFLOADER_MIN_VER, BPFLOADER_MAX_VER, MANDATORY, \
+                        "", "netd_readonly/", LOAD_ON_ENG, LOAD_ON_USER, LOAD_ON_USERDEBUG)
+
+DEFINE_NETD_RO_BPF_PROG("bind4/block_port", bind4_block_port, KVER(4, 19, 0))
 (struct bpf_sock_addr *ctx) {
     return block_port(ctx);
 }
 
-DEFINE_BPF_PROG_KVER("bind6/block_port", AID_ROOT, AID_SYSTEM,
-                     bind6_block_port, KVER(5, 4, 0))
+DEFINE_NETD_RO_BPF_PROG("bind6/block_port", bind6_block_port, KVER(4, 19, 0))
 (struct bpf_sock_addr *ctx) {
     return block_port(ctx);
 }

netd/BpfHandler.cpp

@@ -130,12 +130,21 @@ static Status initPrograms(const char* cg2_path) {
                 attachProgramToCgroup(CGROUP_SOCKET_PROG_PATH, cg_fd, BPF_CGROUP_INET_SOCK_CREATE));
     }
 
+    if (bpf::isAtLeastKernelVersion(4, 19, 0)) {
+        RETURN_IF_NOT_OK(attachProgramToCgroup(
+                "/sys/fs/bpf/netd_readonly/prog_block_bind4_block_port",
+                cg_fd, BPF_CGROUP_INET4_BIND));
+        RETURN_IF_NOT_OK(attachProgramToCgroup(
+                "/sys/fs/bpf/netd_readonly/prog_block_bind6_block_port",
+                cg_fd, BPF_CGROUP_INET6_BIND));
+
         // This should trivially pass, since we just attached up above,
         // but BPF_PROG_QUERY is only implemented on 4.19+ kernels.
-    if (bpf::isAtLeastKernelVersion(4, 19, 0)) {
         if (bpf::queryProgram(cg_fd, BPF_CGROUP_INET_EGRESS) <= 0) abort();
         if (bpf::queryProgram(cg_fd, BPF_CGROUP_INET_INGRESS) <= 0) abort();
         if (bpf::queryProgram(cg_fd, BPF_CGROUP_INET_SOCK_CREATE) <= 0) abort();
+        if (bpf::queryProgram(cg_fd, BPF_CGROUP_INET4_BIND) <= 0) abort();
+        if (bpf::queryProgram(cg_fd, BPF_CGROUP_INET6_BIND) <= 0) abort();
     }
 
     return netdutils::status::ok;

service/src/com/android/server/connectivity/ConnectivityNativeService.java

@@ -46,10 +46,6 @@ public class ConnectivityNativeService extends ConnectivityNative.Stub {
 
     private static final String TAG = ConnectivityNativeService.class.getSimpleName();
     private static final String CGROUP_PATH = "/sys/fs/cgroup";
-    private static final String V4_PROG_PATH =
-            "/sys/fs/bpf/net_shared/prog_block_bind4_block_port";
-    private static final String V6_PROG_PATH =
-            "/sys/fs/bpf/net_shared/prog_block_bind6_block_port";
     private static final String BLOCKED_PORTS_MAP_PATH =
             "/sys/fs/bpf/net_shared/map_block_blocked_ports_map";
 
@@ -95,7 +91,6 @@ public class ConnectivityNativeService extends ConnectivityNative.Stub {
     protected ConnectivityNativeService(final Context context, @NonNull Dependencies deps) {
         mContext = context;
         mBpfBlockedPortsMap = deps.getBlockPortsMap();
-        attachProgram();
     }
 
     @Override
@@ -155,23 +150,4 @@ public class ConnectivityNativeService extends ConnectivityNative.Stub {
     public String getInterfaceHash() {
         return this.HASH;
     }
-
-    /**
-     * Attach BPF program
-     */
-    private void attachProgram() {
-        try {
-            BpfUtils.attachProgram(BPF_CGROUP_INET4_BIND, V4_PROG_PATH, CGROUP_PATH, 0);
-        } catch (IOException e) {
-            throw new UnsupportedOperationException("Unable to attach to BPF_CGROUP_INET4_BIND: "
-                    + e);
-        }
-        try {
-            BpfUtils.attachProgram(BPF_CGROUP_INET6_BIND, V6_PROG_PATH, CGROUP_PATH, 0);
-        } catch (IOException e) {
-            throw new UnsupportedOperationException("Unable to attach to BPF_CGROUP_INET6_BIND: "
-                    + e);
-        }
-        Log.d(TAG, "Attached BPF_CGROUP_INET4_BIND and BPF_CGROUP_INET6_BIND programs");
-    }
 }

tests/mts/bpf_existence_test.cpp

@@ -40,6 +40,7 @@ using android::modules::sdklevel::IsAtLeastV;
 #define TETHERING "/sys/fs/bpf/tethering/"
 #define PRIVATE "/sys/fs/bpf/net_private/"
 #define SHARED "/sys/fs/bpf/net_shared/"
+#define NETD_RO "/sys/fs/bpf/netd_readonly/"
 #define NETD "/sys/fs/bpf/netd_shared/"
 
 class BpfExistenceTest : public ::testing::Test {
@@ -119,9 +120,9 @@ static const set<string> MAINLINE_FOR_T_4_14_PLUS = {
 };
 
 // Provided by *current* mainline module for T+ devices with 5.4+ kernels
-static const set<string> MAINLINE_FOR_T_5_4_PLUS = {
-    SHARED "prog_block_bind4_block_port",
-    SHARED "prog_block_bind6_block_port",
+static const set<string> MAINLINE_FOR_T_4_19_PLUS = {
+    NETD_RO "prog_block_bind4_block_port",
+    NETD_RO "prog_block_bind6_block_port",
 };
 
 // Provided by *current* mainline module for T+ devices with 5.15+ kernels
@@ -176,7 +177,7 @@ TEST_F(BpfExistenceTest, TestPrograms) {
     // T still only requires Linux Kernel 4.9+.
     DO_EXPECT(IsAtLeastT(), MAINLINE_FOR_T_PLUS);
     DO_EXPECT(IsAtLeastT() && isAtLeastKernelVersion(4, 14, 0), MAINLINE_FOR_T_4_14_PLUS);
-    DO_EXPECT(IsAtLeastT() && isAtLeastKernelVersion(5, 4, 0), MAINLINE_FOR_T_5_4_PLUS);
+    DO_EXPECT(IsAtLeastT() && isAtLeastKernelVersion(4, 19, 0), MAINLINE_FOR_T_4_19_PLUS);
     DO_EXPECT(IsAtLeastT() && isAtLeastKernelVersion(5, 15, 0), MAINLINE_FOR_T_5_15_PLUS);
 
     // U requires Linux Kernel 4.14+, but nothing (as yet) added or removed in U.