bpf: extend cgroup hooks to older kernels

We adjust and extend the trivial programs on:
  {connect,recvmsg,sendmsg}{4,6}
  inet_release
  {g,s}etsockopt
so that they also work on older kernels.

Bug: 347584126
Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I925b443f77e081f5eeb9be6c133581900a9f943d
diff --git a/bpf_progs/netd.c b/bpf_progs/netd.c
index c520c3c..5ce2227 100644
--- a/bpf_progs/netd.c
+++ b/bpf_progs/netd.c
@@ -682,7 +682,7 @@
 }
 
 DEFINE_NETD_V_BPF_PROG_KVER("cgroupsockrelease/inet_release", AID_ROOT, AID_ROOT,
-                            inet_socket_release, KVER_5_15)
+                            inet_socket_release, KVER_5_10)
 (struct bpf_sock* sk) {
     uint64_t cookie = bpf_get_sk_cookie(sk);
     if (cookie) bpf_cookie_tag_map_delete_elem(&cookie);
@@ -708,44 +708,50 @@
     return 1;
 }
 
-DEFINE_NETD_V_BPF_PROG_KVER("connect4/inet4_connect", AID_ROOT, AID_ROOT, inet4_connect, KVER_5_15)
+DEFINE_NETD_V_BPF_PROG_KVER("connect4/inet4_connect", AID_ROOT, AID_ROOT, inet4_connect, KVER_4_14)
 (struct bpf_sock_addr *ctx) {
     return check_localhost(ctx);
 }
 
-DEFINE_NETD_V_BPF_PROG_KVER("connect6/inet6_connect", AID_ROOT, AID_ROOT, inet6_connect, KVER_5_15)
+DEFINE_NETD_V_BPF_PROG_KVER("connect6/inet6_connect", AID_ROOT, AID_ROOT, inet6_connect, KVER_4_14)
 (struct bpf_sock_addr *ctx) {
     return check_localhost(ctx);
 }
 
-DEFINE_NETD_V_BPF_PROG_KVER("recvmsg4/udp4_recvmsg", AID_ROOT, AID_ROOT, udp4_recvmsg, KVER_5_15)
+DEFINE_NETD_V_BPF_PROG_KVER("recvmsg4/udp4_recvmsg", AID_ROOT, AID_ROOT, udp4_recvmsg, KVER_4_14)
 (struct bpf_sock_addr *ctx) {
     return check_localhost(ctx);
 }
 
-DEFINE_NETD_V_BPF_PROG_KVER("recvmsg6/udp6_recvmsg", AID_ROOT, AID_ROOT, udp6_recvmsg, KVER_5_15)
+DEFINE_NETD_V_BPF_PROG_KVER("recvmsg6/udp6_recvmsg", AID_ROOT, AID_ROOT, udp6_recvmsg, KVER_4_14)
 (struct bpf_sock_addr *ctx) {
     return check_localhost(ctx);
 }
 
-DEFINE_NETD_V_BPF_PROG_KVER("sendmsg4/udp4_sendmsg", AID_ROOT, AID_ROOT, udp4_sendmsg, KVER_5_15)
+DEFINE_NETD_V_BPF_PROG_KVER("sendmsg4/udp4_sendmsg", AID_ROOT, AID_ROOT, udp4_sendmsg, KVER_4_14)
 (struct bpf_sock_addr *ctx) {
     return check_localhost(ctx);
 }
 
-DEFINE_NETD_V_BPF_PROG_KVER("sendmsg6/udp6_sendmsg", AID_ROOT, AID_ROOT, udp6_sendmsg, KVER_5_15)
+DEFINE_NETD_V_BPF_PROG_KVER("sendmsg6/udp6_sendmsg", AID_ROOT, AID_ROOT, udp6_sendmsg, KVER_4_14)
 (struct bpf_sock_addr *ctx) {
     return check_localhost(ctx);
 }
 
-DEFINE_NETD_V_BPF_PROG_KVER("getsockopt/prog", AID_ROOT, AID_ROOT, getsockopt_prog, KVER_5_15)
+DEFINE_NETD_V_BPF_PROG_KVER("getsockopt/prog", AID_ROOT, AID_ROOT, getsockopt_prog, KVER_5_4)
 (struct bpf_sockopt *ctx) {
-    return 1;
+    // Tell kernel to return 'original' kernel reply (instead of the bpf modified buffer)
+    // This is important if the answer is larger than PAGE_SIZE (max size this bpf hook can provide)
+    ctx->optlen = 0;
+    return 1; // ALLOW
 }
 
-DEFINE_NETD_V_BPF_PROG_KVER("setsockopt/prog", AID_ROOT, AID_ROOT, setsockopt_prog, KVER_5_15)
+DEFINE_NETD_V_BPF_PROG_KVER("setsockopt/prog", AID_ROOT, AID_ROOT, setsockopt_prog, KVER_5_4)
 (struct bpf_sockopt *ctx) {
-    return 1;
+    // Tell kernel to use/process original buffer provided by userspace.
+    // This is important if it is larger than PAGE_SIZE (max size this bpf hook can handle).
+    ctx->optlen = 0;
+    return 1; // ALLOW
 }
 
 LICENSE("Apache 2.0");
diff --git a/netd/BpfHandler.cpp b/netd/BpfHandler.cpp
index fe25255..5d64ae7 100644
--- a/netd/BpfHandler.cpp
+++ b/netd/BpfHandler.cpp
@@ -115,23 +115,27 @@
     }
 
     if (modules::sdklevel::IsAtLeastV()) {
-        if (bpf::isAtLeastKernelVersion(5, 15, 0)) {
-            RETURN_IF_NOT_OK(attachProgramToCgroup(CGROUP_CONNECT4_PROG_PATH,
-                                        cg_fd, BPF_CGROUP_INET4_CONNECT));
-            RETURN_IF_NOT_OK(attachProgramToCgroup(CGROUP_CONNECT6_PROG_PATH,
-                                        cg_fd, BPF_CGROUP_INET6_CONNECT))    ;
-            RETURN_IF_NOT_OK(attachProgramToCgroup(CGROUP_UDP4_RECVMSG_PROG_PATH,
-                                        cg_fd, BPF_CGROUP_UDP4_RECVMSG));
-            RETURN_IF_NOT_OK(attachProgramToCgroup(CGROUP_UDP6_RECVMSG_PROG_PATH,
-                                        cg_fd, BPF_CGROUP_UDP6_RECVMSG));
-            RETURN_IF_NOT_OK(attachProgramToCgroup(CGROUP_UDP4_SENDMSG_PROG_PATH,
-                                        cg_fd, BPF_CGROUP_UDP4_SENDMSG));
-            RETURN_IF_NOT_OK(attachProgramToCgroup(CGROUP_UDP6_SENDMSG_PROG_PATH,
-                                        cg_fd, BPF_CGROUP_UDP6_SENDMSG));
+        RETURN_IF_NOT_OK(attachProgramToCgroup(CGROUP_CONNECT4_PROG_PATH,
+                                    cg_fd, BPF_CGROUP_INET4_CONNECT));
+        RETURN_IF_NOT_OK(attachProgramToCgroup(CGROUP_CONNECT6_PROG_PATH,
+                                    cg_fd, BPF_CGROUP_INET6_CONNECT));
+        RETURN_IF_NOT_OK(attachProgramToCgroup(CGROUP_UDP4_RECVMSG_PROG_PATH,
+                                    cg_fd, BPF_CGROUP_UDP4_RECVMSG));
+        RETURN_IF_NOT_OK(attachProgramToCgroup(CGROUP_UDP6_RECVMSG_PROG_PATH,
+                                    cg_fd, BPF_CGROUP_UDP6_RECVMSG));
+        RETURN_IF_NOT_OK(attachProgramToCgroup(CGROUP_UDP4_SENDMSG_PROG_PATH,
+                                    cg_fd, BPF_CGROUP_UDP4_SENDMSG));
+        RETURN_IF_NOT_OK(attachProgramToCgroup(CGROUP_UDP6_SENDMSG_PROG_PATH,
+                                    cg_fd, BPF_CGROUP_UDP6_SENDMSG));
+
+        if (bpf::isAtLeastKernelVersion(5, 4, 0)) {
             RETURN_IF_NOT_OK(attachProgramToCgroup(CGROUP_GETSOCKOPT_PROG_PATH,
                                         cg_fd, BPF_CGROUP_GETSOCKOPT));
             RETURN_IF_NOT_OK(attachProgramToCgroup(CGROUP_SETSOCKOPT_PROG_PATH,
                                         cg_fd, BPF_CGROUP_SETSOCKOPT));
+        }
+
+        if (bpf::isAtLeastKernelVersion(5, 10, 0)) {
             RETURN_IF_NOT_OK(attachProgramToCgroup(CGROUP_INET_RELEASE_PROG_PATH,
                                         cg_fd, BPF_CGROUP_INET_SOCK_RELEASE));
         }
@@ -155,15 +159,19 @@
     }
 
     if (modules::sdklevel::IsAtLeastV()) {
-        if (bpf::isAtLeastKernelVersion(5, 15, 0)) {
-            if (bpf::queryProgram(cg_fd, BPF_CGROUP_INET4_CONNECT) <= 0) abort();
-            if (bpf::queryProgram(cg_fd, BPF_CGROUP_INET6_CONNECT) <= 0) abort();
-            if (bpf::queryProgram(cg_fd, BPF_CGROUP_UDP4_RECVMSG) <= 0) abort();
-            if (bpf::queryProgram(cg_fd, BPF_CGROUP_UDP6_RECVMSG) <= 0) abort();
-            if (bpf::queryProgram(cg_fd, BPF_CGROUP_UDP4_SENDMSG) <= 0) abort();
-            if (bpf::queryProgram(cg_fd, BPF_CGROUP_UDP6_SENDMSG) <= 0) abort();
+        if (bpf::queryProgram(cg_fd, BPF_CGROUP_INET4_CONNECT) <= 0) abort();
+        if (bpf::queryProgram(cg_fd, BPF_CGROUP_INET6_CONNECT) <= 0) abort();
+        if (bpf::queryProgram(cg_fd, BPF_CGROUP_UDP4_RECVMSG) <= 0) abort();
+        if (bpf::queryProgram(cg_fd, BPF_CGROUP_UDP6_RECVMSG) <= 0) abort();
+        if (bpf::queryProgram(cg_fd, BPF_CGROUP_UDP4_SENDMSG) <= 0) abort();
+        if (bpf::queryProgram(cg_fd, BPF_CGROUP_UDP6_SENDMSG) <= 0) abort();
+
+        if (bpf::isAtLeastKernelVersion(5, 4, 0)) {
             if (bpf::queryProgram(cg_fd, BPF_CGROUP_GETSOCKOPT) <= 0) abort();
             if (bpf::queryProgram(cg_fd, BPF_CGROUP_SETSOCKOPT) <= 0) abort();
+        }
+
+        if (bpf::isAtLeastKernelVersion(5, 10, 0)) {
             if (bpf::queryProgram(cg_fd, BPF_CGROUP_INET_SOCK_RELEASE) <= 0) abort();
         }
     }
diff --git a/tests/mts/bpf_existence_test.cpp b/tests/mts/bpf_existence_test.cpp
index 3f0f3e9..b02c61c 100644
--- a/tests/mts/bpf_existence_test.cpp
+++ b/tests/mts/bpf_existence_test.cpp
@@ -147,18 +147,22 @@
 
 // Provided by *current* mainline module for V+ devices
 static const set<string> MAINLINE_FOR_V_PLUS = {
-};
-
-// Provided by *current* mainline module for V+ devices with 5.15+ kernels
-static const set<string> MAINLINE_FOR_V_5_15_PLUS = {
     NETD "prog_netd_connect4_inet4_connect",
     NETD "prog_netd_connect6_inet6_connect",
     NETD "prog_netd_recvmsg4_udp4_recvmsg",
     NETD "prog_netd_recvmsg6_udp6_recvmsg",
     NETD "prog_netd_sendmsg4_udp4_sendmsg",
     NETD "prog_netd_sendmsg6_udp6_sendmsg",
+};
+
+// Provided by *current* mainline module for V+ devices with 5.4+ kernels
+static const set<string> MAINLINE_FOR_V_5_4_PLUS = {
     NETD "prog_netd_getsockopt_prog",
     NETD "prog_netd_setsockopt_prog",
+};
+
+// Provided by *current* mainline module for U+ devices with 5.10+ kernels
+static const set<string> MAINLINE_FOR_V_5_10_PLUS = {
     NETD "prog_netd_cgroupsockrelease_inet_release",
 };
 
@@ -210,7 +214,8 @@
     // V requires Linux Kernel 4.19+, but nothing (as yet) added or removed in V.
     if (IsAtLeastV()) ASSERT_TRUE(isAtLeastKernelVersion(4, 19, 0));
     DO_EXPECT(IsAtLeastV(), MAINLINE_FOR_V_PLUS);
-    DO_EXPECT(IsAtLeastV() && isAtLeastKernelVersion(5, 15, 0), MAINLINE_FOR_V_5_15_PLUS);
+    DO_EXPECT(IsAtLeastV() && isAtLeastKernelVersion(5, 4, 0), MAINLINE_FOR_V_5_4_PLUS);
+    DO_EXPECT(IsAtLeastV() && isAtLeastKernelVersion(5, 10, 0), MAINLINE_FOR_V_5_10_PLUS);
 
     for (const auto& file : mustExist) {
         EXPECT_EQ(0, access(file.c_str(), R_OK)) << file << " does not exist";