diff mbox series

[bpf-next,20/21] selftests/bpf: Test bpf_strtol and bpf_strtoul helpers

Message ID 5d6307143d553198d41d3080ee6cff135734a0d8.1553385599.git.rdna@fb.com
State Changes Requested
Delegated to: BPF Maintainers
Headers show
Series bpf: Sysctl hook | expand

Commit Message

Andrey Ignatov March 24, 2019, 12:12 a.m. UTC 
Test that bpf_strtol and  bpf_strtoul helpers can be used to convert
provided buffer to long or unsigned long correspondingly and return both
correct result and number of consumed bytes, or proper errno.

Example of output:
  # ./test_sysctl
  ..
  Test case: bpf_strtoul one number string .. [PASS]
  Test case: bpf_strtoul multi number string .. [PASS]
  Test case: bpf_strtoul buf_len = 0, reject .. [PASS]
  Test case: bpf_strtoul supported base, ok .. [PASS]
  Test case: bpf_strtoul unsupported base, EINVAL .. [PASS]
  Test case: bpf_strtoul buf with spaces only, EINVAL .. [PASS]
  Test case: bpf_strtoul negative number, EINVAL .. [PASS]
  Test case: bpf_strtol negative number, ok .. [PASS]
  Test case: bpf_strtol hex number, ok .. [PASS]
  Test case: bpf_strtol max long .. [PASS]
  Test case: bpf_strtol overflow, ERANGE .. [PASS]
  Summary: 36 PASSED, 0 FAILED

Signed-off-by: Andrey Ignatov <rdna@fb.com>
---
 tools/testing/selftests/bpf/test_sysctl.c | 485 ++++++++++++++++++++++
 1 file changed, 485 insertions(+)
diff mbox series

Patch

diff --git a/tools/testing/selftests/bpf/test_sysctl.c b/tools/testing/selftests/bpf/test_sysctl.c
index 43008aae32d3..885675480af9 100644
--- a/tools/testing/selftests/bpf/test_sysctl.c
+++ b/tools/testing/selftests/bpf/test_sysctl.c
@@ -817,6 +817,491 @@  static struct sysctl_test tests[] = {
 		.newval = "606",
 		.result = SUCCESS,
 	},
+	{
+		"bpf_strtoul one number string",
+		.insns = {
+			/* arg1 (buf) */
+			BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			BPF_MOV64_IMM(BPF_REG_0, 0x00303036),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+
+			BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
+
+			/* arg2 (buf_len) */
+			BPF_MOV64_IMM(BPF_REG_2, 4),
+
+			/* arg3 (flags) */
+			BPF_MOV64_IMM(BPF_REG_3, 0),
+
+			/* arg4 (res) */
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+			BPF_MOV64_REG(BPF_REG_4, BPF_REG_7),
+
+			BPF_EMIT_CALL(BPF_FUNC_strtoul),
+
+			/* if (ret == expected && */
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 3, 4),
+			/*     res == expected) */
+			BPF_LDX_MEM(BPF_DW, BPF_REG_9, BPF_REG_7, 0),
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_9, 600, 2),
+
+			/* return ALLOW; */
+			BPF_MOV64_IMM(BPF_REG_0, 1),
+			BPF_JMP_A(1),
+
+			/* else return DENY; */
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_EXIT_INSN(),
+		},
+		.attach_type = BPF_CGROUP_SYSCTL,
+		.sysctl = "net/ipv4/route/mtu_expires",
+		.open_flags = O_RDONLY,
+		.result = SUCCESS,
+	},
+	{
+		"bpf_strtoul multi number string",
+		.insns = {
+			/* arg1 (buf) */
+			BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			/* "600 602\0" */
+			BPF_LD_IMM64(BPF_REG_0, 0x0032303620303036ULL),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+			BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
+
+			/* arg2 (buf_len) */
+			BPF_MOV64_IMM(BPF_REG_2, 8),
+
+			/* arg3 (flags) */
+			BPF_MOV64_IMM(BPF_REG_3, 0),
+
+			/* arg4 (res) */
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+			BPF_MOV64_REG(BPF_REG_4, BPF_REG_7),
+
+			BPF_EMIT_CALL(BPF_FUNC_strtoul),
+
+			/* if (ret == expected && */
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 3, 18),
+			/*     res == expected) */
+			BPF_LDX_MEM(BPF_DW, BPF_REG_9, BPF_REG_7, 0),
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_9, 600, 16),
+
+			/*     arg1 (buf) */
+			BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			BPF_ALU64_REG(BPF_ADD, BPF_REG_7, BPF_REG_0),
+			BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
+
+			/*     arg2 (buf_len) */
+			BPF_MOV64_IMM(BPF_REG_2, 8),
+			BPF_ALU64_REG(BPF_SUB, BPF_REG_2, BPF_REG_0),
+
+			/*     arg3 (flags) */
+			BPF_MOV64_IMM(BPF_REG_3, 0),
+
+			/*     arg4 (res) */
+			BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -16),
+			BPF_MOV64_REG(BPF_REG_4, BPF_REG_7),
+
+			BPF_EMIT_CALL(BPF_FUNC_strtoul),
+
+			/*     if (ret == expected && */
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 4, 4),
+			/*         res == expected) */
+			BPF_LDX_MEM(BPF_DW, BPF_REG_9, BPF_REG_7, 0),
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_9, 602, 2),
+
+			/* return ALLOW; */
+			BPF_MOV64_IMM(BPF_REG_0, 1),
+			BPF_JMP_A(1),
+
+			/* else return DENY; */
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_EXIT_INSN(),
+		},
+		.attach_type = BPF_CGROUP_SYSCTL,
+		.sysctl = "net/ipv4/tcp_mem",
+		.open_flags = O_RDONLY,
+		.result = SUCCESS,
+	},
+	{
+		"bpf_strtoul buf_len = 0, reject",
+		.insns = {
+			/* arg1 (buf) */
+			BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			BPF_MOV64_IMM(BPF_REG_0, 0x00303036),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+
+			BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
+
+			/* arg2 (buf_len) */
+			BPF_MOV64_IMM(BPF_REG_2, 0),
+
+			/* arg3 (flags) */
+			BPF_MOV64_IMM(BPF_REG_3, 0),
+
+			/* arg4 (res) */
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+			BPF_MOV64_REG(BPF_REG_4, BPF_REG_7),
+
+			BPF_EMIT_CALL(BPF_FUNC_strtoul),
+
+			BPF_MOV64_IMM(BPF_REG_0, 1),
+			BPF_EXIT_INSN(),
+		},
+		.attach_type = BPF_CGROUP_SYSCTL,
+		.sysctl = "net/ipv4/route/mtu_expires",
+		.open_flags = O_RDONLY,
+		.result = LOAD_REJECT,
+	},
+	{
+		"bpf_strtoul supported base, ok",
+		.insns = {
+			/* arg1 (buf) */
+			BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			BPF_MOV64_IMM(BPF_REG_0, 0x00373730),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+
+			BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
+
+			/* arg2 (buf_len) */
+			BPF_MOV64_IMM(BPF_REG_2, 4),
+
+			/* arg3 (flags) */
+			BPF_MOV64_IMM(BPF_REG_3, 8),
+
+			/* arg4 (res) */
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+			BPF_MOV64_REG(BPF_REG_4, BPF_REG_7),
+
+			BPF_EMIT_CALL(BPF_FUNC_strtoul),
+
+			/* if (ret == expected && */
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 3, 4),
+			/*     res == expected) */
+			BPF_LDX_MEM(BPF_DW, BPF_REG_9, BPF_REG_7, 0),
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_9, 63, 2),
+
+			/* return ALLOW; */
+			BPF_MOV64_IMM(BPF_REG_0, 1),
+			BPF_JMP_A(1),
+
+			/* else return DENY; */
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_EXIT_INSN(),
+		},
+		.attach_type = BPF_CGROUP_SYSCTL,
+		.sysctl = "net/ipv4/route/mtu_expires",
+		.open_flags = O_RDONLY,
+		.result = SUCCESS,
+	},
+	{
+		"bpf_strtoul unsupported base, EINVAL",
+		.insns = {
+			/* arg1 (buf) */
+			BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			BPF_MOV64_IMM(BPF_REG_0, 0x00303036),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+
+			BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
+
+			/* arg2 (buf_len) */
+			BPF_MOV64_IMM(BPF_REG_2, 4),
+
+			/* arg3 (flags) */
+			BPF_MOV64_IMM(BPF_REG_3, 3),
+
+			/* arg4 (res) */
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+			BPF_MOV64_REG(BPF_REG_4, BPF_REG_7),
+
+			BPF_EMIT_CALL(BPF_FUNC_strtoul),
+
+			/* if (ret == expected) */
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_0, -EINVAL, 2),
+
+			/* return ALLOW; */
+			BPF_MOV64_IMM(BPF_REG_0, 1),
+			BPF_JMP_A(1),
+
+			/* else return DENY; */
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_EXIT_INSN(),
+		},
+		.attach_type = BPF_CGROUP_SYSCTL,
+		.sysctl = "net/ipv4/route/mtu_expires",
+		.open_flags = O_RDONLY,
+		.result = SUCCESS,
+	},
+	{
+		"bpf_strtoul buf with spaces only, EINVAL",
+		.insns = {
+			/* arg1 (buf) */
+			BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			BPF_MOV64_IMM(BPF_REG_0, 0x090a0c0d),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+
+			BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
+
+			/* arg2 (buf_len) */
+			BPF_MOV64_IMM(BPF_REG_2, 4),
+
+			/* arg3 (flags) */
+			BPF_MOV64_IMM(BPF_REG_3, 0),
+
+			/* arg4 (res) */
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+			BPF_MOV64_REG(BPF_REG_4, BPF_REG_7),
+
+			BPF_EMIT_CALL(BPF_FUNC_strtoul),
+
+			/* if (ret == expected) */
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_0, -EINVAL, 2),
+
+			/* return ALLOW; */
+			BPF_MOV64_IMM(BPF_REG_0, 1),
+			BPF_JMP_A(1),
+
+			/* else return DENY; */
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_EXIT_INSN(),
+		},
+		.attach_type = BPF_CGROUP_SYSCTL,
+		.sysctl = "net/ipv4/route/mtu_expires",
+		.open_flags = O_RDONLY,
+		.result = SUCCESS,
+	},
+	{
+		"bpf_strtoul negative number, EINVAL",
+		.insns = {
+			/* arg1 (buf) */
+			BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			BPF_MOV64_IMM(BPF_REG_0, 0x00362d0a), /* " -6\0" */
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+
+			BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
+
+			/* arg2 (buf_len) */
+			BPF_MOV64_IMM(BPF_REG_2, 4),
+
+			/* arg3 (flags) */
+			BPF_MOV64_IMM(BPF_REG_3, 0),
+
+			/* arg4 (res) */
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+			BPF_MOV64_REG(BPF_REG_4, BPF_REG_7),
+
+			BPF_EMIT_CALL(BPF_FUNC_strtoul),
+
+			/* if (ret == expected) */
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_0, -EINVAL, 2),
+
+			/* return ALLOW; */
+			BPF_MOV64_IMM(BPF_REG_0, 1),
+			BPF_JMP_A(1),
+
+			/* else return DENY; */
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_EXIT_INSN(),
+		},
+		.attach_type = BPF_CGROUP_SYSCTL,
+		.sysctl = "net/ipv4/route/mtu_expires",
+		.open_flags = O_RDONLY,
+		.result = SUCCESS,
+	},
+	{
+		"bpf_strtol negative number, ok",
+		.insns = {
+			/* arg1 (buf) */
+			BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			BPF_MOV64_IMM(BPF_REG_0, 0x00362d0a), /* " -6\0" */
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+
+			BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
+
+			/* arg2 (buf_len) */
+			BPF_MOV64_IMM(BPF_REG_2, 4),
+
+			/* arg3 (flags) */
+			BPF_MOV64_IMM(BPF_REG_3, 10),
+
+			/* arg4 (res) */
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+			BPF_MOV64_REG(BPF_REG_4, BPF_REG_7),
+
+			BPF_EMIT_CALL(BPF_FUNC_strtol),
+
+			/* if (ret == expected && */
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 3, 4),
+			/*     res == expected) */
+			BPF_LDX_MEM(BPF_DW, BPF_REG_9, BPF_REG_7, 0),
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_9, -6, 2),
+
+			/* return ALLOW; */
+			BPF_MOV64_IMM(BPF_REG_0, 1),
+			BPF_JMP_A(1),
+
+			/* else return DENY; */
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_EXIT_INSN(),
+		},
+		.attach_type = BPF_CGROUP_SYSCTL,
+		.sysctl = "net/ipv4/route/mtu_expires",
+		.open_flags = O_RDONLY,
+		.result = SUCCESS,
+	},
+	{
+		"bpf_strtol hex number, ok",
+		.insns = {
+			/* arg1 (buf) */
+			BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			BPF_MOV64_IMM(BPF_REG_0, 0x65667830), /* "0xfe" */
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+
+			BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
+
+			/* arg2 (buf_len) */
+			BPF_MOV64_IMM(BPF_REG_2, 4),
+
+			/* arg3 (flags) */
+			BPF_MOV64_IMM(BPF_REG_3, 0),
+
+			/* arg4 (res) */
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+			BPF_MOV64_REG(BPF_REG_4, BPF_REG_7),
+
+			BPF_EMIT_CALL(BPF_FUNC_strtol),
+
+			/* if (ret == expected && */
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 4, 4),
+			/*     res == expected) */
+			BPF_LDX_MEM(BPF_DW, BPF_REG_9, BPF_REG_7, 0),
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_9, 254, 2),
+
+			/* return ALLOW; */
+			BPF_MOV64_IMM(BPF_REG_0, 1),
+			BPF_JMP_A(1),
+
+			/* else return DENY; */
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_EXIT_INSN(),
+		},
+		.attach_type = BPF_CGROUP_SYSCTL,
+		.sysctl = "net/ipv4/route/mtu_expires",
+		.open_flags = O_RDONLY,
+		.result = SUCCESS,
+	},
+	{
+		"bpf_strtol max long",
+		.insns = {
+			/* arg1 (buf) 9223372036854775807 */
+			BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -24),
+			BPF_LD_IMM64(BPF_REG_0, 0x3032373333323239ULL),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+			BPF_LD_IMM64(BPF_REG_0, 0x3537373435383633ULL),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 8),
+			BPF_LD_IMM64(BPF_REG_0, 0x0000000000373038ULL),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 16),
+
+			BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
+
+			/* arg2 (buf_len) */
+			BPF_MOV64_IMM(BPF_REG_2, 19),
+
+			/* arg3 (flags) */
+			BPF_MOV64_IMM(BPF_REG_3, 0),
+
+			/* arg4 (res) */
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+			BPF_MOV64_REG(BPF_REG_4, BPF_REG_7),
+
+			BPF_EMIT_CALL(BPF_FUNC_strtol),
+
+			/* if (ret == expected && */
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 19, 6),
+			/*     res == expected) */
+			BPF_LD_IMM64(BPF_REG_8, 0x7fffffffffffffffULL),
+			BPF_LDX_MEM(BPF_DW, BPF_REG_9, BPF_REG_7, 0),
+			BPF_JMP_REG(BPF_JNE, BPF_REG_8, BPF_REG_9, 2),
+
+			/* return ALLOW; */
+			BPF_MOV64_IMM(BPF_REG_0, 1),
+			BPF_JMP_A(1),
+
+			/* else return DENY; */
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_EXIT_INSN(),
+		},
+		.attach_type = BPF_CGROUP_SYSCTL,
+		.sysctl = "net/ipv4/route/mtu_expires",
+		.open_flags = O_RDONLY,
+		.result = SUCCESS,
+	},
+	{
+		"bpf_strtol overflow, ERANGE",
+		.insns = {
+			/* arg1 (buf) 9223372036854775808 */
+			BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -24),
+			BPF_LD_IMM64(BPF_REG_0, 0x3032373333323239ULL),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+			BPF_LD_IMM64(BPF_REG_0, 0x3537373435383633ULL),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 8),
+			BPF_LD_IMM64(BPF_REG_0, 0x0000000000383038ULL),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 16),
+
+			BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
+
+			/* arg2 (buf_len) */
+			BPF_MOV64_IMM(BPF_REG_2, 19),
+
+			/* arg3 (flags) */
+			BPF_MOV64_IMM(BPF_REG_3, 0),
+
+			/* arg4 (res) */
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+			BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_0, 0),
+			BPF_MOV64_REG(BPF_REG_4, BPF_REG_7),
+
+			BPF_EMIT_CALL(BPF_FUNC_strtol),
+
+			/* if (ret == expected) */
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_0, -ERANGE, 2),
+
+			/* return ALLOW; */
+			BPF_MOV64_IMM(BPF_REG_0, 1),
+			BPF_JMP_A(1),
+
+			/* else return DENY; */
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_EXIT_INSN(),
+		},
+		.attach_type = BPF_CGROUP_SYSCTL,
+		.sysctl = "net/ipv4/route/mtu_expires",
+		.open_flags = O_RDONLY,
+		.result = SUCCESS,
+	},
 };
 
 static size_t probe_prog_length(const struct bpf_insn *fp)