[PATCH v2 bpf-next 6/6] selftests/bpf: Cover BPF_F_REPLACE in test_cgroup_attach

[Andrey Ignatov <rdna@fb.com>]

Test replacement of a cgroup-bpf program attached with BPF_F_ALLOW_MULTI
and possible failure modes: invalid combination of flags, invalid
replace_bpf_fd, replacing a non-attachd to specified cgroup program.

Example of program replacing:

  # gdb -q ./test_cgroup_attach
  Reading symbols from /data/users/rdna/bin/test_cgroup_attach...done.
  ...
  Breakpoint 1, test_multiprog () at test_cgroup_attach.c:443
  443     test_cgroup_attach.c: No such file or directory.
  (gdb)
  [2]+  Stopped                 gdb -q ./test_cgroup_attach
  # bpftool c s /mnt/cgroup2/cgroup-test-work-dir/cg1
  ID       AttachType      AttachFlags     Name
  35       egress          multi
  36       egress          multi
  # fg gdb -q ./test_cgroup_attach
  c
  Continuing.
  Detaching after fork from child process 361.

  Breakpoint 2, test_multiprog () at test_cgroup_attach.c:454
  454     in test_cgroup_attach.c
  (gdb)
  [2]+  Stopped                 gdb -q ./test_cgroup_attach
  # bpftool c s /mnt/cgroup2/cgroup-test-work-dir/cg1
  ID       AttachType      AttachFlags     Name
  41       egress          multi
  36       egress          multi

Signed-off-by: Andrey Ignatov <rdna@fb.com>
---
 .../selftests/bpf/test_cgroup_attach.c        | 62 +++++++++++++++++--
 1 file changed, 57 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/bpf/test_cgroup_attach.c b/tools/testing/selftests/bpf/test_cgroup_attach.c
index 7671909ee1cb..6c7971ffe683 100644
--- a/tools/testing/selftests/bpf/test_cgroup_attach.c
+++ b/tools/testing/selftests/bpf/test_cgroup_attach.c
@@ -250,7 +250,7 @@ static int prog_load_cnt(int verdict, int val)
 		BPF_LD_MAP_FD(BPF_REG_1, map_fd),
 		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
 		BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
-		BPF_MOV64_IMM(BPF_REG_1, val), /* r1 = 1 */
+		BPF_MOV64_IMM(BPF_REG_1, val), /* r1 = val */
 		BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */
 
 		BPF_LD_MAP_FD(BPF_REG_1, cgroup_storage_fd),
@@ -290,11 +290,11 @@ static int test_multiprog(void)
 {
 	__u32 prog_ids[4], prog_cnt = 0, attach_flags, saved_prog_id;
 	int cg1 = 0, cg2 = 0, cg3 = 0, cg4 = 0, cg5 = 0, key = 0;
-	int drop_prog, allow_prog[6] = {}, rc = 0;
+	int drop_prog, allow_prog[7] = {}, rc = 0;
 	unsigned long long value;
 	int i = 0;
 
-	for (i = 0; i < 6; i++) {
+	for (i = 0; i < ARRAY_SIZE(allow_prog); i++) {
 		allow_prog[i] = prog_load_cnt(1, 1 << i);
 		if (!allow_prog[i])
 			goto err;
@@ -400,6 +400,58 @@ static int test_multiprog(void)
 	assert(bpf_map_lookup_elem(map_fd, &key, &value) == 0);
 	assert(value == 1 + 2 + 8 + 16);
 
+	/* invalid input */
+
+	DECLARE_LIBBPF_OPTS(bpf_prog_attach_opts, attach_opts,
+		.target_fd		= cg1,
+		.prog_fd		= allow_prog[6],
+		.replace_prog_fd	= allow_prog[0],
+		.type			= BPF_CGROUP_INET_EGRESS,
+		.flags			= BPF_F_ALLOW_MULTI | BPF_F_REPLACE,
+	);
+
+	attach_opts.flags = BPF_F_ALLOW_OVERRIDE | BPF_F_REPLACE;
+	if (!bpf_prog_attach_xattr(&attach_opts)) {
+		log_err("Unexpected success with OVERRIDE | REPLACE");
+		goto err;
+	}
+	assert(errno == EINVAL);
+
+	attach_opts.flags = BPF_F_REPLACE;
+	if (!bpf_prog_attach_xattr(&attach_opts)) {
+		log_err("Unexpected success with REPLACE alone");
+		goto err;
+	}
+	assert(errno == EINVAL);
+	attach_opts.flags = BPF_F_ALLOW_MULTI | BPF_F_REPLACE;
+
+	attach_opts.replace_prog_fd = -1;
+	if (!bpf_prog_attach_xattr(&attach_opts)) {
+		log_err("Unexpected success with bad replace fd");
+		goto err;
+	}
+	assert(errno == EBADF);
+
+	/* replacing a program that is not attached to cgroup should fail  */
+	attach_opts.replace_prog_fd = allow_prog[3];
+	if (!bpf_prog_attach_xattr(&attach_opts)) {
+		log_err("Unexpected success: replace not-attached prog on cg1");
+		goto err;
+	}
+	assert(errno == ENOENT);
+	attach_opts.replace_prog_fd = allow_prog[0];
+
+	/* replace 1st from the top program */
+	if (bpf_prog_attach_xattr(&attach_opts)) {
+		log_err("Replace prog1 with prog7 on cg1");
+		goto err;
+	}
+	value = 0;
+	assert(bpf_map_update_elem(map_fd, &key, &value, 0) == 0);
+	assert(system(PING_CMD) == 0);
+	assert(bpf_map_lookup_elem(map_fd, &key, &value) == 0);
+	assert(value == 64 + 2 + 8 + 16);
+
 	/* detach 3rd from bottom program and ping again */
 	errno = 0;
 	if (!bpf_prog_detach2(0, cg3, BPF_CGROUP_INET_EGRESS)) {
@@ -414,7 +466,7 @@ static int test_multiprog(void)
 	assert(bpf_map_update_elem(map_fd, &key, &value, 0) == 0);
 	assert(system(PING_CMD) == 0);
 	assert(bpf_map_lookup_elem(map_fd, &key, &value) == 0);
-	assert(value == 1 + 2 + 16);
+	assert(value == 64 + 2 + 16);
 
 	/* detach 2nd from bottom program and ping again */
 	if (bpf_prog_detach2(-1, cg4, BPF_CGROUP_INET_EGRESS)) {
@@ -425,7 +477,7 @@ static int test_multiprog(void)
 	assert(bpf_map_update_elem(map_fd, &key, &value, 0) == 0);
 	assert(system(PING_CMD) == 0);
 	assert(bpf_map_lookup_elem(map_fd, &key, &value) == 0);
-	assert(value == 1 + 2 + 4);
+	assert(value == 64 + 2 + 4);
 
 	prog_cnt = 4;
 	assert(bpf_prog_query(cg5, BPF_CGROUP_INET_EGRESS, BPF_F_QUERY_EFFECTIVE,
-- 
2.17.1