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bpf, selftests: Add test case for mixed cgroup v1/v2
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Minimal selftest which implements a small BPF policy program to the
connect(2) hook which rejects TCP connection requests to port 60123
with EPERM. This is being attached to a non-root cgroup v2 path. The
test asserts that this works under cgroup v2-only and under a mixed
cgroup v1/v2 environment where net_classid is set in the former case.

Before fix:

  # ./test_progs -t cgroup_v1v2
  test_cgroup_v1v2:PASS:server_fd 0 nsec
  test_cgroup_v1v2:PASS:client_fd 0 nsec
  test_cgroup_v1v2:PASS:cgroup_fd 0 nsec
  test_cgroup_v1v2:PASS:server_fd 0 nsec
  run_test:PASS:skel_open 0 nsec
  run_test:PASS:prog_attach 0 nsec
  test_cgroup_v1v2:PASS:cgroup-v2-only 0 nsec
  run_test:PASS:skel_open 0 nsec
  run_test:PASS:prog_attach 0 nsec
  run_test:PASS:join_classid 0 nsec
  (network_helpers.c:219: errno: None) Unexpected success to connect to server
  test_cgroup_v1v2:FAIL:cgroup-v1v2 unexpected error: -1 (errno 0)
  MIPS#27 cgroup_v1v2:FAIL
  Summary: 0/0 PASSED, 0 SKIPPED, 1 FAILED

After fix:

  # ./test_progs -t cgroup_v1v2
  MIPS#27 cgroup_v1v2:OK
  Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210913230759.2313-3-daniel@iogearbox.net
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borkmann authored and Alexei Starovoitov committed Sep 13, 2021
1 parent d8079d8 commit 43d2b88
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Showing 4 changed files with 127 additions and 6 deletions.
27 changes: 21 additions & 6 deletions tools/testing/selftests/bpf/network_helpers.c
Original file line number Diff line number Diff line change
Expand Up @@ -208,11 +208,26 @@ int fastopen_connect(int server_fd, const char *data, unsigned int data_len,

static int connect_fd_to_addr(int fd,
const struct sockaddr_storage *addr,
socklen_t addrlen)
socklen_t addrlen, const bool must_fail)
{
if (connect(fd, (const struct sockaddr *)addr, addrlen)) {
log_err("Failed to connect to server");
return -1;
int ret;

errno = 0;
ret = connect(fd, (const struct sockaddr *)addr, addrlen);
if (must_fail) {
if (!ret) {
log_err("Unexpected success to connect to server");
return -1;
}
if (errno != EPERM) {
log_err("Unexpected error from connect to server");
return -1;
}
} else {
if (ret) {
log_err("Failed to connect to server");
return -1;
}
}

return 0;
Expand Down Expand Up @@ -257,7 +272,7 @@ int connect_to_fd_opts(int server_fd, const struct network_helper_opts *opts)
strlen(opts->cc) + 1))
goto error_close;

if (connect_fd_to_addr(fd, &addr, addrlen))
if (connect_fd_to_addr(fd, &addr, addrlen, opts->must_fail))
goto error_close;

return fd;
Expand Down Expand Up @@ -289,7 +304,7 @@ int connect_fd_to_fd(int client_fd, int server_fd, int timeout_ms)
return -1;
}

if (connect_fd_to_addr(client_fd, &addr, len))
if (connect_fd_to_addr(client_fd, &addr, len, false))
return -1;

return 0;
Expand Down
1 change: 1 addition & 0 deletions tools/testing/selftests/bpf/network_helpers.h
Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@ typedef __u16 __sum16;
struct network_helper_opts {
const char *cc;
int timeout_ms;
bool must_fail;
};

/* ipv4 test vector */
Expand Down
79 changes: 79 additions & 0 deletions tools/testing/selftests/bpf/prog_tests/cgroup_v1v2.c
Original file line number Diff line number Diff line change
@@ -0,0 +1,79 @@
// SPDX-License-Identifier: GPL-2.0

#include <test_progs.h>

#include "connect4_dropper.skel.h"

#include "cgroup_helpers.h"
#include "network_helpers.h"

static int run_test(int cgroup_fd, int server_fd, bool classid)
{
struct network_helper_opts opts = {
.must_fail = true,
};
struct connect4_dropper *skel;
int fd, err = 0;

skel = connect4_dropper__open_and_load();
if (!ASSERT_OK_PTR(skel, "skel_open"))
return -1;

skel->links.connect_v4_dropper =
bpf_program__attach_cgroup(skel->progs.connect_v4_dropper,
cgroup_fd);
if (!ASSERT_OK_PTR(skel->links.connect_v4_dropper, "prog_attach")) {
err = -1;
goto out;
}

if (classid && !ASSERT_OK(join_classid(), "join_classid")) {
err = -1;
goto out;
}

fd = connect_to_fd_opts(server_fd, &opts);
if (fd < 0)
err = -1;
else
close(fd);
out:
connect4_dropper__destroy(skel);
return err;
}

void test_cgroup_v1v2(void)
{
struct network_helper_opts opts = {};
int server_fd, client_fd, cgroup_fd;
static const int port = 60123;

/* Step 1: Check base connectivity works without any BPF. */
server_fd = start_server(AF_INET, SOCK_STREAM, NULL, port, 0);
if (!ASSERT_GE(server_fd, 0, "server_fd"))
return;
client_fd = connect_to_fd_opts(server_fd, &opts);
if (!ASSERT_GE(client_fd, 0, "client_fd")) {
close(server_fd);
return;
}
close(client_fd);
close(server_fd);

/* Step 2: Check BPF policy prog attached to cgroups drops connectivity. */
cgroup_fd = test__join_cgroup("/connect_dropper");
if (!ASSERT_GE(cgroup_fd, 0, "cgroup_fd"))
return;
server_fd = start_server(AF_INET, SOCK_STREAM, NULL, port, 0);
if (!ASSERT_GE(server_fd, 0, "server_fd")) {
close(cgroup_fd);
return;
}
ASSERT_OK(run_test(cgroup_fd, server_fd, false), "cgroup-v2-only");
setup_classid_environment();
set_classid(42);
ASSERT_OK(run_test(cgroup_fd, server_fd, true), "cgroup-v1v2");
cleanup_classid_environment();
close(server_fd);
close(cgroup_fd);
}
26 changes: 26 additions & 0 deletions tools/testing/selftests/bpf/progs/connect4_dropper.c
Original file line number Diff line number Diff line change
@@ -0,0 +1,26 @@
// SPDX-License-Identifier: GPL-2.0

#include <string.h>

#include <linux/stddef.h>
#include <linux/bpf.h>

#include <sys/socket.h>

#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>

#define VERDICT_REJECT 0
#define VERDICT_PROCEED 1

SEC("cgroup/connect4")
int connect_v4_dropper(struct bpf_sock_addr *ctx)
{
if (ctx->type != SOCK_STREAM)
return VERDICT_PROCEED;
if (ctx->user_port == bpf_htons(60123))
return VERDICT_REJECT;
return VERDICT_PROCEED;
}

char _license[] SEC("license") = "GPL";

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