Re: [PATCH bpf-next v3 6/6] selftests: bpf: test sockmap update from BPF

[Yonghong Song <yhs@fb.com>]

On 8/21/20 3:29 AM, Lorenz Bauer wrote:
> Add a test which copies a socket from a sockmap into another sockmap
> or sockhash. This excercises bpf_map_update_elem support from BPF
> context. Compare the socket cookies from source and destination to
> ensure that the copy succeeded.
> 
> Also check that the verifier rejects map_update from unsafe contexts.
> 
> Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>

A few nits below.

Acked-by: Yonghong Song <yhs@fb.com>

> ---
>   .../selftests/bpf/prog_tests/sockmap_basic.c  | 78 +++++++++++++++++++
>   .../bpf/progs/test_sockmap_invalid_update.c   | 23 ++++++
>   .../selftests/bpf/progs/test_sockmap_update.c | 48 ++++++++++++
>   3 files changed, 149 insertions(+)
>   create mode 100644 tools/testing/selftests/bpf/progs/test_sockmap_invalid_update.c
>   create mode 100644 tools/testing/selftests/bpf/progs/test_sockmap_update.c
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
> index 96e7b7f84c65..65ce7c289534 100644
> --- a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
> +++ b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
> @@ -4,6 +4,8 @@
>   
>   #include "test_progs.h"
>   #include "test_skmsg_load_helpers.skel.h"
> +#include "test_sockmap_update.skel.h"
> +#include "test_sockmap_invalid_update.skel.h"
>   
>   #define TCP_REPAIR		19	/* TCP sock is under repair right now */
>   
> @@ -101,6 +103,76 @@ static void test_skmsg_helpers(enum bpf_map_type map_type)
>   	test_skmsg_load_helpers__destroy(skel);
>   }
>   
> +static void test_sockmap_update(enum bpf_map_type map_type)
> +{
> +	struct bpf_prog_test_run_attr tattr;
> +	int err, prog, src, dst, duration = 0;
> +	struct test_sockmap_update *skel;
> +	__u64 src_cookie, dst_cookie;
> +	const __u32 zero = 0;
> +	char dummy[14] = {0};
> +	__s64 sk;
> +
> +	sk = connected_socket_v4();
> +	if (CHECK(sk == -1, "connected_socket_v4", "cannot connect\n"))
> +		return;
> +
> +	skel = test_sockmap_update__open_and_load();
> +	if (CHECK(!skel, "open_and_load", "cannot load skeleton\n")) {
> +		close(sk);
> +		return;
> +	}
> +
> +	prog = bpf_program__fd(skel->progs.copy_sock_map);
> +	src = bpf_map__fd(skel->maps.src);
> +	if (map_type == BPF_MAP_TYPE_SOCKMAP)
> +		dst = bpf_map__fd(skel->maps.dst_sock_map);
> +	else
> +		dst = bpf_map__fd(skel->maps.dst_sock_hash);
> +
> +	err = bpf_map_update_elem(src, &zero, &sk, BPF_NOEXIST);
> +	if (CHECK(err, "update_elem(src)", "errno=%u\n", errno))
> +		goto out;
> +
> +	err = bpf_map_lookup_elem(src, &zero, &src_cookie);
> +	if (CHECK(err, "lookup_elem(src, cookie)", "errno=%u\n", errno))
> +		goto out;
> +
> +	tattr = (struct bpf_prog_test_run_attr){
> +		.prog_fd = prog,
> +		.repeat = 1,
> +		.data_in = dummy,
> +		.data_size_in = sizeof(dummy),
> +	};
> +
> +	err = bpf_prog_test_run_xattr(&tattr);
> +	if (CHECK_ATTR(err || !tattr.retval, "bpf_prog_test_run",
> +		       "errno=%u retval=%u\n", errno, tattr.retval))
> +		goto out;
> +
> +	err = bpf_map_lookup_elem(dst, &zero, &dst_cookie);
> +	if (CHECK(err, "lookup_elem(dst, cookie)", "errno=%u\n", errno))
> +		goto out;
> +
> +	CHECK(dst_cookie != src_cookie, "cookie mismatch", "%llu != %llu\n",
> +	      dst_cookie, src_cookie);
> +
> +out:
> +	close(sk);
> +	test_sockmap_update__destroy(skel);

nit. In the beginning of the function, 'sk' is available and then skel 
is opened and loaded. You can have

out:
	test_sockmap_update__destroy(skel);
close_sk:
	close(sk);

this probably more conforms to linux coding style.

Then you can have
	if (CHECK(!skel, "open_and_load", "cannot load skeleton\n"))
		goto close_sk;

> +}
> +
> +static void test_sockmap_invalid_update(void)
> +{
> +	struct test_sockmap_invalid_update *skel;
> +	int duration = 0;
> +
> +	skel = test_sockmap_invalid_update__open_and_load();
> +	CHECK(skel, "open_and_load", "verifier accepted map_update\n");
> +	if (skel)
> +		test_sockmap_invalid_update__destroy(skel);

nit, you can just have
	if (CHECK(skel, "open_and_load", "verifier accepted map_update\n"))
		test_sockmap_invalid_update__destroy(skel);

> +}
> +
>   void test_sockmap_basic(void)
>   {
>   	if (test__start_subtest("sockmap create_update_free"))
> @@ -111,4 +183,10 @@ void test_sockmap_basic(void)
>   		test_skmsg_helpers(BPF_MAP_TYPE_SOCKMAP);
>   	if (test__start_subtest("sockhash sk_msg load helpers"))
>   		test_skmsg_helpers(BPF_MAP_TYPE_SOCKHASH);
> +	if (test__start_subtest("sockmap update"))
> +		test_sockmap_update(BPF_MAP_TYPE_SOCKMAP);
> +	if (test__start_subtest("sockhash update"))
> +		test_sockmap_update(BPF_MAP_TYPE_SOCKHASH);
> +	if (test__start_subtest("sockmap update in unsafe context"))
> +		test_sockmap_invalid_update();
>   }
> diff --git a/tools/testing/selftests/bpf/progs/test_sockmap_invalid_update.c b/tools/testing/selftests/bpf/progs/test_sockmap_invalid_update.c
> new file mode 100644
> index 000000000000..02a59e220cbc
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_sockmap_invalid_update.c
> @@ -0,0 +1,23 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (c) 2020 Cloudflare
> +#include "vmlinux.h"
> +#include <bpf/bpf_helpers.h>
> +
> +struct {
> +	__uint(type, BPF_MAP_TYPE_SOCKMAP);
> +	__uint(max_entries, 1);
> +	__type(key, __u32);
> +	__type(value, __u64);
> +} map SEC(".maps");
> +
> +SEC("sockops")
> +int bpf_sockmap(struct bpf_sock_ops *skops)
> +{
> +	__u32 key = 0;
> +
> +	if (skops->sk)
> +		bpf_map_update_elem(&map, &key, skops->sk, 0);
> +	return 0;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> diff --git a/tools/testing/selftests/bpf/progs/test_sockmap_update.c b/tools/testing/selftests/bpf/progs/test_sockmap_update.c
> new file mode 100644
> index 000000000000..9d0c9f28cab2
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_sockmap_update.c
> @@ -0,0 +1,48 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (c) 2020 Cloudflare
> +#include "vmlinux.h"
> +#include <bpf/bpf_helpers.h>
> +
> +struct {
> +	__uint(type, BPF_MAP_TYPE_SOCKMAP);
> +	__uint(max_entries, 1);
> +	__type(key, __u32);
> +	__type(value, __u64);
> +} src SEC(".maps");
> +
> +struct {
> +	__uint(type, BPF_MAP_TYPE_SOCKMAP);
> +	__uint(max_entries, 1);
> +	__type(key, __u32);
> +	__type(value, __u64);
> +} dst_sock_map SEC(".maps");
> +
> +struct {
> +	__uint(type, BPF_MAP_TYPE_SOCKHASH);
> +	__uint(max_entries, 1);
> +	__type(key, __u32);
> +	__type(value, __u64);
> +} dst_sock_hash SEC(".maps");
> +
> +SEC("classifier/copy_sock_map")
> +int copy_sock_map(void *ctx)
> +{
> +	struct bpf_sock *sk;
> +	bool failed = false;
> +	__u32 key = 0;
> +
> +	sk = bpf_map_lookup_elem(&src, &key);
> +	if (!sk)
> +		return SK_DROP;
> +
> +	if (bpf_map_update_elem(&dst_sock_map, &key, sk, 0))
> +		failed = true;
> +
> +	if (bpf_map_update_elem(&dst_sock_hash, &key, sk, 0))
> +		failed = true;
> +
> +	bpf_sk_release(sk);
> +	return failed ? SK_DROP : SK_PASS;
> +}
> +
> +char _license[] SEC("license") = "GPL";
>