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Date: Tue, 7 Jul 2020 23:44:34 +0200
From: Daniel Borkmann <daniel@...earbox.net>
To: Stanislav Fomichev <sdf@...gle.com>, netdev@...r.kernel.org,
bpf@...r.kernel.org
Cc: davem@...emloft.net, ast@...nel.org
Subject: Re: [PATCH bpf-next v4 4/4] selftests/bpf: test
BPF_CGROUP_INET_SOCK_RELEASE
On 7/7/20 1:01 AM, Stanislav Fomichev wrote:
> Simple test that enforces a single SOCK_DGRAM socker per cgroup.
>
> Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
> ---
> .../selftests/bpf/prog_tests/udp_limit.c | 75 +++++++++++++++++++
> tools/testing/selftests/bpf/progs/udp_limit.c | 42 +++++++++++
> 2 files changed, 117 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/udp_limit.c
> create mode 100644 tools/testing/selftests/bpf/progs/udp_limit.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/udp_limit.c b/tools/testing/selftests/bpf/prog_tests/udp_limit.c
> new file mode 100644
> index 000000000000..2aba09d4d01b
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/udp_limit.c
> @@ -0,0 +1,75 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <test_progs.h>
> +#include "udp_limit.skel.h"
> +
> +#include <sys/types.h>
> +#include <sys/socket.h>
> +
> +static int duration;
> +
> +void test_udp_limit(void)
> +{
> + struct udp_limit *skel;
> + int fd1 = -1, fd2 = -1;
> + int cgroup_fd;
> +
> + cgroup_fd = test__join_cgroup("/udp_limit");
> + if (CHECK(cgroup_fd < 0, "cg-join", "errno %d", errno))
> + return;
> +
> + skel = udp_limit__open_and_load();
> + if (CHECK(!skel, "skel-load", "errno %d", errno))
> + goto close_cgroup_fd;
> +
> + skel->links.sock = bpf_program__attach_cgroup(skel->progs.sock, cgroup_fd);
> + skel->links.sock_release = bpf_program__attach_cgroup(skel->progs.sock_release, cgroup_fd);
> + if (CHECK(IS_ERR(skel->links.sock) || IS_ERR(skel->links.sock_release),
> + "cg-attach", "sock %ld sock_release %ld",
> + PTR_ERR(skel->links.sock),
> + PTR_ERR(skel->links.sock_release)))
> + goto close_skeleton;
> +
> + /* BPF program enforces a single UDP socket per cgroup,
> + * verify that.
> + */
> + fd1 = socket(AF_INET, SOCK_DGRAM, 0);
> + if (CHECK(fd1 < 0, "fd1", "errno %d", errno))
> + goto close_skeleton;
> +
> + fd2 = socket(AF_INET, SOCK_DGRAM, 0);
> + if (CHECK(fd2 >= 0, "fd2", "errno %d", errno))
> + goto close_skeleton;
> +
> + /* We can reopen again after close. */
> + close(fd1);
> + fd1 = -1;
> +
> + fd1 = socket(AF_INET, SOCK_DGRAM, 0);
> + if (CHECK(fd1 < 0, "fd1-again", "errno %d", errno))
> + goto close_skeleton;
> +
> + /* Make sure the program was invoked the expected
> + * number of times:
> + * - open fd1 - BPF_CGROUP_INET_SOCK_CREATE
> + * - attempt to openfd2 - BPF_CGROUP_INET_SOCK_CREATE
> + * - close fd1 - BPF_CGROUP_INET_SOCK_RELEASE
> + * - open fd1 again - BPF_CGROUP_INET_SOCK_CREATE
> + */
> + if (CHECK(skel->bss->invocations != 4, "bss-invocations",
> + "invocations=%d", skel->bss->invocations))
> + goto close_skeleton;
> +
> + /* We should still have a single socket in use */
> + if (CHECK(skel->bss->in_use != 1, "bss-in_use",
> + "in_use=%d", skel->bss->in_use))
> + goto close_skeleton;
> +
> +close_skeleton:
> + if (fd1 >= 0)
> + close(fd1);
> + if (fd2 >= 0)
> + close(fd2);
> + udp_limit__destroy(skel);
> +close_cgroup_fd:
> + close(cgroup_fd);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/udp_limit.c b/tools/testing/selftests/bpf/progs/udp_limit.c
> new file mode 100644
> index 000000000000..edbb30a27e63
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/udp_limit.c
> @@ -0,0 +1,42 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +#include <sys/socket.h>
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +
> +int invocations = 0, in_use = 0;
> +
> +SEC("cgroup/sock")
nit: Doesn't matter overly much, but given you've added `cgroup/sock_create`
earlier in patch 2/4 intention was probably to use it as well. But either is
fine as it resolved to the same.
> +int sock(struct bpf_sock *ctx)
> +{
> + __u32 key;
> +
> + if (ctx->type != SOCK_DGRAM)
> + return 1;
> +
> + __sync_fetch_and_add(&invocations, 1);
> +
> + if (in_use > 0) {
> + /* BPF_CGROUP_INET_SOCK_RELEASE is _not_ called
> + * when we return an error from the BPF
> + * program!
> + */
> + return 0;
> + }
> +
> + __sync_fetch_and_add(&in_use, 1);
> + return 1;
> +}
> +
> +SEC("cgroup/sock_release")
> +int sock_release(struct bpf_sock *ctx)
> +{
> + __u32 key;
> +
> + if (ctx->type != SOCK_DGRAM)
> + return 1;
> +
> + __sync_fetch_and_add(&invocations, 1);
> + __sync_fetch_and_add(&in_use, -1);
> + return 1;
> +}
>
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