Re: [PATCH bpf-next v3 5/6] bpf: Add an iterator selftest for bpf_sk_storage_get
From: Yonghong Song <hidden>
Date: 2020-11-27 07:00:52
Also in:
bpf, lkml
On 11/26/20 8:44 AM, Florent Revest wrote:
The eBPF program iterates over all files and tasks. For all socket files, it stores the tgid of the last task it encountered with a handle to that socket. This is a heuristic for finding the "owner" of a socket similar to what's done by lsof, ss, netstat or fuser. Potentially, this information could be used from a cgroup_skb/*gress hook to try to associate network traffic with processes. The test makes sure that a socket it created is tagged with prog_tests's pid. Signed-off-by: Florent Revest <redacted>
Ack with two minor comments below. Acked-by: Yonghong Song <redacted>
quoted hunk ↗ jump to hunk
--- .../selftests/bpf/prog_tests/bpf_iter.c | 40 +++++++++++++++++++ .../progs/bpf_iter_bpf_sk_storage_helpers.c | 25 ++++++++++++ 2 files changed, 65 insertions(+)diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c index bb4a638f2e6f..9336d0f18331 100644 --- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c +++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c@@ -975,6 +975,44 @@ static void test_bpf_sk_storage_delete(void) bpf_iter_bpf_sk_storage_helpers__destroy(skel); } +/* This creates a socket and its local storage. It then runs a task_iter BPF + * program that replaces the existing socket local storage with the tgid of the + * only task owning a file descriptor to this socket, this process, prog_tests. + */ +static void test_bpf_sk_storage_get(void) +{ + struct bpf_iter_bpf_sk_storage_helpers *skel; + int err, map_fd, val = -1; + int sock_fd = -1; + + skel = bpf_iter_bpf_sk_storage_helpers__open_and_load(); + if (CHECK(!skel, "bpf_iter_bpf_sk_storage_helpers__open_and_load", + "skeleton open_and_load failed\n")) + return; + + sock_fd = socket(AF_INET6, SOCK_STREAM, 0); + if (CHECK(sock_fd < 0, "socket", "errno: %d\n", errno)) + goto out; + + map_fd = bpf_map__fd(skel->maps.sk_stg_map); + + err = bpf_map_update_elem(map_fd, &sock_fd, &val, BPF_NOEXIST); + if (CHECK(err, "bpf_map_update_elem", "map_update_failed\n")) + goto close_socket; + + do_dummy_read(skel->progs.fill_socket_owner); + + err = bpf_map_lookup_elem(map_fd, &sock_fd, &val); + CHECK(err || val != getpid(), "bpf_map_lookup_elem", + "map value wasn't set correctly (expected %d, got %d, err=%d)\n", + getpid(), val, err); + +close_socket: + close(sock_fd); +out: + bpf_iter_bpf_sk_storage_helpers__destroy(skel); +} + static void test_bpf_sk_storage_map(void) { DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);@@ -1131,6 +1169,8 @@ void test_bpf_iter(void) test_bpf_sk_storage_map(); if (test__start_subtest("bpf_sk_storage_delete")) test_bpf_sk_storage_delete(); + if (test__start_subtest("bpf_sk_storage_get")) + test_bpf_sk_storage_get(); if (test__start_subtest("rdonly-buf-out-of-bound")) test_rdonly_buf_out_of_bound(); if (test__start_subtest("buf-neg-offset"))diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_bpf_sk_storage_helpers.c b/tools/testing/selftests/bpf/progs/bpf_iter_bpf_sk_storage_helpers.c index 01ff3235e413..d7a7a802d172 100644 --- a/tools/testing/selftests/bpf/progs/bpf_iter_bpf_sk_storage_helpers.c +++ b/tools/testing/selftests/bpf/progs/bpf_iter_bpf_sk_storage_helpers.c@@ -21,3 +21,28 @@ int delete_bpf_sk_storage_map(struct bpf_iter__bpf_sk_storage_map *ctx) return 0; } + +SEC("iter/task_file") +int fill_socket_owner(struct bpf_iter__task_file *ctx) +{ + struct task_struct *task = ctx->task; + struct file *file = ctx->file; + struct socket *sock; + int *sock_tgid; + + if (!task || !file || task->tgid != task->pid)
task->tgid != task->pid is not needed here. The task_file iterator already tries to skip task with task->pid if its file table is the same as task->tgid.
+ return 0; + + sock = bpf_sock_from_file(file); + if (!sock) + return 0; + + sock_tgid = bpf_sk_storage_get(&sk_stg_map, sock->sk, 0, 0); + if (!sock_tgid) + return 0; + + *sock_tgid = task->tgid; + + return 0; +} +
Extra empty line.