On 6/18/22 9:43 AM, Jörn-Thorben Hinz wrote:
On Fri, 2022-06-17 at 14:04 -0700, Martin KaFai Lau wrote:
On Tue, Jun 14, 2022 at 12:44:50PM +0200, Jörn-Thorben Hinz wrote:
Test whether a TCP CC implemented in BPF is allowed to write
sk_pacing_rate and sk_pacing_status in struct sock. This is needed
when
cong_control() is implemented and used.
Signed-off-by: Jörn-Thorben Hinz <jthinz@xxxxxxxxxxxxxxxxxxxx>
---
.../selftests/bpf/prog_tests/bpf_tcp_ca.c | 21 +++++++
.../bpf/progs/tcp_ca_write_sk_pacing.c | 60
+++++++++++++++++++
2 files changed, 81 insertions(+)
create mode 100644
tools/testing/selftests/bpf/progs/tcp_ca_write_sk_pacing.c
diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
b/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
index e9a9a31b2ffe..a797497e2864 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
@@ -9,6 +9,7 @@
#include "bpf_cubic.skel.h"
#include "bpf_tcp_nogpl.skel.h"
#include "bpf_dctcp_release.skel.h"
+#include "tcp_ca_write_sk_pacing.skel.h"
#ifndef ENOTSUPP
#define ENOTSUPP 524
@@ -322,6 +323,24 @@ static void test_rel_setsockopt(void)
bpf_dctcp_release__destroy(rel_skel);
}
+static void test_write_sk_pacing(void)
+{
+ struct tcp_ca_write_sk_pacing *skel;
+ struct bpf_link *link;
+
+ skel = tcp_ca_write_sk_pacing__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "open_and_load")) {
nit. Remove this single line '{'.
./scripts/checkpatch.pl has reported that also:
WARNING: braces {} are not necessary for single statement blocks
#43: FILE: tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c:332:
+ if (!ASSERT_OK_PTR(skel, "open_and_load")) {
+ return;
+ }
Have to admit I knowingly disregarded that warning as more of a
recommendation. Out of habit and since I personally don’t see any
compelling reason to generally use single-line statements after ifs,
only multiple disadvantages.
But wrong place to argue here, of course. Will bow to the warning.
+ return;
+ }
+
+ link = bpf_map__attach_struct_ops(skel-
maps.write_sk_pacing);
+ if (ASSERT_OK_PTR(link, "attach_struct_ops")) {
Same here.
and no need to check the link before bpf_link__destroy.
bpf_link__destroy can handle error link. Something like:
ASSERT_OK_PTR(link, "attach_struct_ops");
bpf_link__destroy(link);
tcp_ca_write_sk_pacing__destroy(skel);
The earlier examples in test_cubic and test_dctcp were
written before bpf_link__destroy can handle error link.
You are right, I followed the other two test_*() functions there. Good
to know that it behaves similar to (k)free() and others. Will remove
the ifs around bpf_link__destroy().
+ bpf_link__destroy(link);
+ }
+
+ tcp_ca_write_sk_pacing__destroy(skel);
+}
+
void test_bpf_tcp_ca(void)
{
if (test__start_subtest("dctcp"))
@@ -334,4 +353,6 @@ void test_bpf_tcp_ca(void)
test_dctcp_fallback();
if (test__start_subtest("rel_setsockopt"))
test_rel_setsockopt();
+ if (test__start_subtest("write_sk_pacing"))
+ test_write_sk_pacing();
}
diff --git
a/tools/testing/selftests/bpf/progs/tcp_ca_write_sk_pacing.c
b/tools/testing/selftests/bpf/progs/tcp_ca_write_sk_pacing.c
new file mode 100644
index 000000000000..43447704cf0e
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/tcp_ca_write_sk_pacing.c
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "vmlinux.h"
+
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+#define USEC_PER_SEC 1000000UL
+
+#define min(a, b) ((a) < (b) ? (a) : (b))
+
+static inline struct tcp_sock *tcp_sk(const struct sock *sk)
+{
This helper is already available in bpf_tcp_helpers.h.
Is there a reason not to use that one and redefine
it in both patch 3 and 4? The mss_cache and srtt_us can be added
to bpf_tcp_helpers.h. It will need another effort to move
all selftest's bpf-cc to vmlinux.h.
I fully agree it’s not elegant to redefine tcp_sk() twice more.
It was between either using bpf_tcp_helpers.h and adding and
maintaining additional struct members there. Or using the (as I
understood it) more “modern” approach with vmlinux.h and redefining the
trivial tcp_sk(). I chose the later. Didn’t see a reason not to slowly
introduce vmlinux.h into the CA tests.
I had the same dilemma for the algorithm I’m implementing: Reuse
bpf_tcp_helpers.h from the kernel tree and extend it. Or use vmlinux.h
and copy only some of the (mostly trivial) helper functions. Also chose
the later here.
While doing the above, I also considered extracting the type
declarations from bpf_tcp_helpers.h into an, e.g.,
bpf_tcp_types_helper.h, keeping only the functions in
bpf_tcp_helpers.h. bpf_tcp_helpers.h could have been a base helper for
any BPF CA implementation then and used with either vmlinux.h or the
“old-school” includes. Similar to the way bpf_helpers.h is used. But at
that point, a bpf_tcp_types_helper.h could have probably just been
dropped for good and in favor of vmlinux.h. So I didn’t continue with
that.
Do you insist to use bpf_tcp_helpers.h instead of vmlinux.h? Or could
the described split into two headers make sense after all?
I prefer to use vmlinux.h. Eventually we would like to use vmlinux.h
for progs which include bpf_tcp_healpers.h. Basically remove the struct
definitions in bpf_tcp_helpers.h and replacing "bpf.h, stddef.h, tcp.h
..." with vmlinux.h. We may not be there yet, but that is the goal.
(Will wait for your reply here before sending a v4.)
+ return (struct tcp_sock *)sk;
+}
+
+SEC("struct_ops/write_sk_pacing_init")
+void BPF_PROG(write_sk_pacing_init, struct sock *sk)
+{
+#ifdef ENABLE_ATOMICS_TESTS
+ __sync_bool_compare_and_swap(&sk->sk_pacing_status,
SK_PACING_NONE,
+ SK_PACING_NEEDED);
+#else
+ sk->sk_pacing_status = SK_PACING_NEEDED;
+#endif
+}
+
+SEC("struct_ops/write_sk_pacing_cong_control")
+void BPF_PROG(write_sk_pacing_cong_control, struct sock *sk,
+ const struct rate_sample *rs)
+{
+ const struct tcp_sock *tp = tcp_sk(sk);
+ unsigned long rate =
+ ((tp->snd_cwnd * tp->mss_cache * USEC_PER_SEC) <<
3) /
+ (tp->srtt_us ?: 1U << 3);
+ sk->sk_pacing_rate = min(rate, sk->sk_max_pacing_rate);
+}
+
+SEC("struct_ops/write_sk_pacing_ssthresh")
+__u32 BPF_PROG(write_sk_pacing_ssthresh, struct sock *sk)
+{
+ return tcp_sk(sk)->snd_ssthresh;
+}
+
+SEC("struct_ops/write_sk_pacing_undo_cwnd")
+__u32 BPF_PROG(write_sk_pacing_undo_cwnd, struct sock *sk)
+{
+ return tcp_sk(sk)->snd_cwnd;
+}
+
+SEC(".struct_ops")
+struct tcp_congestion_ops write_sk_pacing = {
+ .init = (void *)write_sk_pacing_init,
+ .cong_control = (void *)write_sk_pacing_cong_control,
+ .ssthresh = (void *)write_sk_pacing_ssthresh,
+ .undo_cwnd = (void *)write_sk_pacing_undo_cwnd,
+ .name = "bpf_w_sk_pacing",
+};
--
2.30.2
