* [PATCH 0/2] Allow BPF TCP CCs to write app_limited
@ 2023-03-28 13:20 Yixin Shen
2023-03-28 13:20 ` [PATCH 1/2] bpf: allow a TCP CC " Yixin Shen
2023-03-28 13:20 ` [PATCH 2/2] selftests/bpf: test a BPF CC writing app_limited Yixin Shen
0 siblings, 2 replies; 4+ messages in thread
From: Yixin Shen @ 2023-03-28 13:20 UTC (permalink / raw)
To: bpf; +Cc: ast, daniel, andrii, martin.lau, song, yhs, bobankhshen
This series allow BPF TCP CCs to write app_limited of struct
tcp_sock. A built-in CC or one from a kernel module is already
able to write to app_limited of struct tcp_sock. Until now,
a BPF CC doesn't have write access to this member of struct
tcp_sock.
Yixin Shen (2):
bpf: allow a TCP CC to write app_limited
selftests/bpf: test a BPF CC writing app_limited
net/ipv4/bpf_tcp_ca.c | 3 +
.../selftests/bpf/prog_tests/bpf_tcp_ca.c | 19 +++++
.../bpf/progs/tcp_ca_write_app_limited.c | 71 +++++++++++++++++++
3 files changed, 93 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/tcp_ca_write_app_limited.c
--
2.25.1
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH 1/2] bpf: allow a TCP CC to write app_limited
2023-03-28 13:20 [PATCH 0/2] Allow BPF TCP CCs to write app_limited Yixin Shen
@ 2023-03-28 13:20 ` Yixin Shen
2023-03-28 13:20 ` [PATCH 2/2] selftests/bpf: test a BPF CC writing app_limited Yixin Shen
1 sibling, 0 replies; 4+ messages in thread
From: Yixin Shen @ 2023-03-28 13:20 UTC (permalink / raw)
To: bpf; +Cc: ast, daniel, andrii, martin.lau, song, yhs, bobankhshen
A CC that implements tcp_congestion_ops.cong_control() should be able to
write app_limited. A built-in CC or one from a kernel module is already
able to write to this member of struct tcp_sock.
For a BPF program, write access has not been allowed, yet.
Signed-off-by: Yixin Shen <bobankhshen@gmail.com>
---
net/ipv4/bpf_tcp_ca.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
index e8b27826283e..d5952c09aaf2 100644
--- a/net/ipv4/bpf_tcp_ca.c
+++ b/net/ipv4/bpf_tcp_ca.c
@@ -113,6 +113,9 @@ static int bpf_tcp_ca_btf_struct_access(struct bpf_verifier_log *log,
case offsetof(struct tcp_sock, ecn_flags):
end = offsetofend(struct tcp_sock, ecn_flags);
break;
+ case offsetof(struct tcp_sock, app_limited):
+ end = offsetofend(struct tcp_sock, app_limited);
+ break;
default:
bpf_log(log, "no write support to tcp_sock at off %d\n", off);
return -EACCES;
--
2.25.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH 2/2] selftests/bpf: test a BPF CC writing app_limited
2023-03-28 13:20 [PATCH 0/2] Allow BPF TCP CCs to write app_limited Yixin Shen
2023-03-28 13:20 ` [PATCH 1/2] bpf: allow a TCP CC " Yixin Shen
@ 2023-03-28 13:20 ` Yixin Shen
2023-03-28 18:31 ` Martin KaFai Lau
1 sibling, 1 reply; 4+ messages in thread
From: Yixin Shen @ 2023-03-28 13:20 UTC (permalink / raw)
To: bpf; +Cc: ast, daniel, andrii, martin.lau, song, yhs, bobankhshen
Test whether a TCP CC implemented in BPF is allowed to write
app_limited in struct tcp_sock. This is already allowed for
the built-in TCP CC.
Signed-off-by: Yixin Shen <bobankhshen@gmail.com>
---
.../selftests/bpf/prog_tests/bpf_tcp_ca.c | 19 +++++
.../bpf/progs/tcp_ca_write_app_limited.c | 71 +++++++++++++++++++
2 files changed, 90 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/tcp_ca_write_app_limited.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 a53c254c6058..1911ed04d4cf 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
@@ -11,6 +11,7 @@
#include "tcp_ca_update.skel.h"
#include "bpf_dctcp_release.skel.h"
#include "tcp_ca_write_sk_pacing.skel.h"
+#include "tcp_ca_write_app_limited.skel.h"
#include "tcp_ca_incompl_cong_ops.skel.h"
#include "tcp_ca_unsupp_cong_op.skel.h"
@@ -346,6 +347,22 @@ static void test_write_sk_pacing(void)
tcp_ca_write_sk_pacing__destroy(skel);
}
+static void test_write_app_limited(void)
+{
+ struct tcp_ca_write_app_limited *skel;
+ struct bpf_link *link;
+
+ skel = tcp_ca_write_app_limited__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "open_and_load"))
+ return;
+
+ link = bpf_map__attach_struct_ops(skel->maps.write_app_limited);
+ ASSERT_OK_PTR(link, "attach_struct_ops");
+
+ bpf_link__destroy(link);
+ tcp_ca_write_app_limited__destroy(skel);
+}
+
static void test_incompl_cong_ops(void)
{
struct tcp_ca_incompl_cong_ops *skel;
@@ -545,6 +562,8 @@ void test_bpf_tcp_ca(void)
test_rel_setsockopt();
if (test__start_subtest("write_sk_pacing"))
test_write_sk_pacing();
+ if (test__start_subtest("write_app_limited"))
+ test_write_app_limited();
if (test__start_subtest("incompl_cong_ops"))
test_incompl_cong_ops();
if (test__start_subtest("unsupp_cong_op"))
diff --git a/tools/testing/selftests/bpf/progs/tcp_ca_write_app_limited.c b/tools/testing/selftests/bpf/progs/tcp_ca_write_app_limited.c
new file mode 100644
index 000000000000..de5c9b5045a1
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/tcp_ca_write_app_limited.c
@@ -0,0 +1,71 @@
+// 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)
+{
+ return (struct tcp_sock *)sk;
+}
+
+static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
+{
+ return tp->sacked_out + tp->lost_out;
+}
+
+static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
+{
+ return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
+}
+
+SEC("struct_ops/write_app_limited_init")
+void BPF_PROG(write_app_limited_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_app_limited_cong_control")
+void BPF_PROG(write_app_limited_cong_control, struct sock *sk,
+ const struct rate_sample *rs)
+{
+ 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);
+ tp->app_limited = (tp->delivered + tcp_packets_in_flight(tp)) ?: 1;
+}
+
+SEC("struct_ops/write_app_limited_ssthresh")
+__u32 BPF_PROG(write_app_limited_ssthresh, struct sock *sk)
+{
+ return tcp_sk(sk)->snd_ssthresh;
+}
+
+SEC("struct_ops/write_app_limited_undo_cwnd")
+__u32 BPF_PROG(write_app_limited_undo_cwnd, struct sock *sk)
+{
+ return tcp_sk(sk)->snd_cwnd;
+}
+
+SEC(".struct_ops")
+struct tcp_congestion_ops write_app_limited = {
+ .init = (void *)write_app_limited_init,
+ .cong_control = (void *)write_app_limited_cong_control,
+ .ssthresh = (void *)write_app_limited_ssthresh,
+ .undo_cwnd = (void *)write_app_limited_undo_cwnd,
+ .name = "bpf_w_app_limit",
+};
--
2.25.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH 2/2] selftests/bpf: test a BPF CC writing app_limited
2023-03-28 13:20 ` [PATCH 2/2] selftests/bpf: test a BPF CC writing app_limited Yixin Shen
@ 2023-03-28 18:31 ` Martin KaFai Lau
0 siblings, 0 replies; 4+ messages in thread
From: Martin KaFai Lau @ 2023-03-28 18:31 UTC (permalink / raw)
To: Yixin Shen; +Cc: ast, daniel, andrii, martin.lau, song, yhs, bpf
On 3/28/23 6:20 AM, Yixin Shen wrote:
> diff --git a/tools/testing/selftests/bpf/progs/tcp_ca_write_app_limited.c b/tools/testing/selftests/bpf/progs/tcp_ca_write_app_limited.c
> new file mode 100644
> index 000000000000..de5c9b5045a1
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/tcp_ca_write_app_limited.c
> @@ -0,0 +1,71 @@
> +// 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)
> +{
> + return (struct tcp_sock *)sk;
> +}
> +
> +static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
> +{
> + return tp->sacked_out + tp->lost_out;
> +}
> +
> +static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
> +{
> + return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
> +}
> +
> +SEC("struct_ops/write_app_limited_init")
> +void BPF_PROG(write_app_limited_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_app_limited_cong_control")
> +void BPF_PROG(write_app_limited_cong_control, struct sock *sk,
> + const struct rate_sample *rs)
> +{
> + 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);
> + tp->app_limited = (tp->delivered + tcp_packets_in_flight(tp)) ?: 1;
Please add this line testing tp->app_limited to tcp_ca_write_sk_pacing.c instead
of creating a new bpf prog that looks pretty much the same.
Also tag the subject with bpf-next in v2.
Others lgtm.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2023-03-28 13:20 [PATCH 0/2] Allow BPF TCP CCs to write app_limited Yixin Shen
2023-03-28 13:20 ` [PATCH 1/2] bpf: allow a TCP CC " Yixin Shen
2023-03-28 13:20 ` [PATCH 2/2] selftests/bpf: test a BPF CC writing app_limited Yixin Shen
2023-03-28 18:31 ` Martin KaFai Lau
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