Re: [PATCH bpf-next v2 2/2] bpf/selftests: add selftest for SMC bpf capability

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On 2/21/23 4:18 AM, D. Wythe wrote:
From: "D. Wythe" <alibuda@xxxxxxxxxxxxxxxxx>

This PATCH adds a tiny selftest for SMC bpf capability,
making decisions on whether to use SMC by collecting
certain information from kernel smc sock.

Follow the steps below to run this test.

make -C tools/testing/selftests/bpf
cd tools/testing/selftests/bpf
sudo ./test_progs -t bpf_smc

Results shows:
18      bpf_smc:OK
Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: D. Wythe <alibuda@xxxxxxxxxxxxxxxxx>
---
  tools/testing/selftests/bpf/prog_tests/bpf_smc.c |  39 +++
  tools/testing/selftests/bpf/progs/bpf_smc.c      | 315 +++++++++++++++++++++++
  2 files changed, 354 insertions(+)
  create mode 100644 tools/testing/selftests/bpf/prog_tests/bpf_smc.c
  create mode 100644 tools/testing/selftests/bpf/progs/bpf_smc.c

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_smc.c b/tools/testing/selftests/bpf/prog_tests/bpf_smc.c
new file mode 100644
index 0000000..b143932
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_smc.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2019 Facebook */

copy-and-paste left-over...

diff --git a/tools/testing/selftests/bpf/progs/bpf_smc.c b/tools/testing/selftests/bpf/progs/bpf_smc.c
new file mode 100644
index 0000000..78c7976
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_smc.c
@@ -0,0 +1,315 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/bpf.h>
+#include <linux/stddef.h>
+#include <linux/smc.h>
+#include <stdbool.h>
+#include <linux/types.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_core_read.h>
+#include <bpf/bpf_tracing.h>
+
+#define BPF_STRUCT_OPS(name, args...) \
+	SEC("struct_ops/"#name) \
+	BPF_PROG(name, args)
+
+#define SMC_LISTEN		(10)
+#define SMC_SOCK_CLOSED_TIMING	(0)
+extern unsigned long CONFIG_HZ __kconfig;
+#define HZ CONFIG_HZ
+
+char _license[] SEC("license") = "GPL";
+#define max(a, b) ((a) > (b) ? (a) : (b))
+
+struct sock_common {
+	unsigned char	skc_state;
+	__u16	skc_num;
+} __attribute__((preserve_access_index));
+
+struct sock {
+	struct sock_common	__sk_common;
+	int	sk_sndbuf;
+} __attribute__((preserve_access_index));
+
+struct inet_sock {
+	struct sock	sk;
+} __attribute__((preserve_access_index));
+
+struct inet_connection_sock {
+	struct inet_sock	icsk_inet;
+} __attribute__((preserve_access_index));
+
+struct tcp_sock {
+	struct inet_connection_sock	inet_conn;
+	__u32	rcv_nxt;
+	__u32	snd_nxt;
+	__u32	snd_una;
+	__u32	delivered;
+	__u8	syn_data:1,	/* SYN includes data */
+		syn_fastopen:1,	/* SYN includes Fast Open option */
+		syn_fastopen_exp:1,/* SYN includes Fast Open exp. option */
+		syn_fastopen_ch:1, /* Active TFO re-enabling probe */
+		syn_data_acked:1,/* data in SYN is acked by SYN-ACK */
+		save_syn:1,	/* Save headers of SYN packet */
+		is_cwnd_limited:1,/* forward progress limited by snd_cwnd? */
+		syn_smc:1;	/* SYN includes SMC */
+} __attribute__((preserve_access_index));
+
+struct socket {
+	struct sock *sk;
+} __attribute__((preserve_access_index));

All these tcp_sock, socket, inet_sock definitions can go away if it includes "vmlinux.h". tcp_ca_write_sk_pacing.c is a better example to follow. Try to define the "common" (eg. tcp, tc...etc) missing macros in bpf_tracing_net.h. The smc specific macros can stay in this file.

+static inline struct smc_prediction *smc_prediction_get(const struct smc_sock *smc,
+							const struct tcp_sock *tp, __u64 tstamp)
+{
+	struct smc_prediction zero = {}, *smc_predictor;
+	__u16 key;
+	__u32 gap;
+	int err;
+
+	err = bpf_core_read(&key, sizeof(__u16), &tp->inet_conn.icsk_inet.sk.__sk_common.skc_num);
+	if (err)
+		return NULL;
+
+	/* BAD key */
+	if (key == 0)
+		return NULL;
+
+	smc_predictor = bpf_map_lookup_elem(&negotiator_map, &key);
+	if (!smc_predictor) {
+		zero.start_tstamp = bpf_jiffies64();
+		zero.pacing_delta = SMC_PREDICTION_MIN_PACING_DELTA;
+		bpf_map_update_elem(&negotiator_map, &key, &zero, 0);
+		smc_predictor =  bpf_map_lookup_elem(&negotiator_map, &key);
+		if (!smc_predictor)
+			return NULL;
+	}
+
+	if (tstamp) {
+		bpf_spin_lock(&smc_predictor->lock);
+		gap = (tstamp - smc_predictor->start_tstamp) / smc_predictor->pacing_delta;
+		/* new splice */
+		if (gap > 0) {
+			smc_predictor->start_tstamp = tstamp;
+			smc_predictor->last_rate_of_lcc =
+				(smc_prediction_calt_rate(smc_predictor) * 7) >> (2 + gap);
+			smc_predictor->closed_long_cc = 0;
+			smc_predictor->closed_total_cc = 0;
+			smc_predictor->incoming_long_cc = 0;
+		}
+		bpf_spin_unlock(&smc_predictor->lock);
+	}
+	return smc_predictor;
+}
+
+/* BPF struct ops for smc protocol negotiator */
+struct smc_sock_negotiator_ops {
+	/* ret for negotiate */
+	int (*negotiate)(struct smc_sock *smc);
+
+	/* info gathering timing */
+	void (*collect_info)(struct smc_sock *smc, int timing);
+};
+
+int BPF_STRUCT_OPS(bpf_smc_negotiate, struct smc_sock *smc)
+{
+	struct smc_prediction *smc_predictor;
+	struct tcp_sock *tp;
+	struct sock *clcsk;
+	int ret = SK_DROP;
+	__u32 rate = 0;
+
+	/* Only make decison during listen */
+	if (smc->sk.__sk_common.skc_state != SMC_LISTEN)
+		return SK_PASS;
+
+	clcsk = BPF_CORE_READ(smc, clcsock, sk);

Instead of using bpf_core_read here, why not directly gets the clcsk like the 'smc->sk.__sk_common.skc_state' above.

+	if (!clcsk)
+		goto error;
+
+	tp = tcp_sk(clcsk);

There is a bpf_skc_to_tcp_sock(). Give it a try after changing the above BPF_CORE_READ.

+	if (!tp)
+		goto error;
+
+	smc_predictor = smc_prediction_get(smc, tp, bpf_jiffies64());
+	if (!smc_predictor)
+		return SK_PASS;
+
+	bpf_spin_lock(&smc_predictor->lock);
+
+	if (smc_predictor->incoming_long_cc == 0)
+		goto out_locked_pass;
+
+	if (smc_predictor->incoming_long_cc > SMC_PREDICTION_MAX_LONGCC_PER_SPLICE) {
+		ret = 100;
+		goto out_locked_drop;
+	}
+
+	rate = smc_prediction_calt_rate(smc_predictor);
+	if (rate < SMC_PREDICTION_LONGCC_RATE_THRESHOLD) {
+		ret = 200;
+		goto out_locked_drop;
+	}
+out_locked_pass:
+	smc_predictor->incoming_long_cc++;
+	bpf_spin_unlock(&smc_predictor->lock);
+	return SK_PASS;
+out_locked_drop:
+	bpf_spin_unlock(&smc_predictor->lock);
+error:
+	return SK_DROP;
+}
+
+void BPF_STRUCT_OPS(bpf_smc_collect_info, struct smc_sock *smc, int timing)

Try to stay with SEC("struct_ops/...") void BPF_PROG(....)




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