[PATCH bpf-next 2/2] bpf/selftests: Test for SMC protocol negotiate

D. Wythe
2023-02-21T07:56:45Z

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@linux.alibaba.com>
---
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 */
+
+#include <linux/err.h>
+#include <netinet/tcp.h>
+#include <test_progs.h>
+#include "bpf_smc.skel.h"
+
+void test_bpf_smc(void)
+{
+ struct bpf_smc *smc_skel;
+ struct bpf_link *link;
+ int err;
+
+ smc_skel = bpf_smc__open();
+ if (!ASSERT_OK_PTR(smc_skel, "skel_open"))
+ return;
+
+ err = bpf_map__set_type(smc_skel->maps.negotiator_map, BPF_MAP_TYPE_HASH);
+ if (!ASSERT_OK(err, "bpf_map__set_type"))
+ goto error;
+
+ err = bpf_map__set_max_entries(smc_skel->maps.negotiator_map, 1);
+ if (!ASSERT_OK(err, "bpf_map__set_type"))
+ goto error;
+
+ err = bpf_smc__load(smc_skel);
+ if (!ASSERT_OK(err, "skel_load"))
+ goto error;
+
+ link = bpf_map__attach_struct_ops(smc_skel->maps.ops);
+ if (!ASSERT_OK_PTR(link, "bpf_map__attach_struct_ops"))
+ goto error;
+
+ bpf_link__destroy(link);
+error:
+ bpf_smc__destroy(smc_skel);
+}
+
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));
+
+union smc_host_cursor {
+ struct {
+ __u16 reserved;
+ __u16 wrap;
+ __u32 count;
+ };
+} __attribute__((preserve_access_index));
+
+struct smc_connection {
+ union smc_host_cursor tx_curs_sent;
+ union smc_host_cursor rx_curs_confirmed;
+} __attribute__((preserve_access_index));
+
+struct smc_sock {
+ struct sock sk;
+ struct socket *clcsock; /* internal tcp socket */
+ struct smc_connection conn;
+ int use_fallback;
+} __attribute__((preserve_access_index));
+
+static __always_inline struct tcp_sock *tcp_sk(const struct sock *sk)
+{
+ return (struct tcp_sock *)sk;
+}
+
+static __always_inline struct smc_sock *smc_sk(struct sock *sk)
+{
+ return (struct smc_sock *)sk;
+}
+
+struct smc_prediction {
+ /* protection for smc_prediction */
+ struct bpf_spin_lock lock;
+ /* start of time slice */
+ __u64 start_tstamp;
+ /* delta of pacing */
+ __u64 pacing_delta;
+ /* N of closed connections determined as long connections
+ * in current time slice
+ */
+ __u32 closed_long_cc;
+ /* N of closed connections in this time slice */
+ __u32 closed_total_cc;
+ /* N of incoming connections determined as long connections
+ * in current time slice
+ */
+ __u32 incoming_long_cc;
+ /* last splice rate of long cc */
+ __u32 last_rate_of_lcc;
+};
+
+#define SMC_PREDICTION_MIN_PACING_DELTA (1llu)
+#define SMC_PREDICTION_MAX_PACING_DELTA (HZ << 3)
+#define SMC_PREDICTION_MAX_LONGCC_PER_SPLICE (8)
+#define SMC_PREDICTION_MAX_PORT (64)
+#define SMC_PREDICTION_MAX_SPLICE_GAP (1)
+#define SMC_PREDICTION_LONGCC_RATE_THRESHOLD (13189)
+#define SMC_PREDICTION_LONGCC_PACKETS_THRESHOLD (100)
+#define SMC_PREDICTION_LONGCC_BYTES_THRESHOLD \
+ (SMC_PREDICTION_LONGCC_PACKETS_THRESHOLD * 1024)
+
+struct {
+ __uint(type, BPF_MAP_TYPE_HASH);
+ __uint(max_entries, SMC_PREDICTION_MAX_PORT);
+ __type(key, __u16);
+ __type(value, struct smc_prediction);
+} negotiator_map SEC(".maps");
+
+
+static inline __u32 smc_prediction_calt_rate(struct smc_prediction *smc_predictor)
+{
+ if (!smc_predictor->closed_total_cc)
+ return smc_predictor->last_rate_of_lcc;
+
+ return (smc_predictor->closed_long_cc << 14) / smc_predictor->closed_total_cc;
+}
+
+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);
+ if (!clcsk)
+ goto error;
+
+ tp = tcp_sk(clcsk);
+ 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)
+{
+ struct smc_prediction *smc_predictor;
+ int use_fallback, sndbuf, err;
+ struct tcp_sock *tp;
+ struct sock *clcsk;
+ __u16 wrap, count;
+ __u32 delivered;
+ bool match = false;
+
+ /* only fouces on closed */
+ if (timing != SMC_SOCK_CLOSED_TIMING)
+ return;
+
+ clcsk = BPF_CORE_READ(smc, clcsock, sk);
+ if (!clcsk)
+ goto error;
+
+ tp = tcp_sk(clcsk);
+ if (!tp)
+ goto error;
+
+ smc_predictor = smc_prediction_get(smc, tp, 0);
+ if (!smc_predictor)
+ goto error;
+
+ err = bpf_core_read(&use_fallback, sizeof(use_fallback), &smc->use_fallback);
+ if (err)
+ goto error;
+
+ if (use_fallback) {
+ err = bpf_core_read(&delivered, sizeof(delivered), &tp->delivered);
+ if (err)
+ goto error;
+
+ match = (delivered > SMC_PREDICTION_LONGCC_PACKETS_THRESHOLD);
+
+ } else {
+ delivered = 0; /* tcp delivered */
+ err = bpf_core_read(&wrap, sizeof(__u16), &smc->conn.tx_curs_sent.wrap);
+ if (err)
+ goto error;
+ err = bpf_core_read(&count, sizeof(__u16), &smc->conn.tx_curs_sent.count);
+ if (err)
+ goto error;
+ err = bpf_core_read(&sndbuf, sizeof(int), &clcsk->sk_sndbuf);
+ if (err)
+ goto error;
+
+ match = (count + wrap * sndbuf) > SMC_PREDICTION_LONGCC_BYTES_THRESHOLD;
+ }
+ bpf_spin_lock(&smc_predictor->lock);
+ smc_predictor->closed_total_cc++;
+ if (match) {
+ /* increase stats */
+ smc_predictor->closed_long_cc++;
+ /* try more aggressive */
+ if (smc_predictor->pacing_delta > SMC_PREDICTION_MIN_PACING_DELTA) {
+ if (use_fallback) {
+ smc_predictor->pacing_delta = max(SMC_PREDICTION_MIN_PACING_DELTA,
+ (smc_predictor->pacing_delta * 3) >> 2);
+ }
+ }
+ } else if (!use_fallback) {
+ smc_predictor->pacing_delta <<= 1;
+ }
+ bpf_spin_unlock(&smc_predictor->lock);
+error:
+ return;
+}
+
+SEC(".struct_ops")
+struct smc_sock_negotiator_ops ops = {
+ .negotiate = (void *)bpf_smc_negotiate,
+ .collect_info = (void *)bpf_smc_collect_info,
+};
--
1.8.3.1