samples/bpf: add sample program that periodically dumps TCP stats

Uses new RTT callback to dump stats every second.

$ mkdir -p /tmp/cgroupv2
$ mount -t cgroup2 none /tmp/cgroupv2
$ mkdir -p /tmp/cgroupv2/foo
$ echo $$ >> /tmp/cgroupv2/foo/cgroup.procs
$ bpftool prog load ./tcp_dumpstats_kern.o /sys/fs/bpf/tcp_prog
$ bpftool cgroup attach /tmp/cgroupv2/foo sock_ops pinned /sys/fs/bpf/tcp_prog
$ bpftool prog tracelog
$ # run neper/netperf/etc

Used neper to compare performance with and without this program attached
and didn't see any noticeable performance impact.

Sample output:
  <idle>-0     [015] ..s.  2074.128800: 0: dsack_dups=0 delivered=242526
  <idle>-0     [015] ..s.  2074.128808: 0: delivered_ce=0 icsk_retransmits=0
  <idle>-0     [015] ..s.  2075.130133: 0: dsack_dups=0 delivered=323599
  <idle>-0     [015] ..s.  2075.130138: 0: delivered_ce=0 icsk_retransmits=0
  <idle>-0     [005] .Ns.  2076.131440: 0: dsack_dups=0 delivered=404648
  <idle>-0     [005] .Ns.  2076.131447: 0: delivered_ce=0 icsk_retransmits=0

Cc: Eric Dumazet <edumazet@google.com>
Cc: Priyaranjan Jha <priyarjha@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 35640414ebb36cc682a4d3eef3debe4e7fb256f3..f90daadfbc89cd59f3df0824864b2f872e66a293 100644 (file)
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -154,6 +154,7 @@ always += tcp_iw_kern.o
 always += tcp_clamp_kern.o
 always += tcp_basertt_kern.o
 always += tcp_tos_reflect_kern.o
+always += tcp_dumpstats_kern.o
 always += xdp_redirect_kern.o
 always += xdp_redirect_map_kern.o
 always += xdp_redirect_cpu_kern.o

diff --git a/samples/bpf/tcp_dumpstats_kern.c b/samples/bpf/tcp_dumpstats_kern.c
new file mode 100644 (file)
index 0000000..8557913
--- /dev/null
+++ b/samples/bpf/tcp_dumpstats_kern.c
@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Refer to samples/bpf/tcp_bpf.readme for the instructions on
+ * how to run this sample program.
+ */
+#include <linux/bpf.h>
+
+#include "bpf_helpers.h"
+#include "bpf_endian.h"
+
+#define INTERVAL                       1000000000ULL
+
+int _version SEC("version") = 1;
+char _license[] SEC("license") = "GPL";
+
+struct {
+       __u32 type;
+       __u32 map_flags;
+       int *key;
+       __u64 *value;
+} bpf_next_dump SEC(".maps") = {
+       .type = BPF_MAP_TYPE_SK_STORAGE,
+       .map_flags = BPF_F_NO_PREALLOC,
+};
+
+SEC("sockops")
+int _sockops(struct bpf_sock_ops *ctx)
+{
+       struct bpf_tcp_sock *tcp_sk;
+       struct bpf_sock *sk;
+       __u64 *next_dump;
+       __u64 now;
+
+       switch (ctx->op) {
+       case BPF_SOCK_OPS_TCP_CONNECT_CB:
+               bpf_sock_ops_cb_flags_set(ctx, BPF_SOCK_OPS_RTT_CB_FLAG);
+               return 1;
+       case BPF_SOCK_OPS_RTT_CB:
+               break;
+       default:
+               return 1;
+       }
+
+       sk = ctx->sk;
+       if (!sk)
+               return 1;
+
+       next_dump = bpf_sk_storage_get(&bpf_next_dump, sk, 0,
+                                      BPF_SK_STORAGE_GET_F_CREATE);
+       if (!next_dump)
+               return 1;
+
+       now = bpf_ktime_get_ns();
+       if (now < *next_dump)
+               return 1;
+
+       tcp_sk = bpf_tcp_sock(sk);
+       if (!tcp_sk)
+               return 1;
+
+       *next_dump = now + INTERVAL;
+
+       bpf_printk("dsack_dups=%u delivered=%u\n",
+                  tcp_sk->dsack_dups, tcp_sk->delivered);
+       bpf_printk("delivered_ce=%u icsk_retransmits=%u\n",
+                  tcp_sk->delivered_ce, tcp_sk->icsk_retransmits);
+
+       return 1;
+}