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 <[email protected]>
Cc: Priyaranjan Jha <[email protected]>
Cc: Yuchung Cheng <[email protected]>
Cc: Soheil Hassas Yeganeh <[email protected]>
Acked-by: Soheil Hassas Yeganeh <[email protected]>
Acked-by: Yuchung Cheng <[email protected]>
Signed-off-by: Stanislav Fomichev <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>

0 files changed, 0 insertions, 0 deletions