#!/usr/bin/python
# @lint-avoid-python-3-compatibility-imports
#
# tcpsynbl      Show TCP SYN backlog.
#               For Linux, uses BCC, eBPF. Embedded C.
#
# Copyright (c) 2019 Brendan Gregg.
# Licensed under the Apache License, Version 2.0 (the "License").
# This was originally created for the BPF Performance Tools book
# published by Addison Wesley. ISBN-13: 9780136554820
# When copying or porting, include this comment.
#
# 03-Jul-2019   Brendan Gregg   Ported from bpftrace to BCC.

from __future__ import print_function
from bcc import BPF
from time import sleep

# load BPF program
b = BPF(text="""
#include <net/sock.h>

typedef struct backlog_key {
    u32 backlog;
    u64 slot;
} backlog_key_t;

BPF_HISTOGRAM(dist, backlog_key_t);

int do_entry(struct pt_regs *ctx) {
    struct sock *sk = (struct sock *)PT_REGS_PARM1(ctx);

    backlog_key_t key = {};
    key.backlog = sk->sk_max_ack_backlog;
    key.slot = bpf_log2l(sk->sk_ack_backlog);
    dist.increment(key);

    return 0;
};
""")
b.attach_kprobe(event="tcp_v4_syn_recv_sock", fn_name="do_entry")
b.attach_kprobe(event="tcp_v6_syn_recv_sock", fn_name="do_entry")

print("Tracing SYN backlog size. Ctrl-C to end.");

try:
    sleep(99999999)
except KeyboardInterrupt:
    print()

dist = b.get_table("dist")
dist.print_log2_hist("backlog", "backlog_max")