#!/usr/bin/env bpftrace
/*
* tcpsynbl - Show TCP SYN backlog as a histogram.
*
* See BPF Performance Tools, Chapter 10, for an explanation of this tool.
*
* 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.
*
* 19-Apr-2019 Brendan Gregg Created this.
*/
#ifndef BPFTRACE_HAVE_BTF
#include <net/sock.h>
#endif
BEGIN
{
printf("Tracing SYN backlog size. Ctrl-C to end.\n");
}
kprobe:tcp_v4_syn_recv_sock,
kprobe:tcp_v6_syn_recv_sock
{
$sock = (struct sock *)arg0;
@backlog[$sock->sk_max_ack_backlog & 0xffffffff] =
hist($sock->sk_ack_backlog);
if ($sock->sk_ack_backlog > $sock->sk_max_ack_backlog) {
time("%H:%M:%S dropping a SYN.\n");
}
}
END
{
printf("\n@backlog[backlog limit]: histogram of backlog size\n");
}
Mini Shell