tcpwin.bt

#!/usr/local/bin/bpftrace
/*
 * tcpwin - Trace TCP send congestion window parameters.
 *
 * 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.
 *
 * 20-Apr-2019  Brendan Gregg   Created this.
 */

#include <net/sock.h>
#include <linux/tcp.h>

BEGIN
{
	printf("event,sock,time_us,snd_cwnd,snd_ssthresh,sk_sndbuf,");
	printf("sk_wmem_queued\n");
}

kprobe:tcp_rcv_established
{
	$sock = (struct sock *)arg0;
	$tcps = (struct tcp_sock *)arg0; // see tcp_sk()
	printf("rcv,0x%llx,%lld,%d,%d,%d,%d\n", arg0, elapsed / 1000,
	    $tcps->snd_cwnd, $tcps->snd_ssthresh, $sock->sk_sndbuf,
	    $sock->sk_wmem_queued);
}