tcp-roccet-kernel-module/roccet_kprobe.c

#include "linux/kprobes.h"

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

/* Include the struct of the ROCCET congestion control algorithm. */
#include "tcp_roccet.h"

// Handler for the pre-call probe
static int handler_pre(struct kprobe *p, struct pt_regs *regs)
{
	/* System V ABI for x86_64 Linux:
	 * arg0: di,
	 * arg1: si,
	 * arg2: dx,
	 * ...
	 */

	/* Get the first argument of the probed function */
	struct sock *sk = (struct sock *)regs->di;
	struct roccettcp *ca = inet_csk_ca(sk);

	u32 ack = (u32)regs->si;
	u32 acked = (u32)regs->dx;

	/* Use `trace_printk` to print debug information to the
	 * `/sys/kernel/tracing/trace buffer`.
	 * This buffer can be read using the debug trace interface of the kernel.
	 */
	trace_printk(
		"roccettcp_cong_avoid: sk=%p ca=%p cnt=%u last_max_cwnd=%u, "
		"last_congestion_event=%u\n",
		sk, ca, ca->cnt, ca->last_max_cwnd,
		ca->roccet_last_event_time_us);
	trace_printk("ack: %u acked: %u\n", ack, acked);

	return 0;
}

static struct kprobe kp = {

	/* Define which function to probe. */
	.symbol_name = "roccettcp_cong_avoid",
	.pre_handler = handler_pre, /* Runs before the probed function. */
	.post_handler = NULL, /* Runs after the probed function. */

};

static int __init kprobe_init(void)
{
	return register_kprobe(&kp);
}
static void __exit kprobe_exit(void)
{
	unregister_kprobe(&kp);
}

module_init(kprobe_init);
module_exit(kprobe_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Makes it possible to probe the ROCCET Congestion "
		   "Control Algrithm with kprobes. This enabled Debugging via a "
		   "loadable kernel module.");
MODULE_AUTHOR("Tim Füchsel");
MODULE_VERSION("0.1");