tcp_probe_fixed.c

/*
 * tcpprobe - Observe the TCP flow with kprobes.
 *
 * The idea for this came from Werner Almesberger's umlsim
 * Copyright (C) 2004, Stephen Hemminger <shemminger@osdl.org>
 * Copyright (C) 2013, Timo Dörr <timo@latecrew.de> (minor fixes and
 *  changes)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/kernel.h>
#include <linux/kprobes.h>
#include <linux/socket.h>
#include <linux/tcp.h>
#include <linux/slab.h>
#include <linux/proc_fs.h>
#include <linux/module.h>
#include <linux/ktime.h>
#include <linux/time.h>
#include <linux/circ_buf.h>
#include <net/net_namespace.h>
#include <net/net_namespace.h>

#include <net/tcp.h>

/* maximum amount of probes to be buffered before forced-output
 * to userspace
 */
// TODO make module parameter
#define EVENT_BUF 1

MODULE_AUTHOR("Stephen Hemminger <shemminger@linux-foundation.org>");
MODULE_DESCRIPTION("TCP cwnd snooper");
MODULE_LICENSE("GPL");
MODULE_VERSION("1.1");

static int port __read_mostly = 0;
MODULE_PARM_DESC(port, "Port to match (0=all)");
module_param(port, int, 0);

static unsigned int bufsize __read_mostly = 4096;
MODULE_PARM_DESC(bufsize, "Log buffer size in packets (4096)");
module_param(bufsize, uint, 0);

static int full __read_mostly;
MODULE_PARM_DESC(full, "Full log (1=every ack packet received,  0=only cwnd changes)");
module_param(full, int, 0);

static const char procname[] = "tcpprobe";

struct tcp_log {
	ktime_t tstamp;
	__be32	saddr, daddr;
	__be16	sport, dport;
	u16	length;
	u32	snd_nxt;
	u32	snd_una;
	u32	snd_wnd;
	u32	snd_cwnd;
	u32	ssthresh;
	u32	srtt;
};

static struct {
	spinlock_t	producer_lock, consumer_lock;
	wait_queue_head_t wait;
	ktime_t		start;
	u32		lastcwnd;

	unsigned long	head, tail;
	struct tcp_log	*log;
} tcp_probe;

/* copies the probe data from the socket */
static inline void copy_to_tcp_probe(const struct sock *sk, const struct sk_buff *skb, struct tcp_log *p) {

	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_sock *inet = inet_sk(sk);
	
	p->tstamp = ktime_get();
	p->saddr = inet->inet_saddr;
	p->sport = inet->inet_sport;
	p->daddr = inet->inet_daddr;
	p->dport = inet->inet_dport;
	p->snd_nxt = tp->snd_nxt;
	p->snd_una = tp->snd_una;
	p->snd_cwnd = tp->snd_cwnd;
	p->snd_wnd = tp->snd_wnd;
	p->ssthresh = tcp_current_ssthresh(sk);
	p->srtt = tp->srtt_us >> 3;
	
	p->length = skb == NULL ? 0 : skb->len;
	
	return;	
}

static inline int tcpprobe_sprint(const struct tcp_log *p, char *tbuf, int n)
{
	struct timespec tv
		= ktime_to_timespec(ktime_sub(ktime_get(), tcp_probe.start));

	int ret = scnprintf(tbuf, n,
			"%lu.%09lu %pI4:%u %pI4:%u %d %#x %#x %u %u %u %u\n",
			(unsigned long) tv.tv_sec,
			(unsigned long) tv.tv_nsec,
			&p->saddr, ntohs(p->sport),
			&p->daddr, ntohs(p->dport),
			p->length, p->snd_nxt, p->snd_una,
			p->snd_cwnd, p->ssthresh, p->snd_wnd, p->srtt);

	return ret;
}

static inline void tcpprobe_add_probe(struct sock *sk, struct sk_buff *skb) {
	
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_sock *inet = inet_sk(sk);
	
	struct tcphdr *th;
	unsigned int head,tail;

	u32 sport, dport;

	if (skb != NULL) {
		th = tcp_hdr(skb);
		dport =	ntohs(th->dest);
		sport =	ntohs(th->source);
	} else {
		sport = ntohs(inet->inet_sport);
		dport = ntohs(inet->inet_dport);
	}
	
	if ((port == 0 || sport == port || dport == port) &&
	    (full || tp->snd_cwnd != tcp_probe.lastcwnd)) {
		
		spin_lock(&tcp_probe.producer_lock);

		// reset timer
		if (tcp_probe.start.tv64 == 0)
			tcp_probe.start = ktime_get();

		head = tcp_probe.head;
		tail = ACCESS_ONCE(tcp_probe.tail);

		if (CIRC_SPACE(head, tail, bufsize) >= 1) {
			struct tcp_log *p = tcp_probe.log + tcp_probe.head;
			copy_to_tcp_probe (sk, skb, p);

			tcp_probe.head = (head + 1) & (bufsize - 1);

			wake_up(&tcp_probe.wait);
		}
		tcp_probe.lastcwnd = tp->snd_cwnd;
		spin_unlock(&tcp_probe.producer_lock);
	}

	return;
}

/*
 * Hook inserted to be called before each receive packet.
 * Note: arguments must match tcp_rcv_established()!
 */
static int jtcp_rcv_established(struct sock *sk, struct sk_buff *skb,
			       struct tcphdr *th, unsigned len) {
	
	tcpprobe_add_probe (sk, skb);
	jprobe_return();
	return 0;
}
/* Other functions that we could use to hook in */
/*
static void jbictcp_cong_avoid_ai (struct tcp_sock *tp, u32 w) {
	printk("jbictcp_cong_avoid_ai\n");
	tcpprobe_add_probe (tp, NULL);
	jprobe_return();
}
static void jbictcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight) {
	tcpprobe_add_probe (sk, NULL);
	jprobe_return();
}

static void jbictcp_acked(struct sock *sk, u32 cnt, s32 tt_us) {
	
	tcpprobe_add_probe (sk, NULL);
	jprobe_return();
}
*/

static struct jprobe tcp_jprobe = {
	.kp = {
		//.symbol_name	= "bictcp_cong_avoid",
		//.symbol_name	= "tcp_cong_avoid_ai",
		//.symbol_name	= "bictcp_acked",
		.symbol_name	= "tcp_rcv_established",
	},
	.entry	= jtcp_rcv_established,
	//.entry	= jbictcp_cong_avoid,
	//.entry	= jbictcp_acked,
	//.entry	= jbictcp_cong_avoid_ai,
	//.entry	= jbictcp_update,
};

static int tcpprobe_open(struct inode * inode, struct file * file)
{
	/* Reset (empty) log */
	spin_lock(&tcp_probe.producer_lock);
	spin_lock(&tcp_probe.consumer_lock);
	tcp_probe.head = tcp_probe.tail = 0;

	// reset the timer
	tcp_probe.start.tv64 = 0;
	spin_unlock(&tcp_probe.consumer_lock);
	spin_unlock(&tcp_probe.producer_lock);

	return 0;
}
static ssize_t tcpprobe_read(struct file *file, char __user *buf,
			     size_t len, loff_t *ppos)
{
	int error = 0;
	size_t cnt = 0;
	
	int eventbuf = EVENT_BUF;

	if (!buf)
		return -EINVAL;

	while (eventbuf >= 0 && cnt < len) {
		char tbuf[163];
		int width = 0;
		unsigned long head, tail;
		
		error = wait_event_interruptible (
				tcp_probe.wait,
				CIRC_CNT(ACCESS_ONCE(tcp_probe.head), tcp_probe.tail, bufsize) > 0
		);

		if (error)
			break;

		spin_lock_bh(&tcp_probe.consumer_lock);

		head = ACCESS_ONCE(tcp_probe.head);
		tail = tcp_probe.tail;

		/* re-check condition as head could have
		   changed before the lock was acquired */	
		if(CIRC_CNT(head, tail, bufsize) > 0) {
			struct tcp_log *p;

			p = tcp_probe.log + tcp_probe.tail;
	
			if (cnt + width < len)
				tcp_probe.tail = (tail + 1) & (bufsize - 1);
		
			width = tcpprobe_sprint(p, tbuf, sizeof(tbuf));
		}

		spin_unlock_bh(&tcp_probe.consumer_lock);
		
		// if record greater than space available
		//   return partial buffer (so far) 
		if (cnt + width >= len) {
			printk("cnt +width is >= len, breaking!\n");
			break;
		}
		
		if (copy_to_user(buf + cnt, tbuf, width)) {
		//if (copy_to_user(buf, tbuf, width)) {
			printk("error copying to user!\n");
			return -EFAULT;
		}
		eventbuf--;
		cnt += width;
	}
	return cnt == 0 ? error : cnt;
}

/*
static int tcpprobe_write (struct file *file, const char *buf,
	size_t count, loff_t *off) {

	return -EFAULT;
}
*/

static int tcpprobe_release(struct inode *inode, struct file *file) {
	
	//printk("closing\n");
	return 0;
}

static const struct file_operations tcpprobe_fops = {
	.owner	 = THIS_MODULE,
	.open	 = tcpprobe_open,
	//.write	 = tcpprobe_write,
	.release = tcpprobe_release,
	.read    = tcpprobe_read,
	.llseek  = noop_llseek,
};

static __init int tcpprobe_init(void)
{
	int ret = -ENOMEM;

	init_waitqueue_head(&tcp_probe.wait);
	spin_lock_init(&tcp_probe.producer_lock);
	spin_lock_init(&tcp_probe.consumer_lock);

	if (bufsize == 0)
		return -EINVAL;

	bufsize = roundup_pow_of_two(bufsize);

	tcp_probe.log = kcalloc(bufsize, sizeof(struct tcp_log), GFP_KERNEL);
	if (!tcp_probe.log)
		goto err0;

	if (!proc_create(procname, S_IRUSR, init_net.proc_net, &tcpprobe_fops))
		goto err0;

	ret = register_jprobe(&tcp_jprobe);
	if (ret)
		goto err1;

	pr_info("TCP probe registered (port=%d) bufsize=%u\n", port, bufsize);
	return 0;
 err1:
	remove_proc_entry(procname, init_net.proc_net);
 err0:
	kfree(tcp_probe.log);
	return ret;
}
module_init(tcpprobe_init);

static __exit void tcpprobe_exit(void)
{
	remove_proc_entry(procname, init_net.proc_net);
	unregister_jprobe(&tcp_jprobe);
	kfree(tcp_probe.log);
}
module_exit(tcpprobe_exit);