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Commit a42e9d6c authored by Stephen Hemminger's avatar Stephen Hemminger Committed by David S. Miller
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[TCP]: TCP Probe congestion window tracing 



This adds a new module for tracking TCP state variables non-intrusively
using kprobes.  It has a simple /proc interface that outputs one line
for each packet received. A sample usage is to collect congestion
window and ssthresh over time graphs.

Signed-off-by: default avatarStephen Hemminger <shemminger@osdl.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 72dc5b92

net/Kconfig

+15 −0
Original line number Original line Diff line number Diff line
@@ -215,6 +215,21 @@ config NET_PKTGEN 
	  To compile this code as a module, choose M here: the

	  To compile this code as a module, choose M here: the

	  module will be called pktgen.

	  module will be called pktgen.





config NET_TCPPROBE

	tristate "TCP connection probing"

	depends on INET && EXPERIMENTAL && PROC_FS && KPROBES

	---help---

	This module allows for capturing the changes to TCP connection

	state in response to incoming patckets. It is used for debugging

	TCP congestion avoidance modules. If you don't understand

	what was just said, you don't need it: say N.



	Documentation on how to use the packet generator can be found

	at http://linux-net.osdl.org/index.php/TcpProbe



	To compile this code as a module, choose M here: the

	module will be called tcp_probe.



endmenu

endmenu





endmenu

endmenu

net/ipv4/Makefile

+1 −0
Original line number Original line Diff line number Diff line
@@ -36,6 +36,7 @@ obj-$(CONFIG_IP_VS) += ipvs/ 
obj-$(CONFIG_INET_DIAG) += inet_diag.o 

obj-$(CONFIG_INET_DIAG) += inet_diag.o 

obj-$(CONFIG_IP_ROUTE_MULTIPATH_CACHED) += multipath.o

obj-$(CONFIG_IP_ROUTE_MULTIPATH_CACHED) += multipath.o

obj-$(CONFIG_INET_TCP_DIAG) += tcp_diag.o

obj-$(CONFIG_INET_TCP_DIAG) += tcp_diag.o

obj-$(CONFIG_NET_TCPPROBE) += tcp_probe.o

obj-$(CONFIG_TCP_CONG_BIC) += tcp_bic.o

obj-$(CONFIG_TCP_CONG_BIC) += tcp_bic.o

obj-$(CONFIG_TCP_CONG_CUBIC) += tcp_cubic.o

obj-$(CONFIG_TCP_CONG_CUBIC) += tcp_cubic.o

obj-$(CONFIG_TCP_CONG_WESTWOOD) += tcp_westwood.o

obj-$(CONFIG_TCP_CONG_WESTWOOD) += tcp_westwood.o

net/ipv4/tcp_probe.c

0 → 100644
+179 −0
Original line number Original line Diff line number Diff line 
/*

 * 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>

 *

 * 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, or

 * (at your option) any later version.

 *

 * 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/proc_fs.h>

#include <linux/module.h>

#include <linux/kfifo.h>

#include <linux/vmalloc.h>



#include <net/tcp.h>



MODULE_AUTHOR("Stephen Hemminger <shemminger@osdl.org>");

MODULE_DESCRIPTION("TCP cwnd snooper");

MODULE_LICENSE("GPL");



static int port = 0;

MODULE_PARM_DESC(port, "Port to match (0=all)");

module_param(port, int, 0);



static int bufsize = 64*1024;

MODULE_PARM_DESC(bufsize, "Log buffer size (default 64k)");

module_param(bufsize, int, 0);



static const char procname[] = "tcpprobe";



struct {

	struct kfifo  *fifo;

	spinlock_t    lock;

	wait_queue_head_t wait;

	struct timeval tstart;

} tcpw;



static void printl(const char *fmt, ...)

{

	va_list args;

	int len;

	struct timeval now;

	char tbuf[256];



	va_start(args, fmt);

	do_gettimeofday(&now);



	now.tv_sec -= tcpw.tstart.tv_sec;

	now.tv_usec -= tcpw.tstart.tv_usec;

	if (now.tv_usec < 0) {

		--now.tv_sec;

		now.tv_usec += 1000000;

	}



	len = sprintf(tbuf, "%lu.%06lu ", now.tv_sec, now.tv_usec);

	len += vscnprintf(tbuf+len, sizeof(tbuf)-len, fmt, args);

	va_end(args);



	kfifo_put(tcpw.fifo, tbuf, len);

	wake_up(&tcpw.wait);

}



static int jtcp_sendmsg(struct kiocb *iocb, struct sock *sk,

			struct msghdr *msg, size_t size)

{

	const struct tcp_sock *tp = tcp_sk(sk);

	const struct inet_sock *inet = inet_sk(sk);



	if (port == 0 || ntohs(inet->dport) == port ||

	    ntohs(inet->sport) == port) {

		printl("%d.%d.%d.%d:%u %d.%d.%d.%d:%u %d %#x %#x %u %u %u\n",

		       NIPQUAD(inet->saddr), ntohs(inet->sport),

		       NIPQUAD(inet->daddr), ntohs(inet->dport),

		       size, tp->snd_nxt, tp->snd_una,

		       tp->snd_cwnd, tcp_current_ssthresh(sk),

		       tp->snd_wnd);

	}



	jprobe_return();

	return 0;

}



static struct jprobe tcp_send_probe = {

	.kp = { .addr = (kprobe_opcode_t *) &tcp_sendmsg, },

	.entry = (kprobe_opcode_t *) &jtcp_sendmsg,

};





static int tcpprobe_open(struct inode * inode, struct file * file)

{

	kfifo_reset(tcpw.fifo);

	do_gettimeofday(&tcpw.tstart);

	return 0;

}



static ssize_t tcpprobe_read(struct file *file, char __user *buf,

			     size_t len, loff_t *ppos)

{

	int error = 0, cnt;

	unsigned char *tbuf;



	if (!buf || len < 0)

		return -EINVAL;



	if (len == 0)

		return 0;



	tbuf = vmalloc(len);

	if (!tbuf)

		return -ENOMEM;



	error = wait_event_interruptible(tcpw.wait,

					 __kfifo_len(tcpw.fifo) != 0);

	if (error)

		return error;



	cnt = kfifo_get(tcpw.fifo, tbuf, len);

	error = copy_to_user(buf, tbuf, cnt);



	vfree(tbuf);



	return error ? error : cnt;

}



static struct file_operations tcpprobe_fops = {

	.owner	 = THIS_MODULE,

	.open	 = tcpprobe_open,

	.read    = tcpprobe_read,

};



static __init int tcpprobe_init(void)

{

	int ret = -ENOMEM;



	init_waitqueue_head(&tcpw.wait);

	spin_lock_init(&tcpw.lock);

	tcpw.fifo = kfifo_alloc(bufsize, GFP_KERNEL, &tcpw.lock);



	if (!proc_net_fops_create(procname, S_IRUSR, &tcpprobe_fops))

		goto err0;



	ret = register_jprobe(&tcp_send_probe);

	if (ret)

		goto err1;



	pr_info("TCP watch registered (port=%d)\n", port);

	return 0;

 err1:

	proc_net_remove(procname);

 err0:

	kfifo_free(tcpw.fifo);

	return ret;

}

module_init(tcpprobe_init);



static __exit void tcpprobe_exit(void)

{

	kfifo_free(tcpw.fifo);

	proc_net_remove(procname);

	unregister_jprobe(&tcp_send_probe);



}

module_exit(tcpprobe_exit);