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/*
* 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/ktime.h>
#include <linux/time.h>
#include <linux/vmalloc.h>
#include <net/tcp.h>
MODULE_AUTHOR("Stephen Hemminger <shemminger@linux-foundation.org>");
MODULE_DESCRIPTION("TCP cwnd snooper");
MODULE_LICENSE("GPL");
static int port __read_mostly = 0;
MODULE_PARM_DESC(port, "Port to match (0=all)");
module_param(port, int, 0);
static int bufsize __read_mostly = 64*1024;
MODULE_PARM_DESC(bufsize, "Log buffer size (default 64k)");
module_param(bufsize, int, 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 {
struct kfifo *fifo;
spinlock_t lock;
wait_queue_head_t wait;
ktime_t start;
u32 lastcwnd;
} tcpw;
/*
* Print to log with timestamps.
* FIXME: causes an extra copy
*/
static void printl(const char *fmt, ...)
{
va_list args;
int len;
struct timespec tv;
char tbuf[256];
va_start(args, fmt);
/* want monotonic time since start of tcp_probe */
tv = ktime_to_timespec(ktime_sub(ktime_get(), tcpw.start));
len = sprintf(tbuf, "%lu.%09lu ",
(unsigned long) tv.tv_sec, (unsigned long) tv.tv_nsec);
len += vscnprintf(tbuf+len, sizeof(tbuf)-len, fmt, args);
va_end(args);
kfifo_put(tcpw.fifo, tbuf, len);
wake_up(&tcpw.wait);
}
/*
* 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)
{
const struct tcp_sock *tp = tcp_sk(sk);
const struct inet_sock *inet = inet_sk(sk);
/* Only update if port matches */
if ((port == 0 || ntohs(inet->dport) == port || ntohs(inet->sport) == port)
&& (full || tp->snd_cwnd != tcpw.lastcwnd)) {
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),
skb->len, tp->snd_nxt, tp->snd_una,
tp->snd_cwnd, tcp_current_ssthresh(sk),
tp->snd_wnd, tp->srtt >> 3);
tcpw.lastcwnd = tp->snd_cwnd;
}
jprobe_return();
return 0;
}
static struct jprobe tcp_probe = {
.kp = {
.symbol_name = "tcp_rcv_established",
},
.entry = JPROBE_ENTRY(jtcp_rcv_established),
};
static int tcpprobe_open(struct inode * inode, struct file * file)
{
kfifo_reset(tcpw.fifo);
tcpw.start = ktime_get();
return 0;
}
static ssize_t tcpprobe_read(struct file *file, char __user *buf,
size_t len, loff_t *ppos)
{
int error = 0, cnt = 0;
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)
goto out_free;
cnt = kfifo_get(tcpw.fifo, tbuf, len);
error = copy_to_user(buf, tbuf, cnt);
out_free:
vfree(tbuf);
return error ? error : cnt;
}
static const 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 (IS_ERR(tcpw.fifo))
return PTR_ERR(tcpw.fifo);
if (!proc_net_fops_create(procname, S_IRUSR, &tcpprobe_fops))
goto err0;
ret = register_jprobe(&tcp_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_probe);
}
module_exit(tcpprobe_exit);
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