/*
* 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.
*
* 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/ktime.h>
#include <linux/time.h>
#include <net/net_namespace.h>
#include <net/tcp.h>
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 int bufsize __read_mostly = 4096;
MODULE_PARM_DESC(bufsize, "Log buffer size in packets (4096)");
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 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 lock;
wait_queue_head_t wait;
ktime_t start;
u32 lastcwnd;
unsigned long head, tail;
struct tcp_log *log;
} tcp_probe;
static inline int tcp_probe_used(void)
{
return (tcp_probe.head - tcp_probe.tail) % bufsize;
}
static inline int tcp_probe_avail(void)
{
return bufsize - tcp_probe_used();
}
/*
* 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 != tcp_probe.lastcwnd)) {
spin_lock(&tcp_probe.lock);
/* If log fills, just silently drop */
if (tcp_probe_avail() > 1) {
struct tcp_log *p = tcp_probe.log + tcp_probe.head;
p->tstamp = ktime_get();
p->saddr = inet->saddr;
p->sport = inet->sport;
p->daddr = inet->daddr;
p->dport = inet->dport;
p->length = skb->len;
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 >> 3;
tcp_probe.head = (tcp_probe.head + 1) % bufsize;
}
tcp_probe.lastcwnd = tp->snd_cwnd;
spin_unlock(&tcp_probe.lock);
wake_up(&tcp_probe.wait);
}
jprobe_return();
return 0;
}
static struct jprobe tcp_jprobe = {
.kp = {
.symbol_name = "tcp_rcv_established",
},
.entry = jtcp_rcv_established,
};
static int tcpprobe_open(struct inode * inode, struct file * file)
{
/* Reset (empty) log */
spin_lock_bh(&tcp_probe.lock);
tcp_probe.head = tcp_probe.tail = 0;
tcp_probe.start = ktime_get();
spin_unlock_bh(&tcp_probe.lock);
return 0;
}
static int tcpprobe_sprint(char *tbuf, int n)
{
const struct tcp_log *p
= tcp_probe.log + tcp_probe.tail % bufsize;
struct timespec tv
= ktime_to_timespec(ktime_sub(p->tstamp, tcp_probe.start));
return snprintf(tbuf, n,
"%lu.%09lu " NIPQUAD_FMT ":%u " NIPQUAD_FMT ":%u"
" %d %#x %#x %u %u %u %u\n",
(unsigned long) tv.tv_sec,
(unsigned long) tv.tv_nsec,
NIPQUAD(p->saddr), ntohs(p->sport),
NIPQUAD(p->daddr), ntohs(p->dport),
p->length, p->snd_nxt, p->snd_una,
p->snd_cwnd, p->ssthresh, p->snd_wnd, p->srtt);
}
static ssize_t tcpprobe_read(struct file *file, char __user *buf,
size_t len, loff_t *ppos)
{
int error = 0, cnt = 0;
if (!buf || len < 0)
return -EINVAL;
while (cnt < len) {
char tbuf[128];
int width;
/* Wait for data in buffer */
error = wait_event_interruptible(tcp_probe.wait,
tcp_probe_used() > 0);
if (error)
break;
spin_lock_bh(&tcp_probe.lock);
if (tcp_probe.head == tcp_probe.tail) {
/* multiple readers race? */
spin_unlock_bh(&tcp_probe.lock);
continue;
}
width = tcpprobe_sprint(tbuf, sizeof(tbuf));
if (cnt + width < len)
tcp_probe.tail = (tcp_probe.tail + 1) % bufsize;
spin_unlock_bh(&tcp_probe.lock);
/* if record greater than space available
return partial buffer (so far) */
if (cnt + width >= len)
break;
if (copy_to_user(buf + cnt, tbuf, width))
return -EFAULT;
cnt += width;
}
return cnt == 0 ? 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(&tcp_probe.wait);
spin_lock_init(&tcp_probe.lock);
if (bufsize < 0)
return -EINVAL;
tcp_probe.log = kcalloc(sizeof(struct tcp_log), bufsize, GFP_KERNEL);
if (!tcp_probe.log)
goto err0;
if (!proc_net_fops_create(&init_net, procname, S_IRUSR, &tcpprobe_fops))
goto err0;
ret = register_jprobe(&tcp_jprobe);
if (ret)
goto err1;
pr_info("TCP probe registered (port=%d)\n", port);
return 0;
err1:
proc_net_remove(&init_net, procname);
err0:
kfree(tcp_probe.log);
return ret;
}
module_init(tcpprobe_init);
static __exit void tcpprobe_exit(void)
{
proc_net_remove(&init_net, procname);
unregister_jprobe(&tcp_jprobe);
kfree(tcp_probe.log);
}
module_exit(tcpprobe_exit);
