summaryrefslogtreecommitdiffstats
path: root/net/ipv4/tcp_probe.c
blob: bb110c5ce1d2cd5229411ff59a755d01ccd8518b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
/*
 * 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->inet_dport) == port ||
	     ntohs(inet->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->inet_saddr;
			p->sport = inet->inet_sport;
			p->daddr = inet->inet_daddr;
			p->dport = inet->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 %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);
}

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

	if (!buf)
		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(bufsize, sizeof(struct tcp_log), 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);