1/*
  2 * tcpprobe - Observe the TCP flow with kprobes.
  3 *
  4 * The idea for this came from Werner Almesberger's umlsim
  5 * Copyright (C) 2004, Stephen Hemminger <shemminger@osdl.org>
  6 *
  7 * This program is free software; you can redistribute it and/or modify
  8 * it under the terms of the GNU General Public License as published by
  9 * the Free Software Foundation; either version 2 of the License.
 10 *
 11 * This program is distributed in the hope that it will be useful,
 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 14 * GNU General Public License for more details.
 15 *
 16 * You should have received a copy of the GNU General Public License
 17 * along with this program; if not, write to the Free Software
 18 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 19 */
 20
 21#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 22
 23#include <linux/kernel.h>
 24#include <linux/kprobes.h>
 25#include <linux/socket.h>
 26#include <linux/tcp.h>
 27#include <linux/slab.h>
 28#include <linux/proc_fs.h>
 29#include <linux/module.h>
 30#include <linux/ktime.h>
 31#include <linux/time.h>
 32#include <net/net_namespace.h>
 33
 34#include <net/tcp.h>
 35
 36MODULE_AUTHOR("Stephen Hemminger <shemminger@linux-foundation.org>");
 37MODULE_DESCRIPTION("TCP cwnd snooper");
 38MODULE_LICENSE("GPL");
 39MODULE_VERSION("1.1");
 40
 41static int port __read_mostly;
 42MODULE_PARM_DESC(port, "Port to match (0=all)");
 43module_param(port, int, 0);
 44
 45static unsigned int bufsize __read_mostly = 4096;
 46MODULE_PARM_DESC(bufsize, "Log buffer size in packets (4096)");
 47module_param(bufsize, uint, 0);
 48
 49static unsigned int fwmark __read_mostly;
 50MODULE_PARM_DESC(fwmark, "skb mark to match (0=no mark)");
 51module_param(fwmark, uint, 0);
 52
 53static int full __read_mostly;
 54MODULE_PARM_DESC(full, "Full log (1=every ack packet received,  0=only cwnd changes)");
 55module_param(full, int, 0);
 56
 57static const char procname[] = "tcpprobe";
 58
 59struct tcp_log {
 60	ktime_t tstamp;
 61	union {
 62		struct sockaddr		raw;
 63		struct sockaddr_in	v4;
 64		struct sockaddr_in6	v6;
 65	}	src, dst;
 66	u16	length;
 67	u32	snd_nxt;
 68	u32	snd_una;
 69	u32	snd_wnd;
 70	u32	rcv_wnd;
 71	u32	snd_cwnd;
 72	u32	ssthresh;
 73	u32	srtt;
 74};
 75
 76static struct {
 77	spinlock_t	lock;
 78	wait_queue_head_t wait;
 79	ktime_t		start;
 80	u32		lastcwnd;
 81
 82	unsigned long	head, tail;
 83	struct tcp_log	*log;
 84} tcp_probe;
 85
 86
 87static inline int tcp_probe_used(void)
 88{
 89	return (tcp_probe.head - tcp_probe.tail) & (bufsize - 1);
 90}
 91
 92static inline int tcp_probe_avail(void)
 93{
 94	return bufsize - tcp_probe_used() - 1;
 95}
 96
 97#define tcp_probe_copy_fl_to_si4(inet, si4, mem)		\
 98	do {							\
 99		si4.sin_family = AF_INET;			\
100		si4.sin_port = inet->inet_##mem##port;		\
101		si4.sin_addr.s_addr = inet->inet_##mem##addr;	\
102	} while (0)						\
103
104
105/*
106 * Hook inserted to be called before each receive packet.
107 * Note: arguments must match tcp_rcv_established()!
108 */
109static void jtcp_rcv_established(struct sock *sk, struct sk_buff *skb,
110				 const struct tcphdr *th, unsigned int len)
111{
112	const struct tcp_sock *tp = tcp_sk(sk);
113	const struct inet_sock *inet = inet_sk(sk);
114
115	/* Only update if port or skb mark matches */
116	if (((port == 0 && fwmark == 0) ||
117	     ntohs(inet->inet_dport) == port ||
118	     ntohs(inet->inet_sport) == port ||
119	     (fwmark > 0 && skb->mark == fwmark)) &&
120	    (full || tp->snd_cwnd != tcp_probe.lastcwnd)) {
121
122		spin_lock(&tcp_probe.lock);
123		/* If log fills, just silently drop */
124		if (tcp_probe_avail() > 1) {
125			struct tcp_log *p = tcp_probe.log + tcp_probe.head;
126
127			p->tstamp = ktime_get();
128			switch (sk->sk_family) {
129			case AF_INET:
130				tcp_probe_copy_fl_to_si4(inet, p->src.v4, s);
131				tcp_probe_copy_fl_to_si4(inet, p->dst.v4, d);
132				break;
133			case AF_INET6:
134				memset(&p->src.v6, 0, sizeof(p->src.v6));
135				memset(&p->dst.v6, 0, sizeof(p->dst.v6));
136#if IS_ENABLED(CONFIG_IPV6)
137				p->src.v6.sin6_family = AF_INET6;
138				p->src.v6.sin6_port = inet->inet_sport;
139				p->src.v6.sin6_addr = inet6_sk(sk)->saddr;
140
141				p->dst.v6.sin6_family = AF_INET6;
142				p->dst.v6.sin6_port = inet->inet_dport;
143				p->dst.v6.sin6_addr = sk->sk_v6_daddr;
144#endif
145				break;
146			default:
147				BUG();
148			}
149
150			p->length = skb->len;
151			p->snd_nxt = tp->snd_nxt;
152			p->snd_una = tp->snd_una;
153			p->snd_cwnd = tp->snd_cwnd;
154			p->snd_wnd = tp->snd_wnd;
155			p->rcv_wnd = tp->rcv_wnd;
156			p->ssthresh = tcp_current_ssthresh(sk);
157			p->srtt = tp->srtt_us >> 3;
158
159			tcp_probe.head = (tcp_probe.head + 1) & (bufsize - 1);
160		}
161		tcp_probe.lastcwnd = tp->snd_cwnd;
162		spin_unlock(&tcp_probe.lock);
163
164		wake_up(&tcp_probe.wait);
165	}
166
167	jprobe_return();
168}
169
170static struct jprobe tcp_jprobe = {
171	.kp = {
172		.symbol_name	= "tcp_rcv_established",
173	},
174	.entry	= jtcp_rcv_established,
175};
176
177static int tcpprobe_open(struct inode *inode, struct file *file)
178{
179	/* Reset (empty) log */
180	spin_lock_bh(&tcp_probe.lock);
181	tcp_probe.head = tcp_probe.tail = 0;
182	tcp_probe.start = ktime_get();
183	spin_unlock_bh(&tcp_probe.lock);
184
185	return 0;
186}
187
188static int tcpprobe_sprint(char *tbuf, int n)
189{
190	const struct tcp_log *p
191		= tcp_probe.log + tcp_probe.tail;
192	struct timespec tv
193		= ktime_to_timespec(ktime_sub(p->tstamp, tcp_probe.start));
194
195	return scnprintf(tbuf, n,
196			"%lu.%09lu %pISpc %pISpc %d %#x %#x %u %u %u %u %u\n",
197			(unsigned long) tv.tv_sec,
198			(unsigned long) tv.tv_nsec,
199			&p->src, &p->dst, p->length, p->snd_nxt, p->snd_una,
200			p->snd_cwnd, p->ssthresh, p->snd_wnd, p->srtt, p->rcv_wnd);
201}
202
203static ssize_t tcpprobe_read(struct file *file, char __user *buf,
204			     size_t len, loff_t *ppos)
205{
206	int error = 0;
207	size_t cnt = 0;
208
209	if (!buf)
210		return -EINVAL;
211
212	while (cnt < len) {
213		char tbuf[256];
214		int width;
215
216		/* Wait for data in buffer */
217		error = wait_event_interruptible(tcp_probe.wait,
218						 tcp_probe_used() > 0);
219		if (error)
220			break;
221
222		spin_lock_bh(&tcp_probe.lock);
223		if (tcp_probe.head == tcp_probe.tail) {
224			/* multiple readers race? */
225			spin_unlock_bh(&tcp_probe.lock);
226			continue;
227		}
228
229		width = tcpprobe_sprint(tbuf, sizeof(tbuf));
230
231		if (cnt + width < len)
232			tcp_probe.tail = (tcp_probe.tail + 1) & (bufsize - 1);
233
234		spin_unlock_bh(&tcp_probe.lock);
235
236		/* if record greater than space available
237		   return partial buffer (so far) */
238		if (cnt + width >= len)
239			break;
240
241		if (copy_to_user(buf + cnt, tbuf, width))
242			return -EFAULT;
243		cnt += width;
244	}
245
246	return cnt == 0 ? error : cnt;
247}
248
249static const struct file_operations tcpprobe_fops = {
250	.owner	 = THIS_MODULE,
251	.open	 = tcpprobe_open,
252	.read    = tcpprobe_read,
253	.llseek  = noop_llseek,
254};
255
256static __init int tcpprobe_init(void)
257{
258	int ret = -ENOMEM;
259
260	/* Warning: if the function signature of tcp_rcv_established,
261	 * has been changed, you also have to change the signature of
262	 * jtcp_rcv_established, otherwise you end up right here!
263	 */
264	BUILD_BUG_ON(__same_type(tcp_rcv_established,
265				 jtcp_rcv_established) == 0);
266
267	init_waitqueue_head(&tcp_probe.wait);
268	spin_lock_init(&tcp_probe.lock);
269
270	if (bufsize == 0)
271		return -EINVAL;
272
273	bufsize = roundup_pow_of_two(bufsize);
274	tcp_probe.log = kcalloc(bufsize, sizeof(struct tcp_log), GFP_KERNEL);
275	if (!tcp_probe.log)
276		goto err0;
277
278	if (!proc_create(procname, S_IRUSR, init_net.proc_net, &tcpprobe_fops))
279		goto err0;
280
281	ret = register_jprobe(&tcp_jprobe);
282	if (ret)
283		goto err1;
284
285	pr_info("probe registered (port=%d/fwmark=%u) bufsize=%u\n",
286		port, fwmark, bufsize);
287	return 0;
288 err1:
289	remove_proc_entry(procname, init_net.proc_net);
290 err0:
291	kfree(tcp_probe.log);
292	return ret;
293}
294module_init(tcpprobe_init);
295
296static __exit void tcpprobe_exit(void)
297{
298	remove_proc_entry(procname, init_net.proc_net);
299	unregister_jprobe(&tcp_jprobe);
300	kfree(tcp_probe.log);
301}
302module_exit(tcpprobe_exit);