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
 86static inline int tcp_probe_used(void)
 87{
 88	return (tcp_probe.head - tcp_probe.tail) & (bufsize - 1);
 89}
 90
 91static inline int tcp_probe_avail(void)
 92{
 93	return bufsize - tcp_probe_used() - 1;
 94}
 95
 96#define tcp_probe_copy_fl_to_si4(inet, si4, mem)		\
 97	do {							\
 98		si4.sin_family = AF_INET;			\
 99		si4.sin_port = inet->inet_##mem##port;		\
100		si4.sin_addr.s_addr = inet->inet_##mem##addr;	\
101	} while (0)						\
102
103/*
104 * Hook inserted to be called before each receive packet.
105 * Note: arguments must match tcp_rcv_established()!
106 */
107static void jtcp_rcv_established(struct sock *sk, struct sk_buff *skb,
108				 const struct tcphdr *th, unsigned int len)
109{
110	const struct tcp_sock *tp = tcp_sk(sk);
111	const struct inet_sock *inet = inet_sk(sk);
112
113	/* Only update if port or skb mark matches */
114	if (((port == 0 && fwmark == 0) ||
115	     ntohs(inet->inet_dport) == port ||
116	     ntohs(inet->inet_sport) == port ||
117	     (fwmark > 0 && skb->mark == fwmark)) &&
118	    (full || tp->snd_cwnd != tcp_probe.lastcwnd)) {
119
120		spin_lock(&tcp_probe.lock);
121		/* If log fills, just silently drop */
122		if (tcp_probe_avail() > 1) {
123			struct tcp_log *p = tcp_probe.log + tcp_probe.head;
124
125			p->tstamp = ktime_get();
126			switch (sk->sk_family) {
127			case AF_INET:
128				tcp_probe_copy_fl_to_si4(inet, p->src.v4, s);
129				tcp_probe_copy_fl_to_si4(inet, p->dst.v4, d);
130				break;
131			case AF_INET6:
132				memset(&p->src.v6, 0, sizeof(p->src.v6));
133				memset(&p->dst.v6, 0, sizeof(p->dst.v6));
134#if IS_ENABLED(CONFIG_IPV6)
135				p->src.v6.sin6_family = AF_INET6;
136				p->src.v6.sin6_port = inet->inet_sport;
137				p->src.v6.sin6_addr = inet6_sk(sk)->saddr;
138
139				p->dst.v6.sin6_family = AF_INET6;
140				p->dst.v6.sin6_port = inet->inet_dport;
141				p->dst.v6.sin6_addr = sk->sk_v6_daddr;
142#endif
143				break;
144			default:
145				BUG();
146			}
147
148			p->length = skb->len;
149			p->snd_nxt = tp->snd_nxt;
150			p->snd_una = tp->snd_una;
151			p->snd_cwnd = tp->snd_cwnd;
152			p->snd_wnd = tp->snd_wnd;
153			p->rcv_wnd = tp->rcv_wnd;
154			p->ssthresh = tcp_current_ssthresh(sk);
155			p->srtt = tp->srtt_us >> 3;
156
157			tcp_probe.head = (tcp_probe.head + 1) & (bufsize - 1);
158		}
159		tcp_probe.lastcwnd = tp->snd_cwnd;
160		spin_unlock(&tcp_probe.lock);
161
162		wake_up(&tcp_probe.wait);
163	}
164
165	jprobe_return();
166}
167
168static struct jprobe tcp_jprobe = {
169	.kp = {
170		.symbol_name	= "tcp_rcv_established",
171	},
172	.entry	= jtcp_rcv_established,
173};
174
175static int tcpprobe_open(struct inode *inode, struct file *file)
176{
177	/* Reset (empty) log */
178	spin_lock_bh(&tcp_probe.lock);
179	tcp_probe.head = tcp_probe.tail = 0;
180	tcp_probe.start = ktime_get();
181	spin_unlock_bh(&tcp_probe.lock);
182
183	return 0;
184}
185
186static int tcpprobe_sprint(char *tbuf, int n)
187{
188	const struct tcp_log *p
189		= tcp_probe.log + tcp_probe.tail;
190	struct timespec64 ts
191		= ktime_to_timespec64(ktime_sub(p->tstamp, tcp_probe.start));
192
193	return scnprintf(tbuf, n,
194			"%lu.%09lu %pISpc %pISpc %d %#x %#x %u %u %u %u %u\n",
195			(unsigned long)ts.tv_sec,
196			(unsigned long)ts.tv_nsec,
197			&p->src, &p->dst, p->length, p->snd_nxt, p->snd_una,
198			p->snd_cwnd, p->ssthresh, p->snd_wnd, p->srtt, p->rcv_wnd);
199}
200
201static ssize_t tcpprobe_read(struct file *file, char __user *buf,
202			     size_t len, loff_t *ppos)
203{
204	int error = 0;
205	size_t cnt = 0;
206
207	if (!buf)
208		return -EINVAL;
209
210	while (cnt < len) {
211		char tbuf[256];
212		int width;
213
214		/* Wait for data in buffer */
215		error = wait_event_interruptible(tcp_probe.wait,
216						 tcp_probe_used() > 0);
217		if (error)
218			break;
219
220		spin_lock_bh(&tcp_probe.lock);
221		if (tcp_probe.head == tcp_probe.tail) {
222			/* multiple readers race? */
223			spin_unlock_bh(&tcp_probe.lock);
224			continue;
225		}
226
227		width = tcpprobe_sprint(tbuf, sizeof(tbuf));
228
229		if (cnt + width < len)
230			tcp_probe.tail = (tcp_probe.tail + 1) & (bufsize - 1);
231
232		spin_unlock_bh(&tcp_probe.lock);
233
234		/* if record greater than space available
235		   return partial buffer (so far) */
236		if (cnt + width >= len)
237			break;
238
239		if (copy_to_user(buf + cnt, tbuf, width))
240			return -EFAULT;
241		cnt += width;
242	}
243
244	return cnt == 0 ? error : cnt;
245}
246
247static const struct file_operations tcpprobe_fops = {
248	.owner	 = THIS_MODULE,
249	.open	 = tcpprobe_open,
250	.read    = tcpprobe_read,
251	.llseek  = noop_llseek,
252};
253
254static __init int tcpprobe_init(void)
255{
256	int ret = -ENOMEM;
257
258	/* Warning: if the function signature of tcp_rcv_established,
259	 * has been changed, you also have to change the signature of
260	 * jtcp_rcv_established, otherwise you end up right here!
261	 */
262	BUILD_BUG_ON(__same_type(tcp_rcv_established,
263				 jtcp_rcv_established) == 0);
264
265	init_waitqueue_head(&tcp_probe.wait);
266	spin_lock_init(&tcp_probe.lock);
267
268	if (bufsize == 0)
269		return -EINVAL;
270
271	bufsize = roundup_pow_of_two(bufsize);
272	tcp_probe.log = kcalloc(bufsize, sizeof(struct tcp_log), GFP_KERNEL);
273	if (!tcp_probe.log)
274		goto err0;
275
276	if (!proc_create(procname, S_IRUSR, init_net.proc_net, &tcpprobe_fops))
277		goto err0;
278
279	ret = register_jprobe(&tcp_jprobe);
280	if (ret)
281		goto err1;
282
283	pr_info("probe registered (port=%d/fwmark=%u) bufsize=%u\n",
284		port, fwmark, bufsize);
285	return 0;
286 err1:
287	remove_proc_entry(procname, init_net.proc_net);
288 err0:
289	kfree(tcp_probe.log);
290	return ret;
291}
292module_init(tcpprobe_init);
293
294static __exit void tcpprobe_exit(void)
295{
296	remove_proc_entry(procname, init_net.proc_net);
297	unregister_jprobe(&tcp_jprobe);
298	kfree(tcp_probe.log);
299}
300module_exit(tcpprobe_exit);