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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 
36 MODULE_AUTHOR("Stephen Hemminger <shemminger@linux-foundation.org>");
37 MODULE_DESCRIPTION("TCP cwnd snooper");
38 MODULE_LICENSE("GPL");
39 MODULE_VERSION("1.1");
40 
41 static int port __read_mostly;
42 MODULE_PARM_DESC(port, "Port to match (0=all)");
43 module_param(port, int, 0);
44 
45 static unsigned int bufsize __read_mostly = 4096;
46 MODULE_PARM_DESC(bufsize, "Log buffer size in packets (4096)");
47 module_param(bufsize, uint, 0);
48 
49 static unsigned int fwmark __read_mostly;
50 MODULE_PARM_DESC(fwmark, "skb mark to match (0=no mark)");
51 module_param(fwmark, uint, 0);
52 
53 static int full __read_mostly;
54 MODULE_PARM_DESC(full, "Full log (1=every ack packet received,  0=only cwnd changes)");
55 module_param(full, int, 0);
56 
57 static const char procname[] = "tcpprobe";
58 
59 struct 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 
76 static 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 
tcp_probe_used(void)86 static inline int tcp_probe_used(void)
87 {
88 	return (tcp_probe.head - tcp_probe.tail) & (bufsize - 1);
89 }
90 
tcp_probe_avail(void)91 static 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  */
jtcp_rcv_established(struct sock * sk,struct sk_buff * skb,const struct tcphdr * th,unsigned int len)107 static 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_bh(&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_bh(&tcp_probe.lock);
161 
162 		wake_up(&tcp_probe.wait);
163 	}
164 
165 	jprobe_return();
166 }
167 
168 static struct jprobe tcp_jprobe = {
169 	.kp = {
170 		.symbol_name	= "tcp_rcv_established",
171 	},
172 	.entry	= jtcp_rcv_established,
173 };
174 
tcpprobe_open(struct inode * inode,struct file * file)175 static 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 
tcpprobe_sprint(char * tbuf,int n)186 static 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 
tcpprobe_read(struct file * file,char __user * buf,size_t len,loff_t * ppos)201 static 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 
247 static const struct file_operations tcpprobe_fops = {
248 	.owner	 = THIS_MODULE,
249 	.open	 = tcpprobe_open,
250 	.read    = tcpprobe_read,
251 	.llseek  = noop_llseek,
252 };
253 
tcpprobe_init(void)254 static __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 }
292 module_init(tcpprobe_init);
293 
tcpprobe_exit(void)294 static __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 }
300 module_exit(tcpprobe_exit);
301