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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 | #include <linux/kernel.h> |
22 | #include <linux/kprobes.h> |
23 | #include <linux/socket.h> |
24 | #include <linux/tcp.h> |
25 | #include <linux/slab.h> |
26 | #include <linux/proc_fs.h> |
27 | #include <linux/module.h> |
28 | #include <linux/ktime.h> |
29 | #include <linux/time.h> |
30 | #include <net/net_namespace.h> |
31 | |
32 | #include <net/tcp.h> |
33 | |
34 | MODULE_AUTHOR("Stephen Hemminger <shemminger@linux-foundation.org>"); |
35 | MODULE_DESCRIPTION("TCP cwnd snooper"); |
36 | MODULE_LICENSE("GPL"); |
37 | MODULE_VERSION("1.1"); |
38 | |
39 | static int port __read_mostly = 0; |
40 | MODULE_PARM_DESC(port, "Port to match (0=all)"); |
41 | module_param(port, int, 0); |
42 | |
43 | static unsigned int bufsize __read_mostly = 4096; |
44 | MODULE_PARM_DESC(bufsize, "Log buffer size in packets (4096)"); |
45 | module_param(bufsize, uint, 0); |
46 | |
47 | static int full __read_mostly; |
48 | MODULE_PARM_DESC(full, "Full log (1=every ack packet received, 0=only cwnd changes)"); |
49 | module_param(full, int, 0); |
50 | |
51 | static const char procname[] = "tcpprobe"; |
52 | |
53 | struct tcp_log { |
54 | ktime_t tstamp; |
55 | __be32 saddr, daddr; |
56 | __be16 sport, dport; |
57 | u16 length; |
58 | u32 snd_nxt; |
59 | u32 snd_una; |
60 | u32 snd_wnd; |
61 | u32 snd_cwnd; |
62 | u32 ssthresh; |
63 | u32 srtt; |
64 | }; |
65 | |
66 | static struct { |
67 | spinlock_t lock; |
68 | wait_queue_head_t wait; |
69 | ktime_t start; |
70 | u32 lastcwnd; |
71 | |
72 | unsigned long head, tail; |
73 | struct tcp_log *log; |
74 | } tcp_probe; |
75 | |
76 | |
77 | static inline int tcp_probe_used(void) |
78 | { |
79 | return (tcp_probe.head - tcp_probe.tail) & (bufsize - 1); |
80 | } |
81 | |
82 | static inline int tcp_probe_avail(void) |
83 | { |
84 | return bufsize - tcp_probe_used() - 1; |
85 | } |
86 | |
87 | /* |
88 | * Hook inserted to be called before each receive packet. |
89 | * Note: arguments must match tcp_rcv_established()! |
90 | */ |
91 | static int jtcp_rcv_established(struct sock *sk, struct sk_buff *skb, |
92 | struct tcphdr *th, unsigned len) |
93 | { |
94 | const struct tcp_sock *tp = tcp_sk(sk); |
95 | const struct inet_sock *inet = inet_sk(sk); |
96 | |
97 | /* Only update if port matches */ |
98 | if ((port == 0 || ntohs(inet->inet_dport) == port || |
99 | ntohs(inet->inet_sport) == port) && |
100 | (full || tp->snd_cwnd != tcp_probe.lastcwnd)) { |
101 | |
102 | spin_lock(&tcp_probe.lock); |
103 | /* If log fills, just silently drop */ |
104 | if (tcp_probe_avail() > 1) { |
105 | struct tcp_log *p = tcp_probe.log + tcp_probe.head; |
106 | |
107 | p->tstamp = ktime_get(); |
108 | p->saddr = inet->inet_saddr; |
109 | p->sport = inet->inet_sport; |
110 | p->daddr = inet->inet_daddr; |
111 | p->dport = inet->inet_dport; |
112 | p->length = skb->len; |
113 | p->snd_nxt = tp->snd_nxt; |
114 | p->snd_una = tp->snd_una; |
115 | p->snd_cwnd = tp->snd_cwnd; |
116 | p->snd_wnd = tp->snd_wnd; |
117 | p->ssthresh = tcp_current_ssthresh(sk); |
118 | p->srtt = tp->srtt >> 3; |
119 | |
120 | tcp_probe.head = (tcp_probe.head + 1) & (bufsize - 1); |
121 | } |
122 | tcp_probe.lastcwnd = tp->snd_cwnd; |
123 | spin_unlock(&tcp_probe.lock); |
124 | |
125 | wake_up(&tcp_probe.wait); |
126 | } |
127 | |
128 | jprobe_return(); |
129 | return 0; |
130 | } |
131 | |
132 | static struct jprobe tcp_jprobe = { |
133 | .kp = { |
134 | .symbol_name = "tcp_rcv_established", |
135 | }, |
136 | .entry = jtcp_rcv_established, |
137 | }; |
138 | |
139 | static int tcpprobe_open(struct inode * inode, struct file * file) |
140 | { |
141 | /* Reset (empty) log */ |
142 | spin_lock_bh(&tcp_probe.lock); |
143 | tcp_probe.head = tcp_probe.tail = 0; |
144 | tcp_probe.start = ktime_get(); |
145 | spin_unlock_bh(&tcp_probe.lock); |
146 | |
147 | return 0; |
148 | } |
149 | |
150 | static int tcpprobe_sprint(char *tbuf, int n) |
151 | { |
152 | const struct tcp_log *p |
153 | = tcp_probe.log + tcp_probe.tail; |
154 | struct timespec tv |
155 | = ktime_to_timespec(ktime_sub(p->tstamp, tcp_probe.start)); |
156 | |
157 | return snprintf(tbuf, n, |
158 | "%lu.%09lu %pI4:%u %pI4:%u %d %#x %#x %u %u %u %u\n", |
159 | (unsigned long) tv.tv_sec, |
160 | (unsigned long) tv.tv_nsec, |
161 | &p->saddr, ntohs(p->sport), |
162 | &p->daddr, ntohs(p->dport), |
163 | p->length, p->snd_nxt, p->snd_una, |
164 | p->snd_cwnd, p->ssthresh, p->snd_wnd, p->srtt); |
165 | } |
166 | |
167 | static ssize_t tcpprobe_read(struct file *file, char __user *buf, |
168 | size_t len, loff_t *ppos) |
169 | { |
170 | int error = 0; |
171 | size_t cnt = 0; |
172 | |
173 | if (!buf) |
174 | return -EINVAL; |
175 | |
176 | while (cnt < len) { |
177 | char tbuf[128]; |
178 | int width; |
179 | |
180 | /* Wait for data in buffer */ |
181 | error = wait_event_interruptible(tcp_probe.wait, |
182 | tcp_probe_used() > 0); |
183 | if (error) |
184 | break; |
185 | |
186 | spin_lock_bh(&tcp_probe.lock); |
187 | if (tcp_probe.head == tcp_probe.tail) { |
188 | /* multiple readers race? */ |
189 | spin_unlock_bh(&tcp_probe.lock); |
190 | continue; |
191 | } |
192 | |
193 | width = tcpprobe_sprint(tbuf, sizeof(tbuf)); |
194 | |
195 | if (cnt + width < len) |
196 | tcp_probe.tail = (tcp_probe.tail + 1) & (bufsize - 1); |
197 | |
198 | spin_unlock_bh(&tcp_probe.lock); |
199 | |
200 | /* if record greater than space available |
201 | return partial buffer (so far) */ |
202 | if (cnt + width >= len) |
203 | break; |
204 | |
205 | if (copy_to_user(buf + cnt, tbuf, width)) |
206 | return -EFAULT; |
207 | cnt += width; |
208 | } |
209 | |
210 | return cnt == 0 ? error : cnt; |
211 | } |
212 | |
213 | static const struct file_operations tcpprobe_fops = { |
214 | .owner = THIS_MODULE, |
215 | .open = tcpprobe_open, |
216 | .read = tcpprobe_read, |
217 | }; |
218 | |
219 | static __init int tcpprobe_init(void) |
220 | { |
221 | int ret = -ENOMEM; |
222 | |
223 | init_waitqueue_head(&tcp_probe.wait); |
224 | spin_lock_init(&tcp_probe.lock); |
225 | |
226 | if (bufsize == 0) |
227 | return -EINVAL; |
228 | |
229 | bufsize = roundup_pow_of_two(bufsize); |
230 | tcp_probe.log = kcalloc(bufsize, sizeof(struct tcp_log), GFP_KERNEL); |
231 | if (!tcp_probe.log) |
232 | goto err0; |
233 | |
234 | if (!proc_net_fops_create(&init_net, procname, S_IRUSR, &tcpprobe_fops)) |
235 | goto err0; |
236 | |
237 | ret = register_jprobe(&tcp_jprobe); |
238 | if (ret) |
239 | goto err1; |
240 | |
241 | pr_info("TCP probe registered (port=%d) bufsize=%u\n", port, bufsize); |
242 | return 0; |
243 | err1: |
244 | proc_net_remove(&init_net, procname); |
245 | err0: |
246 | kfree(tcp_probe.log); |
247 | return ret; |
248 | } |
249 | module_init(tcpprobe_init); |
250 | |
251 | static __exit void tcpprobe_exit(void) |
252 | { |
253 | proc_net_remove(&init_net, procname); |
254 | unregister_jprobe(&tcp_jprobe); |
255 | kfree(tcp_probe.log); |
256 | } |
257 | module_exit(tcpprobe_exit); |
258 |
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