ipv4: fix multicast losses
[linux-2.6.git] / net / ipv4 / tcp_probe.c
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 scnprintf(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[164];
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         .llseek  = noop_llseek,
218 };
219
220 static __init int tcpprobe_init(void)
221 {
222         int ret = -ENOMEM;
223
224         init_waitqueue_head(&tcp_probe.wait);
225         spin_lock_init(&tcp_probe.lock);
226
227         if (bufsize == 0)
228                 return -EINVAL;
229
230         bufsize = roundup_pow_of_two(bufsize);
231         tcp_probe.log = kcalloc(bufsize, sizeof(struct tcp_log), GFP_KERNEL);
232         if (!tcp_probe.log)
233                 goto err0;
234
235         if (!proc_net_fops_create(&init_net, procname, S_IRUSR, &tcpprobe_fops))
236                 goto err0;
237
238         ret = register_jprobe(&tcp_jprobe);
239         if (ret)
240                 goto err1;
241
242         pr_info("TCP probe registered (port=%d) bufsize=%u\n", port, bufsize);
243         return 0;
244  err1:
245         proc_net_remove(&init_net, procname);
246  err0:
247         kfree(tcp_probe.log);
248         return ret;
249 }
250 module_init(tcpprobe_init);
251
252 static __exit void tcpprobe_exit(void)
253 {
254         proc_net_remove(&init_net, procname);
255         unregister_jprobe(&tcp_jprobe);
256         kfree(tcp_probe.log);
257 }
258 module_exit(tcpprobe_exit);