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