2 * tcpprobe - Observe the TCP flow with kprobes.
4 * The idea for this came from Werner Almesberger's umlsim
5 * Copyright (C) 2004, Stephen Hemminger <shemminger@osdl.org>
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.
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.
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.
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 #include <net/net_namespace.h>
33 MODULE_AUTHOR("Stephen Hemminger <shemminger@linux-foundation.org>");
34 MODULE_DESCRIPTION("TCP cwnd snooper");
35 MODULE_LICENSE("GPL");
36 MODULE_VERSION("1.1");
38 static int port __read_mostly = 0;
39 MODULE_PARM_DESC(port, "Port to match (0=all)");
40 module_param(port, int, 0);
42 static int bufsize __read_mostly = 4096;
43 MODULE_PARM_DESC(bufsize, "Log buffer size in packets (4096)");
44 module_param(bufsize, int, 0);
46 static int full __read_mostly;
47 MODULE_PARM_DESC(full, "Full log (1=every ack packet received, 0=only cwnd changes)");
48 module_param(full, int, 0);
50 static const char procname[] = "tcpprobe";
67 wait_queue_head_t wait;
71 unsigned long head, tail;
76 static inline int tcp_probe_used(void)
78 return (tcp_probe.head - tcp_probe.tail) % bufsize;
81 static inline int tcp_probe_avail(void)
83 return bufsize - tcp_probe_used();
87 * Hook inserted to be called before each receive packet.
88 * Note: arguments must match tcp_rcv_established()!
90 static int jtcp_rcv_established(struct sock *sk, struct sk_buff *skb,
91 struct tcphdr *th, unsigned len)
93 const struct tcp_sock *tp = tcp_sk(sk);
94 const struct inet_sock *inet = inet_sk(sk);
96 /* Only update if port matches */
97 if ((port == 0 || ntohs(inet->dport) == port || ntohs(inet->sport) == port)
98 && (full || tp->snd_cwnd != tcp_probe.lastcwnd)) {
100 spin_lock(&tcp_probe.lock);
101 /* If log fills, just silently drop */
102 if (tcp_probe_avail() > 1) {
103 struct tcp_log *p = tcp_probe.log + tcp_probe.head;
105 p->tstamp = ktime_get();
106 p->saddr = inet->saddr;
107 p->sport = inet->sport;
108 p->daddr = inet->daddr;
109 p->dport = inet->dport;
110 p->length = skb->len;
111 p->snd_nxt = tp->snd_nxt;
112 p->snd_una = tp->snd_una;
113 p->snd_cwnd = tp->snd_cwnd;
114 p->snd_wnd = tp->snd_wnd;
115 p->ssthresh = tcp_current_ssthresh(sk);
116 p->srtt = tp->srtt >> 3;
118 tcp_probe.head = (tcp_probe.head + 1) % bufsize;
120 tcp_probe.lastcwnd = tp->snd_cwnd;
121 spin_unlock(&tcp_probe.lock);
123 wake_up(&tcp_probe.wait);
130 static struct jprobe tcp_jprobe = {
132 .symbol_name = "tcp_rcv_established",
134 .entry = jtcp_rcv_established,
137 static int tcpprobe_open(struct inode * inode, struct file * file)
139 /* Reset (empty) log */
140 spin_lock_bh(&tcp_probe.lock);
141 tcp_probe.head = tcp_probe.tail = 0;
142 tcp_probe.start = ktime_get();
143 spin_unlock_bh(&tcp_probe.lock);
148 static int tcpprobe_sprint(char *tbuf, int n)
150 const struct tcp_log *p
151 = tcp_probe.log + tcp_probe.tail % bufsize;
153 = ktime_to_timespec(ktime_sub(p->tstamp, tcp_probe.start));
155 return snprintf(tbuf, n,
156 "%lu.%09lu %pI4:%u %pI4:%u %d %#x %#x %u %u %u %u\n",
157 (unsigned long) tv.tv_sec,
158 (unsigned long) tv.tv_nsec,
159 &p->saddr, ntohs(p->sport),
160 &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);
165 static ssize_t tcpprobe_read(struct file *file, char __user *buf,
166 size_t len, loff_t *ppos)
178 /* Wait for data in buffer */
179 error = wait_event_interruptible(tcp_probe.wait,
180 tcp_probe_used() > 0);
184 spin_lock_bh(&tcp_probe.lock);
185 if (tcp_probe.head == tcp_probe.tail) {
186 /* multiple readers race? */
187 spin_unlock_bh(&tcp_probe.lock);
191 width = tcpprobe_sprint(tbuf, sizeof(tbuf));
193 if (cnt + width < len)
194 tcp_probe.tail = (tcp_probe.tail + 1) % bufsize;
196 spin_unlock_bh(&tcp_probe.lock);
198 /* if record greater than space available
199 return partial buffer (so far) */
200 if (cnt + width >= len)
203 if (copy_to_user(buf + cnt, tbuf, width))
208 return cnt == 0 ? error : cnt;
211 static const struct file_operations tcpprobe_fops = {
212 .owner = THIS_MODULE,
213 .open = tcpprobe_open,
214 .read = tcpprobe_read,
217 static __init int tcpprobe_init(void)
221 init_waitqueue_head(&tcp_probe.wait);
222 spin_lock_init(&tcp_probe.lock);
227 tcp_probe.log = kcalloc(bufsize, sizeof(struct tcp_log), GFP_KERNEL);
231 if (!proc_net_fops_create(&init_net, procname, S_IRUSR, &tcpprobe_fops))
234 ret = register_jprobe(&tcp_jprobe);
238 pr_info("TCP probe registered (port=%d)\n", port);
241 proc_net_remove(&init_net, procname);
243 kfree(tcp_probe.log);
246 module_init(tcpprobe_init);
248 static __exit void tcpprobe_exit(void)
250 proc_net_remove(&init_net, procname);
251 unregister_jprobe(&tcp_jprobe);
252 kfree(tcp_probe.log);
254 module_exit(tcpprobe_exit);