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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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>
36 MODULE_AUTHOR("Stephen Hemminger <shemminger@linux-foundation.org>");
37 MODULE_DESCRIPTION("TCP cwnd snooper");
38 MODULE_LICENSE("GPL");
39 MODULE_VERSION("1.1");
41 static int port __read_mostly = 0;
42 MODULE_PARM_DESC(port, "Port to match (0=all)");
43 module_param(port, int, 0);
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);
49 static unsigned int fwmark __read_mostly = 0;
50 MODULE_PARM_DESC(fwmark, "skb mark to match (0=no mark)");
51 module_param(fwmark, uint, 0);
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);
57 static const char procname[] = "tcpprobe";
63 struct sockaddr_in v4;
64 struct sockaddr_in6 v6;
78 wait_queue_head_t wait;
82 unsigned long head, tail;
87 static inline int tcp_probe_used(void)
89 return (tcp_probe.head - tcp_probe.tail) & (bufsize - 1);
92 static inline int tcp_probe_avail(void)
94 return bufsize - tcp_probe_used() - 1;
97 #define tcp_probe_copy_fl_to_si4(inet, si4, mem) \
99 si4.sin_family = AF_INET; \
100 si4.sin_port = inet->inet_##mem##port; \
101 si4.sin_addr.s_addr = inet->inet_##mem##addr; \
104 #if IS_ENABLED(CONFIG_IPV6)
105 #define tcp_probe_copy_fl_to_si6(inet, si6, mem) \
107 struct ipv6_pinfo *pi6 = inet->pinet6; \
108 si6.sin6_family = AF_INET6; \
109 si6.sin6_port = inet->inet_##mem##port; \
110 si6.sin6_addr = pi6->mem##addr; \
111 si6.sin6_flowinfo = 0; /* No need here. */ \
112 si6.sin6_scope_id = 0; /* No need here. */ \
115 #define tcp_probe_copy_fl_to_si6(fl, si6, mem) \
117 memset(&si6, 0, sizeof(si6)); \
122 * Hook inserted to be called before each receive packet.
123 * Note: arguments must match tcp_rcv_established()!
125 static void jtcp_rcv_established(struct sock *sk, struct sk_buff *skb,
126 const struct tcphdr *th, unsigned int len)
128 const struct tcp_sock *tp = tcp_sk(sk);
129 const struct inet_sock *inet = inet_sk(sk);
131 /* Only update if port or skb mark matches */
132 if (((port == 0 && fwmark == 0) ||
133 ntohs(inet->inet_dport) == port ||
134 ntohs(inet->inet_sport) == port ||
135 (fwmark > 0 && skb->mark == fwmark)) &&
136 (full || tp->snd_cwnd != tcp_probe.lastcwnd)) {
138 spin_lock(&tcp_probe.lock);
139 /* If log fills, just silently drop */
140 if (tcp_probe_avail() > 1) {
141 struct tcp_log *p = tcp_probe.log + tcp_probe.head;
143 p->tstamp = ktime_get();
144 switch (sk->sk_family) {
146 tcp_probe_copy_fl_to_si4(inet, p->src.v4, s);
147 tcp_probe_copy_fl_to_si4(inet, p->dst.v4, d);
150 tcp_probe_copy_fl_to_si6(inet, p->src.v6, s);
151 tcp_probe_copy_fl_to_si6(inet, p->dst.v6, d);
157 p->length = skb->len;
158 p->snd_nxt = tp->snd_nxt;
159 p->snd_una = tp->snd_una;
160 p->snd_cwnd = tp->snd_cwnd;
161 p->snd_wnd = tp->snd_wnd;
162 p->rcv_wnd = tp->rcv_wnd;
163 p->ssthresh = tcp_current_ssthresh(sk);
164 p->srtt = tp->srtt >> 3;
166 tcp_probe.head = (tcp_probe.head + 1) & (bufsize - 1);
168 tcp_probe.lastcwnd = tp->snd_cwnd;
169 spin_unlock(&tcp_probe.lock);
171 wake_up(&tcp_probe.wait);
177 static struct jprobe tcp_jprobe = {
179 .symbol_name = "tcp_rcv_established",
181 .entry = jtcp_rcv_established,
184 static int tcpprobe_open(struct inode *inode, struct file *file)
186 /* Reset (empty) log */
187 spin_lock_bh(&tcp_probe.lock);
188 tcp_probe.head = tcp_probe.tail = 0;
189 tcp_probe.start = ktime_get();
190 spin_unlock_bh(&tcp_probe.lock);
195 static int tcpprobe_sprint(char *tbuf, int n)
197 const struct tcp_log *p
198 = tcp_probe.log + tcp_probe.tail;
200 = ktime_to_timespec(ktime_sub(p->tstamp, tcp_probe.start));
202 return scnprintf(tbuf, n,
203 "%lu.%09lu %pISpc %pISpc %d %#x %#x %u %u %u %u %u\n",
204 (unsigned long) tv.tv_sec,
205 (unsigned long) tv.tv_nsec,
206 &p->src, &p->dst, p->length, p->snd_nxt, p->snd_una,
207 p->snd_cwnd, p->ssthresh, p->snd_wnd, p->srtt, p->rcv_wnd);
210 static ssize_t tcpprobe_read(struct file *file, char __user *buf,
211 size_t len, loff_t *ppos)
223 /* Wait for data in buffer */
224 error = wait_event_interruptible(tcp_probe.wait,
225 tcp_probe_used() > 0);
229 spin_lock_bh(&tcp_probe.lock);
230 if (tcp_probe.head == tcp_probe.tail) {
231 /* multiple readers race? */
232 spin_unlock_bh(&tcp_probe.lock);
236 width = tcpprobe_sprint(tbuf, sizeof(tbuf));
238 if (cnt + width < len)
239 tcp_probe.tail = (tcp_probe.tail + 1) & (bufsize - 1);
241 spin_unlock_bh(&tcp_probe.lock);
243 /* if record greater than space available
244 return partial buffer (so far) */
245 if (cnt + width >= len)
248 if (copy_to_user(buf + cnt, tbuf, width))
253 return cnt == 0 ? error : cnt;
256 static const struct file_operations tcpprobe_fops = {
257 .owner = THIS_MODULE,
258 .open = tcpprobe_open,
259 .read = tcpprobe_read,
260 .llseek = noop_llseek,
263 static __init int tcpprobe_init(void)
267 /* Warning: if the function signature of tcp_rcv_established,
268 * has been changed, you also have to change the signature of
269 * jtcp_rcv_established, otherwise you end up right here!
271 BUILD_BUG_ON(__same_type(tcp_rcv_established,
272 jtcp_rcv_established) == 0);
274 init_waitqueue_head(&tcp_probe.wait);
275 spin_lock_init(&tcp_probe.lock);
280 bufsize = roundup_pow_of_two(bufsize);
281 tcp_probe.log = kcalloc(bufsize, sizeof(struct tcp_log), GFP_KERNEL);
285 if (!proc_create(procname, S_IRUSR, init_net.proc_net, &tcpprobe_fops))
288 ret = register_jprobe(&tcp_jprobe);
292 pr_info("probe registered (port=%d/fwmark=%u) bufsize=%u\n",
293 port, fwmark, bufsize);
296 remove_proc_entry(procname, init_net.proc_net);
298 kfree(tcp_probe.log);
301 module_init(tcpprobe_init);
303 static __exit void tcpprobe_exit(void)
305 remove_proc_entry(procname, init_net.proc_net);
306 unregister_jprobe(&tcp_jprobe);
307 kfree(tcp_probe.log);
309 module_exit(tcpprobe_exit);