1 files changed, 254 insertions, 0 deletions
diff --git a/net/ipv4/tcp_probe.c b/net/ipv4/tcp_probe.c
new file mode 100644
index 0000000..7ddc30f
--- /dev/null
+++ b/net/ipv4/tcp_probe.c
@@ -0,0 +1,254 @@
+/*
+ * tcpprobe - Observe the TCP flow with kprobes.
+ *
+ * The idea for this came from Werner Almesberger's umlsim
+ * Copyright (C) 2004, Stephen Hemminger <shemminger@osdl.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/kernel.h>
+#include <linux/kprobes.h>
+#include <linux/socket.h>
+#include <linux/tcp.h>
+#include <linux/proc_fs.h>
+#include <linux/module.h>
+#include <linux/ktime.h>
+#include <linux/time.h>
+#include <net/net_namespace.h>
+
+#include <net/tcp.h>
+
+MODULE_AUTHOR("Stephen Hemminger <shemminger@linux-foundation.org>");
+MODULE_DESCRIPTION("TCP cwnd snooper");
+MODULE_LICENSE("GPL");
+MODULE_VERSION("1.1");
+
+static int port __read_mostly = 0;
+MODULE_PARM_DESC(port, "Port to match (0=all)");
+module_param(port, int, 0);
+
+static int bufsize __read_mostly = 4096;
+MODULE_PARM_DESC(bufsize, "Log buffer size in packets (4096)");
+module_param(bufsize, int, 0);
+
+static int full __read_mostly;
+MODULE_PARM_DESC(full, "Full log (1=every ack packet received,  0=only cwnd changes)");
+module_param(full, int, 0);
+
+static const char procname[] = "tcpprobe";
+
+struct tcp_log {
+	ktime_t tstamp;
+	__be32	saddr, daddr;
+	__be16	sport, dport;
+	u16	length;
+	u32	snd_nxt;
+	u32	snd_una;
+	u32	snd_wnd;
+	u32	snd_cwnd;
+	u32	ssthresh;
+	u32	srtt;
+};
+
+static struct {
+	spinlock_t	lock;
+	wait_queue_head_t wait;
+	ktime_t		start;
+	u32		lastcwnd;
+
+	unsigned long	head, tail;
+	struct tcp_log	*log;
+} tcp_probe;
+
+
+static inline int tcp_probe_used(void)
+{
+	return (tcp_probe.head - tcp_probe.tail) % bufsize;
+}
+
+static inline int tcp_probe_avail(void)
+{
+	return bufsize - tcp_probe_used();
+}
+
+/*
+ * Hook inserted to be called before each receive packet.
+ * Note: arguments must match tcp_rcv_established()!
+ */
+static int jtcp_rcv_established(struct sock *sk, struct sk_buff *skb,
+			       struct tcphdr *th, unsigned len)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+	const struct inet_sock *inet = inet_sk(sk);
+
+	/* Only update if port matches */
+	if ((port == 0 || ntohs(inet->dport) == port || ntohs(inet->sport) == port)
+	    && (full || tp->snd_cwnd != tcp_probe.lastcwnd)) {
+
+		spin_lock(&tcp_probe.lock);
+		/* If log fills, just silently drop */
+		if (tcp_probe_avail() > 1) {
+			struct tcp_log *p = tcp_probe.log + tcp_probe.head;
+
+			p->tstamp = ktime_get();
+			p->saddr = inet->saddr;
+			p->sport = inet->sport;
+			p->daddr = inet->daddr;
+			p->dport = inet->dport;
+			p->length = skb->len;
+			p->snd_nxt = tp->snd_nxt;
+			p->snd_una = tp->snd_una;
+			p->snd_cwnd = tp->snd_cwnd;
+			p->snd_wnd = tp->snd_wnd;
+			p->ssthresh = tcp_current_ssthresh(sk);
+			p->srtt = tp->srtt >> 3;
+
+			tcp_probe.head = (tcp_probe.head + 1) % bufsize;
+		}
+		tcp_probe.lastcwnd = tp->snd_cwnd;
+		spin_unlock(&tcp_probe.lock);
+
+		wake_up(&tcp_probe.wait);
+	}
+
+	jprobe_return();
+	return 0;
+}
+
+static struct jprobe tcp_jprobe = {
+	.kp = {
+		.symbol_name	= "tcp_rcv_established",
+	},
+	.entry	= jtcp_rcv_established,
+};
+
+static int tcpprobe_open(struct inode * inode, struct file * file)
+{
+	/* Reset (empty) log */
+	spin_lock_bh(&tcp_probe.lock);
+	tcp_probe.head = tcp_probe.tail = 0;
+	tcp_probe.start = ktime_get();
+	spin_unlock_bh(&tcp_probe.lock);
+
+	return 0;
+}
+
+static int tcpprobe_sprint(char *tbuf, int n)
+{
+	const struct tcp_log *p
+		= tcp_probe.log + tcp_probe.tail % bufsize;
+	struct timespec tv
+		= ktime_to_timespec(ktime_sub(p->tstamp, tcp_probe.start));
+
+	return snprintf(tbuf, n,
+			"%lu.%09lu " NIPQUAD_FMT ":%u " NIPQUAD_FMT ":%u"
+			" %d %#x %#x %u %u %u %u\n",
+			(unsigned long) tv.tv_sec,
+			(unsigned long) tv.tv_nsec,
+			NIPQUAD(p->saddr), ntohs(p->sport),
+			NIPQUAD(p->daddr), ntohs(p->dport),
+			p->length, p->snd_nxt, p->snd_una,
+			p->snd_cwnd, p->ssthresh, p->snd_wnd, p->srtt);
+}
+
+static ssize_t tcpprobe_read(struct file *file, char __user *buf,
+			     size_t len, loff_t *ppos)
+{
+	int error = 0, cnt = 0;
+
+	if (!buf || len < 0)
+		return -EINVAL;
+
+	while (cnt < len) {
+		char tbuf[128];
+		int width;
+
+		/* Wait for data in buffer */
+		error = wait_event_interruptible(tcp_probe.wait,
+						 tcp_probe_used() > 0);
+		if (error)
+			break;
+
+		spin_lock_bh(&tcp_probe.lock);
+		if (tcp_probe.head == tcp_probe.tail) {
+			/* multiple readers race? */
+			spin_unlock_bh(&tcp_probe.lock);
+			continue;
+		}
+
+		width = tcpprobe_sprint(tbuf, sizeof(tbuf));
+
+		if (cnt + width < len)
+			tcp_probe.tail = (tcp_probe.tail + 1) % bufsize;
+
+		spin_unlock_bh(&tcp_probe.lock);
+
+		/* if record greater than space available
+		   return partial buffer (so far) */
+		if (cnt + width >= len)
+			break;
+
+		if (copy_to_user(buf + cnt, tbuf, width))
+			return -EFAULT;
+		cnt += width;
+	}
+
+	return cnt == 0 ? error : cnt;
+}
+
+static const struct file_operations tcpprobe_fops = {
+	.owner	 = THIS_MODULE,
+	.open	 = tcpprobe_open,
+	.read    = tcpprobe_read,
+};
+
+static __init int tcpprobe_init(void)
+{
+	int ret = -ENOMEM;
+
+	init_waitqueue_head(&tcp_probe.wait);
+	spin_lock_init(&tcp_probe.lock);
+
+	if (bufsize < 0)
+		return -EINVAL;
+
+	tcp_probe.log = kcalloc(bufsize, sizeof(struct tcp_log), GFP_KERNEL);
+	if (!tcp_probe.log)
+		goto err0;
+
+	if (!proc_net_fops_create(&init_net, procname, S_IRUSR, &tcpprobe_fops))
+		goto err0;
+
+	ret = register_jprobe(&tcp_jprobe);
+	if (ret)
+		goto err1;
+
+	pr_info("TCP probe registered (port=%d)\n", port);
+	return 0;
+ err1:
+	proc_net_remove(&init_net, procname);
+ err0:
+	kfree(tcp_probe.log);
+	return ret;
+}
+module_init(tcpprobe_init);
+
+static __exit void tcpprobe_exit(void)
+{
+	proc_net_remove(&init_net, procname);
+	unregister_jprobe(&tcp_jprobe);
+	kfree(tcp_probe.log);
+}
+module_exit(tcpprobe_exit);