sctp: implement sctp association probing module

This patch implement sctp association probing module, the module
will be called sctp_probe.

This module allows for capturing the changes to SCTP association
state in response to incoming packets. It is used for debugging
SCTP congestion control algorithms.

Usage:
  $ modprobe sctp_probe [full=n] [port=n] [bufsize=n]
  $ cat /proc/net/sctpprobe

  The output format is:
    TIME     ASSOC     LPORT RPORT MTU    RWND  UNACK <REMOTE-ADDR   STATE  CWND   SSTHRESH  INFLIGHT  PARTIAL_BYTES_ACKED MTU> ...

  The output will be like this:
    9.226086 c4064c48  9000  8000  1500    53352     1 *192.168.0.19  1     4380    54784     1252        0     1500
    9.287195 c4064c48  9000  8000  1500    45144     5 *192.168.0.19  1     5880    54784     6500        0     1500
    9.289130 c4064c48  9000  8000  1500    42724     5 *192.168.0.19  1     7380    54784     6500        0     1500
    9.620332 c4064c48  9000  8000  1500    48284     4 *192.168.0.19  1     8880    54784     5200        0     1500
    ......

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>

net/sctp/Kconfig

@@ -37,6 +37,18 @@ menuconfig IP_SCTP
 
 if IP_SCTP
 
+config NET_SCTPPROBE
+	tristate "SCTP: Association probing"
+        depends on PROC_FS && KPROBES
+        ---help---
+        This module allows for capturing the changes to SCTP association
+        state in response to incoming packets. It is used for debugging
+        SCTP congestion control algorithms. If you don't understand
+        what was just said, you don't need it: say N.
+
+        To compile this code as a module, choose M here: the
+        module will be called sctp_probe.
+
 config SCTP_DBG_MSG
 	bool "SCTP: Debug messages"
 	help

net/sctp/Makefile

@@ -3,6 +3,7 @@
 #
 
 obj-$(CONFIG_IP_SCTP) += sctp.o
+obj-$(CONFIG_NET_SCTPPROBE) += sctp_probe.o
 
 sctp-y := sm_statetable.o sm_statefuns.o sm_sideeffect.o \
 	  protocol.o endpointola.o associola.o \
@@ -11,6 +12,8 @@ sctp-y := sm_statetable.o sm_statefuns.o sm_sideeffect.o \
 	  tsnmap.o bind_addr.o socket.o primitive.o \
 	  output.o input.o debug.o ssnmap.o auth.o
 
+sctp_probe-y := probe.o
+
 sctp-$(CONFIG_SCTP_DBG_OBJCNT) += objcnt.o
 sctp-$(CONFIG_PROC_FS) += proc.o
 sctp-$(CONFIG_SYSCTL) += sysctl.o

net/sctp/probe.c

@@ -0,0 +1,213 @@
+/*
+ * sctp_probe - Observe the SCTP flow with kprobes.
+ *
+ * The idea for this came from Werner Almesberger's umlsim
+ * Copyright (C) 2004, Stephen Hemminger <shemminger@osdl.org>
+ *
+ * Modified for SCTP from Stephen Hemminger's code
+ * Copyright (C) 2010, Wei Yongjun <yjwei@cn.fujitsu.com>
+ *
+ * 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, or
+ * (at your option) any later version.
+ *
+ * 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/sctp.h>
+#include <linux/proc_fs.h>
+#include <linux/module.h>
+#include <linux/kfifo.h>
+#include <linux/time.h>
+#include <net/net_namespace.h>
+
+#include <net/sctp/sctp.h>
+#include <net/sctp/sm.h>
+
+MODULE_AUTHOR("Wei Yongjun <yjwei@cn.fujitsu.com>");
+MODULE_DESCRIPTION("SCTP snooper");
+MODULE_LICENSE("GPL");
+
+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 = 64 * 1024;
+MODULE_PARM_DESC(bufsize, "Log buffer size (default 64k)");
+module_param(bufsize, int, 0);
+
+static int full __read_mostly = 1;
+MODULE_PARM_DESC(full, "Full log (1=every ack packet received,  0=only cwnd changes)");
+module_param(full, int, 0);
+
+static const char procname[] = "sctpprobe";
+
+static struct {
+	struct kfifo	  fifo;
+	spinlock_t	  lock;
+	wait_queue_head_t wait;
+	struct timespec	  tstart;
+} sctpw;
+
+static void printl(const char *fmt, ...)
+{
+	va_list args;
+	int len;
+	char tbuf[256];
+
+	va_start(args, fmt);
+	len = vscnprintf(tbuf, sizeof(tbuf), fmt, args);
+	va_end(args);
+
+	kfifo_in_locked(&sctpw.fifo, tbuf, len, &sctpw.lock);
+	wake_up(&sctpw.wait);
+}
+
+static int sctpprobe_open(struct inode *inode, struct file *file)
+{
+	kfifo_reset(&sctpw.fifo);
+	getnstimeofday(&sctpw.tstart);
+
+	return 0;
+}
+
+static ssize_t sctpprobe_read(struct file *file, char __user *buf,
+			      size_t len, loff_t *ppos)
+{
+	int error = 0, cnt = 0;
+	unsigned char *tbuf;
+
+	if (!buf)
+		return -EINVAL;
+
+	if (len == 0)
+		return 0;
+
+	tbuf = vmalloc(len);
+	if (!tbuf)
+		return -ENOMEM;
+
+	error = wait_event_interruptible(sctpw.wait,
+					 kfifo_len(&sctpw.fifo) != 0);
+	if (error)
+		goto out_free;
+
+	cnt = kfifo_out_locked(&sctpw.fifo, tbuf, len, &sctpw.lock);
+	error = copy_to_user(buf, tbuf, cnt) ? -EFAULT : 0;
+
+out_free:
+	vfree(tbuf);
+
+	return error ? error : cnt;
+}
+
+static const struct file_operations sctpprobe_fops = {
+	.owner	= THIS_MODULE,
+	.open	= sctpprobe_open,
+	.read	= sctpprobe_read,
+};
+
+sctp_disposition_t jsctp_sf_eat_sack(const struct sctp_endpoint *ep,
+				     const struct sctp_association *asoc,
+				     const sctp_subtype_t type,
+				     void *arg,
+				     sctp_cmd_seq_t *commands)
+{
+	struct sctp_transport *sp;
+	static __u32 lcwnd = 0;
+	struct timespec now;
+
+	sp = asoc->peer.primary_path;
+
+	if ((full || sp->cwnd != lcwnd) &&
+	    (!port || asoc->peer.port == port ||
+	     ep->base.bind_addr.port == port)) {
+		lcwnd = sp->cwnd;
+
+		getnstimeofday(&now);
+		now = timespec_sub(now, sctpw.tstart);
+
+		printl("%lu.%06lu ", (unsigned long) now.tv_sec,
+		       (unsigned long) now.tv_nsec / NSEC_PER_USEC);
+
+		printl("%p %5d %5d %5d %8d %5d ", asoc,
+		       ep->base.bind_addr.port, asoc->peer.port,
+		       asoc->pathmtu, asoc->peer.rwnd, asoc->unack_data);
+
+		list_for_each_entry(sp, &asoc->peer.transport_addr_list,
+					transports) {
+			if (sp == asoc->peer.primary_path)
+				printl("*");
+
+			if (sp->ipaddr.sa.sa_family == AF_INET)
+				printl("%pI4 ", &sp->ipaddr.v4.sin_addr);
+			else
+				printl("%pI6 ", &sp->ipaddr.v6.sin6_addr);
+
+			printl("%2u %8u %8u %8u %8u %8u ",
+			       sp->state, sp->cwnd, sp->ssthresh,
+			       sp->flight_size, sp->partial_bytes_acked,
+			       sp->pathmtu);
+		}
+		printl("\n");
+	}
+
+	jprobe_return();
+	return 0;
+}
+
+static struct jprobe sctp_recv_probe = {
+	.kp	= {
+		.symbol_name = "sctp_sf_eat_sack_6_2",
+	},
+	.entry	= jsctp_sf_eat_sack,
+};
+
+static __init int sctpprobe_init(void)
+{
+	int ret = -ENOMEM;
+
+	init_waitqueue_head(&sctpw.wait);
+	spin_lock_init(&sctpw.lock);
+	if (kfifo_alloc(&sctpw.fifo, bufsize, GFP_KERNEL))
+		return ret;
+
+	if (!proc_net_fops_create(&init_net, procname, S_IRUSR,
+				  &sctpprobe_fops))
+		goto free_kfifo;
+
+	ret = register_jprobe(&sctp_recv_probe);
+	if (ret)
+		goto remove_proc;
+
+	pr_info("SCTP probe registered (port=%d)\n", port);
+
+	return 0;
+
+remove_proc:
+	proc_net_remove(&init_net, procname);
+free_kfifo:
+	kfifo_free(&sctpw.fifo);
+	return ret;
+}
+
+static __exit void sctpprobe_exit(void)
+{
+	kfifo_free(&sctpw.fifo);
+	proc_net_remove(&init_net, procname);
+	unregister_jprobe(&sctp_recv_probe);
+}
+
+module_init(sctpprobe_init);
+module_exit(sctpprobe_exit);