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>

3 files changed, 228 insertions, 0 deletions

diff --git a/net/sctp/Kconfig b/net/sctp/Kconfig
index 58b3e882a187..126b014eb79b 100644
--- a/net/sctp/Kconfig
+++ b/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
diff --git a/net/sctp/Makefile b/net/sctp/Makefile
index 6b794734380a..5c30b7a873df 100644
--- a/net/sctp/Makefile
+++ b/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
diff --git a/net/sctp/probe.c b/net/sctp/probe.c
new file mode 100644
index 000000000000..8f025d5831aa
--- /dev/null
+++ b/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);