probe.c

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/*
 * sctp_probe - Observe the SCTP flow with kprobes.
 *
 * The idea for this came from Werner Almesberger's umlsim
 * Copyright (C) 2004, Stephen Hemminger <[email protected]>
 *
 * Modified for SCTP from Stephen Hemminger's code
 * Copyright (C) 2010, Wei Yongjun <[email protected]>
 *
 * 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.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/kprobes.h>
#include <linux/socket.h>
#include <linux/sctp.h>
#include <linux/proc_fs.h>
#include <linux/vmalloc.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 <[email protected]>");
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,
    .llseek = noop_llseek,
};

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("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);