probe.c

Go to the documentation of this file.

/*
 * dccp_probe - Observe the DCCP flow with kprobes.
 *
 * The idea for this came from Werner Almesberger's umlsim
 * Copyright (C) 2004, Stephen Hemminger <[email protected]>
 *
 * Modified for DCCP from Stephen Hemminger's code
 * Copyright (C) 2006, Ian McDonald <[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.
 */

#include <linux/kernel.h>
#include <linux/kprobes.h>
#include <linux/socket.h>
#include <linux/dccp.h>
#include <linux/proc_fs.h>
#include <linux/module.h>
#include <linux/kfifo.h>
#include <linux/vmalloc.h>
#include <linux/gfp.h>
#include <net/net_namespace.h>

#include "dccp.h"
#include "ccid.h"
#include "ccids/ccid3.h"

static int port;

static int bufsize = 64 * 1024;

static const char procname[] = "dccpprobe";

static struct {
    struct kfifo      fifo;
    spinlock_t    lock;
    wait_queue_head_t wait;
    struct timespec   tstart;
} dccpw;

static void printl(const char *fmt, ...)
{
    va_list args;
    int len;
    struct timespec now;
    char tbuf[256];

    va_start(args, fmt);
    getnstimeofday(&now);

    now = timespec_sub(now, dccpw.tstart);

    len = sprintf(tbuf, "%lu.%06lu ",
              (unsigned long) now.tv_sec,
              (unsigned long) now.tv_nsec / NSEC_PER_USEC);
    len += vscnprintf(tbuf+len, sizeof(tbuf)-len, fmt, args);
    va_end(args);

    kfifo_in_locked(&dccpw.fifo, tbuf, len, &dccpw.lock);
    wake_up(&dccpw.wait);
}

static int jdccp_sendmsg(struct kiocb *iocb, struct sock *sk,
             struct msghdr *msg, size_t size)
{
    const struct inet_sock *inet = inet_sk(sk);
    struct ccid3_hc_tx_sock *hc = NULL;

    if (ccid_get_current_tx_ccid(dccp_sk(sk)) == DCCPC_CCID3)
        hc = ccid3_hc_tx_sk(sk);

    if (port == 0 || ntohs(inet->inet_dport) == port ||
        ntohs(inet->inet_sport) == port) {
        if (hc)
            printl("%pI4:%u %pI4:%u %d %d %d %d %u %llu %llu %d\n",
                   &inet->inet_saddr, ntohs(inet->inet_sport),
                   &inet->inet_daddr, ntohs(inet->inet_dport), size,
                   hc->tx_s, hc->tx_rtt, hc->tx_p,
                   hc->tx_x_calc, hc->tx_x_recv >> 6,
                   hc->tx_x >> 6, hc->tx_t_ipi);
        else
            printl("%pI4:%u %pI4:%u %d\n",
                   &inet->inet_saddr, ntohs(inet->inet_sport),
                   &inet->inet_daddr, ntohs(inet->inet_dport),
                   size);
    }

    jprobe_return();
    return 0;
}

static struct jprobe dccp_send_probe = {
    .kp = {
        .symbol_name = "dccp_sendmsg",
    },
    .entry  = jdccp_sendmsg,
};

static int dccpprobe_open(struct inode *inode, struct file *file)
{
    kfifo_reset(&dccpw.fifo);
    getnstimeofday(&dccpw.tstart);
    return 0;
}

static ssize_t dccpprobe_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(dccpw.wait,
                     kfifo_len(&dccpw.fifo) != 0);
    if (error)
        goto out_free;

    cnt = kfifo_out_locked(&dccpw.fifo, tbuf, len, &dccpw.lock);
    error = copy_to_user(buf, tbuf, cnt) ? -EFAULT : 0;

out_free:
    vfree(tbuf);

    return error ? error : cnt;
}

static const struct file_operations dccpprobe_fops = {
    .owner   = THIS_MODULE,
    .open    = dccpprobe_open,
    .read    = dccpprobe_read,
    .llseek  = noop_llseek,
};

static __init int setup_jprobe(void)
{
    int ret = register_jprobe(&dccp_send_probe);

    if (ret) {
        request_module("dccp");
        ret = register_jprobe(&dccp_send_probe);
    }
    return ret;
}

static __init int dccpprobe_init(void)
{
    int ret = -ENOMEM;

    init_waitqueue_head(&dccpw.wait);
    spin_lock_init(&dccpw.lock);
    if (kfifo_alloc(&dccpw.fifo, bufsize, GFP_KERNEL))
        return ret;
    if (!proc_net_fops_create(&init_net, procname, S_IRUSR, &dccpprobe_fops))
        goto err0;

    ret = setup_jprobe();
    if (ret)
        goto err1;

    pr_info("DCCP watch registered (port=%d)\n", port);
    return 0;
err1:
    proc_net_remove(&init_net, procname);
err0:
    kfifo_free(&dccpw.fifo);
    return ret;
}
module_init(dccpprobe_init);

static __exit void dccpprobe_exit(void)
{
    kfifo_free(&dccpw.fifo);
    proc_net_remove(&init_net, procname);
    unregister_jprobe(&dccp_send_probe);

}
module_exit(dccpprobe_exit);

MODULE_PARM_DESC(port, "Port to match (0=all)");
module_param(port, int, 0);

MODULE_PARM_DESC(bufsize, "Log buffer size (default 64k)");
module_param(bufsize, int, 0);

MODULE_AUTHOR("Ian McDonald <[email protected]>");
MODULE_DESCRIPTION("DCCP snooper");
MODULE_LICENSE("GPL");