net/ipv4/tcp_probe.c

   1 /*
   2  * tcpprobe - Observe the TCP flow with kprobes.
   3  *
   4  * The idea for this came from Werner Almesberger's umlsim
   5  * Copyright (C) 2004, Stephen Hemminger <shemminger@osdl.org>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20  */
  21
  22 #include <linux/kernel.h>
  23 #include <linux/kprobes.h>
  24 #include <linux/socket.h>
  25 #include <linux/tcp.h>
  26 #include <linux/proc_fs.h>
  27 #include <linux/module.h>
  28 #include <linux/kfifo.h>
  29 #include <linux/vmalloc.h>
  30
  31 #include <net/tcp.h>
  32
  33 MODULE_AUTHOR("Stephen Hemminger <shemminger@osdl.org>");
  34 MODULE_DESCRIPTION("TCP cwnd snooper");
  35 MODULE_LICENSE("GPL");
  36
  37 static int port = 0;
  38 MODULE_PARM_DESC(port, "Port to match (0=all)");
  39 module_param(port, int, 0);
  40
  41 static int bufsize = 64*1024;
  42 MODULE_PARM_DESC(bufsize, "Log buffer size (default 64k)");
  43 module_param(bufsize, int, 0);
  44
  45 static const char procname[] = "tcpprobe";
  46
  47 struct {
  48         struct kfifo  *fifo;
  49         spinlock_t    lock;
  50         wait_queue_head_t wait;
  51         struct timeval tstart;
  52 } tcpw;
  53
  54 static void printl(const char *fmt, ...)
  55 {
  56         va_list args;
  57         int len;
  58         struct timeval now;
  59         char tbuf[256];
  60
  61         va_start(args, fmt);
  62         do_gettimeofday(&now);
  63
  64         now.tv_sec -= tcpw.tstart.tv_sec;
  65         now.tv_usec -= tcpw.tstart.tv_usec;
  66         if (now.tv_usec < 0) {
  67                 --now.tv_sec;
  68                 now.tv_usec += 1000000;
  69         }
  70
  71         len = sprintf(tbuf, "%lu.%06lu ",
  72                       (unsigned long) now.tv_sec,
  73                       (unsigned long) now.tv_usec);
  74         len += vscnprintf(tbuf+len, sizeof(tbuf)-len, fmt, args);
  75         va_end(args);
  76
  77         kfifo_put(tcpw.fifo, tbuf, len);
  78         wake_up(&tcpw.wait);
  79 }
  80
  81 static int jtcp_sendmsg(struct kiocb *iocb, struct sock *sk,
  82                         struct msghdr *msg, size_t size)
  83 {
  84         const struct tcp_sock *tp = tcp_sk(sk);
  85         const struct inet_sock *inet = inet_sk(sk);
  86
  87         if (port == 0 || ntohs(inet->dport) == port ||
  88             ntohs(inet->sport) == port) {
  89                 printl("%d.%d.%d.%d:%u %d.%d.%d.%d:%u %d %#x %#x %u %u %u\n",
  90                        NIPQUAD(inet->saddr), ntohs(inet->sport),
  91                        NIPQUAD(inet->daddr), ntohs(inet->dport),
  92                        size, tp->snd_nxt, tp->snd_una,
  93                        tp->snd_cwnd, tcp_current_ssthresh(sk),
  94                        tp->snd_wnd);
  95         }
  96
  97         jprobe_return();
  98         return 0;
  99 }
 100
 101 static struct jprobe tcp_send_probe = {
 102         .kp = { .addr = (kprobe_opcode_t *) &tcp_sendmsg, },
 103         .entry = (kprobe_opcode_t *) &jtcp_sendmsg,
 104 };
 105
 106
 107 static int tcpprobe_open(struct inode * inode, struct file * file)
 108 {
 109         kfifo_reset(tcpw.fifo);
 110         do_gettimeofday(&tcpw.tstart);
 111         return 0;
 112 }
 113
 114 static ssize_t tcpprobe_read(struct file *file, char __user *buf,
 115                              size_t len, loff_t *ppos)
 116 {
 117         int error = 0, cnt;
 118         unsigned char *tbuf;
 119
 120         if (!buf || len < 0)
 121                 return -EINVAL;
 122
 123         if (len == 0)
 124                 return 0;
 125
 126         tbuf = vmalloc(len);
 127         if (!tbuf)
 128                 return -ENOMEM;
 129
 130         error = wait_event_interruptible(tcpw.wait,
 131                                          __kfifo_len(tcpw.fifo) != 0);
 132         if (error)
 133                 return error;
 134
 135         cnt = kfifo_get(tcpw.fifo, tbuf, len);
 136         error = copy_to_user(buf, tbuf, cnt);
 137
 138         vfree(tbuf);
 139
 140         return error ? error : cnt;
 141 }
 142
 143 static struct file_operations tcpprobe_fops = {
 144         .owner   = THIS_MODULE,
 145         .open    = tcpprobe_open,
 146         .read    = tcpprobe_read,
 147 };
 148
 149 static __init int tcpprobe_init(void)
 150 {
 151         int ret = -ENOMEM;
 152
 153         init_waitqueue_head(&tcpw.wait);
 154         spin_lock_init(&tcpw.lock);
 155         tcpw.fifo = kfifo_alloc(bufsize, GFP_KERNEL, &tcpw.lock);
 156
 157         if (!proc_net_fops_create(procname, S_IRUSR, &tcpprobe_fops))
 158                 goto err0;
 159
 160         ret = register_jprobe(&tcp_send_probe);
 161         if (ret)
 162                 goto err1;
 163
 164         pr_info("TCP watch registered (port=%d)\n", port);
 165         return 0;
 166  err1:
 167         proc_net_remove(procname);
 168  err0:
 169         kfifo_free(tcpw.fifo);
 170         return ret;
 171 }
 172 module_init(tcpprobe_init);
 173
 174 static __exit void tcpprobe_exit(void)
 175 {
 176         kfifo_free(tcpw.fifo);
 177         proc_net_remove(procname);
 178         unregister_jprobe(&tcp_send_probe);
 179
 180 }
 181 module_exit(tcpprobe_exit);