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 = {
 103                 .symbol_name    = "tcp_sendmsg",
 104         },
 105         .entry  = JPROBE_ENTRY(jtcp_sendmsg),
 106 };
 107
 108
 109 static int tcpprobe_open(struct inode * inode, struct file * file)
 110 {
 111         kfifo_reset(tcpw.fifo);
 112         do_gettimeofday(&tcpw.tstart);
 113         return 0;
 114 }
 115
 116 static ssize_t tcpprobe_read(struct file *file, char __user *buf,
 117                              size_t len, loff_t *ppos)
 118 {
 119         int error = 0, cnt = 0;
 120         unsigned char *tbuf;
 121
 122         if (!buf || len < 0)
 123                 return -EINVAL;
 124
 125         if (len == 0)
 126                 return 0;
 127
 128         tbuf = vmalloc(len);
 129         if (!tbuf)
 130                 return -ENOMEM;
 131
 132         error = wait_event_interruptible(tcpw.wait,
 133                                          __kfifo_len(tcpw.fifo) != 0);
 134         if (error)
 135                 goto out_free;
 136
 137         cnt = kfifo_get(tcpw.fifo, tbuf, len);
 138         error = copy_to_user(buf, tbuf, cnt);
 139
 140 out_free:
 141         vfree(tbuf);
 142
 143         return error ? error : cnt;
 144 }
 145
 146 static struct file_operations tcpprobe_fops = {
 147         .owner   = THIS_MODULE,
 148         .open    = tcpprobe_open,
 149         .read    = tcpprobe_read,
 150 };
 151
 152 static __init int tcpprobe_init(void)
 153 {
 154         int ret = -ENOMEM;
 155
 156         init_waitqueue_head(&tcpw.wait);
 157         spin_lock_init(&tcpw.lock);
 158         tcpw.fifo = kfifo_alloc(bufsize, GFP_KERNEL, &tcpw.lock);
 159
 160         if (!proc_net_fops_create(procname, S_IRUSR, &tcpprobe_fops))
 161                 goto err0;
 162
 163         ret = register_jprobe(&tcp_send_probe);
 164         if (ret)
 165                 goto err1;
 166
 167         pr_info("TCP watch registered (port=%d)\n", port);
 168         return 0;
 169  err1:
 170         proc_net_remove(procname);
 171  err0:
 172         kfifo_free(tcpw.fifo);
 173         return ret;
 174 }
 175 module_init(tcpprobe_init);
 176
 177 static __exit void tcpprobe_exit(void)
 178 {
 179         kfifo_free(tcpw.fifo);
 180         proc_net_remove(procname);
 181         unregister_jprobe(&tcp_send_probe);
 182
 183 }
 184 module_exit(tcpprobe_exit);