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/ktime.h>
  30 #include <linux/time.h>
  31 #include <linux/vmalloc.h>
  32
  33 #include <net/tcp.h>
  34
  35 MODULE_AUTHOR("Stephen Hemminger <shemminger@linux-foundation.org>");
  36 MODULE_DESCRIPTION("TCP cwnd snooper");
  37 MODULE_LICENSE("GPL");
  38
  39 static int port __read_mostly = 0;
  40 MODULE_PARM_DESC(port, "Port to match (0=all)");
  41 module_param(port, int, 0);
  42
  43 static int bufsize __read_mostly = 64*1024;
  44 MODULE_PARM_DESC(bufsize, "Log buffer size (default 64k)");
  45 module_param(bufsize, int, 0);
  46
  47 static int full __read_mostly;
  48 MODULE_PARM_DESC(full, "Full log (1=every ack packet received,  0=only cwnd changes)");
  49 module_param(full, int, 0);
  50
  51 static const char procname[] = "tcpprobe";
  52
  53 struct {
  54         struct kfifo    *fifo;
  55         spinlock_t      lock;
  56         wait_queue_head_t wait;
  57         ktime_t         start;
  58         u32             lastcwnd;
  59 } tcpw;
  60
  61 /*
  62  * Print to log with timestamps.
  63  * FIXME: causes an extra copy
  64  */
  65 static void printl(const char *fmt, ...)
  66         __attribute__ ((format (printf, 1, 2)));
  67
  68 static void printl(const char *fmt, ...)
  69 {
  70         va_list args;
  71         int len;
  72         struct timespec tv;
  73         char tbuf[256];
  74
  75         va_start(args, fmt);
  76         /* want monotonic time since start of tcp_probe */
  77         tv = ktime_to_timespec(ktime_sub(ktime_get(), tcpw.start));
  78
  79         len = sprintf(tbuf, "%lu.%09lu ",
  80                       (unsigned long) tv.tv_sec, (unsigned long) tv.tv_nsec);
  81         len += vscnprintf(tbuf+len, sizeof(tbuf)-len, fmt, args);
  82         va_end(args);
  83
  84         kfifo_put(tcpw.fifo, tbuf, len);
  85         wake_up(&tcpw.wait);
  86 }
  87
  88 /*
  89  * Hook inserted to be called before each receive packet.
  90  * Note: arguments must match tcp_rcv_established()!
  91  */
  92 static int jtcp_rcv_established(struct sock *sk, struct sk_buff *skb,
  93                                struct tcphdr *th, unsigned len)
  94 {
  95         const struct tcp_sock *tp = tcp_sk(sk);
  96         const struct inet_sock *inet = inet_sk(sk);
  97
  98         /* Only update if port matches */
  99         if ((port == 0 || ntohs(inet->dport) == port || ntohs(inet->sport) == port)
 100             && (full || tp->snd_cwnd != tcpw.lastcwnd)) {
 101                 printl("%d.%d.%d.%d:%u %d.%d.%d.%d:%u %d %#x %#x %u %u %u %u\n",
 102                        NIPQUAD(inet->saddr), ntohs(inet->sport),
 103                        NIPQUAD(inet->daddr), ntohs(inet->dport),
 104                        skb->len, tp->snd_nxt, tp->snd_una,
 105                        tp->snd_cwnd, tcp_current_ssthresh(sk),
 106                        tp->snd_wnd, tp->srtt >> 3);
 107                 tcpw.lastcwnd = tp->snd_cwnd;
 108         }
 109
 110         jprobe_return();
 111         return 0;
 112 }
 113
 114 static struct jprobe tcp_probe = {
 115         .kp = {
 116                 .symbol_name    = "tcp_rcv_established",
 117         },
 118         .entry  = JPROBE_ENTRY(jtcp_rcv_established),
 119 };
 120
 121
 122 static int tcpprobe_open(struct inode * inode, struct file * file)
 123 {
 124         kfifo_reset(tcpw.fifo);
 125         tcpw.start = ktime_get();
 126         return 0;
 127 }
 128
 129 static ssize_t tcpprobe_read(struct file *file, char __user *buf,
 130                              size_t len, loff_t *ppos)
 131 {
 132         int error = 0, cnt = 0;
 133         unsigned char *tbuf;
 134
 135         if (!buf || len < 0)
 136                 return -EINVAL;
 137
 138         if (len == 0)
 139                 return 0;
 140
 141         tbuf = vmalloc(len);
 142         if (!tbuf)
 143                 return -ENOMEM;
 144
 145         error = wait_event_interruptible(tcpw.wait,
 146                                          __kfifo_len(tcpw.fifo) != 0);
 147         if (error)
 148                 goto out_free;
 149
 150         cnt = kfifo_get(tcpw.fifo, tbuf, len);
 151         error = copy_to_user(buf, tbuf, cnt);
 152
 153 out_free:
 154         vfree(tbuf);
 155
 156         return error ? error : cnt;
 157 }
 158
 159 static const struct file_operations tcpprobe_fops = {
 160         .owner   = THIS_MODULE,
 161         .open    = tcpprobe_open,
 162         .read    = tcpprobe_read,
 163 };
 164
 165 static __init int tcpprobe_init(void)
 166 {
 167         int ret = -ENOMEM;
 168
 169         init_waitqueue_head(&tcpw.wait);
 170         spin_lock_init(&tcpw.lock);
 171         tcpw.fifo = kfifo_alloc(bufsize, GFP_KERNEL, &tcpw.lock);
 172         if (IS_ERR(tcpw.fifo))
 173                 return PTR_ERR(tcpw.fifo);
 174
 175         if (!proc_net_fops_create(procname, S_IRUSR, &tcpprobe_fops))
 176                 goto err0;
 177
 178         ret = register_jprobe(&tcp_probe);
 179         if (ret)
 180                 goto err1;
 181
 182         pr_info("TCP watch registered (port=%d)\n", port);
 183         return 0;
 184  err1:
 185         proc_net_remove(procname);
 186  err0:
 187         kfifo_free(tcpw.fifo);
 188         return ret;
 189 }
 190 module_init(tcpprobe_init);
 191
 192 static __exit void tcpprobe_exit(void)
 193 {
 194         kfifo_free(tcpw.fifo);
 195         proc_net_remove(procname);
 196         unregister_jprobe(&tcp_probe);
 197
 198 }
 199 module_exit(tcpprobe_exit);