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 {
  67         va_list args;
  68         int len;
  69         struct timespec tv;
  70         char tbuf[256];
  71
  72         va_start(args, fmt);
  73         /* want monotonic time since start of tcp_probe */
  74         tv = ktime_to_timespec(ktime_sub(ktime_get(), tcpw.start));
  75
  76         len = sprintf(tbuf, "%lu.%09lu ",
  77                       (unsigned long) tv.tv_sec, (unsigned long) tv.tv_nsec);
  78         len += vscnprintf(tbuf+len, sizeof(tbuf)-len, fmt, args);
  79         va_end(args);
  80
  81         kfifo_put(tcpw.fifo, tbuf, len);
  82         wake_up(&tcpw.wait);
  83 }
  84
  85 /*
  86  * Hook inserted to be called before each receive packet.
  87  * Note: arguments must match tcp_rcv_established()!
  88  */
  89 static int jtcp_rcv_established(struct sock *sk, struct sk_buff *skb,
  90                                struct tcphdr *th, unsigned len)
  91 {
  92         const struct tcp_sock *tp = tcp_sk(sk);
  93         const struct inet_sock *inet = inet_sk(sk);
  94
  95         /* Only update if port matches */
  96         if ((port == 0 || ntohs(inet->dport) == port || ntohs(inet->sport) == port)
  97             && (full || tp->snd_cwnd != tcpw.lastcwnd)) {
  98                 printl("%d.%d.%d.%d:%u %d.%d.%d.%d:%u %d %#x %#x %u %u %u\n",
  99                        NIPQUAD(inet->saddr), ntohs(inet->sport),
 100                        NIPQUAD(inet->daddr), ntohs(inet->dport),
 101                        skb->len, tp->snd_nxt, tp->snd_una,
 102                        tp->snd_cwnd, tcp_current_ssthresh(sk),
 103                        tp->snd_wnd, tp->srtt >> 3);
 104                 tcpw.lastcwnd = tp->snd_cwnd;
 105         }
 106
 107         jprobe_return();
 108         return 0;
 109 }
 110
 111 static struct jprobe tcp_probe = {
 112         .kp = {
 113                 .symbol_name    = "tcp_rcv_established",
 114         },
 115         .entry  = JPROBE_ENTRY(jtcp_rcv_established),
 116 };
 117
 118
 119 static int tcpprobe_open(struct inode * inode, struct file * file)
 120 {
 121         kfifo_reset(tcpw.fifo);
 122         tcpw.start = ktime_get();
 123         return 0;
 124 }
 125
 126 static ssize_t tcpprobe_read(struct file *file, char __user *buf,
 127                              size_t len, loff_t *ppos)
 128 {
 129         int error = 0, cnt = 0;
 130         unsigned char *tbuf;
 131
 132         if (!buf || len < 0)
 133                 return -EINVAL;
 134
 135         if (len == 0)
 136                 return 0;
 137
 138         tbuf = vmalloc(len);
 139         if (!tbuf)
 140                 return -ENOMEM;
 141
 142         error = wait_event_interruptible(tcpw.wait,
 143                                          __kfifo_len(tcpw.fifo) != 0);
 144         if (error)
 145                 goto out_free;
 146
 147         cnt = kfifo_get(tcpw.fifo, tbuf, len);
 148         error = copy_to_user(buf, tbuf, cnt);
 149
 150 out_free:
 151         vfree(tbuf);
 152
 153         return error ? error : cnt;
 154 }
 155
 156 static const struct file_operations tcpprobe_fops = {
 157         .owner   = THIS_MODULE,
 158         .open    = tcpprobe_open,
 159         .read    = tcpprobe_read,
 160 };
 161
 162 static __init int tcpprobe_init(void)
 163 {
 164         int ret = -ENOMEM;
 165
 166         init_waitqueue_head(&tcpw.wait);
 167         spin_lock_init(&tcpw.lock);
 168         tcpw.fifo = kfifo_alloc(bufsize, GFP_KERNEL, &tcpw.lock);
 169         if (IS_ERR(tcpw.fifo))
 170                 return PTR_ERR(tcpw.fifo);
 171
 172         if (!proc_net_fops_create(procname, S_IRUSR, &tcpprobe_fops))
 173                 goto err0;
 174
 175         ret = register_jprobe(&tcp_probe);
 176         if (ret)
 177                 goto err1;
 178
 179         pr_info("TCP watch registered (port=%d)\n", port);
 180         return 0;
 181  err1:
 182         proc_net_remove(procname);
 183  err0:
 184         kfifo_free(tcpw.fifo);
 185         return ret;
 186 }
 187 module_init(tcpprobe_init);
 188
 189 static __exit void tcpprobe_exit(void)
 190 {
 191         kfifo_free(tcpw.fifo);
 192         proc_net_remove(procname);
 193         unregister_jprobe(&tcp_probe);
 194
 195 }
 196 module_exit(tcpprobe_exit);