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.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19  */
  20
  21 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  22
  23 #include <linux/kernel.h>
  24 #include <linux/kprobes.h>
  25 #include <linux/socket.h>
  26 #include <linux/tcp.h>
  27 #include <linux/slab.h>
  28 #include <linux/proc_fs.h>
  29 #include <linux/module.h>
  30 #include <linux/ktime.h>
  31 #include <linux/time.h>
  32 #include <net/net_namespace.h>
  33
  34 #include <net/tcp.h>
  35
  36 MODULE_AUTHOR("Stephen Hemminger <shemminger@linux-foundation.org>");
  37 MODULE_DESCRIPTION("TCP cwnd snooper");
  38 MODULE_LICENSE("GPL");
  39 MODULE_VERSION("1.1");
  40
  41 static int port __read_mostly;
  42 MODULE_PARM_DESC(port, "Port to match (0=all)");
  43 module_param(port, int, 0);
  44
  45 static unsigned int bufsize __read_mostly = 4096;
  46 MODULE_PARM_DESC(bufsize, "Log buffer size in packets (4096)");
  47 module_param(bufsize, uint, 0);
  48
  49 static unsigned int fwmark __read_mostly;
  50 MODULE_PARM_DESC(fwmark, "skb mark to match (0=no mark)");
  51 module_param(fwmark, uint, 0);
  52
  53 static int full __read_mostly;
  54 MODULE_PARM_DESC(full, "Full log (1=every ack packet received,  0=only cwnd changes)");
  55 module_param(full, int, 0);
  56
  57 static const char procname[] = "tcpprobe";
  58
  59 struct tcp_log {
  60         ktime_t tstamp;
  61         union {
  62                 struct sockaddr         raw;
  63                 struct sockaddr_in      v4;
  64                 struct sockaddr_in6     v6;
  65         }       src, dst;
  66         u16     length;
  67         u32     snd_nxt;
  68         u32     snd_una;
  69         u32     snd_wnd;
  70         u32     rcv_wnd;
  71         u32     snd_cwnd;
  72         u32     ssthresh;
  73         u32     srtt;
  74 };
  75
  76 static struct {
  77         spinlock_t      lock;
  78         wait_queue_head_t wait;
  79         ktime_t         start;
  80         u32             lastcwnd;
  81
  82         unsigned long   head, tail;
  83         struct tcp_log  *log;
  84 } tcp_probe;
  85
  86 static inline int tcp_probe_used(void)
  87 {
  88         return (tcp_probe.head - tcp_probe.tail) & (bufsize - 1);
  89 }
  90
  91 static inline int tcp_probe_avail(void)
  92 {
  93         return bufsize - tcp_probe_used() - 1;
  94 }
  95
  96 #define tcp_probe_copy_fl_to_si4(inet, si4, mem)                \
  97         do {                                                    \
  98                 si4.sin_family = AF_INET;                       \
  99                 si4.sin_port = inet->inet_##mem##port;          \
 100                 si4.sin_addr.s_addr = inet->inet_##mem##addr;   \
 101         } while (0)                                             \
 102
 103 /*
 104  * Hook inserted to be called before each receive packet.
 105  * Note: arguments must match tcp_rcv_established()!
 106  */
 107 static void jtcp_rcv_established(struct sock *sk, struct sk_buff *skb,
 108                                  const struct tcphdr *th, unsigned int len)
 109 {
 110         const struct tcp_sock *tp = tcp_sk(sk);
 111         const struct inet_sock *inet = inet_sk(sk);
 112
 113         /* Only update if port or skb mark matches */
 114         if (((port == 0 && fwmark == 0) ||
 115              ntohs(inet->inet_dport) == port ||
 116              ntohs(inet->inet_sport) == port ||
 117              (fwmark > 0 && skb->mark == fwmark)) &&
 118             (full || tp->snd_cwnd != tcp_probe.lastcwnd)) {
 119
 120                 spin_lock(&tcp_probe.lock);
 121                 /* If log fills, just silently drop */
 122                 if (tcp_probe_avail() > 1) {
 123                         struct tcp_log *p = tcp_probe.log + tcp_probe.head;
 124
 125                         p->tstamp = ktime_get();
 126                         switch (sk->sk_family) {
 127                         case AF_INET:
 128                                 tcp_probe_copy_fl_to_si4(inet, p->src.v4, s);
 129                                 tcp_probe_copy_fl_to_si4(inet, p->dst.v4, d);
 130                                 break;
 131                         case AF_INET6:
 132                                 memset(&p->src.v6, 0, sizeof(p->src.v6));
 133                                 memset(&p->dst.v6, 0, sizeof(p->dst.v6));
 134 #if IS_ENABLED(CONFIG_IPV6)
 135                                 p->src.v6.sin6_family = AF_INET6;
 136                                 p->src.v6.sin6_port = inet->inet_sport;
 137                                 p->src.v6.sin6_addr = inet6_sk(sk)->saddr;
 138
 139                                 p->dst.v6.sin6_family = AF_INET6;
 140                                 p->dst.v6.sin6_port = inet->inet_dport;
 141                                 p->dst.v6.sin6_addr = sk->sk_v6_daddr;
 142 #endif
 143                                 break;
 144                         default:
 145                                 BUG();
 146                         }
 147
 148                         p->length = skb->len;
 149                         p->snd_nxt = tp->snd_nxt;
 150                         p->snd_una = tp->snd_una;
 151                         p->snd_cwnd = tp->snd_cwnd;
 152                         p->snd_wnd = tp->snd_wnd;
 153                         p->rcv_wnd = tp->rcv_wnd;
 154                         p->ssthresh = tcp_current_ssthresh(sk);
 155                         p->srtt = tp->srtt_us >> 3;
 156
 157                         tcp_probe.head = (tcp_probe.head + 1) & (bufsize - 1);
 158                 }
 159                 tcp_probe.lastcwnd = tp->snd_cwnd;
 160                 spin_unlock(&tcp_probe.lock);
 161
 162                 wake_up(&tcp_probe.wait);
 163         }
 164
 165         jprobe_return();
 166 }
 167
 168 static struct jprobe tcp_jprobe = {
 169         .kp = {
 170                 .symbol_name    = "tcp_rcv_established",
 171         },
 172         .entry  = jtcp_rcv_established,
 173 };
 174
 175 static int tcpprobe_open(struct inode *inode, struct file *file)
 176 {
 177         /* Reset (empty) log */
 178         spin_lock_bh(&tcp_probe.lock);
 179         tcp_probe.head = tcp_probe.tail = 0;
 180         tcp_probe.start = ktime_get();
 181         spin_unlock_bh(&tcp_probe.lock);
 182
 183         return 0;
 184 }
 185
 186 static int tcpprobe_sprint(char *tbuf, int n)
 187 {
 188         const struct tcp_log *p
 189                 = tcp_probe.log + tcp_probe.tail;
 190         struct timespec tv
 191                 = ktime_to_timespec(ktime_sub(p->tstamp, tcp_probe.start));
 192
 193         return scnprintf(tbuf, n,
 194                         "%lu.%09lu %pISpc %pISpc %d %#x %#x %u %u %u %u %u\n",
 195                         (unsigned long)tv.tv_sec,
 196                         (unsigned long)tv.tv_nsec,
 197                         &p->src, &p->dst, p->length, p->snd_nxt, p->snd_una,
 198                         p->snd_cwnd, p->ssthresh, p->snd_wnd, p->srtt, p->rcv_wnd);
 199 }
 200
 201 static ssize_t tcpprobe_read(struct file *file, char __user *buf,
 202                              size_t len, loff_t *ppos)
 203 {
 204         int error = 0;
 205         size_t cnt = 0;
 206
 207         if (!buf)
 208                 return -EINVAL;
 209
 210         while (cnt < len) {
 211                 char tbuf[256];
 212                 int width;
 213
 214                 /* Wait for data in buffer */
 215                 error = wait_event_interruptible(tcp_probe.wait,
 216                                                  tcp_probe_used() > 0);
 217                 if (error)
 218                         break;
 219
 220                 spin_lock_bh(&tcp_probe.lock);
 221                 if (tcp_probe.head == tcp_probe.tail) {
 222                         /* multiple readers race? */
 223                         spin_unlock_bh(&tcp_probe.lock);
 224                         continue;
 225                 }
 226
 227                 width = tcpprobe_sprint(tbuf, sizeof(tbuf));
 228
 229                 if (cnt + width < len)
 230                         tcp_probe.tail = (tcp_probe.tail + 1) & (bufsize - 1);
 231
 232                 spin_unlock_bh(&tcp_probe.lock);
 233
 234                 /* if record greater than space available
 235                    return partial buffer (so far) */
 236                 if (cnt + width >= len)
 237                         break;
 238
 239                 if (copy_to_user(buf + cnt, tbuf, width))
 240                         return -EFAULT;
 241                 cnt += width;
 242         }
 243
 244         return cnt == 0 ? error : cnt;
 245 }
 246
 247 static const struct file_operations tcpprobe_fops = {
 248         .owner   = THIS_MODULE,
 249         .open    = tcpprobe_open,
 250         .read    = tcpprobe_read,
 251         .llseek  = noop_llseek,
 252 };
 253
 254 static __init int tcpprobe_init(void)
 255 {
 256         int ret = -ENOMEM;
 257
 258         /* Warning: if the function signature of tcp_rcv_established,
 259          * has been changed, you also have to change the signature of
 260          * jtcp_rcv_established, otherwise you end up right here!
 261          */
 262         BUILD_BUG_ON(__same_type(tcp_rcv_established,
 263                                  jtcp_rcv_established) == 0);
 264
 265         init_waitqueue_head(&tcp_probe.wait);
 266         spin_lock_init(&tcp_probe.lock);
 267
 268         if (bufsize == 0)
 269                 return -EINVAL;
 270
 271         bufsize = roundup_pow_of_two(bufsize);
 272         tcp_probe.log = kcalloc(bufsize, sizeof(struct tcp_log), GFP_KERNEL);
 273         if (!tcp_probe.log)
 274                 goto err0;
 275
 276         if (!proc_create(procname, S_IRUSR, init_net.proc_net, &tcpprobe_fops))
 277                 goto err0;
 278
 279         ret = register_jprobe(&tcp_jprobe);
 280         if (ret)
 281                 goto err1;
 282
 283         pr_info("probe registered (port=%d/fwmark=%u) bufsize=%u\n",
 284                 port, fwmark, bufsize);
 285         return 0;
 286  err1:
 287         remove_proc_entry(procname, init_net.proc_net);
 288  err0:
 289         kfree(tcp_probe.log);
 290         return ret;
 291 }
 292 module_init(tcpprobe_init);
 293
 294 static __exit void tcpprobe_exit(void)
 295 {
 296         remove_proc_entry(procname, init_net.proc_net);
 297         unregister_jprobe(&tcp_jprobe);
 298         kfree(tcp_probe.log);
 299 }
 300 module_exit(tcpprobe_exit);