linux/net/ipv4/tcp_probe.c
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   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
  36MODULE_AUTHOR("Stephen Hemminger <shemminger@linux-foundation.org>");
  37MODULE_DESCRIPTION("TCP cwnd snooper");
  38MODULE_LICENSE("GPL");
  39MODULE_VERSION("1.1");
  40
  41static int port __read_mostly = 0;
  42MODULE_PARM_DESC(port, "Port to match (0=all)");
  43module_param(port, int, 0);
  44
  45static unsigned int bufsize __read_mostly = 4096;
  46MODULE_PARM_DESC(bufsize, "Log buffer size in packets (4096)");
  47module_param(bufsize, uint, 0);
  48
  49static unsigned int fwmark __read_mostly = 0;
  50MODULE_PARM_DESC(fwmark, "skb mark to match (0=no mark)");
  51module_param(fwmark, uint, 0);
  52
  53static int full __read_mostly;
  54MODULE_PARM_DESC(full, "Full log (1=every ack packet received,  0=only cwnd changes)");
  55module_param(full, int, 0);
  56
  57static const char procname[] = "tcpprobe";
  58
  59struct 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
  76static 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
  86static inline int tcp_probe_used(void)
  87{
  88        return (tcp_probe.head - tcp_probe.tail) & (bufsize - 1);
  89}
  90
  91static 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 */
 107static 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
 168static struct jprobe tcp_jprobe = {
 169        .kp = {
 170                .symbol_name    = "tcp_rcv_established",
 171        },
 172        .entry  = jtcp_rcv_established,
 173};
 174
 175static 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
 186static 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
 201static 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
 247static const struct file_operations tcpprobe_fops = {
 248        .owner   = THIS_MODULE,
 249        .open    = tcpprobe_open,
 250        .read    = tcpprobe_read,
 251        .llseek  = noop_llseek,
 252};
 253
 254static __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}
 292module_init(tcpprobe_init);
 293
 294static __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}
 300module_exit(tcpprobe_exit);
 301