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#include <linux/kernel.h> 22#include <linux/kprobes.h> 23#include <linux/socket.h> 24#include <linux/tcp.h> 25#include <linux/slab.h> 26#include <linux/proc_fs.h> 27#include <linux/module.h> 28#include <linux/ktime.h> 29#include <linux/time.h> 30#include <net/net_namespace.h> 31 32#include <net/tcp.h> 33 34MODULE_AUTHOR("Stephen Hemminger <shemminger@linux-foundation.org>"); 35MODULE_DESCRIPTION("TCP cwnd snooper"); 36MODULE_LICENSE("GPL"); 37MODULE_VERSION("1.1"); 38 39static int port __read_mostly = 0; 40MODULE_PARM_DESC(port, "Port to match (0=all)"); 41module_param(port, int, 0); 42 43static unsigned int bufsize __read_mostly = 4096; 44MODULE_PARM_DESC(bufsize, "Log buffer size in packets (4096)"); 45module_param(bufsize, uint, 0); 46 47static int full __read_mostly; 48MODULE_PARM_DESC(full, "Full log (1=every ack packet received, 0=only cwnd changes)"); 49module_param(full, int, 0); 50 51static const char procname[] = "tcpprobe"; 52 53struct tcp_log { 54 ktime_t tstamp; 55 __be32 saddr, daddr; 56 __be16 sport, dport; 57 u16 length; 58 u32 snd_nxt; 59 u32 snd_una; 60 u32 snd_wnd; 61 u32 snd_cwnd; 62 u32 ssthresh; 63 u32 srtt; 64}; 65 66static struct { 67 spinlock_t lock; 68 wait_queue_head_t wait; 69 ktime_t start; 70 u32 lastcwnd; 71 72 unsigned long head, tail; 73 struct tcp_log *log; 74} tcp_probe; 75 76 77static inline int tcp_probe_used(void) 78{ 79 return (tcp_probe.head - tcp_probe.tail) & (bufsize - 1); 80} 81 82static inline int tcp_probe_avail(void) 83{ 84 return bufsize - tcp_probe_used() - 1; 85} 86 87/* 88 * Hook inserted to be called before each receive packet. 89 * Note: arguments must match tcp_rcv_established()! 90 */ 91static int jtcp_rcv_established(struct sock *sk, struct sk_buff *skb, 92 struct tcphdr *th, unsigned len) 93{ 94 const struct tcp_sock *tp = tcp_sk(sk); 95 const struct inet_sock *inet = inet_sk(sk); 96 97 /* Only update if port matches */ 98 if ((port == 0 || ntohs(inet->inet_dport) == port || 99 ntohs(inet->inet_sport) == port) && 100 (full || tp->snd_cwnd != tcp_probe.lastcwnd)) { 101 102 spin_lock(&tcp_probe.lock); 103 /* If log fills, just silently drop */ 104 if (tcp_probe_avail() > 1) { 105 struct tcp_log *p = tcp_probe.log + tcp_probe.head; 106 107 p->tstamp = ktime_get(); 108 p->saddr = inet->inet_saddr; 109 p->sport = inet->inet_sport; 110 p->daddr = inet->inet_daddr; 111 p->dport = inet->inet_dport; 112 p->length = skb->len; 113 p->snd_nxt = tp->snd_nxt; 114 p->snd_una = tp->snd_una; 115 p->snd_cwnd = tp->snd_cwnd; 116 p->snd_wnd = tp->snd_wnd; 117 p->ssthresh = tcp_current_ssthresh(sk); 118 p->srtt = tp->srtt >> 3; 119 120 tcp_probe.head = (tcp_probe.head + 1) & (bufsize - 1); 121 } 122 tcp_probe.lastcwnd = tp->snd_cwnd; 123 spin_unlock(&tcp_probe.lock); 124 125 wake_up(&tcp_probe.wait); 126 } 127 128 jprobe_return(); 129 return 0; 130} 131 132static struct jprobe tcp_jprobe = { 133 .kp = { 134 .symbol_name = "tcp_rcv_established", 135 }, 136 .entry = jtcp_rcv_established, 137}; 138 139static int tcpprobe_open(struct inode * inode, struct file * file) 140{ 141 /* Reset (empty) log */ 142 spin_lock_bh(&tcp_probe.lock); 143 tcp_probe.head = tcp_probe.tail = 0; 144 tcp_probe.start = ktime_get(); 145 spin_unlock_bh(&tcp_probe.lock); 146 147 return 0; 148} 149 150static int tcpprobe_sprint(char *tbuf, int n) 151{ 152 const struct tcp_log *p 153 = tcp_probe.log + tcp_probe.tail; 154 struct timespec tv 155 = ktime_to_timespec(ktime_sub(p->tstamp, tcp_probe.start)); 156 157 return snprintf(tbuf, n, 158 "%lu.%09lu %pI4:%u %pI4:%u %d %#x %#x %u %u %u %u\n", 159 (unsigned long) tv.tv_sec, 160 (unsigned long) tv.tv_nsec, 161 &p->saddr, ntohs(p->sport), 162 &p->daddr, ntohs(p->dport), 163 p->length, p->snd_nxt, p->snd_una, 164 p->snd_cwnd, p->ssthresh, p->snd_wnd, p->srtt); 165} 166 167static ssize_t tcpprobe_read(struct file *file, char __user *buf, 168 size_t len, loff_t *ppos) 169{ 170 int error = 0; 171 size_t cnt = 0; 172 173 if (!buf) 174 return -EINVAL; 175 176 while (cnt < len) { 177 char tbuf[128]; 178 int width; 179 180 /* Wait for data in buffer */ 181 error = wait_event_interruptible(tcp_probe.wait, 182 tcp_probe_used() > 0); 183 if (error) 184 break; 185 186 spin_lock_bh(&tcp_probe.lock); 187 if (tcp_probe.head == tcp_probe.tail) { 188 /* multiple readers race? */ 189 spin_unlock_bh(&tcp_probe.lock); 190 continue; 191 } 192 193 width = tcpprobe_sprint(tbuf, sizeof(tbuf)); 194 195 if (cnt + width < len) 196 tcp_probe.tail = (tcp_probe.tail + 1) & (bufsize - 1); 197 198 spin_unlock_bh(&tcp_probe.lock); 199 200 /* if record greater than space available 201 return partial buffer (so far) */ 202 if (cnt + width >= len) 203 break; 204 205 if (copy_to_user(buf + cnt, tbuf, width)) 206 return -EFAULT; 207 cnt += width; 208 } 209 210 return cnt == 0 ? error : cnt; 211} 212 213static const struct file_operations tcpprobe_fops = { 214 .owner = THIS_MODULE, 215 .open = tcpprobe_open, 216 .read = tcpprobe_read, 217}; 218 219static __init int tcpprobe_init(void) 220{ 221 int ret = -ENOMEM; 222 223 init_waitqueue_head(&tcp_probe.wait); 224 spin_lock_init(&tcp_probe.lock); 225 226 if (bufsize == 0) 227 return -EINVAL; 228 229 bufsize = roundup_pow_of_two(bufsize); 230 tcp_probe.log = kcalloc(bufsize, sizeof(struct tcp_log), GFP_KERNEL); 231 if (!tcp_probe.log) 232 goto err0; 233 234 if (!proc_net_fops_create(&init_net, procname, S_IRUSR, &tcpprobe_fops)) 235 goto err0; 236 237 ret = register_jprobe(&tcp_jprobe); 238 if (ret) 239 goto err1; 240 241 pr_info("TCP probe registered (port=%d) bufsize=%u\n", port, bufsize); 242 return 0; 243 err1: 244 proc_net_remove(&init_net, procname); 245 err0: 246 kfree(tcp_probe.log); 247 return ret; 248} 249module_init(tcpprobe_init); 250 251static __exit void tcpprobe_exit(void) 252{ 253 proc_net_remove(&init_net, procname); 254 unregister_jprobe(&tcp_jprobe); 255 kfree(tcp_probe.log); 256} 257module_exit(tcpprobe_exit); 258