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Linux/net/dccp/timer.c

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  1 /*
  2  *  net/dccp/timer.c
  3  *
  4  *  An implementation of the DCCP protocol
  5  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
  6  *
  7  *      This program is free software; you can redistribute it and/or
  8  *      modify it under the terms of the GNU General Public License
  9  *      as published by the Free Software Foundation; either version
 10  *      2 of the License, or (at your option) any later version.
 11  */
 12 
 13 #include <linux/dccp.h>
 14 #include <linux/skbuff.h>
 15 #include <linux/export.h>
 16 
 17 #include "dccp.h"
 18 
 19 /* sysctl variables governing numbers of retransmission attempts */
 20 int  sysctl_dccp_request_retries        __read_mostly = TCP_SYN_RETRIES;
 21 int  sysctl_dccp_retries1               __read_mostly = TCP_RETR1;
 22 int  sysctl_dccp_retries2               __read_mostly = TCP_RETR2;
 23 
 24 static void dccp_write_err(struct sock *sk)
 25 {
 26         sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
 27         sk->sk_error_report(sk);
 28 
 29         dccp_send_reset(sk, DCCP_RESET_CODE_ABORTED);
 30         dccp_done(sk);
 31         DCCP_INC_STATS_BH(DCCP_MIB_ABORTONTIMEOUT);
 32 }
 33 
 34 /* A write timeout has occurred. Process the after effects. */
 35 static int dccp_write_timeout(struct sock *sk)
 36 {
 37         const struct inet_connection_sock *icsk = inet_csk(sk);
 38         int retry_until;
 39 
 40         if (sk->sk_state == DCCP_REQUESTING || sk->sk_state == DCCP_PARTOPEN) {
 41                 if (icsk->icsk_retransmits != 0)
 42                         dst_negative_advice(sk);
 43                 retry_until = icsk->icsk_syn_retries ?
 44                             : sysctl_dccp_request_retries;
 45         } else {
 46                 if (icsk->icsk_retransmits >= sysctl_dccp_retries1) {
 47                         /* NOTE. draft-ietf-tcpimpl-pmtud-01.txt requires pmtu
 48                            black hole detection. :-(
 49 
 50                            It is place to make it. It is not made. I do not want
 51                            to make it. It is disguisting. It does not work in any
 52                            case. Let me to cite the same draft, which requires for
 53                            us to implement this:
 54 
 55    "The one security concern raised by this memo is that ICMP black holes
 56    are often caused by over-zealous security administrators who block
 57    all ICMP messages.  It is vitally important that those who design and
 58    deploy security systems understand the impact of strict filtering on
 59    upper-layer protocols.  The safest web site in the world is worthless
 60    if most TCP implementations cannot transfer data from it.  It would
 61    be far nicer to have all of the black holes fixed rather than fixing
 62    all of the TCP implementations."
 63 
 64                            Golden words :-).
 65                    */
 66 
 67                         dst_negative_advice(sk);
 68                 }
 69 
 70                 retry_until = sysctl_dccp_retries2;
 71                 /*
 72                  * FIXME: see tcp_write_timout and tcp_out_of_resources
 73                  */
 74         }
 75 
 76         if (icsk->icsk_retransmits >= retry_until) {
 77                 /* Has it gone just too far? */
 78                 dccp_write_err(sk);
 79                 return 1;
 80         }
 81         return 0;
 82 }
 83 
 84 /*
 85  *      The DCCP retransmit timer.
 86  */
 87 static void dccp_retransmit_timer(struct sock *sk)
 88 {
 89         struct inet_connection_sock *icsk = inet_csk(sk);
 90 
 91         /*
 92          * More than than 4MSL (8 minutes) has passed, a RESET(aborted) was
 93          * sent, no need to retransmit, this sock is dead.
 94          */
 95         if (dccp_write_timeout(sk))
 96                 return;
 97 
 98         /*
 99          * We want to know the number of packets retransmitted, not the
100          * total number of retransmissions of clones of original packets.
101          */
102         if (icsk->icsk_retransmits == 0)
103                 DCCP_INC_STATS_BH(DCCP_MIB_TIMEOUTS);
104 
105         if (dccp_retransmit_skb(sk) != 0) {
106                 /*
107                  * Retransmission failed because of local congestion,
108                  * do not backoff.
109                  */
110                 if (--icsk->icsk_retransmits == 0)
111                         icsk->icsk_retransmits = 1;
112                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
113                                           min(icsk->icsk_rto,
114                                               TCP_RESOURCE_PROBE_INTERVAL),
115                                           DCCP_RTO_MAX);
116                 return;
117         }
118 
119         icsk->icsk_backoff++;
120 
121         icsk->icsk_rto = min(icsk->icsk_rto << 1, DCCP_RTO_MAX);
122         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto,
123                                   DCCP_RTO_MAX);
124         if (icsk->icsk_retransmits > sysctl_dccp_retries1)
125                 __sk_dst_reset(sk);
126 }
127 
128 static void dccp_write_timer(unsigned long data)
129 {
130         struct sock *sk = (struct sock *)data;
131         struct inet_connection_sock *icsk = inet_csk(sk);
132         int event = 0;
133 
134         bh_lock_sock(sk);
135         if (sock_owned_by_user(sk)) {
136                 /* Try again later */
137                 sk_reset_timer(sk, &icsk->icsk_retransmit_timer,
138                                jiffies + (HZ / 20));
139                 goto out;
140         }
141 
142         if (sk->sk_state == DCCP_CLOSED || !icsk->icsk_pending)
143                 goto out;
144 
145         if (time_after(icsk->icsk_timeout, jiffies)) {
146                 sk_reset_timer(sk, &icsk->icsk_retransmit_timer,
147                                icsk->icsk_timeout);
148                 goto out;
149         }
150 
151         event = icsk->icsk_pending;
152         icsk->icsk_pending = 0;
153 
154         switch (event) {
155         case ICSK_TIME_RETRANS:
156                 dccp_retransmit_timer(sk);
157                 break;
158         }
159 out:
160         bh_unlock_sock(sk);
161         sock_put(sk);
162 }
163 
164 /*
165  *      Timer for listening sockets
166  */
167 static void dccp_response_timer(struct sock *sk)
168 {
169         inet_csk_reqsk_queue_prune(sk, TCP_SYNQ_INTERVAL, DCCP_TIMEOUT_INIT,
170                                    DCCP_RTO_MAX);
171 }
172 
173 static void dccp_keepalive_timer(unsigned long data)
174 {
175         struct sock *sk = (struct sock *)data;
176 
177         /* Only process if socket is not in use. */
178         bh_lock_sock(sk);
179         if (sock_owned_by_user(sk)) {
180                 /* Try again later. */
181                 inet_csk_reset_keepalive_timer(sk, HZ / 20);
182                 goto out;
183         }
184 
185         if (sk->sk_state == DCCP_LISTEN) {
186                 dccp_response_timer(sk);
187                 goto out;
188         }
189 out:
190         bh_unlock_sock(sk);
191         sock_put(sk);
192 }
193 
194 /* This is the same as tcp_delack_timer, sans prequeue & mem_reclaim stuff */
195 static void dccp_delack_timer(unsigned long data)
196 {
197         struct sock *sk = (struct sock *)data;
198         struct inet_connection_sock *icsk = inet_csk(sk);
199 
200         bh_lock_sock(sk);
201         if (sock_owned_by_user(sk)) {
202                 /* Try again later. */
203                 icsk->icsk_ack.blocked = 1;
204                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
205                 sk_reset_timer(sk, &icsk->icsk_delack_timer,
206                                jiffies + TCP_DELACK_MIN);
207                 goto out;
208         }
209 
210         if (sk->sk_state == DCCP_CLOSED ||
211             !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
212                 goto out;
213         if (time_after(icsk->icsk_ack.timeout, jiffies)) {
214                 sk_reset_timer(sk, &icsk->icsk_delack_timer,
215                                icsk->icsk_ack.timeout);
216                 goto out;
217         }
218 
219         icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
220 
221         if (inet_csk_ack_scheduled(sk)) {
222                 if (!icsk->icsk_ack.pingpong) {
223                         /* Delayed ACK missed: inflate ATO. */
224                         icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1,
225                                                  icsk->icsk_rto);
226                 } else {
227                         /* Delayed ACK missed: leave pingpong mode and
228                          * deflate ATO.
229                          */
230                         icsk->icsk_ack.pingpong = 0;
231                         icsk->icsk_ack.ato = TCP_ATO_MIN;
232                 }
233                 dccp_send_ack(sk);
234                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKS);
235         }
236 out:
237         bh_unlock_sock(sk);
238         sock_put(sk);
239 }
240 
241 /**
242  * dccp_write_xmitlet  -  Workhorse for CCID packet dequeueing interface
243  * See the comments above %ccid_dequeueing_decision for supported modes.
244  */
245 static void dccp_write_xmitlet(unsigned long data)
246 {
247         struct sock *sk = (struct sock *)data;
248 
249         bh_lock_sock(sk);
250         if (sock_owned_by_user(sk))
251                 sk_reset_timer(sk, &dccp_sk(sk)->dccps_xmit_timer, jiffies + 1);
252         else
253                 dccp_write_xmit(sk);
254         bh_unlock_sock(sk);
255 }
256 
257 static void dccp_write_xmit_timer(unsigned long data)
258 {
259         dccp_write_xmitlet(data);
260         sock_put((struct sock *)data);
261 }
262 
263 void dccp_init_xmit_timers(struct sock *sk)
264 {
265         struct dccp_sock *dp = dccp_sk(sk);
266 
267         tasklet_init(&dp->dccps_xmitlet, dccp_write_xmitlet, (unsigned long)sk);
268         setup_timer(&dp->dccps_xmit_timer, dccp_write_xmit_timer,
269                                                              (unsigned long)sk);
270         inet_csk_init_xmit_timers(sk, &dccp_write_timer, &dccp_delack_timer,
271                                   &dccp_keepalive_timer);
272 }
273 
274 static ktime_t dccp_timestamp_seed;
275 /**
276  * dccp_timestamp  -  10s of microseconds time source
277  * Returns the number of 10s of microseconds since loading DCCP. This is native
278  * DCCP time difference format (RFC 4340, sec. 13).
279  * Please note: This will wrap around about circa every 11.9 hours.
280  */
281 u32 dccp_timestamp(void)
282 {
283         s64 delta = ktime_us_delta(ktime_get_real(), dccp_timestamp_seed);
284 
285         do_div(delta, 10);
286         return delta;
287 }
288 EXPORT_SYMBOL_GPL(dccp_timestamp);
289 
290 void __init dccp_timestamping_init(void)
291 {
292         dccp_timestamp_seed = ktime_get_real();
293 }
294 

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