net/dccp/timer.c

   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(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(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 static void dccp_keepalive_timer(unsigned long data)
 165 {
 166         struct sock *sk = (struct sock *)data;
 167
 168         pr_err("dccp should not use a keepalive timer !\n");
 169         sock_put(sk);
 170 }
 171
 172 /* This is the same as tcp_delack_timer, sans prequeue & mem_reclaim stuff */
 173 static void dccp_delack_timer(unsigned long data)
 174 {
 175         struct sock *sk = (struct sock *)data;
 176         struct inet_connection_sock *icsk = inet_csk(sk);
 177
 178         bh_lock_sock(sk);
 179         if (sock_owned_by_user(sk)) {
 180                 /* Try again later. */
 181                 icsk->icsk_ack.blocked = 1;
 182                 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
 183                 sk_reset_timer(sk, &icsk->icsk_delack_timer,
 184                                jiffies + TCP_DELACK_MIN);
 185                 goto out;
 186         }
 187
 188         if (sk->sk_state == DCCP_CLOSED ||
 189             !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
 190                 goto out;
 191         if (time_after(icsk->icsk_ack.timeout, jiffies)) {
 192                 sk_reset_timer(sk, &icsk->icsk_delack_timer,
 193                                icsk->icsk_ack.timeout);
 194                 goto out;
 195         }
 196
 197         icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
 198
 199         if (inet_csk_ack_scheduled(sk)) {
 200                 if (!icsk->icsk_ack.pingpong) {
 201                         /* Delayed ACK missed: inflate ATO. */
 202                         icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1,
 203                                                  icsk->icsk_rto);
 204                 } else {
 205                         /* Delayed ACK missed: leave pingpong mode and
 206                          * deflate ATO.
 207                          */
 208                         icsk->icsk_ack.pingpong = 0;
 209                         icsk->icsk_ack.ato = TCP_ATO_MIN;
 210                 }
 211                 dccp_send_ack(sk);
 212                 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKS);
 213         }
 214 out:
 215         bh_unlock_sock(sk);
 216         sock_put(sk);
 217 }
 218
 219 /**
 220  * dccp_write_xmitlet  -  Workhorse for CCID packet dequeueing interface
 221  * See the comments above %ccid_dequeueing_decision for supported modes.
 222  */
 223 static void dccp_write_xmitlet(unsigned long data)
 224 {
 225         struct sock *sk = (struct sock *)data;
 226
 227         bh_lock_sock(sk);
 228         if (sock_owned_by_user(sk))
 229                 sk_reset_timer(sk, &dccp_sk(sk)->dccps_xmit_timer, jiffies + 1);
 230         else
 231                 dccp_write_xmit(sk);
 232         bh_unlock_sock(sk);
 233 }
 234
 235 static void dccp_write_xmit_timer(unsigned long data)
 236 {
 237         dccp_write_xmitlet(data);
 238         sock_put((struct sock *)data);
 239 }
 240
 241 void dccp_init_xmit_timers(struct sock *sk)
 242 {
 243         struct dccp_sock *dp = dccp_sk(sk);
 244
 245         tasklet_init(&dp->dccps_xmitlet, dccp_write_xmitlet, (unsigned long)sk);
 246         setup_timer(&dp->dccps_xmit_timer, dccp_write_xmit_timer,
 247                                                              (unsigned long)sk);
 248         inet_csk_init_xmit_timers(sk, &dccp_write_timer, &dccp_delack_timer,
 249                                   &dccp_keepalive_timer);
 250 }
 251
 252 static ktime_t dccp_timestamp_seed;
 253 /**
 254  * dccp_timestamp  -  10s of microseconds time source
 255  * Returns the number of 10s of microseconds since loading DCCP. This is native
 256  * DCCP time difference format (RFC 4340, sec. 13).
 257  * Please note: This will wrap around about circa every 11.9 hours.
 258  */
 259 u32 dccp_timestamp(void)
 260 {
 261         u64 delta = (u64)ktime_us_delta(ktime_get_real(), dccp_timestamp_seed);
 262
 263         do_div(delta, 10);
 264         return delta;
 265 }
 266 EXPORT_SYMBOL_GPL(dccp_timestamp);
 267
 268 void __init dccp_timestamping_init(void)
 269 {
 270         dccp_timestamp_seed = ktime_get_real();
 271 }