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(struct timer_list *t)
 129 {
 130         struct inet_connection_sock *icsk =
 131                         from_timer(icsk, t, icsk_retransmit_timer);
 132         struct sock *sk = &icsk->icsk_inet.sk;
 133         int event = 0;
 134
 135         bh_lock_sock(sk);
 136         if (sock_owned_by_user(sk)) {
 137                 /* Try again later */
 138                 sk_reset_timer(sk, &icsk->icsk_retransmit_timer,
 139                                jiffies + (HZ / 20));
 140                 goto out;
 141         }
 142
 143         if (sk->sk_state == DCCP_CLOSED || !icsk->icsk_pending)
 144                 goto out;
 145
 146         if (time_after(icsk->icsk_timeout, jiffies)) {
 147                 sk_reset_timer(sk, &icsk->icsk_retransmit_timer,
 148                                icsk->icsk_timeout);
 149                 goto out;
 150         }
 151
 152         event = icsk->icsk_pending;
 153         icsk->icsk_pending = 0;
 154
 155         switch (event) {
 156         case ICSK_TIME_RETRANS:
 157                 dccp_retransmit_timer(sk);
 158                 break;
 159         }
 160 out:
 161         bh_unlock_sock(sk);
 162         sock_put(sk);
 163 }
 164
 165 static void dccp_keepalive_timer(struct timer_list *t)
 166 {
 167         struct sock *sk = from_timer(sk, t, sk_timer);
 168
 169         pr_err("dccp should not use a keepalive timer !\n");
 170         sock_put(sk);
 171 }
 172
 173 /* This is the same as tcp_delack_timer, sans prequeue & mem_reclaim stuff */
 174 static void dccp_delack_timer(struct timer_list *t)
 175 {
 176         struct inet_connection_sock *icsk =
 177                         from_timer(icsk, t, icsk_delack_timer);
 178         struct sock *sk = &icsk->icsk_inet.sk;
 179
 180         bh_lock_sock(sk);
 181         if (sock_owned_by_user(sk)) {
 182                 /* Try again later. */
 183                 icsk->icsk_ack.blocked = 1;
 184                 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
 185                 sk_reset_timer(sk, &icsk->icsk_delack_timer,
 186                                jiffies + TCP_DELACK_MIN);
 187                 goto out;
 188         }
 189
 190         if (sk->sk_state == DCCP_CLOSED ||
 191             !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
 192                 goto out;
 193         if (time_after(icsk->icsk_ack.timeout, jiffies)) {
 194                 sk_reset_timer(sk, &icsk->icsk_delack_timer,
 195                                icsk->icsk_ack.timeout);
 196                 goto out;
 197         }
 198
 199         icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
 200
 201         if (inet_csk_ack_scheduled(sk)) {
 202                 if (!icsk->icsk_ack.pingpong) {
 203                         /* Delayed ACK missed: inflate ATO. */
 204                         icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1,
 205                                                  icsk->icsk_rto);
 206                 } else {
 207                         /* Delayed ACK missed: leave pingpong mode and
 208                          * deflate ATO.
 209                          */
 210                         icsk->icsk_ack.pingpong = 0;
 211                         icsk->icsk_ack.ato = TCP_ATO_MIN;
 212                 }
 213                 dccp_send_ack(sk);
 214                 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKS);
 215         }
 216 out:
 217         bh_unlock_sock(sk);
 218         sock_put(sk);
 219 }
 220
 221 /**
 222  * dccp_write_xmitlet  -  Workhorse for CCID packet dequeueing interface
 223  * See the comments above %ccid_dequeueing_decision for supported modes.
 224  */
 225 static void dccp_write_xmitlet(unsigned long data)
 226 {
 227         struct sock *sk = (struct sock *)data;
 228
 229         bh_lock_sock(sk);
 230         if (sock_owned_by_user(sk))
 231                 sk_reset_timer(sk, &dccp_sk(sk)->dccps_xmit_timer, jiffies + 1);
 232         else
 233                 dccp_write_xmit(sk);
 234         bh_unlock_sock(sk);
 235 }
 236
 237 static void dccp_write_xmit_timer(struct timer_list *t)
 238 {
 239         struct dccp_sock *dp = from_timer(dp, t, dccps_xmit_timer);
 240         struct sock *sk = &dp->dccps_inet_connection.icsk_inet.sk;
 241
 242         dccp_write_xmitlet((unsigned long)sk);
 243         sock_put(sk);
 244 }
 245
 246 void dccp_init_xmit_timers(struct sock *sk)
 247 {
 248         struct dccp_sock *dp = dccp_sk(sk);
 249
 250         tasklet_init(&dp->dccps_xmitlet, dccp_write_xmitlet, (unsigned long)sk);
 251         timer_setup(&dp->dccps_xmit_timer, dccp_write_xmit_timer, 0);
 252         inet_csk_init_xmit_timers(sk, &dccp_write_timer, &dccp_delack_timer,
 253                                   &dccp_keepalive_timer);
 254 }
 255
 256 static ktime_t dccp_timestamp_seed;
 257 /**
 258  * dccp_timestamp  -  10s of microseconds time source
 259  * Returns the number of 10s of microseconds since loading DCCP. This is native
 260  * DCCP time difference format (RFC 4340, sec. 13).
 261  * Please note: This will wrap around about circa every 11.9 hours.
 262  */
 263 u32 dccp_timestamp(void)
 264 {
 265         u64 delta = (u64)ktime_us_delta(ktime_get_real(), dccp_timestamp_seed);
 266
 267         do_div(delta, 10);
 268         return delta;
 269 }
 270 EXPORT_SYMBOL_GPL(dccp_timestamp);
 271
 272 void __init dccp_timestamping_init(void)
 273 {
 274         dccp_timestamp_seed = ktime_get_real();
 275 }