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/config.h>
  14 #include <linux/dccp.h>
  15 #include <linux/skbuff.h>
  16
  17 #include "dccp.h"
  18
  19 static void dccp_write_timer(unsigned long data);
  20 static void dccp_keepalive_timer(unsigned long data);
  21 static void dccp_delack_timer(unsigned long data);
  22
  23 void dccp_init_xmit_timers(struct sock *sk)
  24 {
  25         inet_csk_init_xmit_timers(sk, &dccp_write_timer, &dccp_delack_timer,
  26                                   &dccp_keepalive_timer);
  27 }
  28
  29 static void dccp_write_err(struct sock *sk)
  30 {
  31         sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
  32         sk->sk_error_report(sk);
  33
  34         dccp_send_reset(sk, DCCP_RESET_CODE_ABORTED);
  35         dccp_done(sk);
  36         DCCP_INC_STATS_BH(DCCP_MIB_ABORTONTIMEOUT);
  37 }
  38
  39 /* A write timeout has occurred. Process the after effects. */
  40 static int dccp_write_timeout(struct sock *sk)
  41 {
  42         const struct inet_connection_sock *icsk = inet_csk(sk);
  43         int retry_until;
  44
  45         if (sk->sk_state == DCCP_REQUESTING || sk->sk_state == DCCP_PARTOPEN) {
  46                 if (icsk->icsk_retransmits != 0)
  47                         dst_negative_advice(&sk->sk_dst_cache);
  48                 retry_until = icsk->icsk_syn_retries ? :
  49                             /* FIXME! */ 3 /* FIXME! sysctl_tcp_syn_retries */;
  50         } else {
  51                 if (icsk->icsk_retransmits >=
  52                      /* FIXME! sysctl_tcp_retries1 */ 5 /* FIXME! */) {
  53                         /* NOTE. draft-ietf-tcpimpl-pmtud-01.txt requires pmtu
  54                            black hole detection. :-(
  55
  56                            It is place to make it. It is not made. I do not want
  57                            to make it. It is disguisting. It does not work in any
  58                            case. Let me to cite the same draft, which requires for
  59                            us to implement this:
  60
  61    "The one security concern raised by this memo is that ICMP black holes
  62    are often caused by over-zealous security administrators who block
  63    all ICMP messages.  It is vitally important that those who design and
  64    deploy security systems understand the impact of strict filtering on
  65    upper-layer protocols.  The safest web site in the world is worthless
  66    if most TCP implementations cannot transfer data from it.  It would
  67    be far nicer to have all of the black holes fixed rather than fixing
  68    all of the TCP implementations."
  69
  70                            Golden words :-).
  71                    */
  72
  73                         dst_negative_advice(&sk->sk_dst_cache);
  74                 }
  75
  76                 retry_until = /* FIXME! */ 15 /* FIXME! sysctl_tcp_retries2 */;
  77                 /*
  78                  * FIXME: see tcp_write_timout and tcp_out_of_resources
  79                  */
  80         }
  81
  82         if (icsk->icsk_retransmits >= retry_until) {
  83                 /* Has it gone just too far? */
  84                 dccp_write_err(sk);
  85                 return 1;
  86         }
  87         return 0;
  88 }
  89
  90 /* This is the same as tcp_delack_timer, sans prequeue & mem_reclaim stuff */
  91 static void dccp_delack_timer(unsigned long data)
  92 {
  93         struct sock *sk = (struct sock *)data;
  94         struct inet_connection_sock *icsk = inet_csk(sk);
  95
  96         bh_lock_sock(sk);
  97         if (sock_owned_by_user(sk)) {
  98                 /* Try again later. */
  99                 icsk->icsk_ack.blocked = 1;
 100                 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOCKED);
 101                 sk_reset_timer(sk, &icsk->icsk_delack_timer,
 102                                jiffies + TCP_DELACK_MIN);
 103                 goto out;
 104         }
 105
 106         if (sk->sk_state == DCCP_CLOSED ||
 107             !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
 108                 goto out;
 109         if (time_after(icsk->icsk_ack.timeout, jiffies)) {
 110                 sk_reset_timer(sk, &icsk->icsk_delack_timer,
 111                                icsk->icsk_ack.timeout);
 112                 goto out;
 113         }
 114
 115         icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
 116
 117         if (inet_csk_ack_scheduled(sk)) {
 118                 if (!icsk->icsk_ack.pingpong) {
 119                         /* Delayed ACK missed: inflate ATO. */
 120                         icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1,
 121                                                  icsk->icsk_rto);
 122                 } else {
 123                         /* Delayed ACK missed: leave pingpong mode and
 124                          * deflate ATO.
 125                          */
 126                         icsk->icsk_ack.pingpong = 0;
 127                         icsk->icsk_ack.ato = TCP_ATO_MIN;
 128                 }
 129                 dccp_send_ack(sk);
 130                 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKS);
 131         }
 132 out:
 133         bh_unlock_sock(sk);
 134         sock_put(sk);
 135 }
 136
 137 /*
 138  *      The DCCP retransmit timer.
 139  */
 140 static void dccp_retransmit_timer(struct sock *sk)
 141 {
 142         struct inet_connection_sock *icsk = inet_csk(sk);
 143
 144         /* retransmit timer is used for feature negotiation throughout
 145          * connection.  In this case, no packet is re-transmitted, but rather an
 146          * ack is generated and pending changes are splaced into its options.
 147          */
 148         if (sk->sk_send_head == NULL) {
 149                 dccp_pr_debug("feat negotiation retransmit timeout %p\n", sk);
 150                 if (sk->sk_state == DCCP_OPEN)
 151                         dccp_send_ack(sk);
 152                 goto backoff;
 153         }
 154
 155         /*
 156          * sk->sk_send_head has to have one skb with
 157          * DCCP_SKB_CB(skb)->dccpd_type set to one of the retransmittable DCCP
 158          * packet types (REQUEST, RESPONSE, the ACK in the 3way handshake
 159          * (PARTOPEN timer), etc).
 160          */
 161         BUG_TRAP(sk->sk_send_head != NULL);
 162
 163         /*
 164          * More than than 4MSL (8 minutes) has passed, a RESET(aborted) was
 165          * sent, no need to retransmit, this sock is dead.
 166          */
 167         if (dccp_write_timeout(sk))
 168                 goto out;
 169
 170         /*
 171          * We want to know the number of packets retransmitted, not the
 172          * total number of retransmissions of clones of original packets.
 173          */
 174         if (icsk->icsk_retransmits == 0)
 175                 DCCP_INC_STATS_BH(DCCP_MIB_TIMEOUTS);
 176
 177         if (dccp_retransmit_skb(sk, sk->sk_send_head) < 0) {
 178                 /*
 179                  * Retransmission failed because of local congestion,
 180                  * do not backoff.
 181                  */
 182                 if (icsk->icsk_retransmits == 0)
 183                         icsk->icsk_retransmits = 1;
 184                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 185                                           min(icsk->icsk_rto,
 186                                               TCP_RESOURCE_PROBE_INTERVAL),
 187                                           DCCP_RTO_MAX);
 188                 goto out;
 189         }
 190
 191 backoff:
 192         icsk->icsk_backoff++;
 193         icsk->icsk_retransmits++;
 194
 195         icsk->icsk_rto = min(icsk->icsk_rto << 1, DCCP_RTO_MAX);
 196         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto,
 197                                   DCCP_RTO_MAX);
 198         if (icsk->icsk_retransmits > 3 /* FIXME: sysctl_dccp_retries1 */)
 199                 __sk_dst_reset(sk);
 200 out:;
 201 }
 202
 203 static void dccp_write_timer(unsigned long data)
 204 {
 205         struct sock *sk = (struct sock *)data;
 206         struct inet_connection_sock *icsk = inet_csk(sk);
 207         int event = 0;
 208
 209         bh_lock_sock(sk);
 210         if (sock_owned_by_user(sk)) {
 211                 /* Try again later */
 212                 sk_reset_timer(sk, &icsk->icsk_retransmit_timer,
 213                                jiffies + (HZ / 20));
 214                 goto out;
 215         }
 216
 217         if (sk->sk_state == DCCP_CLOSED || !icsk->icsk_pending)
 218                 goto out;
 219
 220         if (time_after(icsk->icsk_timeout, jiffies)) {
 221                 sk_reset_timer(sk, &icsk->icsk_retransmit_timer,
 222                                icsk->icsk_timeout);
 223                 goto out;
 224         }
 225
 226         event = icsk->icsk_pending;
 227         icsk->icsk_pending = 0;
 228
 229         switch (event) {
 230         case ICSK_TIME_RETRANS:
 231                 dccp_retransmit_timer(sk);
 232                 break;
 233         }
 234 out:
 235         bh_unlock_sock(sk);
 236         sock_put(sk);
 237 }
 238
 239 /*
 240  *      Timer for listening sockets
 241  */
 242 static void dccp_response_timer(struct sock *sk)
 243 {
 244         inet_csk_reqsk_queue_prune(sk, TCP_SYNQ_INTERVAL, DCCP_TIMEOUT_INIT,
 245                                    DCCP_RTO_MAX);
 246 }
 247
 248 static void dccp_keepalive_timer(unsigned long data)
 249 {
 250         struct sock *sk = (struct sock *)data;
 251
 252         /* Only process if socket is not in use. */
 253         bh_lock_sock(sk);
 254         if (sock_owned_by_user(sk)) {
 255                 /* Try again later. */
 256                 inet_csk_reset_keepalive_timer(sk, HZ / 20);
 257                 goto out;
 258         }
 259
 260         if (sk->sk_state == DCCP_LISTEN) {
 261                 dccp_response_timer(sk);
 262                 goto out;
 263         }
 264 out:
 265         bh_unlock_sock(sk);
 266         sock_put(sk);
 267 }