net/decnet/dn_timer.c

   1 /*
   2  * DECnet       An implementation of the DECnet protocol suite for the LINUX
   3  *              operating system.  DECnet is implemented using the  BSD Socket
   4  *              interface as the means of communication with the user level.
   5  *
   6  *              DECnet Socket Timer Functions
   7  *
   8  * Author:      Steve Whitehouse <SteveW@ACM.org>
   9  *
  10  *
  11  * Changes:
  12  *       Steve Whitehouse      : Made keepalive timer part of the same
  13  *                               timer idea.
  14  *       Steve Whitehouse      : Added checks for sk->sock_readers
  15  *       David S. Miller       : New socket locking
  16  *       Steve Whitehouse      : Timer grabs socket ref.
  17  */
  18 #include <linux/net.h>
  19 #include <linux/socket.h>
  20 #include <linux/skbuff.h>
  21 #include <linux/netdevice.h>
  22 #include <linux/timer.h>
  23 #include <linux/spinlock.h>
  24 #include <net/sock.h>
  25 #include <asm/atomic.h>
  26 #include <net/dn.h>
  27
  28 /*
  29  * Fast timer is for delayed acks (200mS max)
  30  * Slow timer is for everything else (n * 500mS)
  31  */
  32
  33 #define FAST_INTERVAL (HZ/5)
  34 #define SLOW_INTERVAL (HZ/2)
  35
  36 static void dn_slow_timer(unsigned long arg);
  37
  38 void dn_start_slow_timer(struct sock *sk)
  39 {
  40         sk->timer.expires = jiffies + SLOW_INTERVAL;
  41         sk->timer.function = dn_slow_timer;
  42         sk->timer.data = (unsigned long)sk;
  43
  44         add_timer(&sk->timer);
  45 }
  46
  47 void dn_stop_slow_timer(struct sock *sk)
  48 {
  49         del_timer(&sk->timer);
  50 }
  51
  52 static void dn_slow_timer(unsigned long arg)
  53 {
  54         struct sock *sk = (struct sock *)arg;
  55         struct dn_scp *scp = &sk->protinfo.dn;
  56
  57         sock_hold(sk);
  58         bh_lock_sock(sk);
  59
  60         if (sk->lock.users != 0) {
  61                 sk->timer.expires = jiffies + HZ / 10;
  62                 add_timer(&sk->timer);
  63                 goto out;
  64         }
  65
  66         /*
  67          * The persist timer is the standard slow timer used for retransmits
  68          * in both connection establishment and disconnection as well as
  69          * in the RUN state. The different states are catered for by changing
  70          * the function pointer in the socket. Setting the timer to a value
  71          * of zero turns it off. We allow the persist_fxn to turn the
  72          * timer off in a permant way by returning non-zero, so that
  73          * timer based routines may remove sockets. This is why we have a
  74          * sock_hold()/sock_put() around the timer to prevent the socket
  75          * going away in the middle.
  76          */
  77         if (scp->persist && scp->persist_fxn) {
  78                 if (scp->persist <= SLOW_INTERVAL) {
  79                         scp->persist = 0;
  80
  81                         if (scp->persist_fxn(sk))
  82                                 goto out;
  83                 } else {
  84                         scp->persist -= SLOW_INTERVAL;
  85                 }
  86         }
  87
  88         /*
  89          * Check for keepalive timeout. After the other timer 'cos if
  90          * the previous timer caused a retransmit, we don't need to
  91          * do this. scp->stamp is the last time that we sent a packet.
  92          * The keepalive function sends a link service packet to the
  93          * other end. If it remains unacknowledged, the standard
  94          * socket timers will eventually shut the socket down. Each
  95          * time we do this, scp->stamp will be updated, thus
  96          * we won't try and send another until scp->keepalive has passed
  97          * since the last successful transmission.
  98          */
  99         if (scp->keepalive && scp->keepalive_fxn && (scp->state == DN_RUN)) {
 100                 if ((jiffies - scp->stamp) >= scp->keepalive)
 101                         scp->keepalive_fxn(sk);
 102         }
 103
 104         sk->timer.expires = jiffies + SLOW_INTERVAL;
 105
 106         add_timer(&sk->timer);
 107 out:
 108         bh_unlock_sock(sk);
 109         sock_put(sk);
 110 }
 111
 112 static void dn_fast_timer(unsigned long arg)
 113 {
 114         struct sock *sk = (struct sock *)arg;
 115         struct dn_scp *scp = &sk->protinfo.dn;
 116
 117         bh_lock_sock(sk);
 118         if (sk->lock.users != 0) {
 119                 scp->delack_timer.expires = jiffies + HZ / 20;
 120                 add_timer(&scp->delack_timer);
 121                 goto out;
 122         }
 123
 124         scp->delack_pending = 0;
 125
 126         if (scp->delack_fxn)
 127                 scp->delack_fxn(sk);
 128 out:
 129         bh_unlock_sock(sk);
 130 }
 131
 132 void dn_start_fast_timer(struct sock *sk)
 133 {
 134         struct dn_scp *scp = &sk->protinfo.dn;
 135
 136         if (!scp->delack_pending) {
 137                 scp->delack_pending = 1;
 138                 init_timer(&scp->delack_timer);
 139                 scp->delack_timer.expires = jiffies + FAST_INTERVAL;
 140                 scp->delack_timer.data = (unsigned long)sk;
 141                 scp->delack_timer.function = dn_fast_timer;
 142                 add_timer(&scp->delack_timer);
 143         }
 144 }
 145
 146 void dn_stop_fast_timer(struct sock *sk)
 147 {
 148         struct dn_scp *scp = &sk->protinfo.dn;
 149
 150         if (scp->delack_pending) {
 151                 scp->delack_pending = 0;
 152                 del_timer(&scp->delack_timer);
 153         }
 154 }
 155