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 <linux/atomic.h>
  26 #include <net/flow.h>
  27 #include <net/dn.h>
  28
  29 /*
  30  * Slow timer is for everything else (n * 500mS)
  31  */
  32
  33 #define SLOW_INTERVAL (HZ/2)
  34
  35 static void dn_slow_timer(unsigned long arg);
  36
  37 void dn_start_slow_timer(struct sock *sk)
  38 {
  39         sk->sk_timer.expires    = jiffies + SLOW_INTERVAL;
  40         sk->sk_timer.function   = dn_slow_timer;
  41         sk->sk_timer.data       = (unsigned long)sk;
  42
  43         add_timer(&sk->sk_timer);
  44 }
  45
  46 void dn_stop_slow_timer(struct sock *sk)
  47 {
  48         del_timer(&sk->sk_timer);
  49 }
  50
  51 static void dn_slow_timer(unsigned long arg)
  52 {
  53         struct sock *sk = (struct sock *)arg;
  54         struct dn_scp *scp = DN_SK(sk);
  55
  56         sock_hold(sk);
  57         bh_lock_sock(sk);
  58
  59         if (sock_owned_by_user(sk)) {
  60                 sk->sk_timer.expires = jiffies + HZ / 10;
  61                 add_timer(&sk->sk_timer);
  62                 goto out;
  63         }
  64
  65         /*
  66          * The persist timer is the standard slow timer used for retransmits
  67          * in both connection establishment and disconnection as well as
  68          * in the RUN state. The different states are catered for by changing
  69          * the function pointer in the socket. Setting the timer to a value
  70          * of zero turns it off. We allow the persist_fxn to turn the
  71          * timer off in a permant way by returning non-zero, so that
  72          * timer based routines may remove sockets. This is why we have a
  73          * sock_hold()/sock_put() around the timer to prevent the socket
  74          * going away in the middle.
  75          */
  76         if (scp->persist && scp->persist_fxn) {
  77                 if (scp->persist <= SLOW_INTERVAL) {
  78                         scp->persist = 0;
  79
  80                         if (scp->persist_fxn(sk))
  81                                 goto out;
  82                 } else {
  83                         scp->persist -= SLOW_INTERVAL;
  84                 }
  85         }
  86
  87         /*
  88          * Check for keepalive timeout. After the other timer 'cos if
  89          * the previous timer caused a retransmit, we don't need to
  90          * do this. scp->stamp is the last time that we sent a packet.
  91          * The keepalive function sends a link service packet to the
  92          * other end. If it remains unacknowledged, the standard
  93          * socket timers will eventually shut the socket down. Each
  94          * time we do this, scp->stamp will be updated, thus
  95          * we won't try and send another until scp->keepalive has passed
  96          * since the last successful transmission.
  97          */
  98         if (scp->keepalive && scp->keepalive_fxn && (scp->state == DN_RUN)) {
  99                 if ((jiffies - scp->stamp) >= scp->keepalive)
 100                         scp->keepalive_fxn(sk);
 101         }
 102
 103         sk->sk_timer.expires = jiffies + SLOW_INTERVAL;
 104
 105         add_timer(&sk->sk_timer);
 106 out:
 107         bh_unlock_sock(sk);
 108         sock_put(sk);
 109 }