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