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