LXR linux/net/decnet/dn

   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/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
  35static void dn_slow_timer(unsigned long arg);
  36
  37void 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
  46void dn_stop_slow_timer(struct sock *sk)
  47{
  48        del_timer(&sk->sk_timer);
  49}
  50
  51static 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);
 106out:
 107        bh_unlock_sock(sk);
 108        sock_put(sk);
 109}
 110