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 <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
  36static void dn_slow_timer(unsigned long arg);
  37
  38void 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
  44void dn_stop_slow_timer(struct sock *sk)
  45{
  46        sk_stop_timer(sk, &sk->sk_timer);
  47}
  48
  49static 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);
 100out:
 101        bh_unlock_sock(sk);
 102        sock_put(sk);
 103}
 104