dn_timer.c

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/*
 * DECnet       An implementation of the DECnet protocol suite for the LINUX
 *              operating system.  DECnet is implemented using the  BSD Socket
 *              interface as the means of communication with the user level.
 *
 *              DECnet Socket Timer Functions
 *
 * Author:      Steve Whitehouse <[email protected]>
 *
 *
 * Changes:
 *       Steve Whitehouse      : Made keepalive timer part of the same
 *                               timer idea.
 *       Steve Whitehouse      : Added checks for sk->sock_readers
 *       David S. Miller       : New socket locking
 *       Steve Whitehouse      : Timer grabs socket ref.
 */
#include <linux/net.h>
#include <linux/socket.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/timer.h>
#include <linux/spinlock.h>
#include <net/sock.h>
#include <linux/atomic.h>
#include <net/flow.h>
#include <net/dn.h>

/*
 * Slow timer is for everything else (n * 500mS)
 */

#define SLOW_INTERVAL (HZ/2)

static void dn_slow_timer(unsigned long arg);

void dn_start_slow_timer(struct sock *sk)
{
    setup_timer(&sk->sk_timer, dn_slow_timer, (unsigned long)sk);
    sk_reset_timer(sk, &sk->sk_timer, jiffies + SLOW_INTERVAL);
}

void dn_stop_slow_timer(struct sock *sk)
{
    sk_stop_timer(sk, &sk->sk_timer);
}

static void dn_slow_timer(unsigned long arg)
{
    struct sock *sk = (struct sock *)arg;
    struct dn_scp *scp = DN_SK(sk);

    bh_lock_sock(sk);

    if (sock_owned_by_user(sk)) {
        sk_reset_timer(sk, &sk->sk_timer, jiffies + HZ / 10);
        goto out;
    }

    /*
     * The persist timer is the standard slow timer used for retransmits
     * in both connection establishment and disconnection as well as
     * in the RUN state. The different states are catered for by changing
     * the function pointer in the socket. Setting the timer to a value
     * of zero turns it off. We allow the persist_fxn to turn the
     * timer off in a permant way by returning non-zero, so that
     * timer based routines may remove sockets. This is why we have a
     * sock_hold()/sock_put() around the timer to prevent the socket
     * going away in the middle.
     */
    if (scp->persist && scp->persist_fxn) {
        if (scp->persist <= SLOW_INTERVAL) {
            scp->persist = 0;

            if (scp->persist_fxn(sk))
                goto out;
        } else {
            scp->persist -= SLOW_INTERVAL;
        }
    }

    /*
     * Check for keepalive timeout. After the other timer 'cos if
     * the previous timer caused a retransmit, we don't need to
     * do this. scp->stamp is the last time that we sent a packet.
     * The keepalive function sends a link service packet to the
     * other end. If it remains unacknowledged, the standard
     * socket timers will eventually shut the socket down. Each
     * time we do this, scp->stamp will be updated, thus
     * we won't try and send another until scp->keepalive has passed
     * since the last successful transmission.
     */
    if (scp->keepalive && scp->keepalive_fxn && (scp->state == DN_RUN)) {
        if ((jiffies - scp->stamp) >= scp->keepalive)
            scp->keepalive_fxn(sk);
    }

    sk_reset_timer(sk, &sk->sk_timer, jiffies + SLOW_INTERVAL);
out:
    bh_unlock_sock(sk);
    sock_put(sk);
}