/* * 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 <SteveW@ACM.org> * * * 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 <linux/jiffies.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 (time_after_eq(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);}