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
 35static void dn_slow_timer(unsigned long arg);
 36
 37void 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
 43void dn_stop_slow_timer(struct sock *sk)
 44{
 45	sk_stop_timer(sk, &sk->sk_timer);
 46}
 47
 48static 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);
 99out:
100	bh_unlock_sock(sk);
101	sock_put(sk);
102}