1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * DECnet       An implementation of the DECnet protocol suite for the LINUX
  4 *              operating system.  DECnet is implemented using the  BSD Socket
  5 *              interface as the means of communication with the user level.
  6 *
  7 *              DECnet Socket Timer Functions
  8 *
  9 * Author:      Steve Whitehouse <SteveW@ACM.org>
 10 *
 11 *
 12 * Changes:
 13 *       Steve Whitehouse      : Made keepalive timer part of the same
 14 *                               timer idea.
 15 *       Steve Whitehouse      : Added checks for sk->sock_readers
 16 *       David S. Miller       : New socket locking
 17 *       Steve Whitehouse      : Timer grabs socket ref.
 18 */
 19#include <linux/net.h>
 20#include <linux/socket.h>
 21#include <linux/skbuff.h>
 22#include <linux/netdevice.h>
 23#include <linux/timer.h>
 24#include <linux/spinlock.h>
 25#include <net/sock.h>
 26#include <linux/atomic.h>
 27#include <linux/jiffies.h>
 28#include <net/flow.h>
 29#include <net/dn.h>
 30
 31/*
 32 * Slow timer is for everything else (n * 500mS)
 33 */
 34
 35#define SLOW_INTERVAL (HZ/2)
 36
 37static void dn_slow_timer(struct timer_list *t);
 38
 39void dn_start_slow_timer(struct sock *sk)
 40{
 41	timer_setup(&sk->sk_timer, dn_slow_timer, 0);
 42	sk_reset_timer(sk, &sk->sk_timer, jiffies + SLOW_INTERVAL);
 43}
 44
 45void dn_stop_slow_timer(struct sock *sk)
 46{
 47	sk_stop_timer(sk, &sk->sk_timer);
 48}
 49
 50static void dn_slow_timer(struct timer_list *t)
 51{
 52	struct sock *sk = from_timer(sk, t, sk_timer);
 53	struct dn_scp *scp = DN_SK(sk);
 54
 55	bh_lock_sock(sk);
 56
 57	if (sock_owned_by_user(sk)) {
 58		sk_reset_timer(sk, &sk->sk_timer, jiffies + HZ / 10);
 59		goto out;
 60	}
 61
 62	/*
 63	 * The persist timer is the standard slow timer used for retransmits
 64	 * in both connection establishment and disconnection as well as
 65	 * in the RUN state. The different states are catered for by changing
 66	 * the function pointer in the socket. Setting the timer to a value
 67	 * of zero turns it off. We allow the persist_fxn to turn the
 68	 * timer off in a permant way by returning non-zero, so that
 69	 * timer based routines may remove sockets. This is why we have a
 70	 * sock_hold()/sock_put() around the timer to prevent the socket
 71	 * going away in the middle.
 72	 */
 73	if (scp->persist && scp->persist_fxn) {
 74		if (scp->persist <= SLOW_INTERVAL) {
 75			scp->persist = 0;
 76
 77			if (scp->persist_fxn(sk))
 78				goto out;
 79		} else {
 80			scp->persist -= SLOW_INTERVAL;
 81		}
 82	}
 83
 84	/*
 85	 * Check for keepalive timeout. After the other timer 'cos if
 86	 * the previous timer caused a retransmit, we don't need to
 87	 * do this. scp->stamp is the last time that we sent a packet.
 88	 * The keepalive function sends a link service packet to the
 89	 * other end. If it remains unacknowledged, the standard
 90	 * socket timers will eventually shut the socket down. Each
 91	 * time we do this, scp->stamp will be updated, thus
 92	 * we won't try and send another until scp->keepalive has passed
 93	 * since the last successful transmission.
 94	 */
 95	if (scp->keepalive && scp->keepalive_fxn && (scp->state == DN_RUN)) {
 96		if (time_after_eq(jiffies, scp->stamp + scp->keepalive))
 97			scp->keepalive_fxn(sk);
 98	}
 99
100	sk_reset_timer(sk, &sk->sk_timer, jiffies + SLOW_INTERVAL);
101out:
102	bh_unlock_sock(sk);
103	sock_put(sk);
104}