LXR linux/net/decnet/dn

   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}
 105