net/decnet/dn_timer.c

   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
  37 static void dn_slow_timer(struct timer_list *t);
  38
  39 void 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
  45 void dn_stop_slow_timer(struct sock *sk)
  46 {
  47         sk_stop_timer(sk, &sk->sk_timer);
  48 }
  49
  50 static 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);
 101 out:
 102         bh_unlock_sock(sk);
 103         sock_put(sk);
 104 }