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 <asm/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 35 static void dn_slow_timer(unsigned long arg); 36 dn_start_slow_timer(struct sock * sk)37void dn_start_slow_timer(struct sock *sk) 38 { 39 sk->sk_timer.expires = jiffies + SLOW_INTERVAL; 40 sk->sk_timer.function = dn_slow_timer; 41 sk->sk_timer.data = (unsigned long)sk; 42 43 add_timer(&sk->sk_timer); 44 } 45 dn_stop_slow_timer(struct sock * sk)46void dn_stop_slow_timer(struct sock *sk) 47 { 48 del_timer(&sk->sk_timer); 49 } 50 dn_slow_timer(unsigned long arg)51static void dn_slow_timer(unsigned long arg) 52 { 53 struct sock *sk = (struct sock *)arg; 54 struct dn_scp *scp = DN_SK(sk); 55 56 sock_hold(sk); 57 bh_lock_sock(sk); 58 59 if (sock_owned_by_user(sk)) { 60 sk->sk_timer.expires = jiffies + HZ / 10; 61 add_timer(&sk->sk_timer); 62 goto out; 63 } 64 65 /* 66 * The persist timer is the standard slow timer used for retransmits 67 * in both connection establishment and disconnection as well as 68 * in the RUN state. The different states are catered for by changing 69 * the function pointer in the socket. Setting the timer to a value 70 * of zero turns it off. We allow the persist_fxn to turn the 71 * timer off in a permant way by returning non-zero, so that 72 * timer based routines may remove sockets. This is why we have a 73 * sock_hold()/sock_put() around the timer to prevent the socket 74 * going away in the middle. 75 */ 76 if (scp->persist && scp->persist_fxn) { 77 if (scp->persist <= SLOW_INTERVAL) { 78 scp->persist = 0; 79 80 if (scp->persist_fxn(sk)) 81 goto out; 82 } else { 83 scp->persist -= SLOW_INTERVAL; 84 } 85 } 86 87 /* 88 * Check for keepalive timeout. After the other timer 'cos if 89 * the previous timer caused a retransmit, we don't need to 90 * do this. scp->stamp is the last time that we sent a packet. 91 * The keepalive function sends a link service packet to the 92 * other end. If it remains unacknowledged, the standard 93 * socket timers will eventually shut the socket down. Each 94 * time we do this, scp->stamp will be updated, thus 95 * we won't try and send another until scp->keepalive has passed 96 * since the last successful transmission. 97 */ 98 if (scp->keepalive && scp->keepalive_fxn && (scp->state == DN_RUN)) { 99 if ((jiffies - scp->stamp) >= scp->keepalive) 100 scp->keepalive_fxn(sk); 101 } 102 103 sk->sk_timer.expires = jiffies + SLOW_INTERVAL; 104 105 add_timer(&sk->sk_timer); 106 out: 107 bh_unlock_sock(sk); 108 sock_put(sk); 109 } 110