[IPV4]: Add sysctl to control ipfrag_secret_interval.

include/linux/sysctl.h

@@ -307,7 +307,8 @@ enum
 	NET_IPV4_ICMP_RATEMASK=90,
 	NET_TCP_TW_REUSE=91,
 	NET_TCP_FRTO=92,
-	NET_TCP_LOW_LATENCY=93
+	NET_TCP_LOW_LATENCY=93,
+	NET_IPV4_IPFRAG_SECRET_INTERVAL=94,
 };
 
 enum {

net/ipv4/ip_fragment.c

@@ -126,7 +126,7 @@ static unsigned int ipqhashfn(u16 id, u32 saddr, u32 daddr, u8 prot)
 }
 
 static struct timer_list ipfrag_secret_timer;
-static int ipfrag_secret_interval = 10 * 60 * HZ;
+int sysctl_ipfrag_secret_interval = 10 * 60 * HZ;
 
 static void ipfrag_secret_rebuild(unsigned long dummy)
 {
@@ -162,7 +162,7 @@ static void ipfrag_secret_rebuild(unsigned long dummy)
 	}
 	write_unlock(&ipfrag_lock);
 
-	mod_timer(&ipfrag_secret_timer, now + ipfrag_secret_interval);
+	mod_timer(&ipfrag_secret_timer, now + sysctl_ipfrag_secret_interval);
 }
 
 atomic_t ip_frag_mem = ATOMIC_INIT(0);	/* Memory used for fragments */
@@ -672,6 +672,6 @@ void ipfrag_init(void)
 
 	init_timer(&ipfrag_secret_timer);
 	ipfrag_secret_timer.function = ipfrag_secret_rebuild;
-	ipfrag_secret_timer.expires = jiffies + ipfrag_secret_interval;
+	ipfrag_secret_timer.expires = jiffies + sysctl_ipfrag_secret_interval;
 	add_timer(&ipfrag_secret_timer);
 }

net/ipv4/sysctl_net_ipv4.c

@@ -27,6 +27,7 @@ extern int sysctl_icmp_ignore_bogus_error_responses;
 extern int sysctl_ipfrag_low_thresh;
 extern int sysctl_ipfrag_high_thresh; 
 extern int sysctl_ipfrag_time;
+extern int sysctl_ipfrag_secret_interval;
 
 /* From ip_output.c */
 extern int sysctl_ip_dynaddr;
@@ -572,6 +573,15 @@ ctl_table ipv4_table[] = {
 		.mode		= 0644,
 		.proc_handler	= &proc_dointvec
 	},
+	{
+		.ctl_name	= NET_IPV4_IPFRAG_SECRET_INTERVAL,
+		.procname	= "ipfrag_secret_interval",
+		.data		= &sysctl_ipfrag_secret_interval,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec_jiffies,
+		.strategy	= &sysctl_jiffies
+	},
 	{ .ctl_name = 0 }
 };