text: #include <linux/sysctl.h>
  #include <linux/slab.h>
  #include <net/net_namespace.h>
  #include <net/xfrm.h>
  
  static void __net_init __xfrm_sysctl_init(struct net *net)
  {
  	net->xfrm.sysctl_aevent_etime = XFRM_AE_ETIME;
  	net->xfrm.sysctl_aevent_rseqth = XFRM_AE_SEQT_SIZE;
  	net->xfrm.sysctl_larval_drop = 1;
  	net->xfrm.sysctl_acq_expires = 30;
  }
  
  #ifdef CONFIG_SYSCTL
  static struct ctl_table xfrm_table[] = {
  	{
  		.procname	= "xfrm_aevent_etime",
  		.maxlen		= sizeof(u32),
  		.mode		= 0644,
  		.proc_handler	= proc_douintvec
  	},
  	{
  		.procname	= "xfrm_aevent_rseqth",
  		.maxlen		= sizeof(u32),
  		.mode		= 0644,
  		.proc_handler	= proc_douintvec
  	},
  	{
  		.procname	= "xfrm_larval_drop",
  		.maxlen		= sizeof(int),
  		.mode		= 0644,
  		.proc_handler	= proc_dointvec
  	},
  	{
  		.procname	= "xfrm_acq_expires",
  		.maxlen		= sizeof(int),
  		.mode		= 0644,
  		.proc_handler	= proc_dointvec
  	},
  	{}
  };
  
  int __net_init xfrm_sysctl_init(struct net *net)
  {
  	struct ctl_table *table;
  
  	__xfrm_sysctl_init(net);
  
  	table = kmemdup(xfrm_table, sizeof(xfrm_table), GFP_KERNEL);
  	if (!table)
  		goto out_kmemdup;
  	table[0].data = &net->xfrm.sysctl_aevent_etime;
  	table[1].data = &net->xfrm.sysctl_aevent_rseqth;
  	table[2].data = &net->xfrm.sysctl_larval_drop;
  	table[3].data = &net->xfrm.sysctl_acq_expires;
  
  	/* Don't export sysctls to unprivileged users */
  	if (net->user_ns != &init_user_ns)
  		table[0].procname = NULL;
  
  	net->xfrm.sysctl_hdr = register_net_sysctl(net, "net/core", table);
  	if (!net->xfrm.sysctl_hdr)
  		goto out_register;
  	return 0;
  
  out_register:
  	kfree(table);
  out_kmemdup:
  	return -ENOMEM;
  }
  
  void __net_exit xfrm_sysctl_fini(struct net *net)
  {
  	struct ctl_table *table;
  
  	table = net->xfrm.sysctl_hdr->ctl_table_arg;
  	unregister_net_sysctl_table(net->xfrm.sysctl_hdr);
  	kfree(table);
  }
  #else
  int __net_init xfrm_sysctl_init(struct net *net)
  {
  	__xfrm_sysctl_init(net);
  	return 0;
  }
  #endif
  