#define KMSG_COMPONENT "IPVS"
  #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  
  #include <linux/module.h>
  #include <linux/spinlock.h>
  #include <linux/interrupt.h>
  #include <asm/string.h>
  #include <linux/kmod.h>
  #include <linux/sysctl.h>
  
  #include <net/ip_vs.h>
  
  /* IPVS pe list */
  static LIST_HEAD(ip_vs_pe);

  /* semaphore for IPVS PEs. */
  static DEFINE_MUTEX(ip_vs_pe_mutex);

  /* Get pe in the pe list by name */

  struct ip_vs_pe *__ip_vs_pe_getbyname(const char *pe_name)

  {
  	struct ip_vs_pe *pe;

  	IP_VS_DBG(10, "%s(): pe_name \"%s\"
  ", __func__,

  		  pe_name);

  	rcu_read_lock();
  	list_for_each_entry_rcu(pe, &ip_vs_pe, n_list) {

  		/* Test and get the modules atomically */
  		if (pe->module &&
  		    !try_module_get(pe->module)) {
  			/* This pe is just deleted */
  			continue;
  		}
  		if (strcmp(pe_name, pe->name)==0) {
  			/* HIT */

  			rcu_read_unlock();

  			return pe;
  		}

  		module_put(pe->module);

  	}

  	rcu_read_unlock();

  	return NULL;
  }
  
  /* Lookup pe and try to load it if it doesn't exist */

  struct ip_vs_pe *ip_vs_pe_getbyname(const char *name)

  {
  	struct ip_vs_pe *pe;
  
  	/* Search for the pe by name */

  	pe = __ip_vs_pe_getbyname(name);

  
  	/* If pe not found, load the module and search again */
  	if (!pe) {
  		request_module("ip_vs_pe_%s", name);

  		pe = __ip_vs_pe_getbyname(name);

  	}
  
  	return pe;
  }

  /* Register a pe in the pe list */
  int register_ip_vs_pe(struct ip_vs_pe *pe)
  {
  	struct ip_vs_pe *tmp;
  
  	/* increase the module use count */
  	ip_vs_use_count_inc();

  	mutex_lock(&ip_vs_pe_mutex);

  	/* Make sure that the pe with this name doesn't exist
  	 * in the pe list.
  	 */
  	list_for_each_entry(tmp, &ip_vs_pe, n_list) {
  		if (strcmp(tmp->name, pe->name) == 0) {

  			mutex_unlock(&ip_vs_pe_mutex);

  			ip_vs_use_count_dec();
  			pr_err("%s(): [%s] pe already existed "
  			       "in the system
  ", __func__, pe->name);
  			return -EINVAL;
  		}
  	}
  	/* Add it into the d-linked pe list */

  	list_add_rcu(&pe->n_list, &ip_vs_pe);
  	mutex_unlock(&ip_vs_pe_mutex);

  
  	pr_info("[%s] pe registered.
  ", pe->name);
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(register_ip_vs_pe);
  
  /* Unregister a pe from the pe list */
  int unregister_ip_vs_pe(struct ip_vs_pe *pe)
  {

  	mutex_lock(&ip_vs_pe_mutex);

  	/* Remove it from the d-linked pe list */

  	list_del_rcu(&pe->n_list);
  	mutex_unlock(&ip_vs_pe_mutex);

  
  	/* decrease the module use count */
  	ip_vs_use_count_dec();
  
  	pr_info("[%s] pe unregistered.
  ", pe->name);
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(unregister_ip_vs_pe);