/* * IPVS:        Destination Hashing scheduling module * * Version:     $Id: ip_vs_dh.c,v 1.5 2002/09/15 08:14:08 wensong Exp $ * * Authors:     Wensong Zhang <wensong@gnuchina.org> * *              Inspired by the consistent hashing scheduler patch from *              Thomas Proell <proellt@gmx.de> * *              This program is free software; you can redistribute it and/or *              modify it under the terms of the GNU General Public License *              as published by the Free Software Foundation; either version *              2 of the License, or (at your option) any later version. * * Changes: * *//* * The dh algorithm is to select server by the hash key of destination IP * address. The pseudo code is as follows: * *       n <- servernode[dest_ip]; *       if (n is dead) OR *          (n is overloaded) OR (n.weight <= 0) then *                 return NULL; * *       return n; * * Notes that servernode is a 256-bucket hash table that maps the hash * index derived from packet destination IP address to the current server * array. If the dh scheduler is used in cache cluster, it is good to * combine it with cache_bypass feature. When the statically assigned * server is dead or overloaded, the load balancer can bypass the cache * server and send requests to the original server directly. * */#include <linux/module.h>#include <linux/kernel.h>#include <net/ip_vs.h>/* *      IPVS DH bucket */struct ip_vs_dh_bucket {	struct ip_vs_dest       *dest;          /* real server (cache) */};/* *     for IPVS DH entry hash table */#ifndef CONFIG_IP_VS_DH_TAB_BITS#define CONFIG_IP_VS_DH_TAB_BITS        8#endif#define IP_VS_DH_TAB_BITS               CONFIG_IP_VS_DH_TAB_BITS#define IP_VS_DH_TAB_SIZE               (1 << IP_VS_DH_TAB_BITS)#define IP_VS_DH_TAB_MASK               (IP_VS_DH_TAB_SIZE - 1)/* *	Returns hash value for IPVS DH entry */static inline unsigned ip_vs_dh_hashkey(__u32 addr){	return (ntohl(addr)*2654435761UL) & IP_VS_DH_TAB_MASK;}/* *      Get ip_vs_dest associated with supplied parameters. */static inline struct ip_vs_dest *ip_vs_dh_get(struct ip_vs_dh_bucket *tbl, __u32 addr){	return (tbl[ip_vs_dh_hashkey(addr)]).dest;}/* *      Assign all the hash buckets of the specified table with the service. */static intip_vs_dh_assign(struct ip_vs_dh_bucket *tbl, struct ip_vs_service *svc){	int i;	struct ip_vs_dh_bucket *b;	struct list_head *p;	struct ip_vs_dest *dest;	b = tbl;	p = &svc->destinations;	for (i=0; i<IP_VS_DH_TAB_SIZE; i++) {		if (list_empty(p)) {			b->dest = NULL;		} else {			if (p == &svc->destinations)				p = p->next;			dest = list_entry(p, struct ip_vs_dest, n_list);			atomic_inc(&dest->refcnt);			b->dest = dest;			p = p->next;		}		b++;	}	return 0;}/* *      Flush all the hash buckets of the specified table. */static void ip_vs_dh_flush(struct ip_vs_dh_bucket *tbl){	int i;	struct ip_vs_dh_bucket *b;	b = tbl;	for (i=0; i<IP_VS_DH_TAB_SIZE; i++) {		if (b->dest) {			atomic_dec(&b->dest->refcnt);			b->dest = NULL;		}		b++;	}}static int ip_vs_dh_init_svc(struct ip_vs_service *svc){	struct ip_vs_dh_bucket *tbl;	/* allocate the DH table for this service */	tbl = kmalloc(sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE,		      GFP_ATOMIC);	if (tbl == NULL) {		IP_VS_ERR("ip_vs_dh_init_svc(): no memory\n");		return -ENOMEM;	}	svc->sched_data = tbl;	IP_VS_DBG(6, "DH hash table (memory=%Zdbytes) allocated for "		  "current service\n",		  sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE);	/* assign the hash buckets with the updated service */	ip_vs_dh_assign(tbl, svc);	return 0;}static int ip_vs_dh_done_svc(struct ip_vs_service *svc){	struct ip_vs_dh_bucket *tbl = svc->sched_data;	/* got to clean up hash buckets here */	ip_vs_dh_flush(tbl);	/* release the table itself */	kfree(svc->sched_data);	IP_VS_DBG(6, "DH hash table (memory=%Zdbytes) released\n",		  sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE);	return 0;}static int ip_vs_dh_update_svc(struct ip_vs_service *svc){	struct ip_vs_dh_bucket *tbl = svc->sched_data;	/* got to clean up hash buckets here */	ip_vs_dh_flush(tbl);	/* assign the hash buckets with the updated service */	ip_vs_dh_assign(tbl, svc);	return 0;}/* *      If the dest flags is set with IP_VS_DEST_F_OVERLOAD, *      consider that the server is overloaded here. */static inline int is_overloaded(struct ip_vs_dest *dest){	return dest->flags & IP_VS_DEST_F_OVERLOAD;}/* *      Destination hashing scheduling */static struct ip_vs_dest *ip_vs_dh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb){	struct ip_vs_dest *dest;	struct ip_vs_dh_bucket *tbl;	struct iphdr *iph = skb->nh.iph;	IP_VS_DBG(6, "ip_vs_dh_schedule(): Scheduling...\n");	tbl = (struct ip_vs_dh_bucket *)svc->sched_data;	dest = ip_vs_dh_get(tbl, iph->daddr);	if (!dest	    || !(dest->flags & IP_VS_DEST_F_AVAILABLE)	    || atomic_read(&dest->weight) <= 0	    || is_overloaded(dest)) {		return NULL;	}	IP_VS_DBG(6, "DH: destination IP address %u.%u.%u.%u "		  "--> server %u.%u.%u.%u:%d\n",		  NIPQUAD(iph->daddr),		  NIPQUAD(dest->addr),		  ntohs(dest->port));	return dest;}/* *      IPVS DH Scheduler structure */static struct ip_vs_scheduler ip_vs_dh_scheduler ={	.name =			"dh",	.refcnt =		ATOMIC_INIT(0),	.module =		THIS_MODULE,	.init_service =		ip_vs_dh_init_svc,	.done_service =		ip_vs_dh_done_svc,	.update_service =	ip_vs_dh_update_svc,	.schedule =		ip_vs_dh_schedule,};static int __init ip_vs_dh_init(void){	INIT_LIST_HEAD(&ip_vs_dh_scheduler.n_list);	return register_ip_vs_scheduler(&ip_vs_dh_scheduler);}static void __exit ip_vs_dh_cleanup(void){	unregister_ip_vs_scheduler(&ip_vs_dh_scheduler);}module_init(ip_vs_dh_init);module_exit(ip_vs_dh_cleanup);MODULE_LICENSE("GPL");