/* * IPVS: Source Hashing scheduling module * * Version: $Id: ip_vs_sh.c,v 1.5 2002/09/15 08:14:08 wensong Exp $ * * Authors: Wensong Zhang <wensong@gnuchina.org> * * 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 sh algorithm is to select server by the hash key of source IP * address. The pseudo code is as follows: * * n <- servernode[src_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 source IP address to the current server * array. If the sh 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/ip.h> #include <linux/module.h> #include <linux/kernel.h> #include <linux/skbuff.h> #include <net/ip_vs.h> /* * IPVS SH bucket */ struct ip_vs_sh_bucket { struct ip_vs_dest *dest; /* real server (cache) */ }; /* * for IPVS SH entry hash table */ #ifndef CONFIG_IP_VS_SH_TAB_BITS #define CONFIG_IP_VS_SH_TAB_BITS 8 #endif #define IP_VS_SH_TAB_BITS CONFIG_IP_VS_SH_TAB_BITS #define IP_VS_SH_TAB_SIZE (1 << IP_VS_SH_TAB_BITS) #define IP_VS_SH_TAB_MASK (IP_VS_SH_TAB_SIZE - 1) /* * Returns hash value for IPVS SH entry */ static inline unsigned ip_vs_sh_hashkey(__be32 addr) { return (ntohl(addr)*2654435761UL) & IP_VS_SH_TAB_MASK; } /* * Get ip_vs_dest associated with supplied parameters. */ static inline struct ip_vs_dest * ip_vs_sh_get(struct ip_vs_sh_bucket *tbl, __be32 addr) { return (tbl[ip_vs_sh_hashkey(addr)]).dest; } /* * Assign all the hash buckets of the specified table with the service. */ static int ip_vs_sh_assign(struct ip_vs_sh_bucket *tbl, struct ip_vs_service *svc) { int i; struct ip_vs_sh_bucket *b; struct list_head *p; struct ip_vs_dest *dest; b = tbl; p = &svc->destinations; for (i=0; i<IP_VS_SH_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_sh_flush(struct ip_vs_sh_bucket *tbl) { int i; struct ip_vs_sh_bucket *b; b = tbl; for (i=0; i<IP_VS_SH_TAB_SIZE; i++) { if (b->dest) { atomic_dec(&b->dest->refcnt); b->dest = NULL; } b++; } } static int ip_vs_sh_init_svc(struct ip_vs_service *svc) { struct ip_vs_sh_bucket *tbl; /* allocate the SH table for this service */ tbl = kmalloc(sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE, GFP_ATOMIC); if (tbl == NULL) { IP_VS_ERR("ip_vs_sh_init_svc(): no memory\n"); return -ENOMEM; } svc->sched_data = tbl; IP_VS_DBG(6, "SH hash table (memory=%Zdbytes) allocated for " "current service\n", sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE); /* assign the hash buckets with the updated service */ ip_vs_sh_assign(tbl, svc); return 0; } static int ip_vs_sh_done_svc(struct ip_vs_service *svc) { struct ip_vs_sh_bucket *tbl = svc->sched_data; /* got to clean up hash buckets here */ ip_vs_sh_flush(tbl); /* release the table itself */ kfree(svc->sched_data); IP_VS_DBG(6, "SH hash table (memory=%Zdbytes) released\n", sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE); return 0; } static int ip_vs_sh_update_svc(struct ip_vs_service *svc) { struct ip_vs_sh_bucket *tbl = svc->sched_data; /* got to clean up hash buckets here */ ip_vs_sh_flush(tbl); /* assign the hash buckets with the updated service */ ip_vs_sh_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; } /* * Source Hashing scheduling */ static struct ip_vs_dest * ip_vs_sh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb) { struct ip_vs_dest *dest; struct ip_vs_sh_bucket *tbl; struct iphdr *iph = ip_hdr(skb); IP_VS_DBG(6, "ip_vs_sh_schedule(): Scheduling...\n"); tbl = (struct ip_vs_sh_bucket *)svc->sched_data; dest = ip_vs_sh_get(tbl, iph->saddr); if (!dest || !(dest->flags & IP_VS_DEST_F_AVAILABLE) || atomic_read(&dest->weight) <= 0 || is_overloaded(dest)) { return NULL; } IP_VS_DBG(6, "SH: source IP address %u.%u.%u.%u " "--> server %u.%u.%u.%u:%d\n", NIPQUAD(iph->saddr), NIPQUAD(dest->addr), ntohs(dest->port)); return dest; } /* * IPVS SH Scheduler structure */ static struct ip_vs_scheduler ip_vs_sh_scheduler = { .name = "sh", .refcnt = ATOMIC_INIT(0), .module = THIS_MODULE, .init_service = ip_vs_sh_init_svc, .done_service = ip_vs_sh_done_svc, .update_service = ip_vs_sh_update_svc, .schedule = ip_vs_sh_schedule, }; static int __init ip_vs_sh_init(void) { INIT_LIST_HEAD(&ip_vs_sh_scheduler.n_list); return register_ip_vs_scheduler(&ip_vs_sh_scheduler); } static void __exit ip_vs_sh_cleanup(void) { unregister_ip_vs_scheduler(&ip_vs_sh_scheduler); } module_init(ip_vs_sh_init); module_exit(ip_vs_sh_cleanup); MODULE_LICENSE("GPL");