--- /dev/null
+/*
+ * IPVS: Destination Hashing scheduling module
+ *
+ * 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/ip.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/skbuff.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(__be32 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, __be32 addr)
+{
+ return (tbl[ip_vs_dh_hashkey(addr)]).dest;
+}
+
+
+/*
+ * Assign all the hash buckets of the specified table with the service.
+ */
+static int
+ip_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 = ip_hdr(skb);
+
+ 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.ip),
+ 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,
+ .n_list = LIST_HEAD_INIT(ip_vs_dh_scheduler.n_list),
+#ifdef CONFIG_IP_VS_IPV6
+ .supports_ipv6 = 0,
+#endif
+ .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)
+{
+ 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");
git.openpandora.org / pandora-kernel.git / commitdiff