// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* IPVS: Destination Hashing scheduling module
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*
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* Authors: Wensong Zhang <wensong@gnuchina.org>
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*
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* Inspired by the consistent hashing scheduler patch from
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* Thomas Proell <proellt@gmx.de>
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*
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* Changes:
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*/
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/*
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* The dh algorithm is to select server by the hash key of destination IP
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* address. The pseudo code is as follows:
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*
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* n <- servernode[dest_ip];
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* if (n is dead) OR
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* (n is overloaded) OR (n.weight <= 0) then
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* return NULL;
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*
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* return n;
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*
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* Notes that servernode is a 256-bucket hash table that maps the hash
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* index derived from packet destination IP address to the current server
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* array. If the dh scheduler is used in cache cluster, it is good to
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* combine it with cache_bypass feature. When the statically assigned
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* server is dead or overloaded, the load balancer can bypass the cache
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* server and send requests to the original server directly.
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*
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*/
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#define KMSG_COMPONENT "IPVS"
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#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
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#include <linux/ip.h>
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#include <linux/slab.h>
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/skbuff.h>
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#include <linux/hash.h>
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#include <net/ip_vs.h>
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/*
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* IPVS DH bucket
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*/
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struct ip_vs_dh_bucket {
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struct ip_vs_dest __rcu *dest; /* real server (cache) */
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};
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/*
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* for IPVS DH entry hash table
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*/
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#ifndef CONFIG_IP_VS_DH_TAB_BITS
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#define CONFIG_IP_VS_DH_TAB_BITS 8
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#endif
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#define IP_VS_DH_TAB_BITS CONFIG_IP_VS_DH_TAB_BITS
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#define IP_VS_DH_TAB_SIZE (1 << IP_VS_DH_TAB_BITS)
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#define IP_VS_DH_TAB_MASK (IP_VS_DH_TAB_SIZE - 1)
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struct ip_vs_dh_state {
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struct ip_vs_dh_bucket buckets[IP_VS_DH_TAB_SIZE];
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struct rcu_head rcu_head;
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};
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/*
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* Returns hash value for IPVS DH entry
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*/
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static inline unsigned int ip_vs_dh_hashkey(int af, const union nf_inet_addr *addr)
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{
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__be32 addr_fold = addr->ip;
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#ifdef CONFIG_IP_VS_IPV6
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if (af == AF_INET6)
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addr_fold = addr->ip6[0]^addr->ip6[1]^
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addr->ip6[2]^addr->ip6[3];
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#endif
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return hash_32(ntohl(addr_fold), IP_VS_DH_TAB_BITS);
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}
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/*
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* Get ip_vs_dest associated with supplied parameters.
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*/
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static inline struct ip_vs_dest *
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ip_vs_dh_get(int af, struct ip_vs_dh_state *s, const union nf_inet_addr *addr)
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{
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return rcu_dereference(s->buckets[ip_vs_dh_hashkey(af, addr)].dest);
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}
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/*
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* Assign all the hash buckets of the specified table with the service.
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*/
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static int
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ip_vs_dh_reassign(struct ip_vs_dh_state *s, struct ip_vs_service *svc)
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{
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int i;
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struct ip_vs_dh_bucket *b;
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struct list_head *p;
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struct ip_vs_dest *dest;
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bool empty;
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b = &s->buckets[0];
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p = &svc->destinations;
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empty = list_empty(p);
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for (i=0; i<IP_VS_DH_TAB_SIZE; i++) {
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dest = rcu_dereference_protected(b->dest, 1);
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if (dest)
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ip_vs_dest_put(dest);
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if (empty)
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RCU_INIT_POINTER(b->dest, NULL);
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else {
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if (p == &svc->destinations)
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p = p->next;
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dest = list_entry(p, struct ip_vs_dest, n_list);
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ip_vs_dest_hold(dest);
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RCU_INIT_POINTER(b->dest, dest);
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p = p->next;
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}
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b++;
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}
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return 0;
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}
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/*
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* Flush all the hash buckets of the specified table.
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*/
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static void ip_vs_dh_flush(struct ip_vs_dh_state *s)
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{
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int i;
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struct ip_vs_dh_bucket *b;
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struct ip_vs_dest *dest;
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b = &s->buckets[0];
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for (i=0; i<IP_VS_DH_TAB_SIZE; i++) {
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dest = rcu_dereference_protected(b->dest, 1);
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if (dest) {
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ip_vs_dest_put(dest);
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RCU_INIT_POINTER(b->dest, NULL);
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}
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b++;
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}
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}
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static int ip_vs_dh_init_svc(struct ip_vs_service *svc)
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{
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struct ip_vs_dh_state *s;
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/* allocate the DH table for this service */
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s = kzalloc(sizeof(struct ip_vs_dh_state), GFP_KERNEL);
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if (s == NULL)
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return -ENOMEM;
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svc->sched_data = s;
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IP_VS_DBG(6, "DH hash table (memory=%zdbytes) allocated for "
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"current service\n",
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sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE);
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/* assign the hash buckets with current dests */
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ip_vs_dh_reassign(s, svc);
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return 0;
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}
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static void ip_vs_dh_done_svc(struct ip_vs_service *svc)
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{
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struct ip_vs_dh_state *s = svc->sched_data;
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/* got to clean up hash buckets here */
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ip_vs_dh_flush(s);
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/* release the table itself */
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kfree_rcu(s, rcu_head);
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IP_VS_DBG(6, "DH hash table (memory=%zdbytes) released\n",
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sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE);
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}
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static int ip_vs_dh_dest_changed(struct ip_vs_service *svc,
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struct ip_vs_dest *dest)
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{
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struct ip_vs_dh_state *s = svc->sched_data;
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/* assign the hash buckets with the updated service */
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ip_vs_dh_reassign(s, svc);
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return 0;
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}
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/*
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* If the dest flags is set with IP_VS_DEST_F_OVERLOAD,
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* consider that the server is overloaded here.
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*/
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static inline int is_overloaded(struct ip_vs_dest *dest)
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{
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return dest->flags & IP_VS_DEST_F_OVERLOAD;
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}
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/*
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* Destination hashing scheduling
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*/
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static struct ip_vs_dest *
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ip_vs_dh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
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struct ip_vs_iphdr *iph)
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{
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struct ip_vs_dest *dest;
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struct ip_vs_dh_state *s;
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IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
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s = (struct ip_vs_dh_state *) svc->sched_data;
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dest = ip_vs_dh_get(svc->af, s, &iph->daddr);
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if (!dest
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|| !(dest->flags & IP_VS_DEST_F_AVAILABLE)
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|| atomic_read(&dest->weight) <= 0
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|| is_overloaded(dest)) {
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ip_vs_scheduler_err(svc, "no destination available");
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return NULL;
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}
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IP_VS_DBG_BUF(6, "DH: destination IP address %s --> server %s:%d\n",
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IP_VS_DBG_ADDR(svc->af, &iph->daddr),
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IP_VS_DBG_ADDR(dest->af, &dest->addr),
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ntohs(dest->port));
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return dest;
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}
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/*
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* IPVS DH Scheduler structure
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*/
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static struct ip_vs_scheduler ip_vs_dh_scheduler =
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{
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.name = "dh",
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.refcnt = ATOMIC_INIT(0),
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.module = THIS_MODULE,
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.n_list = LIST_HEAD_INIT(ip_vs_dh_scheduler.n_list),
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.init_service = ip_vs_dh_init_svc,
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.done_service = ip_vs_dh_done_svc,
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.add_dest = ip_vs_dh_dest_changed,
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.del_dest = ip_vs_dh_dest_changed,
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.schedule = ip_vs_dh_schedule,
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};
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static int __init ip_vs_dh_init(void)
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{
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return register_ip_vs_scheduler(&ip_vs_dh_scheduler);
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}
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static void __exit ip_vs_dh_cleanup(void)
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{
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unregister_ip_vs_scheduler(&ip_vs_dh_scheduler);
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synchronize_rcu();
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}
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module_init(ip_vs_dh_init);
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module_exit(ip_vs_dh_cleanup);
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MODULE_LICENSE("GPL");
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