// SPDX-License-Identifier: GPL-2.0-or-later
/*
* IPVS: Destination Hashing scheduling module
*
* Authors: Wensong Zhang <[email protected]>
*
* Inspired by the consistent hashing scheduler patch from
* Thomas Proell <[email protected]>
*
* 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.
*
*/
#define KMSG_COMPONENT "IPVS"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
#include <linux/ip.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/hash.h>
#include <net/ip_vs.h>
/*
* IPVS DH bucket
*/
struct ip_vs_dh_bucket {
struct ip_vs_dest __rcu *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)
struct ip_vs_dh_state {
struct ip_vs_dh_bucket buckets[IP_VS_DH_TAB_SIZE];
struct rcu_head rcu_head;
};
/*
* Returns hash value for IPVS DH entry
*/
static inline unsigned int ip_vs_dh_hashkey(int af, const union nf_inet_addr *addr)
{
__be32 addr_fold = addr->ip;
#ifdef CONFIG_IP_VS_IPV6
if (af == AF_INET6)
addr_fold = addr->ip6[0]^addr->ip6[1]^
addr->ip6[2]^addr->ip6[3];
#endif
return hash_32(ntohl(addr_fold), IP_VS_DH_TAB_BITS);
}
/*
* Get ip_vs_dest associated with supplied parameters.
*/
static inline struct ip_vs_dest *
ip_vs_dh_get(int af, struct ip_vs_dh_state *s, const union nf_inet_addr *addr)
{
return rcu_dereference(s->buckets[ip_vs_dh_hashkey(af, addr)].dest);
}
/*
* Assign all the hash buckets of the specified table with the service.
*/
static int
ip_vs_dh_reassign(struct ip_vs_dh_state *s, struct ip_vs_service *svc)
{
int i;
struct ip_vs_dh_bucket *b;
struct list_head *p;
struct ip_vs_dest *dest;
bool empty;
b = &s->buckets[0];
p = &svc->destinations;
empty = list_empty(p);
for (i=0; i<IP_VS_DH_TAB_SIZE; i++) {
dest = rcu_dereference_protected(b->dest, 1);
if (dest)
ip_vs_dest_put(dest);
if (empty)
RCU_INIT_POINTER(b->dest, NULL);
else {
if (p == &svc->destinations)
p = p->next;
dest = list_entry(p, struct ip_vs_dest, n_list);
ip_vs_dest_hold(dest);
RCU_INIT_POINTER(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_state *s)
{
int i;
struct ip_vs_dh_bucket *b;
struct ip_vs_dest *dest;
b = &s->buckets[0];
for (i=0; i<IP_VS_DH_TAB_SIZE; i++) {
dest = rcu_dereference_protected(b->dest, 1);
if (dest) {
ip_vs_dest_put(dest);
RCU_INIT_POINTER(b->dest, NULL);
}
b++;
}
}
static int ip_vs_dh_init_svc(struct ip_vs_service *svc)
{
struct ip_vs_dh_state *s;
/* allocate the DH table for this service */
s = kzalloc(sizeof(struct ip_vs_dh_state), GFP_KERNEL);
if (s == NULL)
return -ENOMEM;
svc->sched_data = s;
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 current dests */
ip_vs_dh_reassign(s, svc);
return 0;
}
static void ip_vs_dh_done_svc(struct ip_vs_service *svc)
{
struct ip_vs_dh_state *s = svc->sched_data;
/* got to clean up hash buckets here */
ip_vs_dh_flush(s);
/* release the table itself */
kfree_rcu(s, rcu_head);
IP_VS_DBG(6, "DH hash table (memory=%zdbytes) released\n",
sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE);
}
static int ip_vs_dh_dest_changed(struct ip_vs_service *svc,
struct ip_vs_dest *dest)
{
struct ip_vs_dh_state *s = svc->sched_data;
/* assign the hash buckets with the updated service */
ip_vs_dh_reassign(s, 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_iphdr *iph)
{
struct ip_vs_dest *dest;
struct ip_vs_dh_state *s;
IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
s = (struct ip_vs_dh_state *) svc->sched_data;
dest = ip_vs_dh_get(svc->af, s, &iph->daddr);
if (!dest
|| !(dest->flags & IP_VS_DEST_F_AVAILABLE)
|| atomic_read(&dest->weight) <= 0
|| is_overloaded(dest)) {
ip_vs_scheduler_err(svc, "no destination available");
return NULL;
}
IP_VS_DBG_BUF(6, "DH: destination IP address %s --> server %s:%d\n",
IP_VS_DBG_ADDR(svc->af, &iph->daddr),
IP_VS_DBG_ADDR(dest->af, &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,
.n_list = LIST_HEAD_INIT(ip_vs_dh_scheduler.n_list),
.init_service = ip_vs_dh_init_svc,
.done_service = ip_vs_dh_done_svc,
.add_dest = ip_vs_dh_dest_changed,
.del_dest = ip_vs_dh_dest_changed,
.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);
synchronize_rcu();
}
module_init(ip_vs_dh_init);
module_exit(ip_vs_dh_cleanup);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("ipvs destination hashing scheduler");
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