// SPDX-License-Identifier: GPL-2.0-or-later
/*
* IPVS: Locality-Based Least-Connection scheduling module
*
* Authors: Wensong Zhang <[email protected]>
*
* Changes:
* Martin Hamilton : fixed the terrible locking bugs
* *lock(tbl->lock) ==> *lock(&tbl->lock)
* Wensong Zhang : fixed the uninitialized tbl->lock bug
* Wensong Zhang : added doing full expiration check to
* collect stale entries of 24+ hours when
* no partial expire check in a half hour
* Julian Anastasov : replaced del_timer call with del_timer_sync
* to avoid the possible race between timer
* handler and del_timer thread in SMP
*/
/*
* The lblc algorithm is as follows (pseudo code):
*
* if cachenode[dest_ip] is null then
* n, cachenode[dest_ip] <- {weighted least-conn node};
* else
* n <- cachenode[dest_ip];
* if (n is dead) OR
* (n.conns>n.weight AND
* there is a node m with m.conns<m.weight/2) then
* n, cachenode[dest_ip] <- {weighted least-conn node};
*
* return n;
*
* Thanks must go to Wenzhuo Zhang for talking WCCP to me and pushing
* me to write this module.
*/
#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/jiffies.h>
#include <linux/hash.h>
/* for sysctl */
#include <linux/fs.h>
#include <linux/sysctl.h>
#include <net/ip_vs.h>
/*
* It is for garbage collection of stale IPVS lblc entries,
* when the table is full.
*/
#define CHECK_EXPIRE_INTERVAL (60*HZ)
#define ENTRY_TIMEOUT (6*60*HZ)
#define DEFAULT_EXPIRATION (24*60*60*HZ)
/*
* It is for full expiration check.
* When there is no partial expiration check (garbage collection)
* in a half hour, do a full expiration check to collect stale
* entries that haven't been touched for a day.
*/
#define COUNT_FOR_FULL_EXPIRATION 30
/*
* for IPVS lblc entry hash table
*/
#ifndef CONFIG_IP_VS_LBLC_TAB_BITS
#define CONFIG_IP_VS_LBLC_TAB_BITS 10
#endif
#define IP_VS_LBLC_TAB_BITS CONFIG_IP_VS_LBLC_TAB_BITS
#define IP_VS_LBLC_TAB_SIZE (1 << IP_VS_LBLC_TAB_BITS)
#define IP_VS_LBLC_TAB_MASK (IP_VS_LBLC_TAB_SIZE - 1)
/*
* IPVS lblc entry represents an association between destination
* IP address and its destination server
*/
struct ip_vs_lblc_entry {
struct hlist_node list;
int af; /* address family */
union nf_inet_addr addr; /* destination IP address */
struct ip_vs_dest *dest; /* real server (cache) */
unsigned long lastuse; /* last used time */
struct rcu_head rcu_head;
};
/*
* IPVS lblc hash table
*/
struct ip_vs_lblc_table {
struct rcu_head rcu_head;
struct hlist_head bucket[IP_VS_LBLC_TAB_SIZE]; /* hash bucket */
struct timer_list periodic_timer; /* collect stale entries */
struct ip_vs_service *svc; /* pointer back to service */
atomic_t entries; /* number of entries */
int max_size; /* maximum size of entries */
int rover; /* rover for expire check */
int counter; /* counter for no expire */
bool dead;
};
/*
* IPVS LBLC sysctl table
*/
#ifdef CONFIG_SYSCTL
static struct ctl_table vs_vars_table[] = {
{
.procname = "lblc_expiration",
.data = NULL,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_jiffies,
},
};
#endif
static void ip_vs_lblc_rcu_free(struct rcu_head *head)
{
struct ip_vs_lblc_entry *en = container_of(head,
struct ip_vs_lblc_entry,
rcu_head);
ip_vs_dest_put_and_free(en->dest);
kfree(en);
}
static inline void ip_vs_lblc_del(struct ip_vs_lblc_entry *en)
{
hlist_del_rcu(&en->list);
call_rcu(&en->rcu_head, ip_vs_lblc_rcu_free);
}
/*
* Returns hash value for IPVS LBLC entry
*/
static inline unsigned int
ip_vs_lblc_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_LBLC_TAB_BITS);
}
/*
* Hash an entry in the ip_vs_lblc_table.
* returns bool success.
*/
static void
ip_vs_lblc_hash(struct ip_vs_lblc_table *tbl, struct ip_vs_lblc_entry *en)
{
unsigned int hash = ip_vs_lblc_hashkey(en->af, &en->addr);
hlist_add_head_rcu(&en->list, &tbl->bucket[hash]);
atomic_inc(&tbl->entries);
}
/* Get ip_vs_lblc_entry associated with supplied parameters. */
static inline struct ip_vs_lblc_entry *
ip_vs_lblc_get(int af, struct ip_vs_lblc_table *tbl,
const union nf_inet_addr *addr)
{
unsigned int hash = ip_vs_lblc_hashkey(af, addr);
struct ip_vs_lblc_entry *en;
hlist_for_each_entry_rcu(en, &tbl->bucket[hash], list)
if (ip_vs_addr_equal(af, &en->addr, addr))
return en;
return NULL;
}
/*
* Create or update an ip_vs_lblc_entry, which is a mapping of a destination IP
* address to a server. Called under spin lock.
*/
static inline struct ip_vs_lblc_entry *
ip_vs_lblc_new(struct ip_vs_lblc_table *tbl, const union nf_inet_addr *daddr,
u16 af, struct ip_vs_dest *dest)
{
struct ip_vs_lblc_entry *en;
en = ip_vs_lblc_get(af, tbl, daddr);
if (en) {
if (en->dest == dest)
return en;
ip_vs_lblc_del(en);
}
en = kmalloc(sizeof(*en), GFP_ATOMIC);
if (!en)
return NULL;
en->af = af;
ip_vs_addr_copy(af, &en->addr, daddr);
en->lastuse = jiffies;
ip_vs_dest_hold(dest);
en->dest = dest;
ip_vs_lblc_hash(tbl, en);
return en;
}
/*
* Flush all the entries of the specified table.
*/
static void ip_vs_lblc_flush(struct ip_vs_service *svc)
{
struct ip_vs_lblc_table *tbl = svc->sched_data;
struct ip_vs_lblc_entry *en;
struct hlist_node *next;
int i;
spin_lock_bh(&svc->sched_lock);
tbl->dead = true;
for (i = 0; i < IP_VS_LBLC_TAB_SIZE; i++) {
hlist_for_each_entry_safe(en, next, &tbl->bucket[i], list) {
ip_vs_lblc_del(en);
atomic_dec(&tbl->entries);
}
}
spin_unlock_bh(&svc->sched_lock);
}
static int sysctl_lblc_expiration(struct ip_vs_service *svc)
{
#ifdef CONFIG_SYSCTL
return svc->ipvs->sysctl_lblc_expiration;
#else
return DEFAULT_EXPIRATION;
#endif
}
static inline void ip_vs_lblc_full_check(struct ip_vs_service *svc)
{
struct ip_vs_lblc_table *tbl = svc->sched_data;
struct ip_vs_lblc_entry *en;
struct hlist_node *next;
unsigned long now = jiffies;
int i, j;
for (i = 0, j = tbl->rover; i < IP_VS_LBLC_TAB_SIZE; i++) {
j = (j + 1) & IP_VS_LBLC_TAB_MASK;
spin_lock(&svc->sched_lock);
hlist_for_each_entry_safe(en, next, &tbl->bucket[j], list) {
if (time_before(now,
en->lastuse +
sysctl_lblc_expiration(svc)))
continue;
ip_vs_lblc_del(en);
atomic_dec(&tbl->entries);
}
spin_unlock(&svc->sched_lock);
}
tbl->rover = j;
}
/*
* Periodical timer handler for IPVS lblc table
* It is used to collect stale entries when the number of entries
* exceeds the maximum size of the table.
*
* Fixme: we probably need more complicated algorithm to collect
* entries that have not been used for a long time even
* if the number of entries doesn't exceed the maximum size
* of the table.
* The full expiration check is for this purpose now.
*/
static void ip_vs_lblc_check_expire(struct timer_list *t)
{
struct ip_vs_lblc_table *tbl = from_timer(tbl, t, periodic_timer);
struct ip_vs_service *svc = tbl->svc;
unsigned long now = jiffies;
int goal;
int i, j;
struct ip_vs_lblc_entry *en;
struct hlist_node *next;
if ((tbl->counter % COUNT_FOR_FULL_EXPIRATION) == 0) {
/* do full expiration check */
ip_vs_lblc_full_check(svc);
tbl->counter = 1;
goto out;
}
if (atomic_read(&tbl->entries) <= tbl->max_size) {
tbl->counter++;
goto out;
}
goal = (atomic_read(&tbl->entries) - tbl->max_size)*4/3;
if (goal > tbl->max_size/2)
goal = tbl->max_size/2;
for (i = 0, j = tbl->rover; i < IP_VS_LBLC_TAB_SIZE; i++) {
j = (j + 1) & IP_VS_LBLC_TAB_MASK;
spin_lock(&svc->sched_lock);
hlist_for_each_entry_safe(en, next, &tbl->bucket[j], list) {
if (time_before(now, en->lastuse + ENTRY_TIMEOUT))
continue;
ip_vs_lblc_del(en);
atomic_dec(&tbl->entries);
goal--;
}
spin_unlock(&svc->sched_lock);
if (goal <= 0)
break;
}
tbl->rover = j;
out:
mod_timer(&tbl->periodic_timer, jiffies + CHECK_EXPIRE_INTERVAL);
}
static int ip_vs_lblc_init_svc(struct ip_vs_service *svc)
{
int i;
struct ip_vs_lblc_table *tbl;
/*
* Allocate the ip_vs_lblc_table for this service
*/
tbl = kmalloc(sizeof(*tbl), GFP_KERNEL);
if (tbl == NULL)
return -ENOMEM;
svc->sched_data = tbl;
IP_VS_DBG(6, "LBLC hash table (memory=%zdbytes) allocated for "
"current service\n", sizeof(*tbl));
/*
* Initialize the hash buckets
*/
for (i = 0; i < IP_VS_LBLC_TAB_SIZE; i++) {
INIT_HLIST_HEAD(&tbl->bucket[i]);
}
tbl->max_size = IP_VS_LBLC_TAB_SIZE*16;
tbl->rover = 0;
tbl->counter = 1;
tbl->dead = false;
tbl->svc = svc;
atomic_set(&tbl->entries, 0);
/*
* Hook periodic timer for garbage collection
*/
timer_setup(&tbl->periodic_timer, ip_vs_lblc_check_expire, 0);
mod_timer(&tbl->periodic_timer, jiffies + CHECK_EXPIRE_INTERVAL);
return 0;
}
static void ip_vs_lblc_done_svc(struct ip_vs_service *svc)
{
struct ip_vs_lblc_table *tbl = svc->sched_data;
/* remove periodic timer */
timer_shutdown_sync(&tbl->periodic_timer);
/* got to clean up table entries here */
ip_vs_lblc_flush(svc);
/* release the table itself */
kfree_rcu(tbl, rcu_head);
IP_VS_DBG(6, "LBLC hash table (memory=%zdbytes) released\n",
sizeof(*tbl));
}
static inline struct ip_vs_dest *
__ip_vs_lblc_schedule(struct ip_vs_service *svc)
{
struct ip_vs_dest *dest, *least;
int loh, doh;
/*
* We use the following formula to estimate the load:
* (dest overhead) / dest->weight
*
* Remember -- no floats in kernel mode!!!
* The comparison of h1*w2 > h2*w1 is equivalent to that of
* h1/w1 > h2/w2
* if every weight is larger than zero.
*
* The server with weight=0 is quiesced and will not receive any
* new connection.
*/
list_for_each_entry_rcu(dest, &svc->destinations, n_list) {
if (dest->flags & IP_VS_DEST_F_OVERLOAD)
continue;
if (atomic_read(&dest->weight) > 0) {
least = dest;
loh = ip_vs_dest_conn_overhead(least);
goto nextstage;
}
}
return NULL;
/*
* Find the destination with the least load.
*/
nextstage:
list_for_each_entry_continue_rcu(dest, &svc->destinations, n_list) {
if (dest->flags & IP_VS_DEST_F_OVERLOAD)
continue;
doh = ip_vs_dest_conn_overhead(dest);
if ((__s64)loh * atomic_read(&dest->weight) >
(__s64)doh * atomic_read(&least->weight)) {
least = dest;
loh = doh;
}
}
IP_VS_DBG_BUF(6, "LBLC: server %s:%d "
"activeconns %d refcnt %d weight %d overhead %d\n",
IP_VS_DBG_ADDR(least->af, &least->addr),
ntohs(least->port),
atomic_read(&least->activeconns),
refcount_read(&least->refcnt),
atomic_read(&least->weight), loh);
return least;
}
/*
* If this destination server is overloaded and there is a less loaded
* server, then return true.
*/
static inline int
is_overloaded(struct ip_vs_dest *dest, struct ip_vs_service *svc)
{
if (atomic_read(&dest->activeconns) > atomic_read(&dest->weight)) {
struct ip_vs_dest *d;
list_for_each_entry_rcu(d, &svc->destinations, n_list) {
if (atomic_read(&d->activeconns)*2
< atomic_read(&d->weight)) {
return 1;
}
}
}
return 0;
}
/*
* Locality-Based (weighted) Least-Connection scheduling
*/
static struct ip_vs_dest *
ip_vs_lblc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
struct ip_vs_iphdr *iph)
{
struct ip_vs_lblc_table *tbl = svc->sched_data;
struct ip_vs_dest *dest = NULL;
struct ip_vs_lblc_entry *en;
IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
/* First look in our cache */
en = ip_vs_lblc_get(svc->af, tbl, &iph->daddr);
if (en) {
/* We only hold a read lock, but this is atomic */
en->lastuse = jiffies;
/*
* If the destination is not available, i.e. it's in the trash,
* we must ignore it, as it may be removed from under our feet,
* if someone drops our reference count. Our caller only makes
* sure that destinations, that are not in the trash, are not
* moved to the trash, while we are scheduling. But anyone can
* free up entries from the trash at any time.
*/
dest = en->dest;
if ((dest->flags & IP_VS_DEST_F_AVAILABLE) &&
atomic_read(&dest->weight) > 0 && !is_overloaded(dest, svc))
goto out;
}
/* No cache entry or it is invalid, time to schedule */
dest = __ip_vs_lblc_schedule(svc);
if (!dest) {
ip_vs_scheduler_err(svc, "no destination available");
return NULL;
}
/* If we fail to create a cache entry, we'll just use the valid dest */
spin_lock_bh(&svc->sched_lock);
if (!tbl->dead)
ip_vs_lblc_new(tbl, &iph->daddr, svc->af, dest);
spin_unlock_bh(&svc->sched_lock);
out:
IP_VS_DBG_BUF(6, "LBLC: 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 LBLC Scheduler structure
*/
static struct ip_vs_scheduler ip_vs_lblc_scheduler = {
.name = "lblc",
.refcnt = ATOMIC_INIT(0),
.module = THIS_MODULE,
.n_list = LIST_HEAD_INIT(ip_vs_lblc_scheduler.n_list),
.init_service = ip_vs_lblc_init_svc,
.done_service = ip_vs_lblc_done_svc,
.schedule = ip_vs_lblc_schedule,
};
/*
* per netns init.
*/
#ifdef CONFIG_SYSCTL
static int __net_init __ip_vs_lblc_init(struct net *net)
{
struct netns_ipvs *ipvs = net_ipvs(net);
size_t vars_table_size = ARRAY_SIZE(vs_vars_table);
if (!ipvs)
return -ENOENT;
if (!net_eq(net, &init_net)) {
ipvs->lblc_ctl_table = kmemdup(vs_vars_table,
sizeof(vs_vars_table),
GFP_KERNEL);
if (ipvs->lblc_ctl_table == NULL)
return -ENOMEM;
/* Don't export sysctls to unprivileged users */
if (net->user_ns != &init_user_ns)
vars_table_size = 0;
} else
ipvs->lblc_ctl_table = vs_vars_table;
ipvs->sysctl_lblc_expiration = DEFAULT_EXPIRATION;
ipvs->lblc_ctl_table[0].data = &ipvs->sysctl_lblc_expiration;
ipvs->lblc_ctl_header = register_net_sysctl_sz(net, "net/ipv4/vs",
ipvs->lblc_ctl_table,
vars_table_size);
if (!ipvs->lblc_ctl_header) {
if (!net_eq(net, &init_net))
kfree(ipvs->lblc_ctl_table);
return -ENOMEM;
}
return 0;
}
static void __net_exit __ip_vs_lblc_exit(struct net *net)
{
struct netns_ipvs *ipvs = net_ipvs(net);
unregister_net_sysctl_table(ipvs->lblc_ctl_header);
if (!net_eq(net, &init_net))
kfree(ipvs->lblc_ctl_table);
}
#else
static int __net_init __ip_vs_lblc_init(struct net *net) { return 0; }
static void __net_exit __ip_vs_lblc_exit(struct net *net) { }
#endif
static struct pernet_operations ip_vs_lblc_ops = {
.init = __ip_vs_lblc_init,
.exit = __ip_vs_lblc_exit,
};
static int __init ip_vs_lblc_init(void)
{
int ret;
ret = register_pernet_subsys(&ip_vs_lblc_ops);
if (ret)
return ret;
ret = register_ip_vs_scheduler(&ip_vs_lblc_scheduler);
if (ret)
unregister_pernet_subsys(&ip_vs_lblc_ops);
return ret;
}
static void __exit ip_vs_lblc_cleanup(void)
{
unregister_ip_vs_scheduler(&ip_vs_lblc_scheduler);
unregister_pernet_subsys(&ip_vs_lblc_ops);
rcu_barrier();
}
module_init(ip_vs_lblc_init);
module_exit(ip_vs_lblc_cleanup);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("ipvs locality-based least-connection scheduler");
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