2 * IPVS: Source Hashing scheduling module
4 * Authors: Wensong Zhang <wensong@gnuchina.org>
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
16 * The sh algorithm is to select server by the hash key of source IP
17 * address. The pseudo code is as follows:
19 * n <- servernode[src_ip];
21 * (n is overloaded) or (n.weight <= 0) then
26 * Notes that servernode is a 256-bucket hash table that maps the hash
27 * index derived from packet source IP address to the current server
28 * array. If the sh scheduler is used in cache cluster, it is good to
29 * combine it with cache_bypass feature. When the statically assigned
30 * server is dead or overloaded, the load balancer can bypass the cache
31 * server and send requests to the original server directly.
33 * The weight destination attribute can be used to control the
34 * distribution of connections to the destinations in servernode. The
35 * greater the weight, the more connections the destination
40 #define KMSG_COMPONENT "IPVS"
41 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
44 #include <linux/slab.h>
45 #include <linux/module.h>
46 #include <linux/kernel.h>
47 #include <linux/skbuff.h>
49 #include <net/ip_vs.h>
52 #include <linux/udp.h>
53 #include <linux/sctp.h>
59 struct ip_vs_sh_bucket
{
60 struct ip_vs_dest __rcu
*dest
; /* real server (cache) */
64 * for IPVS SH entry hash table
66 #ifndef CONFIG_IP_VS_SH_TAB_BITS
67 #define CONFIG_IP_VS_SH_TAB_BITS 8
69 #define IP_VS_SH_TAB_BITS CONFIG_IP_VS_SH_TAB_BITS
70 #define IP_VS_SH_TAB_SIZE (1 << IP_VS_SH_TAB_BITS)
71 #define IP_VS_SH_TAB_MASK (IP_VS_SH_TAB_SIZE - 1)
73 struct ip_vs_sh_state
{
74 struct rcu_head rcu_head
;
75 struct ip_vs_sh_bucket buckets
[IP_VS_SH_TAB_SIZE
];
78 /* Helper function to determine if server is unavailable */
79 static inline bool is_unavailable(struct ip_vs_dest
*dest
)
81 return atomic_read(&dest
->weight
) <= 0 ||
82 dest
->flags
& IP_VS_DEST_F_OVERLOAD
;
86 * Returns hash value for IPVS SH entry
88 static inline unsigned int
89 ip_vs_sh_hashkey(int af
, const union nf_inet_addr
*addr
,
90 __be16 port
, unsigned int offset
)
92 __be32 addr_fold
= addr
->ip
;
94 #ifdef CONFIG_IP_VS_IPV6
96 addr_fold
= addr
->ip6
[0]^addr
->ip6
[1]^
97 addr
->ip6
[2]^addr
->ip6
[3];
99 return (offset
+ (ntohs(port
) + ntohl(addr_fold
))*2654435761UL) &
105 * Get ip_vs_dest associated with supplied parameters.
107 static inline struct ip_vs_dest
*
108 ip_vs_sh_get(struct ip_vs_service
*svc
, struct ip_vs_sh_state
*s
,
109 const union nf_inet_addr
*addr
, __be16 port
)
111 unsigned int hash
= ip_vs_sh_hashkey(svc
->af
, addr
, port
, 0);
112 struct ip_vs_dest
*dest
= rcu_dereference(s
->buckets
[hash
].dest
);
114 return (!dest
|| is_unavailable(dest
)) ? NULL
: dest
;
118 /* As ip_vs_sh_get, but with fallback if selected server is unavailable
120 * The fallback strategy loops around the table starting from a "random"
121 * point (in fact, it is chosen to be the original hash value to make the
122 * algorithm deterministic) to find a new server.
124 static inline struct ip_vs_dest
*
125 ip_vs_sh_get_fallback(struct ip_vs_service
*svc
, struct ip_vs_sh_state
*s
,
126 const union nf_inet_addr
*addr
, __be16 port
)
128 unsigned int offset
, roffset
;
129 unsigned int hash
, ihash
;
130 struct ip_vs_dest
*dest
;
132 /* first try the dest it's supposed to go to */
133 ihash
= ip_vs_sh_hashkey(svc
->af
, addr
, port
, 0);
134 dest
= rcu_dereference(s
->buckets
[ihash
].dest
);
137 if (!is_unavailable(dest
))
140 IP_VS_DBG_BUF(6, "SH: selected unavailable server %s:%d, reselecting",
141 IP_VS_DBG_ADDR(dest
->af
, &dest
->addr
), ntohs(dest
->port
));
143 /* if the original dest is unavailable, loop around the table
144 * starting from ihash to find a new dest
146 for (offset
= 0; offset
< IP_VS_SH_TAB_SIZE
; offset
++) {
147 roffset
= (offset
+ ihash
) % IP_VS_SH_TAB_SIZE
;
148 hash
= ip_vs_sh_hashkey(svc
->af
, addr
, port
, roffset
);
149 dest
= rcu_dereference(s
->buckets
[hash
].dest
);
152 if (!is_unavailable(dest
))
154 IP_VS_DBG_BUF(6, "SH: selected unavailable "
155 "server %s:%d (offset %d), reselecting",
156 IP_VS_DBG_ADDR(dest
->af
, &dest
->addr
),
157 ntohs(dest
->port
), roffset
);
164 * Assign all the hash buckets of the specified table with the service.
167 ip_vs_sh_reassign(struct ip_vs_sh_state
*s
, struct ip_vs_service
*svc
)
170 struct ip_vs_sh_bucket
*b
;
172 struct ip_vs_dest
*dest
;
177 p
= &svc
->destinations
;
178 empty
= list_empty(p
);
180 for (i
=0; i
<IP_VS_SH_TAB_SIZE
; i
++) {
181 dest
= rcu_dereference_protected(b
->dest
, 1);
183 ip_vs_dest_put(dest
);
185 RCU_INIT_POINTER(b
->dest
, NULL
);
187 if (p
== &svc
->destinations
)
190 dest
= list_entry(p
, struct ip_vs_dest
, n_list
);
191 ip_vs_dest_hold(dest
);
192 RCU_INIT_POINTER(b
->dest
, dest
);
194 IP_VS_DBG_BUF(6, "assigned i: %d dest: %s weight: %d\n",
195 i
, IP_VS_DBG_ADDR(dest
->af
, &dest
->addr
),
196 atomic_read(&dest
->weight
));
198 /* Don't move to next dest until filling weight */
199 if (++d_count
>= atomic_read(&dest
->weight
)) {
212 * Flush all the hash buckets of the specified table.
214 static void ip_vs_sh_flush(struct ip_vs_sh_state
*s
)
217 struct ip_vs_sh_bucket
*b
;
218 struct ip_vs_dest
*dest
;
221 for (i
=0; i
<IP_VS_SH_TAB_SIZE
; i
++) {
222 dest
= rcu_dereference_protected(b
->dest
, 1);
224 ip_vs_dest_put(dest
);
225 RCU_INIT_POINTER(b
->dest
, NULL
);
232 static int ip_vs_sh_init_svc(struct ip_vs_service
*svc
)
234 struct ip_vs_sh_state
*s
;
236 /* allocate the SH table for this service */
237 s
= kzalloc(sizeof(struct ip_vs_sh_state
), GFP_KERNEL
);
242 IP_VS_DBG(6, "SH hash table (memory=%Zdbytes) allocated for "
244 sizeof(struct ip_vs_sh_bucket
)*IP_VS_SH_TAB_SIZE
);
246 /* assign the hash buckets with current dests */
247 ip_vs_sh_reassign(s
, svc
);
253 static void ip_vs_sh_done_svc(struct ip_vs_service
*svc
)
255 struct ip_vs_sh_state
*s
= svc
->sched_data
;
257 /* got to clean up hash buckets here */
260 /* release the table itself */
261 kfree_rcu(s
, rcu_head
);
262 IP_VS_DBG(6, "SH hash table (memory=%Zdbytes) released\n",
263 sizeof(struct ip_vs_sh_bucket
)*IP_VS_SH_TAB_SIZE
);
267 static int ip_vs_sh_dest_changed(struct ip_vs_service
*svc
,
268 struct ip_vs_dest
*dest
)
270 struct ip_vs_sh_state
*s
= svc
->sched_data
;
272 /* assign the hash buckets with the updated service */
273 ip_vs_sh_reassign(s
, svc
);
279 /* Helper function to get port number */
281 ip_vs_sh_get_port(const struct sk_buff
*skb
, struct ip_vs_iphdr
*iph
)
283 __be16 _ports
[2], *ports
;
285 /* At this point we know that we have a valid packet of some kind.
286 * Because ICMP packets are only guaranteed to have the first 8
287 * bytes, let's just grab the ports. Fortunately they're in the
288 * same position for all three of the protocols we care about.
290 switch (iph
->protocol
) {
294 ports
= skb_header_pointer(skb
, iph
->len
, sizeof(_ports
),
296 if (unlikely(!ports
))
299 if (likely(!ip_vs_iph_inverse(iph
)))
310 * Source Hashing scheduling
312 static struct ip_vs_dest
*
313 ip_vs_sh_schedule(struct ip_vs_service
*svc
, const struct sk_buff
*skb
,
314 struct ip_vs_iphdr
*iph
)
316 struct ip_vs_dest
*dest
;
317 struct ip_vs_sh_state
*s
;
319 const union nf_inet_addr
*hash_addr
;
321 hash_addr
= ip_vs_iph_inverse(iph
) ? &iph
->daddr
: &iph
->saddr
;
323 IP_VS_DBG(6, "ip_vs_sh_schedule(): Scheduling...\n");
325 if (svc
->flags
& IP_VS_SVC_F_SCHED_SH_PORT
)
326 port
= ip_vs_sh_get_port(skb
, iph
);
328 s
= (struct ip_vs_sh_state
*) svc
->sched_data
;
330 if (svc
->flags
& IP_VS_SVC_F_SCHED_SH_FALLBACK
)
331 dest
= ip_vs_sh_get_fallback(svc
, s
, hash_addr
, port
);
333 dest
= ip_vs_sh_get(svc
, s
, hash_addr
, port
);
336 ip_vs_scheduler_err(svc
, "no destination available");
340 IP_VS_DBG_BUF(6, "SH: source IP address %s --> server %s:%d\n",
341 IP_VS_DBG_ADDR(svc
->af
, hash_addr
),
342 IP_VS_DBG_ADDR(dest
->af
, &dest
->addr
),
350 * IPVS SH Scheduler structure
352 static struct ip_vs_scheduler ip_vs_sh_scheduler
=
355 .refcnt
= ATOMIC_INIT(0),
356 .module
= THIS_MODULE
,
357 .n_list
= LIST_HEAD_INIT(ip_vs_sh_scheduler
.n_list
),
358 .init_service
= ip_vs_sh_init_svc
,
359 .done_service
= ip_vs_sh_done_svc
,
360 .add_dest
= ip_vs_sh_dest_changed
,
361 .del_dest
= ip_vs_sh_dest_changed
,
362 .upd_dest
= ip_vs_sh_dest_changed
,
363 .schedule
= ip_vs_sh_schedule
,
367 static int __init
ip_vs_sh_init(void)
369 return register_ip_vs_scheduler(&ip_vs_sh_scheduler
);
373 static void __exit
ip_vs_sh_cleanup(void)
375 unregister_ip_vs_scheduler(&ip_vs_sh_scheduler
);
380 module_init(ip_vs_sh_init
);
381 module_exit(ip_vs_sh_cleanup
);
382 MODULE_LICENSE("GPL");