1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * IPVS:        Source Hashing scheduling module
4 *
5 * Authors:     Wensong Zhang <wensong@gnuchina.org>
6 *
7 * Changes:
8 */
9
10/*
11 * The sh algorithm is to select server by the hash key of source IP
12 * address. The pseudo code is as follows:
13 *
14 *       n <- servernode[src_ip];
15 *       if (n is dead) OR
16 *          (n is overloaded) or (n.weight <= 0) then
17 *                 return NULL;
18 *
19 *       return n;
20 *
21 * Notes that servernode is a 256-bucket hash table that maps the hash
22 * index derived from packet source IP address to the current server
23 * array. If the sh scheduler is used in cache cluster, it is good to
24 * combine it with cache_bypass feature. When the statically assigned
25 * server is dead or overloaded, the load balancer can bypass the cache
26 * server and send requests to the original server directly.
27 *
28 * The weight destination attribute can be used to control the
29 * distribution of connections to the destinations in servernode. The
30 * greater the weight, the more connections the destination
31 * will receive.
32 *
33 */
34
35#define KMSG_COMPONENT "IPVS"
36#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
37
38#include <linux/ip.h>
39#include <linux/slab.h>
40#include <linux/module.h>
41#include <linux/kernel.h>
42#include <linux/skbuff.h>
43
44#include <net/ip_vs.h>
45
46#include <net/tcp.h>
47#include <linux/udp.h>
48#include <linux/sctp.h>
49
50
51/*
52 *      IPVS SH bucket
53 */
54struct ip_vs_sh_bucket {
55	struct ip_vs_dest __rcu	*dest;	/* real server (cache) */
56};
57
58/*
59 *     for IPVS SH entry hash table
60 */
61#ifndef CONFIG_IP_VS_SH_TAB_BITS
62#define CONFIG_IP_VS_SH_TAB_BITS        8
63#endif
64#define IP_VS_SH_TAB_BITS               CONFIG_IP_VS_SH_TAB_BITS
65#define IP_VS_SH_TAB_SIZE               (1 << IP_VS_SH_TAB_BITS)
66#define IP_VS_SH_TAB_MASK               (IP_VS_SH_TAB_SIZE - 1)
67
68struct ip_vs_sh_state {
69	struct rcu_head			rcu_head;
70	struct ip_vs_sh_bucket		buckets[IP_VS_SH_TAB_SIZE];
71};
72
73/* Helper function to determine if server is unavailable */
74static inline bool is_unavailable(struct ip_vs_dest *dest)
75{
76	return atomic_read(&dest->weight) <= 0 ||
77	       dest->flags & IP_VS_DEST_F_OVERLOAD;
78}
79
80/*
81 *	Returns hash value for IPVS SH entry
82 */
83static inline unsigned int
84ip_vs_sh_hashkey(int af, const union nf_inet_addr *addr,
85		 __be16 port, unsigned int offset)
86{
87	__be32 addr_fold = addr->ip;
88
89#ifdef CONFIG_IP_VS_IPV6
90	if (af == AF_INET6)
91		addr_fold = addr->ip6[0]^addr->ip6[1]^
92			    addr->ip6[2]^addr->ip6[3];
93#endif
94	return (offset + hash_32(ntohs(port) + ntohl(addr_fold),
95				 IP_VS_SH_TAB_BITS)) &
96		IP_VS_SH_TAB_MASK;
97}
98
99
100/*
101 *      Get ip_vs_dest associated with supplied parameters.
102 */
103static inline struct ip_vs_dest *
104ip_vs_sh_get(struct ip_vs_service *svc, struct ip_vs_sh_state *s,
105	     const union nf_inet_addr *addr, __be16 port)
106{
107	unsigned int hash = ip_vs_sh_hashkey(svc->af, addr, port, 0);
108	struct ip_vs_dest *dest = rcu_dereference(s->buckets[hash].dest);
109
110	return (!dest || is_unavailable(dest)) ? NULL : dest;
111}
112
113
114/* As ip_vs_sh_get, but with fallback if selected server is unavailable
115 *
116 * The fallback strategy loops around the table starting from a "random"
117 * point (in fact, it is chosen to be the original hash value to make the
118 * algorithm deterministic) to find a new server.
119 */
120static inline struct ip_vs_dest *
121ip_vs_sh_get_fallback(struct ip_vs_service *svc, struct ip_vs_sh_state *s,
122		      const union nf_inet_addr *addr, __be16 port)
123{
124	unsigned int offset, roffset;
125	unsigned int hash, ihash;
126	struct ip_vs_dest *dest;
127
128	/* first try the dest it's supposed to go to */
129	ihash = ip_vs_sh_hashkey(svc->af, addr, port, 0);
130	dest = rcu_dereference(s->buckets[ihash].dest);
131	if (!dest)
132		return NULL;
133	if (!is_unavailable(dest))
134		return dest;
135
136	IP_VS_DBG_BUF(6, "SH: selected unavailable server %s:%d, reselecting",
137		      IP_VS_DBG_ADDR(dest->af, &dest->addr), ntohs(dest->port));
138
139	/* if the original dest is unavailable, loop around the table
140	 * starting from ihash to find a new dest
141	 */
142	for (offset = 0; offset < IP_VS_SH_TAB_SIZE; offset++) {
143		roffset = (offset + ihash) % IP_VS_SH_TAB_SIZE;
144		hash = ip_vs_sh_hashkey(svc->af, addr, port, roffset);
145		dest = rcu_dereference(s->buckets[hash].dest);
146		if (!dest)
147			break;
148		if (!is_unavailable(dest))
149			return dest;
150		IP_VS_DBG_BUF(6, "SH: selected unavailable "
151			      "server %s:%d (offset %d), reselecting",
152			      IP_VS_DBG_ADDR(dest->af, &dest->addr),
153			      ntohs(dest->port), roffset);
154	}
155
156	return NULL;
157}
158
159/*
160 *      Assign all the hash buckets of the specified table with the service.
161 */
162static int
163ip_vs_sh_reassign(struct ip_vs_sh_state *s, struct ip_vs_service *svc)
164{
165	int i;
166	struct ip_vs_sh_bucket *b;
167	struct list_head *p;
168	struct ip_vs_dest *dest;
169	int d_count;
170	bool empty;
171
172	b = &s->buckets[0];
173	p = &svc->destinations;
174	empty = list_empty(p);
175	d_count = 0;
176	for (i=0; i<IP_VS_SH_TAB_SIZE; i++) {
177		dest = rcu_dereference_protected(b->dest, 1);
178		if (dest)
179			ip_vs_dest_put(dest);
180		if (empty)
181			RCU_INIT_POINTER(b->dest, NULL);
182		else {
183			if (p == &svc->destinations)
184				p = p->next;
185
186			dest = list_entry(p, struct ip_vs_dest, n_list);
187			ip_vs_dest_hold(dest);
188			RCU_INIT_POINTER(b->dest, dest);
189
190			IP_VS_DBG_BUF(6, "assigned i: %d dest: %s weight: %d\n",
191				      i, IP_VS_DBG_ADDR(dest->af, &dest->addr),
192				      atomic_read(&dest->weight));
193
194			/* Don't move to next dest until filling weight */
195			if (++d_count >= atomic_read(&dest->weight)) {
196				p = p->next;
197				d_count = 0;
198			}
199
200		}
201		b++;
202	}
203	return 0;
204}
205
206
207/*
208 *      Flush all the hash buckets of the specified table.
209 */
210static void ip_vs_sh_flush(struct ip_vs_sh_state *s)
211{
212	int i;
213	struct ip_vs_sh_bucket *b;
214	struct ip_vs_dest *dest;
215
216	b = &s->buckets[0];
217	for (i=0; i<IP_VS_SH_TAB_SIZE; i++) {
218		dest = rcu_dereference_protected(b->dest, 1);
219		if (dest) {
220			ip_vs_dest_put(dest);
221			RCU_INIT_POINTER(b->dest, NULL);
222		}
223		b++;
224	}
225}
226
227
228static int ip_vs_sh_init_svc(struct ip_vs_service *svc)
229{
230	struct ip_vs_sh_state *s;
231
232	/* allocate the SH table for this service */
233	s = kzalloc(sizeof(struct ip_vs_sh_state), GFP_KERNEL);
234	if (s == NULL)
235		return -ENOMEM;
236
237	svc->sched_data = s;
238	IP_VS_DBG(6, "SH hash table (memory=%zdbytes) allocated for "
239		  "current service\n",
240		  sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE);
241
242	/* assign the hash buckets with current dests */
243	ip_vs_sh_reassign(s, svc);
244
245	return 0;
246}
247
248
249static void ip_vs_sh_done_svc(struct ip_vs_service *svc)
250{
251	struct ip_vs_sh_state *s = svc->sched_data;
252
253	/* got to clean up hash buckets here */
254	ip_vs_sh_flush(s);
255
256	/* release the table itself */
257	kfree_rcu(s, rcu_head);
258	IP_VS_DBG(6, "SH hash table (memory=%zdbytes) released\n",
259		  sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE);
260}
261
262
263static int ip_vs_sh_dest_changed(struct ip_vs_service *svc,
264				 struct ip_vs_dest *dest)
265{
266	struct ip_vs_sh_state *s = svc->sched_data;
267
268	/* assign the hash buckets with the updated service */
269	ip_vs_sh_reassign(s, svc);
270
271	return 0;
272}
273
274
275/* Helper function to get port number */
276static inline __be16
277ip_vs_sh_get_port(const struct sk_buff *skb, struct ip_vs_iphdr *iph)
278{
279	__be16 _ports[2], *ports;
280
281	/* At this point we know that we have a valid packet of some kind.
282	 * Because ICMP packets are only guaranteed to have the first 8
283	 * bytes, let's just grab the ports.  Fortunately they're in the
284	 * same position for all three of the protocols we care about.
285	 */
286	switch (iph->protocol) {
287	case IPPROTO_TCP:
288	case IPPROTO_UDP:
289	case IPPROTO_SCTP:
290		ports = skb_header_pointer(skb, iph->len, sizeof(_ports),
291					   &_ports);
292		if (unlikely(!ports))
293			return 0;
294
295		if (likely(!ip_vs_iph_inverse(iph)))
296			return ports[0];
297		else
298			return ports[1];
299	default:
300		return 0;
301	}
302}
303
304
305/*
306 *      Source Hashing scheduling
307 */
308static struct ip_vs_dest *
309ip_vs_sh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
310		  struct ip_vs_iphdr *iph)
311{
312	struct ip_vs_dest *dest;
313	struct ip_vs_sh_state *s;
314	__be16 port = 0;
315	const union nf_inet_addr *hash_addr;
316
317	hash_addr = ip_vs_iph_inverse(iph) ? &iph->daddr : &iph->saddr;
318
319	IP_VS_DBG(6, "ip_vs_sh_schedule(): Scheduling...\n");
320
321	if (svc->flags & IP_VS_SVC_F_SCHED_SH_PORT)
322		port = ip_vs_sh_get_port(skb, iph);
323
324	s = (struct ip_vs_sh_state *) svc->sched_data;
325
326	if (svc->flags & IP_VS_SVC_F_SCHED_SH_FALLBACK)
327		dest = ip_vs_sh_get_fallback(svc, s, hash_addr, port);
328	else
329		dest = ip_vs_sh_get(svc, s, hash_addr, port);
330
331	if (!dest) {
332		ip_vs_scheduler_err(svc, "no destination available");
333		return NULL;
334	}
335
336	IP_VS_DBG_BUF(6, "SH: source IP address %s --> server %s:%d\n",
337		      IP_VS_DBG_ADDR(svc->af, hash_addr),
338		      IP_VS_DBG_ADDR(dest->af, &dest->addr),
339		      ntohs(dest->port));
340
341	return dest;
342}
343
344
345/*
346 *      IPVS SH Scheduler structure
347 */
348static struct ip_vs_scheduler ip_vs_sh_scheduler =
349{
350	.name =			"sh",
351	.refcnt =		ATOMIC_INIT(0),
352	.module =		THIS_MODULE,
353	.n_list	 =		LIST_HEAD_INIT(ip_vs_sh_scheduler.n_list),
354	.init_service =		ip_vs_sh_init_svc,
355	.done_service =		ip_vs_sh_done_svc,
356	.add_dest =		ip_vs_sh_dest_changed,
357	.del_dest =		ip_vs_sh_dest_changed,
358	.upd_dest =		ip_vs_sh_dest_changed,
359	.schedule =		ip_vs_sh_schedule,
360};
361
362
363static int __init ip_vs_sh_init(void)
364{
365	return register_ip_vs_scheduler(&ip_vs_sh_scheduler);
366}
367
368
369static void __exit ip_vs_sh_cleanup(void)
370{
371	unregister_ip_vs_scheduler(&ip_vs_sh_scheduler);
372	synchronize_rcu();
373}
374
375
376module_init(ip_vs_sh_init);
377module_exit(ip_vs_sh_cleanup);
378MODULE_LICENSE("GPL");
379MODULE_DESCRIPTION("ipvs source hashing scheduler");
380