1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * IPVS:        Round-Robin Scheduling module
4  *
5  * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
6  *              Peter Kese <peter.kese@ijs.si>
7  *
8  * Fixes/Changes:
9  *     Wensong Zhang            :     changed the ip_vs_rr_schedule to return dest
10  *     Julian Anastasov         :     fixed the NULL pointer access bug in debugging
11  *     Wensong Zhang            :     changed some comestics things for debugging
12  *     Wensong Zhang            :     changed for the d-linked destination list
13  *     Wensong Zhang            :     added the ip_vs_rr_update_svc
14  *     Wensong Zhang            :     added any dest with weight=0 is quiesced
15  */
16 
17 #define KMSG_COMPONENT "IPVS"
18 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
19 
20 #include <linux/module.h>
21 #include <linux/kernel.h>
22 
23 #include <net/ip_vs.h>
24 
25 
ip_vs_rr_init_svc(struct ip_vs_service * svc)26 static int ip_vs_rr_init_svc(struct ip_vs_service *svc)
27 {
28 	svc->sched_data = &svc->destinations;
29 	return 0;
30 }
31 
32 
ip_vs_rr_del_dest(struct ip_vs_service * svc,struct ip_vs_dest * dest)33 static int ip_vs_rr_del_dest(struct ip_vs_service *svc, struct ip_vs_dest *dest)
34 {
35 	struct list_head *p;
36 
37 	spin_lock_bh(&svc->sched_lock);
38 	p = (struct list_head *) svc->sched_data;
39 	/* dest is already unlinked, so p->prev is not valid but
40 	 * p->next is valid, use it to reach previous entry.
41 	 */
42 	if (p == &dest->n_list)
43 		svc->sched_data = p->next->prev;
44 	spin_unlock_bh(&svc->sched_lock);
45 	return 0;
46 }
47 
48 
49 /*
50  * Round-Robin Scheduling
51  */
52 static struct ip_vs_dest *
ip_vs_rr_schedule(struct ip_vs_service * svc,const struct sk_buff * skb,struct ip_vs_iphdr * iph)53 ip_vs_rr_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
54 		  struct ip_vs_iphdr *iph)
55 {
56 	struct list_head *p;
57 	struct ip_vs_dest *dest, *last;
58 	int pass = 0;
59 
60 	IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
61 
62 	spin_lock_bh(&svc->sched_lock);
63 	p = (struct list_head *) svc->sched_data;
64 	last = dest = list_entry(p, struct ip_vs_dest, n_list);
65 
66 	do {
67 		list_for_each_entry_continue_rcu(dest,
68 						 &svc->destinations,
69 						 n_list) {
70 			if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
71 			    atomic_read(&dest->weight) > 0)
72 				/* HIT */
73 				goto out;
74 			if (dest == last)
75 				goto stop;
76 		}
77 		pass++;
78 		/* Previous dest could be unlinked, do not loop forever.
79 		 * If we stay at head there is no need for 2nd pass.
80 		 */
81 	} while (pass < 2 && p != &svc->destinations);
82 
83 stop:
84 	spin_unlock_bh(&svc->sched_lock);
85 	ip_vs_scheduler_err(svc, "no destination available");
86 	return NULL;
87 
88   out:
89 	svc->sched_data = &dest->n_list;
90 	spin_unlock_bh(&svc->sched_lock);
91 	IP_VS_DBG_BUF(6, "RR: server %s:%u "
92 		      "activeconns %d refcnt %d weight %d\n",
93 		      IP_VS_DBG_ADDR(dest->af, &dest->addr), ntohs(dest->port),
94 		      atomic_read(&dest->activeconns),
95 		      refcount_read(&dest->refcnt), atomic_read(&dest->weight));
96 
97 	return dest;
98 }
99 
100 
101 static struct ip_vs_scheduler ip_vs_rr_scheduler = {
102 	.name =			"rr",			/* name */
103 	.refcnt =		ATOMIC_INIT(0),
104 	.module =		THIS_MODULE,
105 	.n_list =		LIST_HEAD_INIT(ip_vs_rr_scheduler.n_list),
106 	.init_service =		ip_vs_rr_init_svc,
107 	.add_dest =		NULL,
108 	.del_dest =		ip_vs_rr_del_dest,
109 	.schedule =		ip_vs_rr_schedule,
110 };
111 
ip_vs_rr_init(void)112 static int __init ip_vs_rr_init(void)
113 {
114 	return register_ip_vs_scheduler(&ip_vs_rr_scheduler);
115 }
116 
ip_vs_rr_cleanup(void)117 static void __exit ip_vs_rr_cleanup(void)
118 {
119 	unregister_ip_vs_scheduler(&ip_vs_rr_scheduler);
120 	synchronize_rcu();
121 }
122 
123 module_init(ip_vs_rr_init);
124 module_exit(ip_vs_rr_cleanup);
125 MODULE_LICENSE("GPL");
126