ipvs: Add ovf scheduler

The weighted overflow scheduling algorithm directs network connections
to the server with the highest weight that is currently available
and overflows to the next when active connections exceed the node's weight.

Signed-off-by: Raducu Deaconu <rhadoo.io88@gmail.com>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>

net/netfilter/ipvs/Kconfig

@@ -162,6 +162,17 @@ config  IP_VS_FO
 	  If you want to compile it in kernel, say Y. To compile it as a
 	  module, choose M here. If unsure, say N.
 
+config  IP_VS_OVF
+	tristate "weighted overflow scheduling"
+	---help---
+	  The weighted overflow scheduling algorithm directs network
+	  connections to the server with the highest weight that is
+	  currently available and overflows to the next when active
+	  connections exceed the node's weight.
+
+	  If you want to compile it in kernel, say Y. To compile it as a
+	  module, choose M here. If unsure, say N.
+
 config	IP_VS_LBLC
 	tristate "locality-based least-connection scheduling"
 	---help---

net/netfilter/ipvs/Makefile

@@ -27,6 +27,7 @@ obj-$(CONFIG_IP_VS_WRR) += ip_vs_wrr.o
 obj-$(CONFIG_IP_VS_LC) += ip_vs_lc.o
 obj-$(CONFIG_IP_VS_WLC) += ip_vs_wlc.o
 obj-$(CONFIG_IP_VS_FO) += ip_vs_fo.o
+obj-$(CONFIG_IP_VS_OVF) += ip_vs_ovf.o
 obj-$(CONFIG_IP_VS_LBLC) += ip_vs_lblc.o
 obj-$(CONFIG_IP_VS_LBLCR) += ip_vs_lblcr.o
 obj-$(CONFIG_IP_VS_DH) += ip_vs_dh.o

net/netfilter/ipvs/ip_vs_ovf.c

@@ -0,0 +1,86 @@
+/*
+ * IPVS:        Overflow-Connection Scheduling module
+ *
+ * Authors:     Raducu Deaconu <rhadoo_io@yahoo.com>
+ *
+ *              This program is free software; you can redistribute it and/or
+ *              modify it under the terms of the GNU General Public License
+ *              as published by the Free Software Foundation; either version
+ *              2 of the License, or (at your option) any later version.
+ *
+ * Scheduler implements "overflow" loadbalancing according to number of active
+ * connections , will keep all conections to the node with the highest weight
+ * and overflow to the next node if the number of connections exceeds the node's
+ * weight.
+ * Note that this scheduler might not be suitable for UDP because it only uses
+ * active connections
+ *
+ */
+
+#define KMSG_COMPONENT "IPVS"
+#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+
+#include <net/ip_vs.h>
+
+/* OVF Connection scheduling  */
+static struct ip_vs_dest *
+ip_vs_ovf_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
+		   struct ip_vs_iphdr *iph)
+{
+	struct ip_vs_dest *dest, *h = NULL;
+	int hw = 0, w;
+
+	IP_VS_DBG(6, "ip_vs_ovf_schedule(): Scheduling...\n");
+	/* select the node with highest weight, go to next in line if active
+	* connections exceed weight
+	*/
+	list_for_each_entry_rcu(dest, &svc->destinations, n_list) {
+		w = atomic_read(&dest->weight);
+		if ((dest->flags & IP_VS_DEST_F_OVERLOAD) ||
+		    atomic_read(&dest->activeconns) > w ||
+		    w == 0)
+			continue;
+		if (!h || w > hw) {
+			h = dest;
+			hw = w;
+		}
+	}
+
+	if (h) {
+		IP_VS_DBG_BUF(6, "OVF: server %s:%u active %d w %d\n",
+			      IP_VS_DBG_ADDR(h->af, &h->addr),
+			      ntohs(h->port),
+			      atomic_read(&h->activeconns),
+			      atomic_read(&h->weight));
+		return h;
+	}
+
+	ip_vs_scheduler_err(svc, "no destination available");
+	return NULL;
+}
+
+static struct ip_vs_scheduler ip_vs_ovf_scheduler = {
+	.name =			"ovf",
+	.refcnt =		ATOMIC_INIT(0),
+	.module =		THIS_MODULE,
+	.n_list =		LIST_HEAD_INIT(ip_vs_ovf_scheduler.n_list),
+	.schedule =		ip_vs_ovf_schedule,
+};
+
+static int __init ip_vs_ovf_init(void)
+{
+	return register_ip_vs_scheduler(&ip_vs_ovf_scheduler);
+}
+
+static void __exit ip_vs_ovf_cleanup(void)
+{
+	unregister_ip_vs_scheduler(&ip_vs_ovf_scheduler);
+	synchronize_rcu();
+}
+
+module_init(ip_vs_ovf_init);
+module_exit(ip_vs_ovf_cleanup);
+MODULE_LICENSE("GPL");