[PATCH ipvs v2] ipvs: Add simple weighted failover scheduler

[Kenny Mathis <kmathis@chokepoint.net>]

Please consider this patch for addition in 3.17

Add simple weighted IPVS failover support to the Linux kernel. All
other scheduling modules implement some form of load balancing, while
this offers a simple failover solution. Connections are directed to
the appropriate server based solely on highest weight value and server
availability. Tested functionality with keepalived.

Signed-off-by: Kenny Mathis <kmathis@chokepoint.net>
---
 net/netfilter/ipvs/Kconfig    |   10 ++++++
 net/netfilter/ipvs/Makefile   |    1 +
 net/netfilter/ipvs/ip_vs_fo.c |   79 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 90 insertions(+)
 create mode 100644 net/netfilter/ipvs/ip_vs_fo.c

diff --git a/net/netfilter/ipvs/Kconfig b/net/netfilter/ipvs/Kconfig
index 0c3b167..3b6929d 100644
--- a/net/netfilter/ipvs/Kconfig
+++ b/net/netfilter/ipvs/Kconfig
@@ -152,6 +152,16 @@ config	IP_VS_WLC
 	  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_FO
+		tristate "weighted failover scheduling"
+	---help---
+	  The weighted failover scheduling algorithm directs network
+	  connections to the server with the highest weight that is
+	  currently available.
+
+	  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---
diff --git a/net/netfilter/ipvs/Makefile b/net/netfilter/ipvs/Makefile
index 34ee602..38b2723 100644
--- a/net/netfilter/ipvs/Makefile
+++ b/net/netfilter/ipvs/Makefile
@@ -26,6 +26,7 @@ obj-$(CONFIG_IP_VS_RR) += ip_vs_rr.o
 obj-$(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_LBLC) += ip_vs_lblc.o
 obj-$(CONFIG_IP_VS_LBLCR) += ip_vs_lblcr.o
 obj-$(CONFIG_IP_VS_DH) += ip_vs_dh.o
diff --git a/net/netfilter/ipvs/ip_vs_fo.c b/net/netfilter/ipvs/ip_vs_fo.c
new file mode 100644
index 0000000..6a2647d
--- /dev/null
+++ b/net/netfilter/ipvs/ip_vs_fo.c
@@ -0,0 +1,79 @@
+/*
+ * IPVS:        Weighted Fail Over module
+ *
+ * Authors:     Kenny Mathis <kmathis@chokepoint.net>
+ *
+ *              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.
+ *
+ * Changes:
+ *     Kenny Mathis            :     added initial functionality based on weight
+ *
+ */
+
+#define KMSG_COMPONENT "IPVS"
+#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+
+#include <net/ip_vs.h>
+
+/* Weighted Fail Over Module */
+static struct ip_vs_dest *
+ip_vs_fo_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
+		  struct ip_vs_iphdr *iph)
+{
+	struct ip_vs_dest *dest, *hweight = NULL;
+	int hw = 0; /* Track highest weight */
+
+	IP_VS_DBG(6, "ip_vs_fo_schedule(): Scheduling...\n");
+
+	/* Basic failover functionality
+	 * Find virtual server with highest weight and send it traffic
+	 */
+	list_for_each_entry_rcu(dest, &svc->destinations, n_list) {
+		if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
+		    atomic_read(&dest->weight) > hw) {
+			hweight = dest;
+			hw = atomic_read(&dest->weight);
+		}
+	}
+
+	if (hweight) {
+		IP_VS_DBG_BUF(6, "FO: server %s:%u activeconns %d weight %d\n",
+			      IP_VS_DBG_ADDR(svc->af, &hweight->addr),
+			      ntohs(hweight->port),
+			      atomic_read(&hweight->activeconns),
+			      atomic_read(&hweight->weight));
+		return hweight;
+	}
+
+	ip_vs_scheduler_err(svc, "no destination available");
+	return NULL;
+}
+
+static struct ip_vs_scheduler ip_vs_fo_scheduler = {
+	.name =			"fo",
+	.refcnt =		ATOMIC_INIT(0),
+	.module =		THIS_MODULE,
+	.n_list =		LIST_HEAD_INIT(ip_vs_fo_scheduler.n_list),
+	.schedule =		ip_vs_fo_schedule,
+};
+
+static int __init ip_vs_fo_init(void)
+{
+	return register_ip_vs_scheduler(&ip_vs_fo_scheduler);
+}
+
+static void __exit ip_vs_fo_cleanup(void)
+{
+	unregister_ip_vs_scheduler(&ip_vs_fo_scheduler);
+	synchronize_rcu();
+}
+
+module_init(ip_vs_fo_init);
+module_exit(ip_vs_fo_cleanup);
+MODULE_LICENSE("GPL");
-- 
1.7.9.5