1 files changed, 265 insertions, 0 deletions
diff --git a/net/netfilter/ipvs/ip_vs_wrr.c b/net/netfilter/ipvs/ip_vs_wrr.c
new file mode 100644
index 000000000..1bc7a0789
--- /dev/null
+++ b/net/netfilter/ipvs/ip_vs_wrr.c
@@ -0,0 +1,265 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * IPVS:        Weighted Round-Robin Scheduling module
+ *
+ * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
+ *
+ * Changes:
+ *     Wensong Zhang            :     changed the ip_vs_wrr_schedule to return dest
+ *     Wensong Zhang            :     changed some comestics things for debugging
+ *     Wensong Zhang            :     changed for the d-linked destination list
+ *     Wensong Zhang            :     added the ip_vs_wrr_update_svc
+ *     Julian Anastasov         :     fixed the bug of returning destination
+ *                                    with weight 0 when all weights are zero
+ */
+
+#define KMSG_COMPONENT "IPVS"
+#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/net.h>
+#include <linux/gcd.h>
+
+#include <net/ip_vs.h>
+
+/* The WRR algorithm depends on some caclulations:
+ * - mw: maximum weight
+ * - di: weight step, greatest common divisor from all weights
+ * - cw: current required weight
+ * As result, all weights are in the [di..mw] range with a step=di.
+ *
+ * First, we start with cw = mw and select dests with weight >= cw.
+ * Then cw is reduced with di and all dests are checked again.
+ * Last pass should be with cw = di. We have mw/di passes in total:
+ *
+ * pass 1: cw = max weight
+ * pass 2: cw = max weight - di
+ * pass 3: cw = max weight - 2 * di
+ * ...
+ * last pass: cw = di
+ *
+ * Weights are supposed to be >= di but we run in parallel with
+ * weight changes, it is possible some dest weight to be reduced
+ * below di, bad if it is the only available dest.
+ *
+ * So, we modify how mw is calculated, now it is reduced with (di - 1),
+ * so that last cw is 1 to catch such dests with weight below di:
+ * pass 1: cw = max weight - (di - 1)
+ * pass 2: cw = max weight - di - (di - 1)
+ * pass 3: cw = max weight - 2 * di - (di - 1)
+ * ...
+ * last pass: cw = 1
+ *
+ */
+
+/*
+ * current destination pointer for weighted round-robin scheduling
+ */
+struct ip_vs_wrr_mark {
+	struct ip_vs_dest *cl;	/* current dest or head */
+	int cw;			/* current weight */
+	int mw;			/* maximum weight */
+	int di;			/* decreasing interval */
+	struct rcu_head		rcu_head;
+};
+
+
+static int ip_vs_wrr_gcd_weight(struct ip_vs_service *svc)
+{
+	struct ip_vs_dest *dest;
+	int weight;
+	int g = 0;
+
+	list_for_each_entry(dest, &svc->destinations, n_list) {
+		weight = atomic_read(&dest->weight);
+		if (weight > 0) {
+			if (g > 0)
+				g = gcd(weight, g);
+			else
+				g = weight;
+		}
+	}
+	return g ? g : 1;
+}
+
+
+/*
+ *    Get the maximum weight of the service destinations.
+ */
+static int ip_vs_wrr_max_weight(struct ip_vs_service *svc)
+{
+	struct ip_vs_dest *dest;
+	int new_weight, weight = 0;
+
+	list_for_each_entry(dest, &svc->destinations, n_list) {
+		new_weight = atomic_read(&dest->weight);
+		if (new_weight > weight)
+			weight = new_weight;
+	}
+
+	return weight;
+}
+
+
+static int ip_vs_wrr_init_svc(struct ip_vs_service *svc)
+{
+	struct ip_vs_wrr_mark *mark;
+
+	/*
+	 *    Allocate the mark variable for WRR scheduling
+	 */
+	mark = kmalloc(sizeof(struct ip_vs_wrr_mark), GFP_KERNEL);
+	if (mark == NULL)
+		return -ENOMEM;
+
+	mark->cl = list_entry(&svc->destinations, struct ip_vs_dest, n_list);
+	mark->di = ip_vs_wrr_gcd_weight(svc);
+	mark->mw = ip_vs_wrr_max_weight(svc) - (mark->di - 1);
+	mark->cw = mark->mw;
+	svc->sched_data = mark;
+
+	return 0;
+}
+
+
+static void ip_vs_wrr_done_svc(struct ip_vs_service *svc)
+{
+	struct ip_vs_wrr_mark *mark = svc->sched_data;
+
+	/*
+	 *    Release the mark variable
+	 */
+	kfree_rcu(mark, rcu_head);
+}
+
+
+static int ip_vs_wrr_dest_changed(struct ip_vs_service *svc,
+				  struct ip_vs_dest *dest)
+{
+	struct ip_vs_wrr_mark *mark = svc->sched_data;
+
+	spin_lock_bh(&svc->sched_lock);
+	mark->cl = list_entry(&svc->destinations, struct ip_vs_dest, n_list);
+	mark->di = ip_vs_wrr_gcd_weight(svc);
+	mark->mw = ip_vs_wrr_max_weight(svc) - (mark->di - 1);
+	if (mark->cw > mark->mw || !mark->cw)
+		mark->cw = mark->mw;
+	else if (mark->di > 1)
+		mark->cw = (mark->cw / mark->di) * mark->di + 1;
+	spin_unlock_bh(&svc->sched_lock);
+	return 0;
+}
+
+
+/*
+ *    Weighted Round-Robin Scheduling
+ */
+static struct ip_vs_dest *
+ip_vs_wrr_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
+		   struct ip_vs_iphdr *iph)
+{
+	struct ip_vs_dest *dest, *last, *stop = NULL;
+	struct ip_vs_wrr_mark *mark = svc->sched_data;
+	bool last_pass = false, restarted = false;
+
+	IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
+
+	spin_lock_bh(&svc->sched_lock);
+	dest = mark->cl;
+	/* No available dests? */
+	if (mark->mw == 0)
+		goto err_noavail;
+	last = dest;
+	/* Stop only after all dests were checked for weight >= 1 (last pass) */
+	while (1) {
+		list_for_each_entry_continue_rcu(dest,
+						 &svc->destinations,
+						 n_list) {
+			if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
+			    atomic_read(&dest->weight) >= mark->cw)
+				goto found;
+			if (dest == stop)
+				goto err_over;
+		}
+		mark->cw -= mark->di;
+		if (mark->cw <= 0) {
+			mark->cw = mark->mw;
+			/* Stop if we tried last pass from first dest:
+			 * 1. last_pass: we started checks when cw > di but
+			 *	then all dests were checked for w >= 1
+			 * 2. last was head: the first and only traversal
+			 *	was for weight >= 1, for all dests.
+			 */
+			if (last_pass ||
+			    &last->n_list == &svc->destinations)
+				goto err_over;
+			restarted = true;
+		}
+		last_pass = mark->cw <= mark->di;
+		if (last_pass && restarted &&
+		    &last->n_list != &svc->destinations) {
+			/* First traversal was for w >= 1 but only
+			 * for dests after 'last', now do the same
+			 * for all dests up to 'last'.
+			 */
+			stop = last;
+		}
+	}
+
+found:
+	IP_VS_DBG_BUF(6, "WRR: server %s:%u "
+		      "activeconns %d refcnt %d weight %d\n",
+		      IP_VS_DBG_ADDR(dest->af, &dest->addr), ntohs(dest->port),
+		      atomic_read(&dest->activeconns),
+		      refcount_read(&dest->refcnt),
+		      atomic_read(&dest->weight));
+	mark->cl = dest;
+
+  out:
+	spin_unlock_bh(&svc->sched_lock);
+	return dest;
+
+err_noavail:
+	mark->cl = dest;
+	dest = NULL;
+	ip_vs_scheduler_err(svc, "no destination available");
+	goto out;
+
+err_over:
+	mark->cl = dest;
+	dest = NULL;
+	ip_vs_scheduler_err(svc, "no destination available: "
+			    "all destinations are overloaded");
+	goto out;
+}
+
+
+static struct ip_vs_scheduler ip_vs_wrr_scheduler = {
+	.name =			"wrr",
+	.refcnt =		ATOMIC_INIT(0),
+	.module =		THIS_MODULE,
+	.n_list =		LIST_HEAD_INIT(ip_vs_wrr_scheduler.n_list),
+	.init_service =		ip_vs_wrr_init_svc,
+	.done_service =		ip_vs_wrr_done_svc,
+	.add_dest =		ip_vs_wrr_dest_changed,
+	.del_dest =		ip_vs_wrr_dest_changed,
+	.upd_dest =		ip_vs_wrr_dest_changed,
+	.schedule =		ip_vs_wrr_schedule,
+};
+
+static int __init ip_vs_wrr_init(void)
+{
+	return register_ip_vs_scheduler(&ip_vs_wrr_scheduler) ;
+}
+
+static void __exit ip_vs_wrr_cleanup(void)
+{
+	unregister_ip_vs_scheduler(&ip_vs_wrr_scheduler);
+	synchronize_rcu();
+}
+
+module_init(ip_vs_wrr_init);
+module_exit(ip_vs_wrr_cleanup);
+MODULE_LICENSE("GPL");