[v3,net-next,6/9] net: Generic resolver backend

diff --git a/include/net/resolver.h b/include/net/resolver.h
new file mode 100644
index 000000000000..f38c7e9f1205
--- /dev/null
+++ b/include/net/resolver.h
@@ -0,0 +1,43 @@ 
+/*
+ * Generic network address resovler backend
+ *
+ * Copyright (c) 2017 Tom Herbert <tom@quantonium.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.
+ */
+
+#ifndef __NET_RESOLVER_H
+#define __NET_RESOLVER_H
+
+#include <linux/rhashtable.h>
+#include <linux/types.h>
+
+struct net_rslv;
+
+typedef int (*net_rslv_cmpfn)(struct net_rslv *nrslv, const void *key,
+			      const void *object);
+
+struct net_rslv {
+	struct rhashtable rhash_table;
+	struct rhashtable_params params;
+	net_rslv_cmpfn rslv_cmp;
+	size_t obj_size;
+	spinlock_t *locks;
+	unsigned int locks_mask;
+	unsigned int hash_rnd;
+};
+
+struct net_rslv *net_rslv_create(size_t obj_size, size_t key_len,
+				 size_t max_size, net_rslv_cmpfn cmp_fn);
+
+void net_rslv_destroy(struct net_rslv *nrslv);
+
+int net_rslv_lookup_and_create(struct net_rslv *nrslv, void *key,
+			       unsigned int timeout);
+
+void net_rslv_resolved(struct net_rslv *nrslv, void *key);
+
+#endif /* __NET_RESOLVER_H */
diff --git a/net/Kconfig b/net/Kconfig
index 9dba2715919d..b1e73325de6a 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -399,6 +399,7 @@  source "net/ceph/Kconfig"
 source "net/nfc/Kconfig"
 source "net/psample/Kconfig"
 source "net/ife/Kconfig"
+source "net/resolver/Kconfig"
 
 config LWTUNNEL
 	bool "Network light weight tunnels"
diff --git a/net/Makefile b/net/Makefile
index 14fede520840..6b3b0c5e676a 100644
--- a/net/Makefile
+++ b/net/Makefile
@@ -86,3 +86,4 @@  obj-y				+= l3mdev/
 endif
 obj-$(CONFIG_QRTR)		+= qrtr/
 obj-$(CONFIG_NET_NCSI)		+= ncsi/
+obj-$(CONFIG_NET_RESOLVER)	+= resolver/
diff --git a/net/resolver/Kconfig b/net/resolver/Kconfig
new file mode 100644
index 000000000000..99eff276e0b7
--- /dev/null
+++ b/net/resolver/Kconfig
@@ -0,0 +1,7 @@ 
+#
+# Net resolver configuration
+#
+
+menuconfig NET_RESOLVER
+        tristate
+	default n
diff --git a/net/resolver/Makefile b/net/resolver/Makefile
new file mode 100644
index 000000000000..fc15e6e5f19f
--- /dev/null
+++ b/net/resolver/Makefile
@@ -0,0 +1,8 @@ 
+#
+# Makefile for the generic network resolver
+#
+
+obj-$(CONFIG_NET_RESOLVER) += net_resolver.o
+
+net_resolver-objs := resolver.o
+
diff --git a/net/resolver/resolver.c b/net/resolver/resolver.c
new file mode 100644
index 000000000000..32a915ed8f93
--- /dev/null
+++ b/net/resolver/resolver.c
@@ -0,0 +1,283 @@ 
+/*
+ * net/core/resolver.c - Generic network address resolver backend
+ *
+ * Copyright (c) 2017 Tom Herbert <tom@quantonium.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.
+ */
+
+#include <linux/errno.h>
+#include <linux/ip.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/netlink.h>
+#include <linux/skbuff.h>
+#include <linux/socket.h>
+#include <linux/types.h>
+#include <linux/vmalloc.h>
+#include <net/checksum.h>
+#include <net/ip.h>
+#include <net/ip6_fib.h>
+#include <net/lwtunnel.h>
+#include <net/protocol.h>
+#include <net/resolver.h>
+
+struct net_rslv_ent {
+	struct rhash_head node;
+	struct delayed_work timeout_work;
+	struct net_rslv *nrslv;
+
+	struct rcu_head rcu;
+
+	char object[];
+};
+
+static void net_rslv_destroy_rcu(struct rcu_head *head)
+{
+	struct net_rslv_ent *nrent = container_of(head, struct net_rslv_ent,
+						  rcu);
+	kfree(nrent);
+}
+
+static void net_rslv_destroy_entry(struct net_rslv *nrslv,
+				   struct net_rslv_ent *nrent)
+{
+	call_rcu(&nrent->rcu, net_rslv_destroy_rcu);
+}
+
+static inline spinlock_t *net_rslv_get_lock(struct net_rslv *nrslv, void *key)
+{
+	unsigned int hash;
+
+	/* Use the rhashtable hash function */
+	hash = rht_key_get_hash(&nrslv->rhash_table, key, nrslv->params,
+				nrslv->hash_rnd);
+
+	return &nrslv->locks[hash & nrslv->locks_mask];
+}
+
+static void net_rslv_delayed_work(struct work_struct *w)
+{
+	struct delayed_work *delayed_work = to_delayed_work(w);
+	struct net_rslv_ent *nrent = container_of(delayed_work,
+						  struct net_rslv_ent,
+						  timeout_work);
+	struct net_rslv *nrslv = nrent->nrslv;
+	spinlock_t *lock = net_rslv_get_lock(nrslv, nrent->object);
+
+	spin_lock(lock);
+	rhashtable_remove_fast(&nrslv->rhash_table, &nrent->node,
+			       nrslv->params);
+	spin_unlock(lock);
+
+	net_rslv_destroy_entry(nrslv, nrent);
+}
+
+static void net_rslv_ent_free_cb(void *ptr, void *arg)
+{
+	struct net_rslv_ent *nrent = (struct net_rslv_ent *)ptr;
+	struct net_rslv *nrslv = nrent->nrslv;
+
+	net_rslv_destroy_entry(nrslv, nrent);
+}
+
+void net_rslv_resolved(struct net_rslv *nrslv, void *key)
+{
+	spinlock_t *lock = net_rslv_get_lock(nrslv, key);
+	struct net_rslv_ent *nrent;
+
+	rcu_read_lock();
+
+	nrent = rhashtable_lookup_fast(&nrslv->rhash_table, key,
+				       nrslv->params);
+	if (!nrent)
+		goto out;
+
+	/* Cancel timer first */
+	cancel_delayed_work_sync(&nrent->timeout_work);
+
+	spin_lock(lock);
+
+	/* Lookup again just in case someone already removed */
+	nrent = rhashtable_lookup_fast(&nrslv->rhash_table, key,
+				       nrslv->params);
+	if (unlikely(!nrent)) {
+		spin_unlock(lock);
+		goto out;
+	}
+
+	rhashtable_remove_fast(&nrslv->rhash_table, &nrent->node,
+			       nrslv->params);
+	spin_unlock(lock);
+
+	net_rslv_destroy_entry(nrslv, nrent);
+
+out:
+	rcu_read_unlock();
+}
+EXPORT_SYMBOL_GPL(net_rslv_resolved);
+
+/* Called with hash bucket lock held */
+static int net_rslv_new_ent(struct net_rslv *nrslv, void *key,
+			    unsigned int timeout)
+{
+	struct net_rslv_ent *nrent;
+	int err;
+
+	nrent = kzalloc(sizeof(*nrent) + nrslv->obj_size, GFP_KERNEL);
+	if (!nrent)
+		return -ENOMEM;
+
+	/* Key is always at beginning of object data */
+	memcpy(nrent->object, key, nrslv->params.key_len);
+
+	nrent->nrslv = nrslv;
+
+	/* Put in hash table */
+	err = rhashtable_lookup_insert_fast(&nrslv->rhash_table,
+					    &nrent->node, nrslv->params);
+	if (err) {
+		kfree(nrent);
+		return err;
+	}
+
+	if (timeout) {
+		/* Schedule timeout for resolver */
+		INIT_DELAYED_WORK(&nrent->timeout_work, net_rslv_delayed_work);
+		schedule_delayed_work(&nrent->timeout_work,
+				      msecs_to_jiffies(timeout));
+	}
+
+	return 0;
+}
+
+int net_rslv_lookup_and_create(struct net_rslv *nrslv, void *key,
+			       unsigned int timeout)
+{
+	spinlock_t *lock = net_rslv_get_lock(nrslv, key);
+	int ret;
+
+	if (rhashtable_lookup_fast(&nrslv->rhash_table, key, nrslv->params))
+		return -EEXIST;
+
+	spin_lock(lock);
+
+	/* Check if someone beat us to the punch */
+	if (rhashtable_lookup_fast(&nrslv->rhash_table, key, nrslv->params)) {
+		spin_unlock(lock);
+		return -EEXIST;
+	}
+
+	ret = net_rslv_new_ent(nrslv, key, timeout);
+
+	spin_unlock(lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(net_rslv_lookup_and_create);
+
+static int net_rslv_cmp(struct rhashtable_compare_arg *arg,
+			const void *obj)
+{
+	struct net_rslv *nrslv = container_of(arg->ht, struct net_rslv,
+					      rhash_table);
+
+	return nrslv->rslv_cmp(nrslv, arg->key, obj);
+}
+
+#define LOCKS_PER_CPU	10
+#define MAX_LOCKS 1024
+
+struct net_rslv *net_rslv_create(size_t obj_size, size_t key_len,
+				 size_t max_size,
+				 net_rslv_cmpfn cmp_fn)
+{
+	struct net_rslv *nrslv;
+	int err;
+
+	if (key_len < obj_size)
+		return ERR_PTR(-EINVAL);
+
+	nrslv = kzalloc(sizeof(*nrslv), GFP_KERNEL);
+	if (!nrslv)
+		return ERR_PTR(-ENOMEM);
+
+	err = alloc_bucket_spinlocks(&nrslv->locks, &nrslv->locks_mask,
+				     MAX_LOCKS, LOCKS_PER_CPU, GFP_KERNEL);
+	if (err)
+		return ERR_PTR(err);
+
+	nrslv->obj_size = obj_size;
+	nrslv->rslv_cmp = cmp_fn;
+	get_random_bytes(&nrslv->hash_rnd, sizeof(nrslv->hash_rnd));
+
+	nrslv->params.head_offset = offsetof(struct net_rslv_ent, node);
+	nrslv->params.key_offset = offsetof(struct net_rslv_ent, object);
+	nrslv->params.key_len = key_len;
+	nrslv->params.max_size = max_size;
+	nrslv->params.min_size = 256;
+	nrslv->params.automatic_shrinking = true;
+	nrslv->params.obj_cmpfn = cmp_fn ? net_rslv_cmp : NULL;
+
+	rhashtable_init(&nrslv->rhash_table, &nrslv->params);
+
+	return nrslv;
+}
+EXPORT_SYMBOL_GPL(net_rslv_create);
+
+static void net_rslv_cancel_all_delayed_work(struct net_rslv *nrslv)
+{
+	struct rhashtable_iter iter;
+	struct net_rslv_ent *nrent;
+	int ret;
+
+	ret = rhashtable_walk_init(&nrslv->rhash_table, &iter, GFP_ATOMIC);
+	if (WARN_ON(ret))
+		return;
+
+	rhashtable_walk_start(&iter);
+
+	for (;;) {
+		nrent = rhashtable_walk_next(&iter);
+
+		if (IS_ERR(nrent)) {
+			if (PTR_ERR(nrent) == -EAGAIN) {
+				/* New table, we're okay to continue */
+				continue;
+			}
+			ret = PTR_ERR(nrent);
+			break;
+		} else if (!nrent) {
+			break;
+		}
+
+		cancel_delayed_work_sync(&nrent->timeout_work);
+	}
+
+	rhashtable_walk_stop(&iter);
+	rhashtable_walk_exit(&iter);
+}
+
+void net_rslv_destroy(struct net_rslv *nrslv)
+{
+	/* First cancel delayed work in all the nodes. We don't want
+	 * delayed work trying to remove nodes from the table while
+	 * rhashtable_free_and_destroy is walking.
+	 */
+	net_rslv_cancel_all_delayed_work(nrslv);
+
+	rhashtable_free_and_destroy(&nrslv->rhash_table,
+				    net_rslv_ent_free_cb, NULL);
+
+	free_bucket_spinlocks(nrslv->locks);
+
+	kfree(nrslv);
+}
+EXPORT_SYMBOL_GPL(net_rslv_destroy);
+
+MODULE_AUTHOR("Tom Herbert <tom@quantonium.net>");
+MODULE_LICENSE("GPL");
+