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Subject[RFC,net-next, 2/5] vrf: track associations between VRF devices and tables
Date
Add the data structures and the processing logic to keep track of the
associations between VRF devices and routing tables.
When a VRF is instantiated, it needs to refer to a given routing table.
For each table, we explicitly keep track of the existing VRFs that refer to
the table.

Signed-off-by: Andrea Mayer <andrea.mayer@uniroma2.it>
---
drivers/net/vrf.c | 272 +++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 267 insertions(+), 5 deletions(-)

diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c
index 43928a1c2f2a..f772aac6a04c 100644
--- a/drivers/net/vrf.c
+++ b/drivers/net/vrf.c
@@ -21,6 +21,7 @@
#include <net/rtnetlink.h>
#include <linux/u64_stats_sync.h>
#include <linux/hashtable.h>
+#include <linux/spinlock_types.h>

#include <linux/inetdevice.h>
#include <net/arp.h>
@@ -35,12 +36,74 @@
#include <net/netns/generic.h>

#define DRV_NAME "vrf"
-#define DRV_VERSION "1.0"
+#define DRV_VERSION "1.1"

#define FIB_RULE_PREF 1000 /* default preference for FIB rules */

+#define HT_MAP_BITS 4
+#define HASH_INITVAL ((u32)0xcafef00d)
+
+struct vrf_map {
+ DECLARE_HASHTABLE(ht, HT_MAP_BITS);
+ spinlock_t vmap_lock;
+
+ /* shared_tables:
+ * count how many distinct tables does not comply with the
+ * strict mode requirement.
+ * shared_table value must be 0 in order to switch to strict mode.
+ *
+ * example of evolution of shared_table:
+ * | time
+ * add vrf0 --> table 100 shared_tables = 0 | t0
+ * add vrf1 --> table 101 shared_tables = 0 | t1
+ * add vrf2 --> table 100 shared_tables = 1 | t2
+ * add vrf3 --> table 100 shared_tables = 1 | t3
+ * add vrf4 --> table 101 shared_tables = 2 v t4
+ *
+ * shared_tables is a "step function" (or "staircase function")
+ * and is increased by one when the second vrf is associated to a table
+ *
+ * at t2, vrf0 and vrf2 are bound to table 100: shared_table = 1.
+ *
+ * at t3, another dev (vrf3) is bound to the same table 100 but the
+ * shared_table counters is still 1.
+ * This means that no matter how many new vrfs will register on the
+ * table 100, the shared_table will not increase (considering only
+ * table 100).
+ *
+ * at t4, vrf4 is bound to table 101, and shared_table = 2.
+ *
+ * Looking at the value of shared_tables we can immediately know if
+ * the strict_mode can or cannot be enforced. Indeed, strict_mode
+ * can be enforced iff shared_table = 0.
+ *
+ * Conversely, shared_table is decreased when a vrf is de-associated
+ * from a table with exactly two associated vrfs.
+ */
+ int shared_tables;
+
+ bool strict_mode;
+};
+
+struct vrf_map_elem {
+ struct hlist_node hnode;
+ struct list_head vrf_list; /* VRFs registered to this table */
+
+ u32 table_id;
+ int users;
+ int ifindex;
+};
+
static unsigned int vrf_net_id;

+/* per netns vrf data */
+struct netns_vrf {
+ /* protected by rtnl lock */
+ bool add_fib_rules;
+
+ struct vrf_map vmap;
+};
+
struct net_vrf {
struct rtable __rcu *rth;
struct rt6_info __rcu *rt6;
@@ -48,6 +111,9 @@ struct net_vrf {
struct fib6_table *fib6_table;
#endif
u32 tb_id;
+
+ struct list_head me_list; /* entry in vrf_map_elem */
+ int ifindex;
};

struct pcpu_dstats {
@@ -103,6 +169,173 @@ static void vrf_get_stats64(struct net_device *dev,
}
}

+static struct vrf_map *netns_vrf_map(struct net *net)
+{
+ struct netns_vrf *nn_vrf = net_generic(net, vrf_net_id);
+
+ return &nn_vrf->vmap;
+}
+
+static struct vrf_map *netns_vrf_map_by_dev(struct net_device *dev)
+{
+ return netns_vrf_map(dev_net(dev));
+}
+
+static struct vrf_map_elem *vrf_map_elem_alloc(gfp_t flags)
+{
+ struct vrf_map_elem *me;
+
+ me = kmalloc(sizeof(*me), flags);
+ if (!me)
+ return NULL;
+
+ return me;
+}
+
+static void vrf_map_elem_free(struct vrf_map_elem *me)
+{
+ kfree(me);
+}
+
+static void vrf_map_elem_init(struct vrf_map_elem *me, int table_id,
+ int ifindex, int users)
+{
+ me->table_id = table_id;
+ me->ifindex = ifindex;
+ me->users = users;
+ INIT_LIST_HEAD(&me->vrf_list);
+}
+
+static struct vrf_map_elem *vrf_map_lookup_elem(struct vrf_map *vmap,
+ u32 table_id)
+{
+ struct vrf_map_elem *me;
+ u32 key;
+
+ key = jhash_1word(table_id, HASH_INITVAL);
+ hash_for_each_possible(vmap->ht, me, hnode, key) {
+ if (me->table_id == table_id)
+ return me;
+ }
+
+ return NULL;
+}
+
+static void vrf_map_add_elem(struct vrf_map *vmap, struct vrf_map_elem *me)
+{
+ u32 table_id = me->table_id;
+ u32 key;
+
+ key = jhash_1word(table_id, HASH_INITVAL);
+ hash_add(vmap->ht, &me->hnode, key);
+}
+
+static void vrf_map_del_elem(struct vrf_map_elem *me)
+{
+ hash_del(&me->hnode);
+}
+
+static void vrf_map_lock(struct vrf_map *vmap) __acquires(&vmap->vmap_lock)
+{
+ spin_lock(&vmap->vmap_lock);
+}
+
+static void vrf_map_unlock(struct vrf_map *vmap) __releases(&vmap->vmap_lock)
+{
+ spin_unlock(&vmap->vmap_lock);
+}
+
+/* called with rtnl lock held */
+static int
+vrf_map_register_dev(struct net_device *dev, struct netlink_ext_ack *extack)
+{
+ struct vrf_map *vmap = netns_vrf_map_by_dev(dev);
+ struct net_vrf *vrf = netdev_priv(dev);
+ struct vrf_map_elem *new_me, *me;
+ u32 table_id = vrf->tb_id;
+ bool free_new_me = false;
+ int users;
+ int res;
+
+ /* we pre-allocate elements used in the spin-locked section (so that we
+ * keep the spinlock as short as possibile).
+ */
+ new_me = vrf_map_elem_alloc(GFP_KERNEL);
+ if (!new_me)
+ return -ENOMEM;
+
+ vrf_map_elem_init(new_me, table_id, dev->ifindex, 0);
+
+ vrf_map_lock(vmap);
+
+ me = vrf_map_lookup_elem(vmap, table_id);
+ if (!me) {
+ me = new_me;
+ vrf_map_add_elem(vmap, me);
+ goto link_vrf;
+ }
+
+ /* we already have an entry in the vrf_map, so it means there is (at
+ * least) a vrf registered on the specific table.
+ */
+ free_new_me = true;
+ if (vmap->strict_mode) {
+ /* vrfs cannot share the same table */
+ NL_SET_ERR_MSG(extack, "Table is used by another VRF");
+ res = -EBUSY;
+ goto unlock;
+ }
+
+link_vrf:
+ users = ++me->users;
+ if (users == 2)
+ ++vmap->shared_tables;
+
+ list_add(&vrf->me_list, &me->vrf_list);
+
+ res = 0;
+
+unlock:
+ vrf_map_unlock(vmap);
+
+ /* clean-up, if needed */
+ if (free_new_me)
+ vrf_map_elem_free(new_me);
+
+ return res;
+}
+
+/* called with rtnl lock held */
+static void vrf_map_unregister_dev(struct net_device *dev)
+{
+ struct vrf_map *vmap = netns_vrf_map_by_dev(dev);
+ struct net_vrf *vrf = netdev_priv(dev);
+ u32 table_id = vrf->tb_id;
+ struct vrf_map_elem *me;
+ int users;
+
+ vrf_map_lock(vmap);
+
+ me = vrf_map_lookup_elem(vmap, table_id);
+ if (!me)
+ goto unlock;
+
+ list_del(&vrf->me_list);
+
+ users = --me->users;
+ if (users == 1) {
+ --vmap->shared_tables;
+ } else if (users == 0) {
+ vrf_map_del_elem(me);
+
+ /* no one will refer to this element anymore */
+ vrf_map_elem_free(me);
+ }
+
+unlock:
+ vrf_map_unlock(vmap);
+}
+
/* by default VRF devices do not have a qdisc and are expected
* to be created with only a single queue.
*/
@@ -1319,6 +1552,8 @@ static void vrf_dellink(struct net_device *dev, struct list_head *head)
netdev_for_each_lower_dev(dev, port_dev, iter)
vrf_del_slave(dev, port_dev);

+ vrf_map_unregister_dev(dev);
+
unregister_netdevice_queue(dev, head);
}

@@ -1327,6 +1562,7 @@ static int vrf_newlink(struct net *src_net, struct net_device *dev,
struct netlink_ext_ack *extack)
{
struct net_vrf *vrf = netdev_priv(dev);
+ struct netns_vrf *nn_vrf;
bool *add_fib_rules;
struct net *net;
int err;
@@ -1349,11 +1585,26 @@ static int vrf_newlink(struct net *src_net, struct net_device *dev,
if (err)
goto out;

+ /* mapping between table_id and vrf;
+ * note: such binding could not be done in the dev init function
+ * because dev->ifindex id is not available yet.
+ */
+ vrf->ifindex = dev->ifindex;
+
+ err = vrf_map_register_dev(dev, extack);
+ if (err) {
+ unregister_netdevice(dev);
+ goto out;
+ }
+
net = dev_net(dev);
- add_fib_rules = net_generic(net, vrf_net_id);
+ nn_vrf = net_generic(net, vrf_net_id);
+
+ add_fib_rules = &nn_vrf->add_fib_rules;
if (*add_fib_rules) {
err = vrf_add_fib_rules(dev);
if (err) {
+ vrf_map_unregister_dev(dev);
unregister_netdevice(dev);
goto out;
}
@@ -1440,12 +1691,23 @@ static struct notifier_block vrf_notifier_block __read_mostly = {
.notifier_call = vrf_device_event,
};

+static int vrf_map_init(struct vrf_map *vmap)
+{
+ spin_lock_init(&vmap->vmap_lock);
+ hash_init(vmap->ht);
+
+ vmap->strict_mode = false;
+
+ return 0;
+}
+
/* Initialize per network namespace state */
static int __net_init vrf_netns_init(struct net *net)
{
- bool *add_fib_rules = net_generic(net, vrf_net_id);
+ struct netns_vrf *nn_vrf = net_generic(net, vrf_net_id);

- *add_fib_rules = true;
+ nn_vrf->add_fib_rules = true;
+ vrf_map_init(&nn_vrf->vmap);

return 0;
}
@@ -1453,7 +1715,7 @@ static int __net_init vrf_netns_init(struct net *net)
static struct pernet_operations vrf_net_ops __net_initdata = {
.init = vrf_netns_init,
.id = &vrf_net_id,
- .size = sizeof(bool),
+ .size = sizeof(struct netns_vrf),
};

static int __init vrf_init_module(void)
--
2.20.1
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