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Date: Fri, 6 Jan 2017 16:33:11 -0800
From: Mahesh Bandewar <mahesh@...dewar.net>
To: David Miller <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>,
Mahesh Bandewar <mahesh@...dewar.net>,
Mahesh Bandewar <maheshb@...gle.com>,
Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH next v1] ipvlan: don't use IDR for generating dev_id
From: Mahesh Bandewar <maheshb@...gle.com>
The patch 009146d117b ("ipvlan: assign unique dev-id for each slave
device.") used ida_simple_get() to generate dev_ids assigned to the
slave devices. However (Eric has pointed out that) there is a shortcoming
with that approach as it always uses the first available ID. This
becomes a problem when a slave gets deleted and a new slave gets added.
The ID gets reassigned causing the new slave to get the same link-local
address. This side-effect is undesirable.
This patch replaces IDR logic with a simple per-port variable that keeps
incrementing and wraps around when the MAX (0xFFFE) is reached. The
only downside is that this is an inefficient (n^2) search if there are
64k (or close to 64k) slaves in the system, the dev-id search takes time.
However having these many devices in the system has it's own challenges.
Fixes: 009146d117b ("ipvlan: assign unique dev-id for each slave device.")
Signed-off-by: Mahesh Bandewar <maheshb@...gle.com>
CC: Eric Dumazet <edumazet@...gle.com>
---
drivers/net/ipvlan/ipvlan.h | 2 +-
drivers/net/ipvlan/ipvlan_main.c | 69 ++++++++++++++++++++++++++++++++++------
2 files changed, 61 insertions(+), 10 deletions(-)
diff --git a/drivers/net/ipvlan/ipvlan.h b/drivers/net/ipvlan/ipvlan.h
index 0a9068fdee0f..535f254324ba 100644
--- a/drivers/net/ipvlan/ipvlan.h
+++ b/drivers/net/ipvlan/ipvlan.h
@@ -94,10 +94,10 @@ struct ipvl_port {
struct hlist_head hlhead[IPVLAN_HASH_SIZE];
struct list_head ipvlans;
u16 mode;
+ u16 dev_id_base;
struct work_struct wq;
struct sk_buff_head backlog;
int count;
- struct ida ida;
};
struct ipvl_skb_cb {
diff --git a/drivers/net/ipvlan/ipvlan_main.c b/drivers/net/ipvlan/ipvlan_main.c
index ce7ca6a5aa8a..691662e02abb 100644
--- a/drivers/net/ipvlan/ipvlan_main.c
+++ b/drivers/net/ipvlan/ipvlan_main.c
@@ -119,7 +119,7 @@ static int ipvlan_port_create(struct net_device *dev)
skb_queue_head_init(&port->backlog);
INIT_WORK(&port->wq, ipvlan_process_multicast);
- ida_init(&port->ida);
+ port->dev_id_base = 1;
err = netdev_rx_handler_register(dev, ipvlan_handle_frame, port);
if (err)
@@ -151,7 +151,6 @@ static void ipvlan_port_destroy(struct net_device *dev)
dev_put(skb->dev);
kfree_skb(skb);
}
- ida_destroy(&port->ida);
kfree(port);
}
@@ -496,6 +495,60 @@ static int ipvlan_nl_fillinfo(struct sk_buff *skb,
return ret;
}
+static u16 ipvlan_get_dev_id(struct ipvl_port *port)
+{
+ struct ipvl_dev *ipvlan;
+ u16 tid, dev_id = 0;
+ bool found, exhausted = false, second_round = false;
+
+ /* Idea here is to get the next available ID while avoiding
+ * reuse of already used IDs. Per port variable (dev_id_base)
+ * is used to get the next available ID.
+ *
+ * Possibilities are from 0x1 to 0xfffe so finding next available
+ * ID is not be that difficult. However if the system is up for a
+ * long time and these slave devices are getting added / deleted
+ * routinely and it reaches the MAX, then only the assignment will
+ * attempt to recycle previously used IDs starting from 0x1 (Provided
+ * these are not currently in use).
+ *
+ * In case of a failure, dev-id search will return 0. All IDs in-use
+ * case is very inefficient (n^2 search) but having close to 64k
+ * slaves has it's own system limitations.
+ */
+ while (!exhausted) {
+ tid = port->dev_id_base++;
+
+ if (tid == 0xFFFE) {
+ /* Reached MAX; restart from 1 */
+ port->dev_id_base = 1;
+ if (second_round)
+ exhausted = true;
+ else
+ second_round = true;
+ continue;
+ }
+ /* Should not be same as the masters' (if present) */
+ if (tid == port->dev->dev_id)
+ continue;
+ /* Make sure that it's already not assigned to any of the
+ * existing slaves.
+ */
+ found = false;
+ list_for_each_entry(ipvlan, &port->ipvlans, pnode) {
+ if (ipvlan->dev->dev_id == tid) {
+ found = true;
+ break;
+ }
+ }
+ if (!found) {
+ dev_id = tid;
+ break;
+ }
+ }
+ return dev_id;
+}
+
static int ipvlan_link_new(struct net *src_net, struct net_device *dev,
struct nlattr *tb[], struct nlattr *data[])
{
@@ -540,10 +593,11 @@ static int ipvlan_link_new(struct net *src_net, struct net_device *dev,
* Assign IDs between 0x1 and 0xFFFE (used by the master) to each
* slave link [see addrconf_ifid_eui48()].
*/
- err = ida_simple_get(&port->ida, 1, 0xFFFE, GFP_KERNEL);
- if (err < 0)
+ dev->dev_id = ipvlan_get_dev_id(port);
+ if (dev->dev_id == 0) {
+ err = -ENOSPC;
goto destroy_ipvlan_port;
- dev->dev_id = err;
+ }
/* TODO Probably put random address here to be presented to the
* world but keep using the physical-dev address for the outgoing
@@ -555,7 +609,7 @@ static int ipvlan_link_new(struct net *src_net, struct net_device *dev,
err = register_netdevice(dev);
if (err < 0)
- goto remove_ida;
+ goto destroy_ipvlan_port;
err = netdev_upper_dev_link(phy_dev, dev);
if (err) {
@@ -574,8 +628,6 @@ static int ipvlan_link_new(struct net *src_net, struct net_device *dev,
netdev_upper_dev_unlink(phy_dev, dev);
unregister_netdev:
unregister_netdevice(dev);
-remove_ida:
- ida_simple_remove(&port->ida, dev->dev_id);
destroy_ipvlan_port:
if (create)
ipvlan_port_destroy(phy_dev);
@@ -593,7 +645,6 @@ static void ipvlan_link_delete(struct net_device *dev, struct list_head *head)
kfree_rcu(addr, rcu);
}
- ida_simple_remove(&ipvlan->port->ida, dev->dev_id);
list_del_rcu(&ipvlan->pnode);
unregister_netdevice_queue(dev, head);
netdev_upper_dev_unlink(ipvlan->phy_dev, dev);
--
2.11.0.390.gc69c2f50cf-goog
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