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Date: Thu, 21 May 2015 14:38:20 +0300
From: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To: Mahesh Bandewar <maheshb@...gle.com>
CC: linux-netdev <netdev@...r.kernel.org>,
"David S. Miller" <davem@...emloft.net>,
Jiri Benc <jbenc@...hat.com>,
Hannes Frederic Sowa <hannes@...essinduktion.org>
Subject: Re: [PATCH 3/3] ipvlan: set dev_id for l2 ports to generate unique
IPv6 addresses
On 20.05.2015 02:59, Mahesh Bandewar wrote:
> On Thu, May 14, 2015 at 6:56 AM, Konstantin Khlebnikov
> <khlebnikov@...dex-team.ru> wrote:
>> All ipvlan ports use one MAC address, this way ipv6 RA tries to assign
>> one ipv6 address to all of them. This patch assigns unique dev_id to each
>> ipvlan port. This field is used instead of common FF-FE in Modified EUI-64.
>>
>> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
>> ---
>> Documentation/networking/ipvlan.txt | 12 +++++++++++-
>> drivers/net/ipvlan/ipvlan.h | 1 +
>> drivers/net/ipvlan/ipvlan_main.c | 20 ++++++++++++++++++++
>> 3 files changed, 32 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/networking/ipvlan.txt b/Documentation/networking/ipvlan.txt
>> index cf996394e466..cb0b777bce58 100644
>> --- a/Documentation/networking/ipvlan.txt
>> +++ b/Documentation/networking/ipvlan.txt
>> @@ -24,7 +24,7 @@ using IProute2/ip utility.
>>
>> ip link add link <master-dev> <slave-dev> type ipvlan mode { l2 | L3 }
>>
>> - e.g. ip link add link ipvl0 eth0 type ipvlan mode l2
>> + e.g. ip link add link eth0 ipvl0 type ipvlan mode l2
>>
>>
>> 4. Operating modes:
>> @@ -41,6 +41,15 @@ slave device and packets are switched and queued to the master device to send
>> out. In this mode the slaves will RX/TX multicast and broadcast (if applicable)
>> as well.
>>
>> + In L2 mode slave devices receive Router Advertisements from the network
>> +and perform autoconfiguration as well as master device. Each port has unique
>> +16-bit device id which is used for filling octets 4-5 of Modified EUI-64.
>> +That gives 65533 addresses (FF-FE used by master, FF-FF/00-00 reserved/not used).
>> +
> This is nice, thanks for fixing this! However how is "unique" id
> guaranteed? Especially when multiple virtual drivers are stacked? Not
> necessarily all of them may use the dev_id, but to avoid any possible
> collision, shouldn't the device hierarchy (especially lower_dev) be
> traversed before settling on the initial value?
Well, uniqueness isn't guaranteed but that should work in most cases.
ipv6 anyway checks for duplicate addresses after configuration.
As I see creation of ipvlan on ipvlan just creates slave at original
master device, so this will work as expected. And ipvlan cannot share
physical device with bonding/bridge/macvlan, so I don't see how to
stack more than one layer of ipvlans accidentally.
>
>> + Also lower half of IPv6 address could be set as interface token:
>> +
>> + ip token set ::aaaa:bbbb:cccc:dddd dev ipvl0
>> +
>> 4.2 L3 mode:
>> In this mode TX processing upto L3 happens on the stack instance attached
>> to the slave device and packets are switched to the stack instance of the
>> @@ -105,3 +114,4 @@ namespace where L2 on the slave could be changed / misused.
>> (4) ip -4 addr add 127.0.0.1 dev lo
>> (5) ip -4 addr add $IPADDR dev ipvl1
>> (6) ip -4 route add default via $ROUTER dev ipvl1
>> +
>> diff --git a/drivers/net/ipvlan/ipvlan.h b/drivers/net/ipvlan/ipvlan.h
>> index 54549a6223dd..1ebab84e7a0e 100644
>> --- a/drivers/net/ipvlan/ipvlan.h
>> +++ b/drivers/net/ipvlan/ipvlan.h
>> @@ -95,6 +95,7 @@ struct ipvl_port {
>> struct rcu_head rcu;
>> int count;
>> u16 mode;
>> + struct ida ida;
>> };
>>
>> static inline struct ipvl_port *ipvlan_port_get_rcu(const struct net_device *d)
>> diff --git a/drivers/net/ipvlan/ipvlan_main.c b/drivers/net/ipvlan/ipvlan_main.c
>> index 0cafd3e6f02d..dee0e8441150 100644
>> --- a/drivers/net/ipvlan/ipvlan_main.c
>> +++ b/drivers/net/ipvlan/ipvlan_main.c
>> @@ -53,6 +53,7 @@ static int ipvlan_port_create(struct net_device *dev)
>> INIT_LIST_HEAD(&port->ipvlans);
>> for (idx = 0; idx < IPVLAN_HASH_SIZE; idx++)
>> INIT_HLIST_HEAD(&port->hlhead[idx]);
>> + ida_init(&port->ida);
>>
>> err = netdev_rx_handler_register(dev, ipvlan_handle_frame, port);
>> if (err)
>> @@ -72,6 +73,7 @@ static void ipvlan_port_destroy(struct net_device *dev)
>>
>> dev->priv_flags &= ~IFF_IPVLAN_MASTER;
>> netdev_rx_handler_unregister(dev);
>> + ida_destroy(&port->ida);
>> kfree_rcu(port, rcu);
>> }
>>
>> @@ -484,6 +486,18 @@ static int ipvlan_link_new(struct net *src_net, struct net_device *dev,
>> */
>> memcpy(dev->dev_addr, phy_dev->dev_addr, ETH_ALEN);
>>
>> + if (port->mode == IPVLAN_MODE_L2) {
>> + /*
>> + * IPv6 addrconf uses it to produce unique addresses,
>> + * see function addrconf_ifid_eui48.
>> + */
>> + err = ida_simple_get(&port->ida, 1, 0xFFFE, GFP_KERNEL);
>> + if (err > 0)
>> + dev->dev_id = err;
>> + else if (err != -ENOSPC)
>> + goto ipvlan_destroy_port;
>> + }
>> +
>> dev->priv_flags |= IFF_IPVLAN_SLAVE;
>>
>> port->count += 1;
>> @@ -518,6 +532,12 @@ static void ipvlan_link_delete(struct net_device *dev, struct list_head *head)
>> list_del(&addr->anode);
>> }
>> }
>> +
>> + if (dev->dev_id) {
>> + ida_simple_remove(&ipvlan->port->ida, dev->dev_id);
>> + dev->dev_id = 0;
>> + }
>> +
>> list_del_rcu(&ipvlan->pnode);
>> unregister_netdevice_queue(dev, head);
>> netdev_upper_dev_unlink(ipvlan->phy_dev, dev);
>>
--
Konstantin
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