* [Patch net-next] bridge: fix seq check in br_mdb_dump()
@ 2012-12-10 12:15 Cong Wang
2012-12-10 18:46 ` David Miller
0 siblings, 1 reply; 3+ messages in thread
From: Cong Wang @ 2012-12-10 12:15 UTC (permalink / raw)
To: netdev
Cc: Herbert Xu, Stephen Hemminger, David S. Miller, Thomas Graf,
Jesper Dangaard Brouer, Cong Wang
From: Cong Wang <amwang@redhat.com>
In case of rehashing, introduce a global variable 'br_mdb_rehash_seq'
which gets increased every time when rehashing, and assign
net->dev_base_seq + br_mdb_rehash_seq to cb->seq.
In theory cb->seq could be wrapped to zero, but this is not
easy to fix, as net->dev_base_seq is not visible inside
br_mdb_rehash(). In practice, this is rare.
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Thomas Graf <tgraf@suug.ch>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Cong Wang <amwang@redhat.com>
---
net/bridge/br_mdb.c | 6 ++----
net/bridge/br_multicast.c | 2 ++
net/bridge/br_private.h | 1 +
3 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/net/bridge/br_mdb.c b/net/bridge/br_mdb.c
index edc0d73..ccc43a9 100644
--- a/net/bridge/br_mdb.c
+++ b/net/bridge/br_mdb.c
@@ -117,10 +117,8 @@ static int br_mdb_dump(struct sk_buff *skb, struct netlink_callback *cb)
rcu_read_lock();
- /* TODO: in case of rehashing, we need to check
- * consistency for dumping.
- */
- cb->seq = net->dev_base_seq;
+ /* In theory this could be wrapped to 0... */
+ cb->seq = net->dev_base_seq + br_mdb_rehash_seq;
for_each_netdev_rcu(net, dev) {
if (dev->priv_flags & IFF_EBRIDGE) {
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 68e375a..847b98a1 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -37,6 +37,7 @@
rcu_dereference_protected(X, lockdep_is_held(&br->multicast_lock))
static void br_multicast_start_querier(struct net_bridge *br);
+unsigned int br_mdb_rehash_seq;
#if IS_ENABLED(CONFIG_IPV6)
static inline int ipv6_is_transient_multicast(const struct in6_addr *addr)
@@ -338,6 +339,7 @@ static int br_mdb_rehash(struct net_bridge_mdb_htable __rcu **mdbp, int max,
return err;
}
+ br_mdb_rehash_seq++;
call_rcu_bh(&mdb->rcu, br_mdb_free);
out:
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index ae0a6ec..f95b766 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -411,6 +411,7 @@ extern int br_ioctl_deviceless_stub(struct net *net, unsigned int cmd, void __us
/* br_multicast.c */
#ifdef CONFIG_BRIDGE_IGMP_SNOOPING
+extern unsigned int br_mdb_rehash_seq;
extern int br_multicast_rcv(struct net_bridge *br,
struct net_bridge_port *port,
struct sk_buff *skb);
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [Patch net-next] bridge: fix seq check in br_mdb_dump()
2012-12-10 12:15 [Patch net-next] bridge: fix seq check in br_mdb_dump() Cong Wang
@ 2012-12-10 18:46 ` David Miller
[not found] ` <1355197772.13991.1.camel@cr0>
0 siblings, 1 reply; 3+ messages in thread
From: David Miller @ 2012-12-10 18:46 UTC (permalink / raw)
To: amwang; +Cc: netdev, herbert, shemminger, tgraf, brouer
From: Cong Wang <amwang@redhat.com>
Date: Mon, 10 Dec 2012 20:15:35 +0800
> From: Cong Wang <amwang@redhat.com>
>
> In case of rehashing, introduce a global variable 'br_mdb_rehash_seq'
> which gets increased every time when rehashing, and assign
> net->dev_base_seq + br_mdb_rehash_seq to cb->seq.
>
> In theory cb->seq could be wrapped to zero, but this is not
> easy to fix, as net->dev_base_seq is not visible inside
> br_mdb_rehash(). In practice, this is rare.
>
> Cc: Herbert Xu <herbert@gondor.apana.org.au>
> Cc: Stephen Hemminger <shemminger@vyatta.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Thomas Graf <tgraf@suug.ch>
> Cc: Jesper Dangaard Brouer <brouer@redhat.com>
> Signed-off-by: Cong Wang <amwang@redhat.com>
No synchronization at all is applied to this variable, I can't
see how this is OK.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Patch net-next] bridge: fix seq check in br_mdb_dump()
[not found] ` <1355197772.13991.1.camel@cr0>
@ 2012-12-11 18:45 ` David Miller
0 siblings, 0 replies; 3+ messages in thread
From: David Miller @ 2012-12-11 18:45 UTC (permalink / raw)
To: amwang; +Cc: netdev, herbert, shemminger, tgraf, brouer
From: Cong Wang <amwang@redhat.com>
Date: Tue, 11 Dec 2012 11:49:32 +0800
> On Mon, 2012-12-10 at 13:46 -0500, David Miller wrote:
>> From: Cong Wang <amwang@redhat.com>
>> Date: Mon, 10 Dec 2012 20:15:35 +0800
>>
>> > From: Cong Wang <amwang@redhat.com>
>> >
>> > In case of rehashing, introduce a global variable 'br_mdb_rehash_seq'
>> > which gets increased every time when rehashing, and assign
>> > net->dev_base_seq + br_mdb_rehash_seq to cb->seq.
>> >
>> > In theory cb->seq could be wrapped to zero, but this is not
>> > easy to fix, as net->dev_base_seq is not visible inside
>> > br_mdb_rehash(). In practice, this is rare.
>> >
>> > Cc: Herbert Xu <herbert@gondor.apana.org.au>
>> > Cc: Stephen Hemminger <shemminger@vyatta.com>
>> > Cc: "David S. Miller" <davem@davemloft.net>
>> > Cc: Thomas Graf <tgraf@suug.ch>
>> > Cc: Jesper Dangaard Brouer <brouer@redhat.com>
>> > Signed-off-by: Cong Wang <amwang@redhat.com>
>>
>> No synchronization at all is applied to this variable, I can't
>> see how this is OK.
>
> br_mdb_rehash() is protected by the multicast spinlock, so increasing
> this variable is protected by it, and reading the variable doesn't need
> locking. Am I missing anything? Or should we use atomic_t?
I missed that locking, ok, looks good.
Applied, thanks.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2012-12-10 12:15 [Patch net-next] bridge: fix seq check in br_mdb_dump() Cong Wang
2012-12-10 18:46 ` David Miller
[not found] ` <1355197772.13991.1.camel@cr0>
2012-12-11 18:45 ` David Miller
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