rtnl: provide link dump consistency info
This patch adds a change sequence counter to each net namespace
which is bumped whenever a netdevice is added or removed from
the list. If such a change occurred while a link dump took place,
the dump will have the NLM_F_DUMP_INTR flag set in the first
message which has been interrupted and in all subsequent messages
of the same dump.
Note that links may still be modified or renamed while a dump is
taking place but we can guarantee for userspace to receive a
complete list of links and not miss any.
Testing:
I have added 500 VLAN netdevices to make sure the dump is split
over multiple messages. Then while continuously dumping links in
one process I also continuously deleted and re-added a dummy
netdevice in another process. Multiple dumps per seconds have
had the NLM_F_DUMP_INTR flag set.
I guess we can wait for Johannes patch to hit net-next via the
wireless tree. I just wanted to give this some testing right away.
Signed-off-by: Thomas Graf <tgraf@infradead.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/dev.c b/net/core/dev.c
index 6b6ef14..4577e67 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -199,6 +199,11 @@
DEFINE_RWLOCK(dev_base_lock);
EXPORT_SYMBOL(dev_base_lock);
+static inline void dev_base_seq_inc(struct net *net)
+{
+ while (++net->dev_base_seq == 0);
+}
+
static inline struct hlist_head *dev_name_hash(struct net *net, const char *name)
{
unsigned hash = full_name_hash(name, strnlen(name, IFNAMSIZ));
@@ -237,6 +242,9 @@
hlist_add_head_rcu(&dev->index_hlist,
dev_index_hash(net, dev->ifindex));
write_unlock_bh(&dev_base_lock);
+
+ dev_base_seq_inc(net);
+
return 0;
}
@@ -253,6 +261,8 @@
hlist_del_rcu(&dev->name_hlist);
hlist_del_rcu(&dev->index_hlist);
write_unlock_bh(&dev_base_lock);
+
+ dev_base_seq_inc(dev_net(dev));
}
/*
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index ea489db..5bbdbf0 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -129,6 +129,7 @@
atomic_set(&net->count, 1);
atomic_set(&net->passive, 1);
+ net->dev_base_seq = 1;
#ifdef NETNS_REFCNT_DEBUG
atomic_set(&net->use_count, 0);
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index a798fc6..99d9e95 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1032,6 +1032,8 @@
s_idx = cb->args[1];
rcu_read_lock();
+ cb->seq = net->dev_base_seq;
+
for (h = s_h; h < NETDEV_HASHENTRIES; h++, s_idx = 0) {
idx = 0;
head = &net->dev_index_head[h];
@@ -1043,6 +1045,8 @@
cb->nlh->nlmsg_seq, 0,
NLM_F_MULTI) <= 0)
goto out;
+
+ nl_dump_check_consistent(cb, nlmsg_hdr(skb));
cont:
idx++;
}
