Commit 4e985ada authored by Thomas Graf's avatar Thomas Graf Committed by David S. Miller

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.

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: default avatarThomas Graf <>
Signed-off-by: default avatarDavid S. Miller <>
parent e77aeb71
......@@ -65,6 +65,7 @@ struct net {
struct list_head dev_base_head;
struct hlist_head *dev_name_head;
struct hlist_head *dev_index_head;
unsigned int dev_base_seq; /* protected by rtnl_mutex */
/* core fib_rules */
struct list_head rules_ops;
......@@ -199,6 +199,11 @@ static struct list_head ptype_all __read_mostly; /* Taps */
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 @@ static int list_netdevice(struct net_device *dev)
dev_index_hash(net, dev->ifindex));
return 0;
......@@ -253,6 +261,8 @@ static void unlist_netdevice(struct net_device *dev)
......@@ -129,6 +129,7 @@ static __net_init int setup_net(struct net *net)
atomic_set(&net->count, 1);
atomic_set(&net->passive, 1);
net->dev_base_seq = 1;
atomic_set(&net->use_count, 0);
......@@ -1032,6 +1032,8 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
s_idx = cb->args[1];
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 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
cb->nlh->nlmsg_seq, 0,
NLM_F_MULTI) <= 0)
goto out;
nl_dump_check_consistent(cb, nlmsg_hdr(skb));
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