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authorEric W. Biederman <ebiederm@aristanetworks.com>2009-02-22 00:11:09 -0800
committerDavid S. Miller <davem@davemloft.net>2009-03-03 01:14:27 -0800
commit17edde520927070a6bf14a6a75027c0b843443e5 (patch)
treedcd940213c93bc943c670f48aa52ec8571351912 /include
parent2f20d2e667ab1ca44cde5fb361386dff5bb6081d (diff)
downloadblackbird-op-linux-17edde520927070a6bf14a6a75027c0b843443e5.tar.gz
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netns: Remove net_alive
It turns out that net_alive is unnecessary, and the original problem that led to it being added was simply that the icmp code thought it was a network device and wound up being unable to handle packets while there were still packets in the network namespace. Now that icmp and tcp have been fixed to properly register themselves this problem is no longer present and we have a stronger guarantee that packets will not arrive in a network namespace then that provided by net_alive in netif_receive_skb. So remove net_alive allowing packet reception run a little faster. Additionally document the strong reason why network namespace cleanup is safe so that if something happens again someone else will have a chance of figuring it out. Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include')
-rw-r--r--include/net/net_namespace.h27
1 files changed, 17 insertions, 10 deletions
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 6fc13d905c5f..ded434b032a4 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -109,11 +109,6 @@ extern struct list_head net_namespace_list;
#ifdef CONFIG_NET_NS
extern void __put_net(struct net *net);
-static inline int net_alive(struct net *net)
-{
- return net && atomic_read(&net->count);
-}
-
static inline struct net *get_net(struct net *net)
{
atomic_inc(&net->count);
@@ -145,11 +140,6 @@ int net_eq(const struct net *net1, const struct net *net2)
}
#else
-static inline int net_alive(struct net *net)
-{
- return 1;
-}
-
static inline struct net *get_net(struct net *net)
{
return net;
@@ -234,6 +224,23 @@ struct pernet_operations {
void (*exit)(struct net *net);
};
+/*
+ * Use these carefully. If you implement a network device and it
+ * needs per network namespace operations use device pernet operations,
+ * otherwise use pernet subsys operations.
+ *
+ * This is critically important. Most of the network code cleanup
+ * runs with the assumption that dev_remove_pack has been called so no
+ * new packets will arrive during and after the cleanup functions have
+ * been called. dev_remove_pack is not per namespace so instead the
+ * guarantee of no more packets arriving in a network namespace is
+ * provided by ensuring that all network devices and all sockets have
+ * left the network namespace before the cleanup methods are called.
+ *
+ * For the longest time the ipv4 icmp code was registered as a pernet
+ * device which caused kernel oops, and panics during network
+ * namespace cleanup. So please don't get this wrong.
+ */
extern int register_pernet_subsys(struct pernet_operations *);
extern void unregister_pernet_subsys(struct pernet_operations *);
extern int register_pernet_gen_subsys(int *id, struct pernet_operations *);
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