From cf9094a861013cbc5dd436a411505226925cebe4 Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <ebiederm@aristanetworks.com>
Date: Sun, 22 Feb 2009 00:11:09 -0800
Subject: [PATCH] --- yaml --- r: 134660 b: refs/heads/master c:
 ce16c5337ab0d165f95c88aa857207efd7c01139 h: refs/heads/master v: v3

---
 [refs]                            |  2 +-
 trunk/include/net/net_namespace.h | 27 +++++++++++++++++----------
 trunk/net/core/dev.c              |  6 ------
 trunk/net/core/net_namespace.c    |  3 ---
 4 files changed, 18 insertions(+), 20 deletions(-)

diff --git a/[refs] b/[refs]
index 745ec84cc996..a82a52234483 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 6a1b3054d9fd98001a6631501caf1969138ee00d
+refs/heads/master: ce16c5337ab0d165f95c88aa857207efd7c01139
diff --git a/trunk/include/net/net_namespace.h b/trunk/include/net/net_namespace.h
index 6fc13d905c5f..ded434b032a4 100644
--- a/trunk/include/net/net_namespace.h
+++ b/trunk/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 *);
diff --git a/trunk/net/core/dev.c b/trunk/net/core/dev.c
index 88dc082b47d1..ac6ab12d3297 100644
--- a/trunk/net/core/dev.c
+++ b/trunk/net/core/dev.c
@@ -2254,12 +2254,6 @@ int netif_receive_skb(struct sk_buff *skb)
 
 	rcu_read_lock();
 
-	/* Don't receive packets in an exiting network namespace */
-	if (!net_alive(dev_net(skb->dev))) {
-		kfree_skb(skb);
-		goto out;
-	}
-
 #ifdef CONFIG_NET_CLS_ACT
 	if (skb->tc_verd & TC_NCLS) {
 		skb->tc_verd = CLR_TC_NCLS(skb->tc_verd);
diff --git a/trunk/net/core/net_namespace.c b/trunk/net/core/net_namespace.c
index 55151faaf90c..516c7b154327 100644
--- a/trunk/net/core/net_namespace.c
+++ b/trunk/net/core/net_namespace.c
@@ -140,9 +140,6 @@ static void cleanup_net(struct work_struct *work)
 	struct pernet_operations *ops;
 	struct net *net;
 
-	/* Be very certain incoming network packets will not find us */
-	rcu_barrier();
-
 	net = container_of(work, struct net, work);
 
 	mutex_lock(&net_mutex);