From aa79e66eee5d525e2fcbd2a5fcb87ae3dd4aa9e9 Mon Sep 17 00:00:00 2001
From: Pavel Emelyanov <xemul@parallels.com>
Date: Wed, 8 Aug 2012 21:53:19 +0000
Subject: [PATCH] net: Make ifindex generation per-net namespace
Strictly speaking this is only _really_ required for checkpoint-restore to
make loopback device always have the same index.
This change appears to be safe wrt "ifindex should be unique per-system"
concept, as all the ifindex usage is either already made per net namespace
of is explicitly limited with init_net only.
There are two cool side effects of this. The first one -- ifindices of
devices in container are always small, regardless of how many containers
we've started (and re-started) so far. The second one is -- we can speed
up the loopback ifidex access as shown in the next patch.
v2: Place ifindex right after dev_base_seq : avoid two holes and use the
same cache line, dirtied in list_netdevice()/unlist_netdevice()
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
include/net/net_namespace.h | 1 +
net/core/dev.c | 4 ++--
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index ae1cd6c9ba521..6dc3db3466bfb 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -66,6 +66,7 @@ struct net {
struct hlist_head *dev_name_head;
struct hlist_head *dev_index_head;
unsigned int dev_base_seq; /* protected by rtnl_mutex */
+ int ifindex;
/* core fib_rules */
struct list_head rules_ops;
diff --git a/net/core/dev.c b/net/core/dev.c
index 3ca300d852713..1f06df8d10a38 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5221,12 +5221,12 @@ int dev_ioctl(struct net *net, unsigned int cmd, void __user *arg)
*/
static int dev_new_index(struct net *net)
{
- static int ifindex;
+ int ifindex = net->ifindex;
for (;;) {
if (++ifindex <= 0)
ifindex = 1;
if (!__dev_get_by_index(net, ifindex))
- return ifindex;
+ return net->ifindex = ifindex;
}
}
--
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