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>

diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index ae1cd6c9ba521bb6ca9a57706b4ca77180bdcc7a..6dc3db3466bfb68b64e0e2643ca4088b0007e3b7 100644 (file)
--- 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 3ca300d8527134b82735b65c0cffa55637bbb571..1f06df8d10a38e9f0ac2e73781c27c0dae659d5d 100644 (file)
--- 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;
        }
 }