IPoIB: Report operstate consistently when brought up without a link

IPoIB: Report operstate consistently when brought up without a link

After booting without a working link, "ip link" shows:

 5: mlx4_ib1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 2044 qdisc pfifo_fast
 state DOWN qlen 256
    ...
 7: mlx4_ib1.8003@mlx4_ib1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 2044 qdisc
 pfifo_fast state DOWN qlen 256
    ...

Then after connecting and disconnecting the link, which should result
in exactly the same state as before, it shows:

 5: mlx4_ib1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 2044 qdisc pfifo_fast
 state DOWN qlen 256
    ...
 7: mlx4_ib1.8003@mlx4_ib1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 2044 qdisc
 pfifo_fast state LOWERLAYERDOWN qlen 256
    ...

Notice the (now correct) LOWERLAYERDOWN operstate shown for the
mlx4_ib1.8003 interface. Ideally the identical state would be shown
right after boot.

The problem is related to the calling of netif_carrier_off() in
network drivers.  For a long time it was known that doing
netif_carrier_off() before registering the netdevice would result in
the interface's operstate being shown as UNKNOWN if the device was
brought up without a working link. This problem was fixed in commit
8f4cccbbd92 ('net: Set device operstate at registration time'), but
still there remains the minor inconsistency demonstrated above.

This patch fixes it by moving ipoib's call to netif_carrier_off() into
the .ndo_open method, which is where network drivers ordinarily do it.
With the patch when doing the same test as above, the operstate of
mlx4_ib1.8003 is shown as LOWERLAYERDOWN right after boot.

Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Acked-by: Erez Shitrit <erezsh@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>