bonding: require speed/duplex only for 802.3ad, alb and tlb

The patch c4adfc822b ("bonding: make speed, duplex setting consistent
with link state") puts the link state to down if
bond_update_speed_duplex() cannot retrieve speed and duplex settings.
Assumably the patch was written with 802.3ad mode in mind which relies
on link speed/duplex settings. For other modes like active-backup these
settings are not required. Thus, only for these other modes, this patch
reintroduces support for slaves that do not support reporting speed or
duplex such as wireless devices. This fixes the regression reported in
bug 196547 (https://bugzilla.kernel.org/show_bug.cgi?id=196547).

Fixes: c4adfc822b ("bonding: make speed, duplex setting consistent
with link state")
Signed-off-by: Andreas Born <futur.andy@googlemail.com>
Acked-by: Mahesh Bandewar <maheshb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_main.c

@@ -1569,7 +1569,8 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
 	new_slave->delay = 0;
 	new_slave->link_failure_count = 0;
 
-	if (bond_update_speed_duplex(new_slave))
+	if (bond_update_speed_duplex(new_slave) &&
+	    bond_needs_speed_duplex(bond))
 		new_slave->link = BOND_LINK_DOWN;
 
 	new_slave->last_rx = jiffies -
@@ -2140,7 +2141,8 @@ static void bond_miimon_commit(struct bonding *bond)
 			continue;
 
 		case BOND_LINK_UP:
-			if (bond_update_speed_duplex(slave)) {
+			if (bond_update_speed_duplex(slave) &&
+			    bond_needs_speed_duplex(bond)) {
 				slave->link = BOND_LINK_DOWN;
 				netdev_warn(bond->dev,
 					    "failed to get link speed/duplex for %s\n",