bonding: prevent sysfs from allowing arp monitoring with alb/tlb

When using module options arp monitoring and balance-alb/balance-tlb
are mutually exclusive options.  Anytime balance-alb/balance-tlb are
enabled mii monitoring is forced to 100ms if not set.  When configuring
via sysfs no checking is currently done.

Handling these cases with sysfs has to be done a bit differently because
we do not have all configuration information available at once.  This
patch will not allow a mode change to balance-alb/balance-tlb if
arp_interval is already non-zero.  It will also not allow the user to
set a non-zero arp_interval value if the mode is already set to
balance-alb/balance-tlb.  They are still mutually exclusive on a
first-come, first serve basis.

Tested with initscripts on Fedora and manual setting via sysfs.
Signed-off-by: Andy Gospodarek <gospo@redhat.com>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_sysfs.c

@@ -313,7 +313,15 @@ static ssize_t bonding_store_mode(struct device *d,
 		       bond->dev->name, (int)strlen(buf) - 1, buf);
 		ret = -EINVAL;
 		goto out;
-	} else {
+	}
+	if ((new_value == BOND_MODE_ALB ||
+	     new_value == BOND_MODE_TLB) &&
+	    bond->params.arp_interval) {
+		pr_err("%s: %s mode is incompatible with arp monitoring.\n",
+		       bond->dev->name, bond_mode_tbl[new_value].modename);
+		ret = -EINVAL;
+		goto out;
+	}
 	if (bond->params.mode == BOND_MODE_8023AD)
 		bond_unset_master_3ad_flags(bond);
 
@@ -325,7 +333,6 @@ static ssize_t bonding_store_mode(struct device *d,
 	pr_info("%s: setting mode to %s (%d).\n",
 		bond->dev->name, bond_mode_tbl[new_value].modename,
 		new_value);
-	}
 out:
 	return ret;
 }
@@ -510,7 +517,13 @@ static ssize_t bonding_store_arp_interval(struct device *d,
 		ret = -EINVAL;
 		goto out;
 	}
-
+	if (bond->params.mode == BOND_MODE_ALB ||
+	    bond->params.mode == BOND_MODE_TLB) {
+		pr_info("%s: ARP monitoring cannot be used with ALB/TLB. Only MII monitoring is supported on %s.\n",
+			bond->dev->name, bond->dev->name);
+		ret = -EINVAL;
+		goto out;
+	}
 	pr_info("%s: Setting ARP monitoring interval to %d.\n",
 		bond->dev->name, new_value);
 	bond->params.arp_interval = new_value;