netdev - Re: [patch net-next V2] bond: have random dev address by default instead of zeroes

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Date:	Thu, 24 Jan 2013 17:35:01 -0800
From:	Jay Vosburgh <fubar@...ibm.com>
To:	Jiri Pirko <jiri@...nulli.us>
cc:	netdev@...r.kernel.org, davem@...emloft.net, andy@...yhouse.net,
	stephen@...workplumber.org, psimerda@...hat.com, dcbw@...hat.com
Subject: Re: [patch net-next V2] bond: have random dev address by default instead of zeroes

Jiri Pirko <jiri@...nulli.us> wrote:

>Makes more sense to have randomly generated address by default than to
>have all zeroes. It also allows user to for example put the bond into
>bridge without need to have any slaves in it.
>
>Also note that this changes only behaviour of bonds with no slaves. Once
>the first slave device is enslaved, its address will be used (no change
>here).
>
>Also, fix dev_assign_type values on the way.
>
>Reported-by: Pavel Šimerda <psimerda@...hat.com>
>Signed-off-by: Jiri Pirko <jiri@...nulli.us>

	Maybe I don't see it, but this feels like a bit of a hack just
to get a bond with no slaves into a bridge.  Am I missing something
here?  I just have this feeling that down the road I'm going to get
questions as to why the bond gets a MAC, and then, poof, it vanishes
when a slave is added.  What's the point of the MAC address if it's only
used to fool the bridge code?

	Also, when the bond's MAC changes from the random MAC to the
first slave's MAC, does a notifier call need to happen?  There isn't one
now from the all zeroes to the first slave's, but that's from an invalid
MAC to a valid one.  There is already a notifier when the bond goes back
to all zeroes, though.

	-J

---
	-Jay Vosburgh, IBM Linux Technology Center, fubar@...ibm.com

>
>v1->v2:
>- fixed assign value of bond_dev->addr_assign_type in bond_set_dev_addr()
>- added note to patch description
>
> drivers/net/bonding/bond_main.c | 28 ++++++++++++++++------------
> 1 file changed, 16 insertions(+), 12 deletions(-)
>
>diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>index 564cf42..1d56ac9 100644
>--- a/drivers/net/bonding/bond_main.c
>+++ b/drivers/net/bonding/bond_main.c
>@@ -1320,14 +1320,14 @@ static void bond_netpoll_cleanup(struct net_device *bond_dev)
>
> /*---------------------------------- IOCTL ----------------------------------*/
>
>-static int bond_sethwaddr(struct net_device *bond_dev,
>-			  struct net_device *slave_dev)
>+static void bond_set_dev_addr(struct net_device *bond_dev,
>+			      struct net_device *slave_dev)
> {
> 	pr_debug("bond_dev=%p\n", bond_dev);
> 	pr_debug("slave_dev=%p\n", slave_dev);
> 	pr_debug("slave_dev->addr_len=%d\n", slave_dev->addr_len);
> 	memcpy(bond_dev->dev_addr, slave_dev->dev_addr, slave_dev->addr_len);
>-	return 0;
>+	bond_dev->addr_assign_type = NET_ADDR_SET;
> }
>
> static netdev_features_t bond_fix_features(struct net_device *dev,
>@@ -1628,10 +1628,8 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
>
> 	/* If this is the first slave, then we need to set the master's hardware
> 	 * address to be the same as the slave's. */
>-	if (is_zero_ether_addr(bond->dev->dev_addr))
>-		memcpy(bond->dev->dev_addr, slave_dev->dev_addr,
>-		       slave_dev->addr_len);
>-
>+	if (bond->dev->addr_assign_type != NET_ADDR_SET)
>+		bond_set_dev_addr(bond->dev, slave_dev);
>
> 	new_slave = kzalloc(sizeof(struct slave), GFP_KERNEL);
> 	if (!new_slave) {
>@@ -2049,11 +2047,11 @@ int bond_release(struct net_device *bond_dev, struct net_device *slave_dev)
> 	if (bond->slave_cnt == 0) {
> 		bond_set_carrier(bond);
>
>-		/* if the last slave was removed, zero the mac address
>-		 * of the master so it will be set by the application
>-		 * to the mac address of the first slave
>+		/* If the last slave was removed, set random mac address
>+		 * of the master so it will be set by bond_enslave()
>+		 * to the mac address of the first slave.
> 		 */
>-		memset(bond_dev->dev_addr, 0, bond_dev->addr_len);
>+		eth_hw_addr_random(bond_dev);
>
> 		if (bond_vlan_used(bond)) {
> 			pr_warning("%s: Warning: clearing HW address of %s while it still has VLANs.\n",
>@@ -3708,7 +3706,8 @@ static int bond_do_ioctl(struct net_device *bond_dev, struct ifreq *ifr, int cmd
> 			break;
> 		case BOND_SETHWADDR_OLD:
> 		case SIOCBONDSETHWADDR:
>-			res = bond_sethwaddr(bond_dev, slave_dev);
>+			bond_set_dev_addr(bond_dev, slave_dev);
>+			res = 0;
> 			break;
> 		case BOND_CHANGE_ACTIVE_OLD:
> 		case SIOCBONDCHANGEACTIVE:
>@@ -4858,6 +4857,11 @@ static int bond_init(struct net_device *bond_dev)
>
> 	bond_debug_register(bond);
>
>+	/* Ensure valid dev_addr */
>+	if (is_zero_ether_addr(bond_dev->dev_addr) &&
>+	    bond_dev->addr_assign_type == NET_ADDR_PERM)
>+		eth_hw_addr_random(bond_dev);
>+
> 	__hw_addr_init(&bond->mc_list);
> 	return 0;
> }
>-- 
>1.8.1
>

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