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

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Message-ID: <20130124191839.GA4177@minipsycho.orion>
Date:	Thu, 24 Jan 2013 20:18:39 +0100
From:	Jiri Pirko <jiri@...nulli.us>
To:	Jay Vosburgh <fubar@...ibm.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net, andy@...yhouse.net,
	stephen@...workplumber.org
Subject: Re: [patch net-next] bond: have random dev address by default
 instead of zeroes

Thu, Jan 24, 2013 at 06:12:49PM CET, fubar@...ibm.com wrote:
>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, fix dev_assign_type values on the way.
>>
>>Signed-off-by: Jiri Pirko <jiri@...nulli.us>
>
>	This patch appears to provide a random MAC, which is then
>replaced with the first slave's MAC at enslavement time.  A more in
>depth commit message would be helpful here; I presumed from the above
>that the bond's MAC was being set to a random MAC and the first slave
>behavior was changing, but inspection of the code suggests otherwise.

Sure, I will make sthi clear in commit message.

>
>	Does this have any practical change other than permitting
>enslavement to a bridge prior to the bond having any slaves?

Nothing I can think of.

>
>	I also have one code comment, below.
>
>> 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..af3a777 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;
>
>	This is a bitwise assignment, but addr_assign_type is not a
>bitmask.  If addr_assign_type is not 0 prior to this, this will create
>an illegal value in the field.

You are right. I'll correct this.

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