netdev - Re: [PATCH] ipv6: slightly simplify keeping IPv6 addresses on link down

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Date:	Wed, 01 Dec 2010 11:38:58 -0800
From:	Lorenzo Colitti <lorenzo@...gle.com>
To:	netdev@...r.kernel.org
Cc:	Lorenzo Colitti <lorenzo@...gle.com>,
	David Miller <davem@...emloft.net>
Subject: Re: [PATCH] ipv6: slightly simplify keeping IPv6 addresses on link down

ipv6: slightly simplify keeping IPv6 addresses on link down

When link goes down, all statically-configured (i.e.,
permanent and not link-local) IPv6 addresses are kept on
the interface. Instead of moving addresses to a temporary
keep list and then splicing that back on to the interface
address list, use list_for_each_entry_safe and delete the
ones we don't want.

Tested by configuring two static addresses on an interface
and verifying that pings from the addresses keep working
when bringing link down and up again and when disabling and
re-enabling IPv6 on the interface.

Signed-off-by: Lorenzo Colitti <lorenzo@...gle.com>

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 6dfd5c5..23cc8e1 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -2663,7 +2663,8 @@ static int addrconf_ifdown(struct net_device *dev, int how)
 {
 	struct net *net = dev_net(dev);
 	struct inet6_dev *idev;
-	struct inet6_ifaddr *ifa, *ifn;
+	struct inet6_ifaddr *ifa;
+	LIST_HEAD(keep_list);
 	int state;
 
 	ASSERT_RTNL();
@@ -2718,7 +2719,9 @@ static int addrconf_ifdown(struct net_device *dev, int how)
 	}
 #endif
 
-	list_for_each_entry_safe(ifa, ifn, &idev->addr_list, if_list) {
+	while (!list_empty(&idev->addr_list)) {
+		ifa = list_first_entry(&idev->addr_list,
+				       struct inet6_ifaddr, if_list);
 		addrconf_del_timer(ifa);
 
 		/* If just doing link down, and address is permanent
@@ -2726,13 +2729,15 @@ static int addrconf_ifdown(struct net_device *dev, int how)
 		if (!how &&
 		    (ifa->flags&IFA_F_PERMANENT) &&
 		    !(ipv6_addr_type(&ifa->addr) & IPV6_ADDR_LINKLOCAL)) {
+			list_move_tail(&ifa->if_list, &keep_list);
+
 			/* If not doing DAD on this address, just keep it. */
 			if ((dev->flags&(IFF_NOARP|IFF_LOOPBACK)) ||
 			    idev->cnf.accept_dad <= 0 ||
 			    (ifa->flags & IFA_F_NODAD))
 				continue;
 
-			/* If it was tentative already, don't do anything */
+			/* If it was tentative already, no need to notify */
 			if (ifa->flags & IFA_F_TENTATIVE)
 				continue;
 
@@ -2764,6 +2769,8 @@ static int addrconf_ifdown(struct net_device *dev, int how)
 		}
 	}
 
+	list_splice(&keep_list, &idev->addr_list);
+
 	write_unlock_bh(&idev->lock);
 
 	/* Step 5: Discard multicast list */
--
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