Patch "ipv6: Fix IPv6 packet loss in scenarios involving roaming + snooping switches" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

ipv6: Fix IPv6 packet loss in scenarios involving roaming + snooping switches

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ipv6-fix-ipv6-packet-loss-in-scenarios-involving-roaming-snooping-switches.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Linus L�ssing <[email protected]>
Date: Tue, 23 May 2017 21:53:52 -0400
Subject: ipv6: Fix IPv6 packet loss in scenarios involving roaming + snooping switches

From: Linus L�ssing <[email protected]>

[ Upstream commit a088d1d73a4bcfd7bc482f8d08375b9b665dc3e5 ]

When for instance a mobile Linux device roams from one access point to another with both APs sharing the same broadcast domain and a multicast snooping switch in between:

1) (c) <~~~> (AP1) <--[SSW]--> (AP2)

2) (AP1) <--[SSW]--> (AP2) <~~~> (c)

Then currently IPv6 multicast packets will get lost for (c) until an MLD Querier sends its next query message. The packet loss occurs because upon roaming the Linux host so far stayed silent regarding MLD and the snooping switch will therefore be unaware of the multicast topology change for a while.

This patch fixes this by always resending MLD reports when an interface change happens, for instance from NO-CARRIER to CARRIER state.

---
 net/ipv6/addrconf.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

@@ -3387,9 +3387,15 @@ static int addrconf_notify(struct notifi
 			}
 
 			if (idev) {
-				if (idev->if_flags & IF_READY)
-					/* device is already configured. */
+				if (idev->if_flags & IF_READY) {
+					/* device is already configured -
+					 * but resend MLD reports, we might
+					 * have roamed and need to update
+					 * multicast snooping switches
+					 */
+					ipv6_mc_up(idev);
 					break;
+				}
 				idev->if_flags |= IF_READY;
 			}
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/ipv6-fix-ipv6-packet-loss-in-scenarios-involving-roaming-snooping-switches.patch