Patch "ipvs: fix bind to link-local mcast IPv6 address in backup" has been added to the 4.4-stable tree

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

ipvs: fix bind to link-local mcast IPv6 address in backup

to the 4.4-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:
ipvs-fix-bind-to-link-local-mcast-ipv6-address-in-backup.patch
and it can be found in the queue-4.4 subdirectory.

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

From: Quentin Armitage <[email protected]>
Date: Thu, 16 Jun 2016 08:00:14 +0100
Subject: ipvs: fix bind to link-local mcast IPv6 address in backup

From: Quentin Armitage <[email protected]>

commit 3777ed688fba82d0bd43f9fc1ebbc6abe788576d upstream.

When using HEAD from
https://git.kernel.org/cgit/utils/kernel/ipvsadm/ipvsadm.git/,
the command:

ipvsadm --start-daemon backup --mcast-interface eth0.60 \
    --mcast-group ff02::1:81

fails with the error message:
Argument list too long

whereas both:

ipvsadm --start-daemon master --mcast-interface eth0.60 \
    --mcast-group ff02::1:81
and:
ipvsadm --start-daemon backup --mcast-interface eth0.60 \
    --mcast-group 224.0.0.81

are successful.

The error message "Argument list too long" isn't helpful. The error occurs because an IPv6 address is given in backup mode.

The error is in make_receive_sock() in net/netfilter/ipvs/ip_vs_sync.c, since it fails to set the interface on the address or the socket before calling inet6_bind() (via sock->ops->bind), where the test 'if (!sk->sk_bound_dev_if)' failed.

Setting sock->sk->sk_bound_dev_if on the socket before calling inet6_bind() resolves the issue.

---
 net/netfilter/ipvs/ip_vs_sync.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

@@ -1545,7 +1545,8 @@ error:
 /*
  *      Set up receiving multicast socket over UDP
  */
-static struct socket *make_receive_sock(struct netns_ipvs *ipvs, int id)
+static struct socket *make_receive_sock(struct netns_ipvs *ipvs, int id,
+					int ifindex)
 {
 	/* multicast addr */
 	union ipvs_sockaddr mcast_addr;

@@ -1566,6 +1567,7 @@ static struct socket *make_receive_sock(
 		set_sock_size(sock->sk, 0, result);
 
 	get_mcast_sockaddr(&mcast_addr, &salen, &ipvs->bcfg, id);
+	sock->sk->sk_bound_dev_if = ifindex;
 	result = sock->ops->bind(sock, (struct sockaddr *)&mcast_addr, salen);
 	if (result < 0) {
 		pr_err("Error binding to the multicast addr\n");

@@ -1868,7 +1870,7 @@ int start_sync_thread(struct netns_ipvs
 		if (state == IP_VS_STATE_MASTER)
 			sock = make_send_sock(ipvs, id);
 		else
-			sock = make_receive_sock(ipvs, id);
+			sock = make_receive_sock(ipvs, id, dev->ifindex);
 		if (IS_ERR(sock)) {
 			result = PTR_ERR(sock);
 			goto outtinfo;

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

queue-4.4/ipvs-fix-bind-to-link-local-mcast-ipv6-address-in-backup.patch