[PATCH v4 net] ipvs: fix bind to link-local mcast IPv6 address in backup

To: Wensong Zhang <wensong@xxxxxxxxxxxx>, Simon Horman <horms@xxxxxxxxxxxx>, Julian Anastasov <ja@xxxxxx>, Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>, Patrick McHardy <kaber@xxxxxxxxx>, Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>, netdev@xxxxxxxxxxxxxxx, lvs-devel@xxxxxxxxxxxxxxx, netfilter-devel@xxxxxxxxxxxxxxx, coreteam@xxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
Subject: [PATCH v4 net] ipvs: fix bind to link-local mcast IPv6 address in backup
Cc: Quentin Armitage <quentin@xxxxxxxxxxxxxxx>
From: Quentin Armitage <quentin@xxxxxxxxxxxxxxx>
Date: Thu, 16 Jun 2016 08:00:14 +0100
When using HEAD from,
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
ipvsadm --start-daemon backup --mcast-interface eth0.60 \
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.

Fixes: d33288172e72 ("ipvs: add more mcast parameters for the sync daemon")
Signed-off-by: Quentin Armitage <quentin@xxxxxxxxxxxxxxx>
 net/netfilter/ipvs/ip_vs_sync.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_sync.c b/net/netfilter/ipvs/ip_vs_sync.c
index 803001a..1b07578 100644
--- a/net/netfilter/ipvs/ip_vs_sync.c
+++ b/net/netfilter/ipvs/ip_vs_sync.c
@@ -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(struct netns_ipvs 
*ipvs, int id)
                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 *ipvs, struct 
ipvs_sync_daemon_cfg *c,
                if (state == IP_VS_STATE_MASTER)
                        sock = make_send_sock(ipvs, id);
-                       sock = make_receive_sock(ipvs, id);
+                       sock = make_receive_sock(ipvs, id, dev->ifindex);
                if (IS_ERR(sock)) {
                        result = PTR_ERR(sock);
                        goto outtinfo;

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