As per RFC 3493 the default multicast hops setting
for a socket should be "1" just like ipv4.
Ironically we have a IPV6_DEFAULT_MCASTHOPS macro
it just wasn't being used.
Reported-by: Elliot Hughes <enh@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
 
        inet_sk(sk)->pinet6 = np = inet6_sk_generic(sk);
        np->hop_limit   = -1;
-       np->mcast_hops  = -1;
+       np->mcast_hops  = IPV6_DEFAULT_MCASTHOPS;
        np->mc_loop     = 1;
        np->pmtudisc    = IPV6_PMTUDISC_WANT;
        np->ipv6only    = net->ipv6.sysctl.bindv6only;