ipv6: allow PMTU exceptions to local routes

IPVS setups with local client and remote tunnel server need
to create exception for the local virtual IP. What we do is to
change PMTU from 64KB (on "lo") to 1460 in the common case.
Suggested-by: NMartin KaFai Lau <kafai@fb.com>
Fixes: 45e4fd26 ("ipv6: Only create RTF_CACHE routes after encountering pmtu exception")
Fixes: 7343ff31 ("ipv6: Don't create clones of host routes.")
Signed-off-by: NJulian Anastasov <ja@ssi.bg>
Acked-by: NDavid Ahern <dsahern@gmail.com>
Acked-by: NMartin KaFai Lau <kafai@fb.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/route.c

@@ -2307,9 +2307,6 @@ static void __ip6_rt_update_pmtu(struct dst_entry *dst, const struct sock *sk,
 	const struct in6_addr *daddr, *saddr;
 	struct rt6_info *rt6 = (struct rt6_info *)dst;
 
-	if (rt6->rt6i_flags & RTF_LOCAL)
-		return;
-
 	if (dst_metric_locked(dst, RTAX_MTU))
 		return;