ipv6 addrconf: Allow infinite prefix lifetime.

We need to handle infinite prefix lifetime specially.
With help from original reporter "Bonitch, Joseph"
<Joseph.Bonitch@xerox.com>.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index b45a7c0..b7a4a87 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1106,7 +1106,9 @@
 	}
 
 	rt->u.dst.obsolete = -1;
-	rt->rt6i_expires = jiffies + clock_t_to_jiffies(cfg->fc_expires);
+	rt->rt6i_expires = (cfg->fc_flags & RTF_EXPIRES) ?
+				jiffies + clock_t_to_jiffies(cfg->fc_expires) :
+				0;
 
 	if (cfg->fc_protocol == RTPROT_UNSPEC)
 		cfg->fc_protocol = RTPROT_BOOT;