[IPV6]: Fix sending extension headers before and including routing header.

Based on suggestion from Masahide Nakamura <nakam@linux-ipv6.org>.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index bf95193..e2b87cc 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -778,7 +778,9 @@
 	}
 	if (opt == NULL)
 		opt = np->opt;
-	opt = fl6_merge_options(&opt_space, flowlabel, opt);
+	if (flowlabel)
+		opt = fl6_merge_options(&opt_space, flowlabel, opt);
+	opt = ipv6_fixup_options(&opt_space, opt);
 
 	fl->proto = IPPROTO_UDP;
 	ipv6_addr_copy(&fl->fl6_dst, daddr);