ip6_tunnel: Fix encapsulation layout

sbrivio-rh · davem330 · commit d4d576f5ab7e · 2018-10-18T16:54:40.000-07:00
Commit 058214a ("ip6_tun: Add infrastructure for doing encapsulation") added the ip6_tnl_encap() call in ip6_tnl_xmit(), before the call to ipv6_push_frag_opts() to append the IPv6 Tunnel Encapsulation Limit option (option 4, RFC 2473, par. 5.1) to the outer IPv6 header. As long as the option didn't actually end up in generated packets, this wasn't an issue. Then commit 89a23c8 ("ip6_tunnel: Fix missing tunnel encapsulation limit option") fixed sending of this option, and the resulting layout, e.g. for FoU, is: .-------------------.------------.----------.-------------------.----- - - | Outer IPv6 Header | UDP header | Option 4 | Inner IPv6 Header | Payload '-------------------'------------'----------'-------------------'----- - - Needless to say, FoU and GUE (at least) won't work over IPv6. The option is appended by default, and I couldn't find a way to disable it with the current iproute2. Turn this into a more reasonable: .-------------------.----------.------------.-------------------.----- - - | Outer IPv6 Header | Option 4 | UDP header | Inner IPv6 Header | Payload '-------------------'----------'------------'-------------------'----- - - With this, and with 84dad55 ("udp6: fix encap return code for resubmitting"), FoU and GUE work again over IPv6. Fixes: 058214a ("ip6_tun: Add infrastructure for doing encapsulation") Signed-off-by: Stefano Brivio <sbrivio@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
@@ -1184,11 +1184,6 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield,
 	}
 	skb_dst_set(skb, dst);
 
-	if (encap_limit >= 0) {
-		init_tel_txopt(&opt, encap_limit);
-		ipv6_push_frag_opts(skb, &opt.ops, &proto);
-	}
-
 	if (hop_limit == 0) {
 		if (skb->protocol == htons(ETH_P_IP))
 			hop_limit = ip_hdr(skb)->ttl;
@@ -1210,6 +1205,11 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield,
 	if (err)
 		return err;
 
+	if (encap_limit >= 0) {
+		init_tel_txopt(&opt, encap_limit);
+		ipv6_push_frag_opts(skb, &opt.ops, &proto);
+	}
+
 	skb_push(skb, sizeof(struct ipv6hdr));
 	skb_reset_network_header(skb);
 	ipv6h = ipv6_hdr(skb);
