net/xfrm: IPsec tunnel mode fix inner_ipproto setting in sec_path

The inner_ipproto saves the inner IP protocol of the plain
text packet. This allows vendor's IPsec feature making offload
decision at skb's features_check and configuring hardware at
ndo_start_xmit, current code implenetation did not handle the
case where IPsec is used in tunnel mode.

Fix by handling the case when IPsec is used in tunnel mode by
reading the protocol of the plain text packet IP protocol.

Fixes: fa453523 ("net/xfrm: Add inner_ipproto into sec_path")
Signed-off-by: Raed Salem <raeds@nvidia.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/xfrm/xfrm_output.c

@@ -647,10 +647,12 @@ static int xfrm_output_gso(struct net *net, struct sock *sk, struct sk_buff *skb
  * This requires hardware to know the inner packet type to calculate
  * the inner header checksum. Save inner ip protocol here to avoid
  * traversing the packet in the vendor's xmit code.
- * If the encap type is IPIP, just save skb->inner_ipproto. Otherwise,
- * get the ip protocol from the IP header.
+ * For IPsec tunnel mode save the ip protocol from the IP header of the
+ * plain text packet. Otherwise If the encap type is IPIP, just save
+ * skb->inner_ipproto in any other case get the ip protocol from the IP
+ * header.
  */
-static void xfrm_get_inner_ipproto(struct sk_buff *skb)
+static void xfrm_get_inner_ipproto(struct sk_buff *skb, struct xfrm_state *x)
 {
 	struct xfrm_offload *xo = xfrm_offload(skb);
 	const struct ethhdr *eth;
@@ -658,6 +660,25 @@ static void xfrm_get_inner_ipproto(struct sk_buff *skb)
 	if (!xo)
 		return;
 
+	if (x->outer_mode.encap == XFRM_MODE_TUNNEL) {
+		switch (x->outer_mode.family) {
+		case AF_INET:
+			xo->inner_ipproto = ip_hdr(skb)->protocol;
+			break;
+		case AF_INET6:
+			xo->inner_ipproto = ipv6_hdr(skb)->nexthdr;
+			break;
+		default:
+			break;
+		}
+
+		return;
+	}
+
+	/* non-Tunnel Mode */
+	if (!skb->encapsulation)
+		return;
+
 	if (skb->inner_protocol_type == ENCAP_TYPE_IPPROTO) {
 		xo->inner_ipproto = skb->inner_ipproto;
 		return;
@@ -712,8 +733,7 @@ int xfrm_output(struct sock *sk, struct sk_buff *skb)
 		sp->xvec[sp->len++] = x;
 		xfrm_state_hold(x);
 
-		if (skb->encapsulation)
-			xfrm_get_inner_ipproto(skb);
+		xfrm_get_inner_ipproto(skb, x);
 		skb->encapsulation = 1;
 
 		if (skb_is_gso(skb)) {