ah4/esp4: set transport header correctly for IPsec tunnel mode.

IPsec tunnel does not set ECN field to CE in inner header when
the ECN field in the outer header is CE, and the ECN field in
the inner header is ECT(0) or ECT(1).

The cause is ipip_hdr() does not return the correct address of
inner header since skb->transport-header is not the inner header
after esp_input_done2(), or ah_input().
Signed-off-by: Li RongQing <roy.qing.li@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/ipv4/ah4.c

@@ -269,6 +269,10 @@ static void ah_input_done(struct crypto_async_request *base, int err)
 	skb->network_header += ah_hlen;
 	memcpy(skb_network_header(skb), work_iph, ihl);
 	__skb_pull(skb, ah_hlen + ihl);
+
+	if (x->props.mode == XFRM_MODE_TUNNEL)
+		skb_reset_transport_header(skb);
+	else
 		skb_set_transport_header(skb, -ihl);
 out:
 	kfree(AH_SKB_CB(skb)->tmp);
@@ -381,6 +385,9 @@ static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
 	skb->network_header += ah_hlen;
 	memcpy(skb_network_header(skb), work_iph, ihl);
 	__skb_pull(skb, ah_hlen + ihl);
+	if (x->props.mode == XFRM_MODE_TUNNEL)
+		skb_reset_transport_header(skb);
+	else
 		skb_set_transport_header(skb, -ihl);
 
 	err = nexthdr;

net/ipv4/esp4.c

@@ -346,6 +346,9 @@ static int esp_input_done2(struct sk_buff *skb, int err)
 
 	pskb_trim(skb, skb->len - alen - padlen - 2);
 	__skb_pull(skb, hlen);
+	if (x->props.mode == XFRM_MODE_TUNNEL)
+		skb_reset_transport_header(skb);
+	else
 		skb_set_transport_header(skb, -ihl);
 
 	err = nexthdr[1];