[RFC PATCH] ah4/esp4: set transport header correctly for IPsec tunnel mode.

[roy.qing.li@gmail.com]

From: Li RongQing <roy.qing.li@gmail.com>

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>
---
I know this bug, but no lab to verify if my patch is correct,
hope netdev experts can inspect this patch carefully, if this
can be accepted, I will do same fix for ah6/esp6

 net/ipv4/ah4.c  |   11 +++++++++--
 net/ipv4/esp4.c |    5 ++++-
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/ah4.c b/net/ipv4/ah4.c
index a0d8392..a154d0a 100644
--- a/net/ipv4/ah4.c
+++ b/net/ipv4/ah4.c
@@ -269,7 +269,11 @@ 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);
-	skb_set_transport_header(skb, -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);
 	xfrm_input_resume(skb, err);
@@ -381,7 +385,10 @@ 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);
-	skb_set_transport_header(skb, -ihl);
+	if (x->props.mode == XFRM_MODE_TUNNEL)
+		skb_reset_transport_header(skb);
+	else
+		skb_set_transport_header(skb, -ihl);
 
 	err = nexthdr;
 
diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index b61e9de..fd26ff4 100644
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -346,7 +346,10 @@ static int esp_input_done2(struct sk_buff *skb, int err)
 
 	pskb_trim(skb, skb->len - alen - padlen - 2);
 	__skb_pull(skb, hlen);
-	skb_set_transport_header(skb, -ihl);
+	if (x->props.mode == XFRM_MODE_TUNNEL)
+		skb_reset_transport_header(skb);
+	else
+		skb_set_transport_header(skb, -ihl);
 
 	err = nexthdr[1];
 
-- 
1.7.10.4