xfrm: allow to avoid copying DSCP during encapsulation

By default, DSCP is copying during encapsulation.
Copying the DSCP in IPsec tunneling may be a bit dangerous because packets with
different DSCP may get reordered relative to each other in the network and then
dropped by the remote IPsec GW if the reordering becomes too big compared to the
replay window.

It is possible to avoid this copy with netfilter rules, but it's very convenient
to be able to configure it for each SA directly.

This patch adds a toogle for this purpose. By default, it's not set to maintain
backward compatibility.

Field flags in struct xfrm_usersa_info is full, hence I add a new attribute.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/uapi/linux/xfrm.h b/include/uapi/linux/xfrm.h
index 28e493b5b94c..a8cd6a4a2970 100644
--- a/include/uapi/linux/xfrm.h
+++ b/include/uapi/linux/xfrm.h
@@ -297,6 +297,7 @@ enum xfrm_attr_type_t {
         XFRMA_MARK,             /* struct xfrm_mark */
         XFRMA_TFCPAD,           /* __u32 */
         XFRMA_REPLAY_ESN_VAL,   /* struct xfrm_replay_esn */
+        XFRMA_SA_EXTRA_FLAGS,   /* __u32 */
         __XFRMA_MAX
 
 #define XFRMA_MAX (__XFRMA_MAX - 1)
@@ -367,6 +368,8 @@ struct xfrm_usersa_info {
 #define XFRM_STATE_ESN          128
 };
 
+#define XFRM_SA_XFLAG_DONT_ENCAP_DSCP   1
+
 struct xfrm_usersa_id {
         xfrm_address_t                  daddr;
         __be32                          spi;