[PATCH v4] public/io/netif.h: add a new extra type for XDP

[Denis Kirjanov <kda@xxxxxxxxxxxxxxxxx>]

The patch adds a new extra type to be able to diffirentiate
between RX responses on xen-netfront side with the adjusted offset
required for XDP processing.

The offset value from a guest is passed via xenstore.

Signed-off-by: Denis Kirjanov <denis.kirjanov@xxxxxxxx>
---
v4:
- updated the commit and documenation

v3:
- updated the commit message

v2:
- added documentation
- fixed padding for netif_extra_info
---
---
 xen/include/public/io/netif.h | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/xen/include/public/io/netif.h b/xen/include/public/io/netif.h
index 9fcf91a..a92bf04 100644
--- a/xen/include/public/io/netif.h
+++ b/xen/include/public/io/netif.h
@@ -161,6 +161,17 @@
  */
 
 /*
+ * "xdp-headroom" is used to request that extra space is added
+ * for XDP processing.  The value is measured in bytes and passed by
+ * the frontend to be consistent between both ends.
+ * If the value is greater than zero that means that
+ * an RX response is going to be passed to an XDP program for processing.
+ *
+ * "feature-xdp-headroom" is set to "1" by the netback side like other features
+ * so a guest can check if an XDP program can be processed.
+ */
+
+/*
  * Control ring
  * ============
  *
@@ -985,7 +996,8 @@ typedef struct netif_tx_request netif_tx_request_t;
 #define XEN_NETIF_EXTRA_TYPE_MCAST_ADD (2)  /* u.mcast */
 #define XEN_NETIF_EXTRA_TYPE_MCAST_DEL (3)  /* u.mcast */
 #define XEN_NETIF_EXTRA_TYPE_HASH      (4)  /* u.hash */
-#define XEN_NETIF_EXTRA_TYPE_MAX       (5)
+#define XEN_NETIF_EXTRA_TYPE_XDP       (5)  /* u.xdp */
+#define XEN_NETIF_EXTRA_TYPE_MAX       (6)
 
 /* netif_extra_info_t flags. */
 #define _XEN_NETIF_EXTRA_FLAG_MORE (0)
@@ -1018,6 +1030,10 @@ struct netif_extra_info {
             uint8_t algorithm;
             uint8_t value[4];
         } hash;
+        struct {
+            uint16_t headroom;
+            uint16_t pad[2]
+        } xdp;
         uint16_t pad[3];
     } u;
 };
-- 
1.8.3.1