[PATCH v3 3/3] public/io/netif.h: document new extra info for passing hash values

[Paul Durrant <paul.durrant@citrix.com>]

To properly support NDIS RSS, the Windows frontend PV driver needs the
toeplitz hash value calculated by the backend (otherwise it would have to
duplicate the calculation).

This patch adds documentation for "feature-hash" and a definition of a
new XEN_NETIF_EXTRA_TYPE_HASH extra info segment which both frontends
and backends can use to pass hash values to the other end.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Keir Fraser <keir@xen.org>
Cc: Tim Deegan <tim@xen.org>
---
 xen/include/public/io/netif.h | 36 +++++++++++++++++++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/xen/include/public/io/netif.h b/xen/include/public/io/netif.h
index ace74f3..e12c73f 100644
--- a/xen/include/public/io/netif.h
+++ b/xen/include/public/io/netif.h
@@ -151,6 +151,12 @@
  */
 
 /*
+ * "feature-hash" advertises the capability to accept extra info slots of
+ * type XEN_NETIF_EXTRA_TYPE_HASH. They will not be sent by either end
+ * unless the other end advertises this feature.
+ */
+
+/*
  * Control ring
  * ============
  *
@@ -574,6 +580,18 @@ DEFINE_RING_TYPES(netif_ctrl, struct netif_ctrl_request, struct netif_ctrl_respo
  * type: Must be XEN_NETIF_EXTRA_TYPE_MCAST_{ADD,DEL}
  * flags: XEN_NETIF_EXTRA_FLAG_*
  * addr: address to add/remove
+ *
+ * XEN_NETIF_EXTRA_TYPE_HASH:
+ *
+ *    0     1     2     3     4     5     6     7  octet
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |type |flags|htype| pad |LSB ---- value ---- MSB|
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ *
+ * type: Must be XEN_NETIF_EXTRA_TYPE_HASH
+ * flags: XEN_NETIF_EXTRA_FLAG_*
+ * htype: XEN_NETIF_HASH_TYPE_*
+ * value: Hash value
  */
 
 /* Protocol checksum field is blank in the packet (hardware offload)? */
@@ -607,7 +625,8 @@ typedef struct netif_tx_request netif_tx_request_t;
 #define XEN_NETIF_EXTRA_TYPE_GSO       (1)  /* u.gso */
 #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_MAX       (4)
+#define XEN_NETIF_EXTRA_TYPE_HASH      (4)  /* u.hash */
+#define XEN_NETIF_EXTRA_TYPE_MAX       (5)
 
 /* netif_extra_info_t flags. */
 #define _XEN_NETIF_EXTRA_FLAG_MORE (0)
@@ -619,6 +638,16 @@ typedef struct netif_tx_request netif_tx_request_t;
 #define XEN_NETIF_GSO_TYPE_TCPV6        (2)
 
 /*
+ * Hash types. (See NETIF_CTRL_TOEPLITZ_FLAG_* definitions above
+ * for more information).
+ */
+#define XEN_NETIF_HASH_TYPE_NONE        0
+#define XEN_NETIF_HASH_TYPE_IPV4        1
+#define XEN_NETIF_HASH_TYPE_IPV4_TCP    2
+#define XEN_NETIF_HASH_TYPE_IPV6        3
+#define XEN_NETIF_HASH_TYPE_IPV6_TCP    4
+
+/*
  * This structure needs to fit within both netif_tx_request_t and
  * netif_rx_response_t for compatibility.
  */
@@ -635,6 +664,11 @@ struct netif_extra_info {
         struct {
             uint8_t addr[6];
         } mcast;
+        struct {
+            uint8_t type;
+            uint8_t pad;
+            uint8_t value[4];
+        } hash;
         uint16_t pad[3];
     } u;
 };
-- 
2.1.4