[PATCH net-next 5/6] net: Add GRE keyid in flow_keys

[Tom Herbert <tom@herbertland.com>]

In flow dissector if a GRE header contains a keyid this is saved in the
new extra entropy field of flow_keys. The GRE keyid is then represented
in the flow hash function input.

Signed-off-by: Tom Herbert <tom@herbertland.com>
---
 include/net/flow_keys.h   |  1 +
 net/core/flow_dissector.c | 15 ++++++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/include/net/flow_keys.h b/include/net/flow_keys.h
index 906d47a..779e42f 100644
--- a/include/net/flow_keys.h
+++ b/include/net/flow_keys.h
@@ -28,6 +28,7 @@ struct flow_keys {
 	u8	padding;
 	u32	vlan_id:12,
 		flow_label:20;
+	u32	extra_entropy;
 
 	union {
 		__be32 ports;
diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index de71e42..025b91f 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -195,8 +195,21 @@ ipv6:
 			nhoff += 4;
 			if (hdr->flags & GRE_CSUM)
 				nhoff += 4;
-			if (hdr->flags & GRE_KEY)
+			if (hdr->flags & GRE_KEY) {
+				const __be32 *keyid;
+				__be32 _keyid;
+
+				keyid = __skb_header_pointer(skb, nhoff,
+							     sizeof(_keyid),
+							     data, hlen,
+							     &_keyid);
+				if (!keyid)
+					return false;
+
+				flow->extra_entropy ^= *keyid;
+
 				nhoff += 4;
+			}
 			if (hdr->flags & GRE_SEQ)
 				nhoff += 4;
 			if (proto == htons(ETH_P_TEB)) {
-- 
1.8.1