flow: Add helper to determine a flow's protocol

Each flow already has a type field.  This implies the protocol the
flow represents, but also has more information: we have two ways to
represent TCP flows, "tap" and "spliced".  In order to generalise some
of the flow mechanics, we'll need to determine a flow's protocol in
terms of the IP (L4) protocol number.

Introduce a constant table and helper macro to derive this from the flow
type.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

2 files changed, 11 insertions, 0 deletions

diff --git a/flow.c b/flow.c
index 5e94a7a..beb9749 100644
--- a/flow.c
+++ b/flow.c
@@ -25,6 +25,13 @@ const char *flow_type_str[] = {
 static_assert(ARRAY_SIZE(flow_type_str) == FLOW_NUM_TYPES,
 	      "flow_type_str[] doesn't match enum flow_type");
 
+const uint8_t flow_proto[] = {
+	[FLOW_TCP]		= IPPROTO_TCP,
+	[FLOW_TCP_SPLICE]	= IPPROTO_TCP,
+};
+static_assert(ARRAY_SIZE(flow_proto) == FLOW_NUM_TYPES,
+	      "flow_proto[] doesn't match enum flow_type");
+
 /* Global Flow Table */
 
 /**
diff --git a/flow.h b/flow.h
index 48a0ab4..e9b3ce3 100644
--- a/flow.h
+++ b/flow.h
@@ -27,6 +27,10 @@ extern const char *flow_type_str[];
 #define FLOW_TYPE(f)							\
         ((f)->type < FLOW_NUM_TYPES ? flow_type_str[(f)->type] : "?")
 
+extern const uint8_t flow_proto[];
+#define FLOW_PROTO(f)				\
+	((f)->type < FLOW_NUM_TYPES ? flow_proto[(f)->type] : 0)
+
 /**
  * struct flow_common - Common fields for packet flows
  * @type:	Type of packet flow