[PATCH v3 07/15] flow: Add helper to determine a flow's protocol

[David Gibson <david@gibson.dropbear.id.au>]

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>
---
 flow.c | 7 +++++++
 flow.h | 4 ++++
 2 files changed, 11 insertions(+)

diff --git a/flow.c b/flow.c
index 263633e..70036fc 100644
--- a/flow.c
+++ b/flow.c
@@ -26,6 +26,13 @@ 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 */
 unsigned flow_first_free;
 union flow flowtab[FLOW_MAX];
diff --git a/flow.h b/flow.h
index 72ded54..ab831d1 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 flowside - Common information for one side of a flow
  * @eaddr:	Endpoint address (remote address from passt's PoV)
-- 
@@ -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 flowside - Common information for one side of a flow
  * @eaddr:	Endpoint address (remote address from passt's PoV)
-- 
2.43.0