[PATCH v2 07/11] flow: Introduce 'sidx' type to represent one side of one flow

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

In a number of places, we use indices into the flow table to identify a
specific flow.  We also have cases where we need to identify a particular
side of a particular flow, and we expect those to become more common as
we generalise the flow table to cover more things.

To assist with that, introduces flow_sidx_t, an index type which identifies
a specific side of a specific flow in the table.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 flow.h       | 13 +++++++++++++
 flow_table.h | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/flow.h b/flow.h
index b6da516..3c90bbd 100644
--- a/flow.h
+++ b/flow.h
@@ -39,6 +39,19 @@ struct flow_common {
 #define FLOW_TABLE_PRESSURE		30	/* % of FLOW_MAX */
 #define FLOW_FILE_PRESSURE		30	/* % of c->nofile */
 
+/**
+ * struct flow_sidx - ID for one side of a specific flow
+ * @side:	Side referenced (0 or 1)
+ * @flow:	Index of flow referenced
+ */
+typedef struct flow_sidx {
+	int		side :1;
+	unsigned	flow :FLOW_INDEX_BITS;
+} flow_sidx_t;
+static_assert(sizeof(flow_sidx_t) <= sizeof(uint32_t));
+
+#define FLOW_SIDX_NONE ((flow_sidx_t){ .flow = FLOW_MAX })
+
 union flow;
 
 void flow_table_compact(struct ctx *c, union flow *hole);
diff --git a/flow_table.h b/flow_table.h
index 5e897bd..3c68d4a 100644
--- a/flow_table.h
+++ b/flow_table.h
@@ -47,4 +47,40 @@ static inline unsigned flow_idx(const struct flow_common *f)
  */
 #define FLOW(idx)		(&flowtab[(idx)])
 
+/** flow_at_sidx - Flow entry for a given sidx
+ * @sidx:	Flow & side index
+ *
+ * Return: pointer to the corresponding flow entry, or NULL
+ */
+static inline union flow *flow_at_sidx(flow_sidx_t sidx)
+{
+	if (sidx.flow >= FLOW_MAX)
+		return NULL;
+	return FLOW(sidx.flow);
+}
+
+/** flow_sidx_t - Index of one side of a flow from common structure
+ * @f:		Common flow fields pointer
+ * @side:	Which side to refer to (0 or 1)
+ *
+ * Return: index of @f and @side in the flow table
+ */
+static inline flow_sidx_t flow_sidx(const struct flow_common *f,
+				    int side)
+{
+	ASSERT(side == !!side);
+	return (flow_sidx_t){
+		.side = side,
+		.flow = flow_idx(f),
+	};
+}
+
+/** FLOW_SIDX - Find the index of one side of a flow
+ * @f_:		Flow pointer, either union flow * or protocol specific
+ * @side:	Which side to index (0 or 1)
+ *
+ * Return: index of @f and @side in the flow table
+ */
+#define FLOW_SIDX(f_, side)	(flow_sidx(&(f_)->f, (side)))
+
 #endif /* FLOW_TABLE_H */
-- 
@@ -47,4 +47,40 @@ static inline unsigned flow_idx(const struct flow_common *f)
  */
 #define FLOW(idx)		(&flowtab[(idx)])
 
+/** flow_at_sidx - Flow entry for a given sidx
+ * @sidx:	Flow & side index
+ *
+ * Return: pointer to the corresponding flow entry, or NULL
+ */
+static inline union flow *flow_at_sidx(flow_sidx_t sidx)
+{
+	if (sidx.flow >= FLOW_MAX)
+		return NULL;
+	return FLOW(sidx.flow);
+}
+
+/** flow_sidx_t - Index of one side of a flow from common structure
+ * @f:		Common flow fields pointer
+ * @side:	Which side to refer to (0 or 1)
+ *
+ * Return: index of @f and @side in the flow table
+ */
+static inline flow_sidx_t flow_sidx(const struct flow_common *f,
+				    int side)
+{
+	ASSERT(side == !!side);
+	return (flow_sidx_t){
+		.side = side,
+		.flow = flow_idx(f),
+	};
+}
+
+/** FLOW_SIDX - Find the index of one side of a flow
+ * @f_:		Flow pointer, either union flow * or protocol specific
+ * @side:	Which side to index (0 or 1)
+ *
+ * Return: index of @f and @side in the flow table
+ */
+#define FLOW_SIDX(f_, side)	(flow_sidx(&(f_)->f, (side)))
+
 #endif /* FLOW_TABLE_H */
-- 
2.43.0