From df96a4cb5d4f3907f1019ba50511ee9787443acf Mon Sep 17 00:00:00 2001
From: David Gibson <david@gibson.dropbear.id.au>
Date: Thu, 30 Nov 2023 13:02:14 +1100
Subject: flow: Introduce 'sidx' type to represent one side of one flow

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>
[sbrivio: Suppress false cppcheck positive in flow_sidx()]
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
---
 flow.h       | 14 ++++++++++++++
 flow_table.h | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/flow.h b/flow.h
index c820a15..4f12831 100644
--- a/flow.h
+++ b/flow.h
@@ -39,6 +39,20 @@ 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),
+	      "flow_sidx_t must fit within 32 bits");
+
+#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..0dee66f 100644
--- a/flow_table.h
+++ b/flow_table.h
@@ -47,4 +47,42 @@ 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)
+{
+	/* cppcheck-suppress [knownConditionTrueFalse, unmatchedSuppression] */
+	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 */
-- 
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