[PATCH 2/7] flow, flow_table: Pad flow table entries to 128 bytes, hash entries to 32 bits

[Stefano Brivio <sbrivio@redhat.com>]

...to keep migration sane. Right now, the biggest struct in union flow
is struct tcp_splice_conn with 120 bytes on x86_64, which should also
have the biggest storage and alignment requirements of any
architecture we might run on.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
---
 flow.h       | 18 ++++++++++++------
 flow_table.h | 13 ++++++++++---
 2 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/flow.h b/flow.h
index 24ba3ef..8eb5964 100644
--- a/flow.h
+++ b/flow.h
@@ -202,15 +202,21 @@ struct flow_common {
 
 /**
  * struct flow_sidx - ID for one side of a specific flow
- * @sidei:	Index of side referenced (0 or 1)
- * @flowi:	Index of flow referenced
+ * @sidei:		Index of side referenced (0 or 1)
+ * @flowi:		Index of flow referenced
+ * @flow_sidx_storage:	Pad to 32 bits
  */
 typedef struct flow_sidx {
-	unsigned	sidei :1;
-	unsigned	flowi :FLOW_INDEX_BITS;
+	union {
+		struct {
+			unsigned	sidei :1;
+			unsigned	flowi :FLOW_INDEX_BITS;
+		};
+		uint32_t flow_sidx_storage;
+	};
 } flow_sidx_t;
-static_assert(sizeof(flow_sidx_t) <= sizeof(uint32_t),
-	      "flow_sidx_t must fit within 32 bits");
+static_assert(sizeof(flow_sidx_t) == sizeof(uint32_t),
+	      "flow_sidx_t must be 32-bit wide");
 
 #define FLOW_SIDX_NONE ((flow_sidx_t){ .flowi = FLOW_MAX })
 
diff --git a/flow_table.h b/flow_table.h
index f15db53..007f4dd 100644
--- a/flow_table.h
+++ b/flow_table.h
@@ -26,9 +26,13 @@ struct flow_free_cluster {
 
 /**
  * union flow - Descriptor for a logical packet flow (e.g. connection)
- * @f:		Fields common between all variants
- * @tcp:	Fields for non-spliced TCP connections
- * @tcp_splice:	Fields for spliced TCP connections
+ * @f:			Fields common between all variants
+ * @free:		Entry in a cluster of free entries
+ * @tcp:		Fields for non-spliced TCP connections
+ * @tcp_splice:		Fields for spliced TCP connections
+ * @ping:		Tracking for ping flows
+ * @udp:		Tracking for UDP flows
+ * @flow_storage:	Pad flow entries to 128 bytes to ease state migration
 */
 union flow {
 	struct flow_common f;
@@ -37,8 +41,11 @@ union flow {
 	struct tcp_splice_conn tcp_splice;
 	struct icmp_ping_flow ping;
 	struct udp_flow udp;
+	char flow_storage[128];
 };
 
+static_assert(sizeof(union flow) == 128, "union flow should be 128-byte wide");
+
 /* Global Flow Table */
 extern unsigned flow_first_free;
 extern union flow flowtab[];
-- 
@@ -26,9 +26,13 @@ struct flow_free_cluster {
 
 /**
  * union flow - Descriptor for a logical packet flow (e.g. connection)
- * @f:		Fields common between all variants
- * @tcp:	Fields for non-spliced TCP connections
- * @tcp_splice:	Fields for spliced TCP connections
+ * @f:			Fields common between all variants
+ * @free:		Entry in a cluster of free entries
+ * @tcp:		Fields for non-spliced TCP connections
+ * @tcp_splice:		Fields for spliced TCP connections
+ * @ping:		Tracking for ping flows
+ * @udp:		Tracking for UDP flows
+ * @flow_storage:	Pad flow entries to 128 bytes to ease state migration
 */
 union flow {
 	struct flow_common f;
@@ -37,8 +41,11 @@ union flow {
 	struct tcp_splice_conn tcp_splice;
 	struct icmp_ping_flow ping;
 	struct udp_flow udp;
+	char flow_storage[128];
 };
 
+static_assert(sizeof(union flow) == 128, "union flow should be 128-byte wide");
+
 /* Global Flow Table */
 extern unsigned flow_first_free;
 extern union flow flowtab[];
-- 
2.43.0