[ovs-dev] [PATCH v4 09/14] ofp-actions: Introduce macro for padding struct members.
Ben Pfaff
blp at ovn.org
Fri Feb 19 08:34:19 UTC 2016
An upcoming commit will add another case where it's desirable to ensure
that a variable-length array is aligned on an 8-byte boundary. This macro
makes that a little easier.
Signed-off-by: Ben Pfaff <blp at ovn.org>
CC: Joe Stringer <joe at ovn.org>
---
lib/ofp-actions.h | 43 ++++++++++++++++++++++---------------------
1 file changed, 22 insertions(+), 21 deletions(-)
diff --git a/lib/ofp-actions.h b/lib/ofp-actions.h
index 58d7857..24143d3 100644
--- a/lib/ofp-actions.h
+++ b/lib/ofp-actions.h
@@ -185,6 +185,19 @@ BUILD_ASSERT_DECL(sizeof(struct ofpact) == 4);
#define OFPACT_ALIGNTO 8
#define OFPACT_ALIGN(SIZE) ROUND_UP(SIZE, OFPACT_ALIGNTO)
+/* Expands to an anonymous union that contains:
+ *
+ * - MEMBERS in a nested anonymous struct.
+ *
+ * - An array as large as MEMBERS plus padding to a multiple of 8 bytes.
+ *
+ * The effect is to pad MEMBERS to a multiple of 8 bytes. */
+#define OFPACT_PADDED_MEMBERS(MEMBERS) \
+ union { \
+ struct { MEMBERS }; \
+ uint8_t pad[OFPACT_ALIGN(sizeof(struct { MEMBERS }))]; \
+ }
+
/* Returns the ofpact following 'ofpact'. */
static inline struct ofpact *
ofpact_next(const struct ofpact *ofpact)
@@ -487,8 +500,7 @@ struct ofpact_meter {
*
* Used for OFPIT11_WRITE_ACTIONS. */
struct ofpact_nest {
- struct ofpact ofpact;
- uint8_t pad[PAD_SIZE(sizeof(struct ofpact), OFPACT_ALIGNTO)];
+ OFPACT_PADDED_MEMBERS(struct ofpact ofpact;);
struct ofpact actions[];
};
BUILD_ASSERT_DECL(offsetof(struct ofpact_nest, actions) % OFPACT_ALIGNTO == 0);
@@ -507,21 +519,6 @@ enum nx_conntrack_flags {
* that the packet should not be recirculated. */
#define NX_CT_RECIRC_NONE OFPTT_ALL
-/* We want to determine the size of these elements at compile time to ensure
- * actions alignment, but we also want to allow ofpact_conntrack to have
- * basic _put(), _get(), etc accessors defined below which access these
- * members directly from ofpact_conntrack. An anonymous struct will serve
- * both of these purposes. */
-#define CT_MEMBERS \
-struct { \
- struct ofpact ofpact; \
- uint16_t flags; \
- uint16_t zone_imm; \
- struct mf_subfield zone_src; \
- uint16_t alg; \
- uint8_t recirc_table; \
-}
-
#if !defined(IPPORT_FTP)
#define IPPORT_FTP 21
#endif
@@ -530,10 +527,14 @@ struct { \
*
* Used for NXAST_CT. */
struct ofpact_conntrack {
- union {
- CT_MEMBERS;
- uint8_t pad[OFPACT_ALIGN(sizeof(CT_MEMBERS))];
- };
+ OFPACT_PADDED_MEMBERS(
+ struct ofpact ofpact;
+ uint16_t flags;
+ uint16_t zone_imm;
+ struct mf_subfield zone_src;
+ uint16_t alg;
+ uint8_t recirc_table;
+ );
struct ofpact actions[0];
};
BUILD_ASSERT_DECL(offsetof(struct ofpact_conntrack, actions)
--
2.1.3
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