From: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Date: Thu, 4 Jul 2019 12:59:08 +0000 (-0400)
Subject: Use a "comm" variant of the LTTNG_OPTIONAL helper in sessiond-comm
X-Git-Tag: v2.12.0-rc1~539
X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=commitdiff_plain;h=0a30bf9be799ddb162530ea7581172e923055973

Use a "comm" variant of the LTTNG_OPTIONAL helper in sessiond-comm

The LTTNG_OPTIONAL helper is currently communication safe (as long
as LTTNG_PACKED is used). However, this could change in the future.
An LTTNG_OPTIONAL_COMM alias is introduced in order to make it easier
to change the layout of LTTNG_OPTIONAL should it become necessary
in the future.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---

diff --git a/src/common/optional.h b/src/common/optional.h
index 1da5fda5d..aee5fcc5e 100644
--- a/src/common/optional.h
+++ b/src/common/optional.h
@@ -32,9 +32,6 @@
  * Prefer using this macro where "special" values would be used, e.g.
  * -1ULL for uint64_t types.
  *
- * LTTNG_OPTIONAL should be combined with the LTTNG_PACKED macro when
- * used for IPC / network communication.
- *
  * Declaration example:
  * struct my_struct {
  * 	int a;
@@ -57,6 +54,16 @@
 		type value;  \
 	}
 
+/*
+ * Alias used for communication structures. If the layout of an LTTNG_OPTIONAL
+ * is changed, the original layout should still be used for communication
+ * purposes.
+ *
+ * LTTNG_OPTIONAL_COMM should be combined with the LTTNG_PACKED macro when
+ * used for IPC / network communication.
+ */
+#define LTTNG_OPTIONAL_COMM LTTNG_OPTIONAL
+
 /*
  * This macro is available as a 'convenience' to allow sites that assume
  * an optional value is set to assert() that it is set when accessing it.
diff --git a/src/common/sessiond-comm/sessiond-comm.h b/src/common/sessiond-comm/sessiond-comm.h
index 3b0093bfb..d9177cf37 100644
--- a/src/common/sessiond-comm/sessiond-comm.h
+++ b/src/common/sessiond-comm/sessiond-comm.h
@@ -480,7 +480,7 @@ struct lttcomm_consumer_msg {
 			uint64_t channel_key;
 			uint64_t session_id;
 			/* ID of the session's current trace chunk. */
-			LTTNG_OPTIONAL(uint64_t) LTTNG_PACKED chunk_id;
+			LTTNG_OPTIONAL_COMM(uint64_t) LTTNG_PACKED chunk_id;
 			char pathname[PATH_MAX];
 			uint64_t relayd_id;
 			/* nb_init_streams is the number of streams open initially. */
@@ -542,7 +542,7 @@ struct lttcomm_consumer_msg {
 			uint64_t relayd_id;			/* Relayd id if apply. */
 			uint64_t key;				/* Unique channel key. */
 			/* ID of the session's current trace chunk. */
-			LTTNG_OPTIONAL(uint64_t) LTTNG_PACKED chunk_id;
+			LTTNG_OPTIONAL_COMM(uint64_t) LTTNG_PACKED chunk_id;
 			unsigned char uuid[UUID_LEN];	/* uuid for ust tracer. */
 			uint32_t chan_id;			/* Channel ID on the tracer side. */
 			uint64_t tracefile_size;	/* bytes */
@@ -634,7 +634,7 @@ struct lttcomm_consumer_msg {
 			 * `override_name` is left NULL (all-zeroes) if the
 			 * chunk's name is not overriden.
 			 */
-			LTTNG_OPTIONAL(uint64_t) LTTNG_PACKED relayd_id;
+			LTTNG_OPTIONAL_COMM(uint64_t) LTTNG_PACKED relayd_id;
 			char override_name[LTTNG_NAME_MAX];
 			uint64_t session_id;
 			uint64_t chunk_id;
@@ -645,13 +645,13 @@ struct lttcomm_consumer_msg {
 			} LTTNG_PACKED credentials;
 		} LTTNG_PACKED create_trace_chunk;
 		struct {
-			LTTNG_OPTIONAL(uint64_t) LTTNG_PACKED relayd_id;
+			LTTNG_OPTIONAL_COMM(uint64_t) LTTNG_PACKED relayd_id;
 			uint64_t session_id;
 			uint64_t chunk_id;
 			uint64_t close_timestamp;
 		} LTTNG_PACKED close_trace_chunk;
 		struct {
-			LTTNG_OPTIONAL(uint64_t) LTTNG_PACKED relayd_id;
+			LTTNG_OPTIONAL_COMM(uint64_t) LTTNG_PACKED relayd_id;
 			uint64_t session_id;
 			uint64_t chunk_id;
 		} LTTNG_PACKED trace_chunk_exists;