Fix: Relayd and sessiond version check

[lttng-tools.git] / src / common / relayd / relayd.c

diff --git a/src/common/relayd/relayd.c b/src/common/relayd/relayd.c
index daaf44ef04561a40725afdc618e7b91061ef83ae..9cc682713ca7368b6d0b21255bbf84c4740a39b2 100644 (file)
--- a/src/common/relayd/relayd.c
+++ b/src/common/relayd/relayd.c
@@ -163,42 +163,61 @@ int relayd_version_check(struct lttcomm_sock *sock, uint32_t major,
                uint32_t minor)
 {
        int ret;
-       struct lttcomm_relayd_version reply;
+       struct lttcomm_relayd_version msg;
 
        /* Code flow error. Safety net. */
        assert(sock);
 
        DBG("Relayd version check for major.minor %u.%u", major, minor);
 
+       /* Prepare network byte order before transmission. */
+       msg.major = htobe32(major);
+       msg.minor = htobe32(minor);
+
        /* Send command */
-       ret = send_command(sock, RELAYD_VERSION, NULL, 0, 0);
+       ret = send_command(sock, RELAYD_VERSION, (void *) &msg, sizeof(msg), 0);
        if (ret < 0) {
                goto error;
        }
 
        /* Recevie response */
-       ret = recv_reply(sock, (void *) &reply, sizeof(reply));
+       ret = recv_reply(sock, (void *) &msg, sizeof(msg));
        if (ret < 0) {
                goto error;
        }
 
        /* Set back to host bytes order */
-       reply.major = be32toh(reply.major);
-       reply.minor = be32toh(reply.minor);
-
-       /* Validate version */
-       if (reply.major <= major) {
-               if (reply.minor <= minor) {
-                       /* Compatible */
-                       ret = 0;
-                       DBG2("Relayd version is compatible");
-                       goto error;
-               }
+       msg.major = be32toh(msg.major);
+       msg.minor = be32toh(msg.minor);
+
+       /*
+        * Only validate the major version. If the other side is higher,
+        * communication is not possible. Only major version equal can talk to each
+        * other. If the minor version differs, the lowest version is used by both
+        * sides.
+        *
+        * For now, before 2.1.0 stable release, we don't have to check the minor
+        * because this new mechanism with the relayd will only be available with
+        * 2.1 and NOT 2.0.x.
+        */
+       if (msg.major == major) {
+               /* Compatible */
+               ret = 0;
+               DBG2("Relayd version is compatible");
+               goto error;
        }
 
+       /*
+        * After 2.1.0 release, for the 2.2 release, at this point will have to
+        * check the minor version in order for the session daemon to know which
+        * structure to use to communicate with the relayd. If the relayd's minor
+        * version is higher, it will adapt to our version so we can continue to
+        * use the latest relayd communication data structure.
+        */
+
        /* Version number not compatible */
-       DBG2("Relayd version is NOT compatible %u.%u > %u.%u", reply.major,
-                       reply.minor, major, minor);
+       DBG2("Relayd version is NOT compatible. Relayd version %u != %u (us)",
+                       msg.major, major);
        ret = -1;
 
 error: