mctp-bench: check getrandom return value

Some compiles will warn with:

    ../src/mctp-bench.c: In function ‘command’:
    ../src/mctp-bench.c:686:9: warning: ignoring return value of ‘getrandom’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
      686 |         getrandom(&req->iid, sizeof(req->iid), 0);
          |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

getrandom() cannot fail with the length we're requesting, so suppress
the warning.

Signed-off-by: Jeremy Kerr <[email protected]>

Author: jk-ozlabs

src/mctp-bench.c

@@ -683,7 +683,10 @@ static int command(mctp_eid_t eid, int net, enum command command,
 	req->magic = COMMAND_MAGIC;
 	req->version = COMMAND_VERSION;
 	req->command = command;
-	getrandom(&req->iid, sizeof(req->iid), 0);
+	/* on a recent kernel (ie., any with MCTP support), getrandom is
+	 * infallible with <=256-byte lengths
+	 */
+	(void)getrandom(&req->iid, sizeof(req->iid), 0);
 	memcpy(req->body, body, body_len);
 
 	rc = sendto(sd, req, req_len, 0, (struct sockaddr *)&addr,