rados: add a more direct argv config wrapper ParseConfigArgv

Previously, ParseCmdLineArgs was the function directly wrapping the
ceph rados_conf_parse_argv function. This function has the improper
(IMO) behavior of assuming you didn't know your own argv[0] and just
always stuck "placeholder" in argv[0]. This function adds a more
direct wrapper ParseConfigArgv that allows the caller to pass an
full argv, and they can put any placholder value desired if they want.

Signed-off-by: John Mulligan <jmulligan@redhat.com>

rados/conn.go

@@ -12,6 +12,8 @@ import (
 	"github.com/ceph/go-ceph/internal/retry"
 )
 
+var argvPlaceholder = "placeholder"
+
 // ClusterStat represents Ceph cluster statistics.
 type ClusterStat struct {
 	Kb          uint64
@@ -190,26 +192,45 @@ func (c *Conn) GetClusterStats() (stat ClusterStat, err error) {
 	}, nil
 }
 
-// ParseCmdLineArgs configures the connection from command line arguments.
-func (c *Conn) ParseCmdLineArgs(args []string) error {
-	// add an empty element 0 -- Ceph treats the array as the actual contents
-	// of argv and skips the first element (the executable name)
-	argc := C.int(len(args) + 1)
-	argv := make([]*C.char, argc)
-
-	// make the first element a string just in case it is ever examined
-	argv[0] = C.CString("placeholder")
-	defer C.free(unsafe.Pointer(argv[0]))
-
-	for i, arg := range args {
-		argv[i+1] = C.CString(arg)
-		defer C.free(unsafe.Pointer(argv[i+1]))
+// ParseConfigArgv configures the connection using a unix style command line
+// argument vector.
+//
+// Implements:
+//  int rados_conf_parse_argv(rados_t cluster, int argc,
+//                            const char **argv);
+func (c *Conn) ParseConfigArgv(argv []string) error {
+	if c.cluster == nil {
+		return ErrNotConnected
+	}
+	if len(argv) == 0 {
+		return ErrEmptyArgument
+	}
+	cargv := make([]*C.char, len(argv))
+	for i := range argv {
+		cargv[i] = C.CString(argv[i])
+		defer C.free(unsafe.Pointer(cargv[i]))
 	}
 
-	ret := C.rados_conf_parse_argv(c.cluster, argc, &argv[0])
+	ret := C.rados_conf_parse_argv(c.cluster, C.int(len(cargv)), &cargv[0])
 	return getError(ret)
 }
 
+// ParseCmdLineArgs configures the connection from command line arguments.
+//
+// This function passes a placeholder value to Ceph as argv[0], see
+// ParseConfigArgv for a version of this function that allows the caller to
+// specify argv[0].
+func (c *Conn) ParseCmdLineArgs(args []string) error {
+	argv := make([]string, len(args)+1)
+	// Ceph expects a proper argv array as the actual contents with the
+	// first element containing the executable name
+	argv[0] = argvPlaceholder
+	for i := range args {
+		argv[i+1] = args[i]
+	}
+	return c.ParseConfigArgv(argv)
+}
+
 // ParseDefaultConfigEnv configures the connection from the default Ceph
 // environment variable(s).
 func (c *Conn) ParseDefaultConfigEnv() error {

rados/rados_test.go

@@ -167,6 +167,31 @@ func (suite *RadosTestSuite) TestParseDefaultConfigEnv() {
 	assert.Equal(suite.T(), curr_val, "/dev/null")
 }
 
+func (suite *RadosTestSuite) TestParseConfigArgv() {
+	prev_val, err := suite.conn.GetConfigOption("log_file")
+	assert.NoError(suite.T(), err, "Invalid option")
+
+	argv := []string{"rados.test", "--log_file", "/dev/null"}
+	err = suite.conn.ParseConfigArgv(argv)
+	assert.NoError(suite.T(), err)
+
+	curr_val, err := suite.conn.GetConfigOption("log_file")
+	assert.NoError(suite.T(), err, "Invalid option")
+
+	assert.NotEqual(suite.T(), prev_val, "/dev/null")
+	assert.Equal(suite.T(), curr_val, "/dev/null")
+
+	// ensure that an empty slice triggers an error (not a crash)
+	err = suite.conn.ParseConfigArgv([]string{})
+	assert.Error(suite.T(), err)
+
+	// ensure we get an error for an invalid conn value
+	badConn := &Conn{}
+	err = badConn.ParseConfigArgv(
+		[]string{"cephfs.test", "--log_file", "/dev/null"})
+	assert.Error(suite.T(), err)
+}
+
 func (suite *RadosTestSuite) TestParseCmdLineArgs() {
 	prev_val, err := suite.conn.GetConfigOption("log_file")
 	assert.NoError(suite.T(), err, "Invalid option")