+ /**
+ * Resolve target-specific URL string
+ *
+ * This method must be defined if the sender supports the add/delete
+ * subcommands. It interprets a string specifying a target URL in a
+ * sender-specific fashion (e.g. embedded FEC string). It can also
+ * fill in sender-specific defaults if necessary.
+ */
+ int (*resolve_target)(const char *, struct sender_command_data *);