int sd_rtnl_message_open_container_union(sd_rtnl_message *m, unsigned short type, const char *key);
int sd_rtnl_message_close_container(sd_rtnl_message *m);
-int sd_rtnl_message_read_string(sd_rtnl_message *m, unsigned short type, char **data);
+int sd_rtnl_message_read_string(sd_rtnl_message *m, unsigned short type, const char **data);
int sd_rtnl_message_read_u8(sd_rtnl_message *m, unsigned short type, uint8_t *data);
int sd_rtnl_message_read_u16(sd_rtnl_message *m, unsigned short type, uint16_t *data);
int sd_rtnl_message_read_u32(sd_rtnl_message *m, unsigned short type, uint32_t *data);