int band, bool dont_free);
__printf_3_4 int send_sb_va(struct stream_cipher_context *scc, int band,
const char *fmt, ...);
+int send_strerror(struct command_context *cc, int err);
int recv_sb(struct stream_cipher_context *scc,
enum sb_designator expected_band,
size_t max_size, struct iovec *result);