BIO_dgram_sctp_wait_for_dry
ret = BIO_dgram_sctp_wait_for_dry(b);
int BIO_dgram_sctp_wait_for_dry(BIO *b);
ret = BIO_dgram_sctp_wait_for_dry(wbio);
ret = BIO_dgram_sctp_wait_for_dry(SSL_get_wbio(ssl));