EVP_PKEY_CTRL_HKDF_MODE

Undocumented in source but is binding to C. You might be able to learn more by searching the web for its name.
extern (C) nothrow
static if(OPENSSL_VERSION_AT_LEAST(1, 1, 1))
enum EVP_PKEY_CTRL_HKDF_MODE = (EVP_PKEY_ALG_CTRL + 7);

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