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    use libc::*;
    use std::ptr;

    use *;

    #[cfg(not(any(libressl, ossl110)))]
    pub const SSL_MAX_KRB5_PRINCIPAL_LENGTH: c_int = 256;

    #[cfg(not(ossl110))]
    pub const SSL_MAX_SSL_SESSION_ID_LENGTH: c_int = 32;
    #[cfg(not(ossl110))]
    pub const SSL_MAX_SID_CTX_LENGTH: c_int = 32;

    #[cfg(not(any(libressl, ossl110)))]
    pub const SSL_MAX_KEY_ARG_LENGTH: c_int = 8;
    #[cfg(not(ossl110))]
    pub const SSL_MAX_MASTER_KEY_LENGTH: c_int = 48;

    pub const SSL_SENT_SHUTDOWN: c_int = 1;
    pub const SSL_RECEIVED_SHUTDOWN: c_int = 2;

    pub const SSL_FILETYPE_PEM: c_int = X509_FILETYPE_PEM;
    pub const SSL_FILETYPE_ASN1: c_int = X509_FILETYPE_ASN1;

    pub enum SSL_METHOD {}
    pub enum SSL_CIPHER {}
    cfg_if! {
        if #[cfg(any(ossl110, libressl280))] {
            pub enum SSL_SESSION {}
        } else if #[cfg(libressl251)] {
            #[repr(C)]
            pub struct SSL_SESSION {
                ssl_version: c_int,
                pub master_key_length: c_int,
                pub master_key: [c_uchar; 48],
                session_id_length: c_uint,
                session_id: [c_uchar; ::SSL_MAX_SSL_SESSION_ID_LENGTH as usize],
                sid_ctx_length: c_uint,
                sid_ctx: [c_uchar; ::SSL_MAX_SID_CTX_LENGTH as usize],
                peer: *mut ::X509,
                verify_result: c_long,
                timeout: c_long,
                time: time_t,
                pub references: c_int,
                cipher: *const ::SSL_CIPHER,
                cipher_id: c_long,
                ciphers: *mut stack_st_SSL_CIPHER,
                tlsext_hostname: *mut c_char,
                tlsext_tick: *mut c_uchar,
                tlsext_ticklen: size_t,
                tlsext_tick_lifetime_int: c_long,
                internal: *mut c_void,
            }
        } else if #[cfg(libressl)] {
            #[repr(C)]
            pub struct SSL_SESSION {
                ssl_version: c_int,
                pub master_key_length: c_int,
                pub master_key: [c_uchar; 48],
                session_id_length: c_uint,
                session_id: [c_uchar; SSL_MAX_SSL_SESSION_ID_LENGTH as usize],
                sid_ctx_length: c_uint,
                sid_ctx: [c_uchar; SSL_MAX_SID_CTX_LENGTH as usize],
                not_resumable: c_int,
                sess_cert: *mut c_void,
                peer: *mut X509,
                verify_result: c_long,
                timeout: c_long,
                time: time_t,
                pub references: c_int,
                cipher: *const c_void,
                cipher_id: c_ulong,
                ciphers: *mut c_void,
                ex_data: ::CRYPTO_EX_DATA,
                prev: *mut c_void,
                next: *mut c_void,
                tlsext_hostname: *mut c_char,
                tlsext_ecpointformatlist_length: size_t,
                tlsext_ecpointformatlist: *mut u8,
                tlsext_ellipticcurvelist_length: size_t,
                tlsext_ellipticcurvelist: *mut u16,
                tlsext_tick: *mut c_uchar,
                tlsext_ticklen: size_t,
                tlsext_tick_lifetime_hint: c_long,
            }
        } else {
            #[repr(C)]
            pub struct SSL_SESSION {
                ssl_version: c_int,
                key_arg_length: c_uint,
                key_arg: [c_uchar; SSL_MAX_KEY_ARG_LENGTH as usize],
                pub master_key_length: c_int,
                pub master_key: [c_uchar; 48],
                session_id_length: c_uint,
                session_id: [c_uchar; SSL_MAX_SSL_SESSION_ID_LENGTH as usize],
                sid_ctx_length: c_uint,
                sid_ctx: [c_uchar; SSL_MAX_SID_CTX_LENGTH as usize],
                #[cfg(not(osslconf = "OPENSSL_NO_KRB5"))]
                krb5_client_princ_len: c_uint,
                #[cfg(not(osslconf = "OPENSSL_NO_KRB5"))]
                krb5_client_princ: [c_uchar; SSL_MAX_KRB5_PRINCIPAL_LENGTH as usize],
                #[cfg(not(osslconf = "OPENSSL_NO_PSK"))]
                psk_identity_hint: *mut c_char,
                #[cfg(not(osslconf = "OPENSSL_NO_PSK"))]
                psk_identity: *mut c_char,
                not_resumable: c_int,
                sess_cert: *mut c_void,
                peer: *mut X509,
                verify_result: c_long,
                pub references: c_int,
                timeout: c_long,
                time: c_long,
                compress_meth: c_uint,
                cipher: *const c_void,
                cipher_id: c_ulong,
                ciphers: *mut c_void,
                ex_data: ::CRYPTO_EX_DATA,
                prev: *mut c_void,
                next: *mut c_void,
                #[cfg(not(osslconf = "OPENSSL_NO_TLSEXT"))]
                tlsext_hostname: *mut c_char,
                #[cfg(all(
                    not(osslconf = "OPENSSL_NO_TLSEXT"),
                    not(osslconf = "OPENSSL_NO_EC")
                ))]
                tlsext_ecpointformatlist_length: size_t,
                #[cfg(all(
                    not(osslconf = "OPENSSL_NO_TLSEXT"),
                    not(osslconf = "OPENSSL_NO_EC")
                ))]
                tlsext_ecpointformatlist: *mut c_uchar,
                #[cfg(all(
                    not(osslconf = "OPENSSL_NO_TLSEXT"),
                    not(osslconf = "OPENSSL_NO_EC")
                ))]
                tlsext_ellipticcurvelist_length: size_t,
                #[cfg(all(
                    not(osslconf = "OPENSSL_NO_TLSEXT"),
                    not(osslconf = "OPENSSL_NO_EC")
                ))]
                tlsext_ellipticcurvelist: *mut c_uchar,
                #[cfg(not(osslconf = "OPENSSL_NO_TLSEXT"))]
                tlsext_tick: *mut c_uchar,
                #[cfg(not(osslconf = "OPENSSL_NO_TLSEXT"))]
                tlsext_ticklen: size_t,
                #[cfg(not(osslconf = "OPENSSL_NO_TLSEXT"))]
                tlsext_tick_lifetime_hint: c_long,
                #[cfg(not(osslconf = "OPENSSL_NO_SRP"))]
                srp_username: *mut c_char,
            }
        }
    }

    stack!(stack_st_SSL_CIPHER);

    #[repr(C)]
    pub struct SRTP_PROTECTION_PROFILE {
        pub name: *const c_char,
        pub id: c_ulong,
    }

    stack!(stack_st_SRTP_PROTECTION_PROFILE);

    pub type tls_session_ticket_ext_cb_fn =
        Option<unsafe extern "C" fn(*mut SSL, *const c_uchar, c_int, *mut c_void) -> c_int>;
    pub type tls_session_secret_cb_fn = Option<
        unsafe extern "C" fn(
            *mut SSL,
            *mut c_void,
            *mut c_int,
            *mut stack_st_SSL_CIPHER,
            *mut *mut SSL_CIPHER,
            *mut c_void,
        ) -> c_int,
    >;

    #[cfg(ossl111)]
    pub const SSL_EXT_TLS_ONLY: c_uint = 0x0001;
    /* This extension is only allowed in DTLS */
    #[cfg(ossl111)]
    pub const SSL_EXT_DTLS_ONLY: c_uint = 0x0002;
    /* Some extensions may be allowed in DTLS but we don't implement them for it */
    #[cfg(ossl111)]
    pub const SSL_EXT_TLS_IMPLEMENTATION_ONLY: c_uint = 0x0004;
    /* Most extensions are not defined for SSLv3 but EXT_TYPE_renegotiate is */
    #[cfg(ossl111)]
    pub const SSL_EXT_SSL3_ALLOWED: c_uint = 0x0008;
    /* Extension is only defined for TLS1.2 and below */
    #[cfg(ossl111)]
    pub const SSL_EXT_TLS1_2_AND_BELOW_ONLY: c_uint = 0x0010;
    /* Extension is only defined for TLS1.3 and above */
    #[cfg(ossl111)]
    pub const SSL_EXT_TLS1_3_ONLY: c_uint = 0x0020;
    /* Ignore this extension during parsing if we are resuming */
    #[cfg(ossl111)]
    pub const SSL_EXT_IGNORE_ON_RESUMPTION: c_uint = 0x0040;
    #[cfg(ossl111)]
    pub const SSL_EXT_CLIENT_HELLO: c_uint = 0x0080;
    /* Really means TLS1.2 or below */
    #[cfg(ossl111)]
    pub const SSL_EXT_TLS1_2_SERVER_HELLO: c_uint = 0x0100;
    #[cfg(ossl111)]
    pub const SSL_EXT_TLS1_3_SERVER_HELLO: c_uint = 0x0200;
    #[cfg(ossl111)]
    pub const SSL_EXT_TLS1_3_ENCRYPTED_EXTENSIONS: c_uint = 0x0400;
    #[cfg(ossl111)]
    pub const SSL_EXT_TLS1_3_HELLO_RETRY_REQUEST: c_uint = 0x0800;
    #[cfg(ossl111)]
    pub const SSL_EXT_TLS1_3_CERTIFICATE: c_uint = 0x1000;
    #[cfg(ossl111)]
    pub const SSL_EXT_TLS1_3_NEW_SESSION_TICKET: c_uint = 0x2000;
    #[cfg(ossl111)]
    pub const SSL_EXT_TLS1_3_CERTIFICATE_REQUEST: c_uint = 0x4000;

    #[cfg(ossl111)]
    pub type SSL_custom_ext_add_cb_ex = Option<
        unsafe extern "C" fn(
            ssl: *mut ::SSL,
            ext_type: c_uint,
            context: c_uint,
            out: *mut *const c_uchar,
            outlen: *mut size_t,
            x: *mut ::X509,
            chainidx: size_t,
            al: *mut c_int,
            add_arg: *mut c_void,
        ) -> c_int,
    >;

    #[cfg(ossl111)]
    pub type SSL_custom_ext_free_cb_ex = Option<
        unsafe extern "C" fn(
            ssl: *mut ::SSL,
            ext_type: c_uint,
            context: c_uint,
            out: *mut *const c_uchar,
            add_arg: *mut c_void,
        ),
    >;

    #[cfg(ossl111)]
    pub type SSL_custom_ext_parse_cb_ex = Option<
        unsafe extern "C" fn(
            ssl: *mut ::SSL,
            ext_type: c_uint,
            context: c_uint,
            input: *const c_uchar,
            inlen: size_t,
            x: *mut ::X509,
            chainidx: size_t,
            al: *mut c_int,
            parse_arg: *mut c_void,
        ) -> c_int,
    >;

    pub const SSL_OP_LEGACY_SERVER_CONNECT: c_ulong = 0x00000004;
    cfg_if! {
        if #[cfg(libressl261)] {
            pub const SSL_OP_TLSEXT_PADDING: c_ulong = 0x0;
        } else if #[cfg(any(ossl102, libressl))] {
            pub const SSL_OP_TLSEXT_PADDING: c_ulong = 0x10;
        }
    }
    #[cfg(ossl101)]
    pub const SSL_OP_SAFARI_ECDHE_ECDSA_BUG: c_ulong = 0x00000040;

    pub const SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS: c_ulong = 0x00000800;

    pub const SSL_OP_NO_QUERY_MTU: c_ulong = 0x00001000;
    pub const SSL_OP_COOKIE_EXCHANGE: c_ulong = 0x00002000;
    pub const SSL_OP_NO_TICKET: c_ulong = 0x00004000;
    cfg_if! {
        if #[cfg(ossl101)] {
            pub const SSL_OP_CISCO_ANYCONNECT: c_ulong = 0x00008000;
        } else {
            pub const SSL_OP_CISCO_ANYCONNECT: c_ulong = 0x0;
        }
    }

    pub const SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION: c_ulong = 0x00010000;
    cfg_if! {
        if #[cfg(ossl101)] {
            pub const SSL_OP_NO_COMPRESSION: c_ulong = 0x00020000;
            pub const SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION: c_ulong = 0x00040000;
        } else {
            pub const SSL_OP_NO_COMPRESSION: c_ulong = 0x0;
            pub const SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION: c_ulong = 0x0;
        }
    }

    #[cfg(ossl111)]
    pub const SSL_OP_ENABLE_MIDDLEBOX_COMPAT: c_ulong = 0x00100000;

    pub const SSL_OP_CIPHER_SERVER_PREFERENCE: c_ulong = 0x00400000;
    cfg_if! {
        if #[cfg(libressl280)] {
            pub const SSL_OP_TLS_ROLLBACK_BUG: c_ulong = 0;
        } else {
            pub const SSL_OP_TLS_ROLLBACK_BUG: c_ulong = 0x00800000;
        }
    }

    cfg_if! {
        if #[cfg(ossl101)] {
            pub const SSL_OP_NO_SSLv3: c_ulong = 0x02000000;
        } else {
            pub const SSL_OP_NO_SSLv3: c_ulong = 0x0;
        }
    }
    pub const SSL_OP_NO_TLSv1_1: c_ulong = 0x10000000;
    pub const SSL_OP_NO_TLSv1_2: c_ulong = 0x08000000;

    pub const SSL_OP_NO_TLSv1: c_ulong = 0x04000000;
    #[cfg(ossl102)]
    pub const SSL_OP_NO_DTLSv1: c_ulong = 0x04000000;
    #[cfg(ossl102)]
    pub const SSL_OP_NO_DTLSv1_2: c_ulong = 0x08000000;
    #[cfg(ossl111)]
    pub const SSL_OP_NO_TLSv1_3: c_ulong = 0x20000000;

    #[cfg(ossl110h)]
    pub const SSL_OP_NO_RENEGOTIATION: c_ulong = 0x40000000;

    cfg_if! {
        if #[cfg(ossl111)] {
            pub const SSL_OP_NO_SSL_MASK: c_ulong = SSL_OP_NO_SSLv2
                | SSL_OP_NO_SSLv3
                | SSL_OP_NO_TLSv1
                | SSL_OP_NO_TLSv1_1
                | SSL_OP_NO_TLSv1_2
                | SSL_OP_NO_TLSv1_3;
        } else if #[cfg(ossl102)] {
            pub const SSL_OP_NO_SSL_MASK: c_ulong =
                SSL_OP_NO_SSLv2 | SSL_OP_NO_SSLv3 | SSL_OP_NO_TLSv1 | SSL_OP_NO_TLSv1_1 | SSL_OP_NO_TLSv1_2;
        }
    }

    cfg_if! {
        if #[cfg(libressl261)] {
            pub const SSL_OP_CRYPTOPRO_TLSEXT_BUG: c_ulong = 0x0;
        } else {
            pub const SSL_OP_CRYPTOPRO_TLSEXT_BUG: c_ulong = 0x80000000;
        }
    }

    cfg_if! {
        if #[cfg(ossl110f)] {
            pub const SSL_OP_ALL: c_ulong = SSL_OP_CRYPTOPRO_TLSEXT_BUG
                | SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
                | SSL_OP_LEGACY_SERVER_CONNECT
                | SSL_OP_TLSEXT_PADDING
                | SSL_OP_SAFARI_ECDHE_ECDSA_BUG;
        } else if #[cfg(libressl261)] {
            pub const SSL_OP_ALL: c_ulong = 0x4;
        } else if #[cfg(libressl)] {
            pub const SSL_OP_ALL: c_ulong = 0x80000014;
        } else {
            pub const SSL_OP_ALL: c_ulong = 0x80000BFF;
        }
    }

    cfg_if! {
        if #[cfg(ossl110)] {
            pub const SSL_OP_MICROSOFT_SESS_ID_BUG: c_ulong = 0x00000000;
            pub const SSL_OP_NETSCAPE_CHALLENGE_BUG: c_ulong = 0x00000000;
            pub const SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG: c_ulong = 0x00000000;
            pub const SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER: c_ulong = 0x00000000;
            pub const SSL_OP_SSLEAY_080_CLIENT_DH_BUG: c_ulong = 0x00000000;
            pub const SSL_OP_TLS_D5_BUG: c_ulong = 0x00000000;
            pub const SSL_OP_TLS_BLOCK_PADDING_BUG: c_ulong = 0x00000000;
            pub const SSL_OP_SINGLE_ECDH_USE: c_ulong = 0x00000000;
            pub const SSL_OP_SINGLE_DH_USE: c_ulong = 0x00000000;
            pub const SSL_OP_NO_SSLv2: c_ulong = 0x00000000;
        } else if #[cfg(ossl101)] {
            pub const SSL_OP_MICROSOFT_SESS_ID_BUG: c_ulong = 0x00000001;
            pub const SSL_OP_NETSCAPE_CHALLENGE_BUG: c_ulong = 0x00000002;
            pub const SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG: c_ulong = 0x00000008;
            pub const SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER: c_ulong = 0x00000020;
            pub const SSL_OP_SSLEAY_080_CLIENT_DH_BUG: c_ulong = 0x00000080;
            pub const SSL_OP_TLS_D5_BUG: c_ulong = 0x00000100;
            pub const SSL_OP_TLS_BLOCK_PADDING_BUG: c_ulong = 0x00000200;
            pub const SSL_OP_SINGLE_ECDH_USE: c_ulong = 0x00080000;
            pub const SSL_OP_SINGLE_DH_USE: c_ulong = 0x00100000;
            pub const SSL_OP_NO_SSLv2: c_ulong = 0x01000000;
        } else {
            pub const SSL_OP_MICROSOFT_SESS_ID_BUG: c_ulong = 0x0;
            pub const SSL_OP_NETSCAPE_CHALLENGE_BUG: c_ulong = 0x0;
            pub const SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG: c_ulong = 0x0;
            pub const SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER: c_ulong = 0x0;
            pub const SSL_OP_SSLEAY_080_CLIENT_DH_BUG: c_ulong = 0x0;
            pub const SSL_OP_TLS_D5_BUG: c_ulong = 0x0;
            pub const SSL_OP_TLS_BLOCK_PADDING_BUG: c_ulong = 0x0;
            #[cfg(libressl261)]
            pub const SSL_OP_SINGLE_ECDH_USE: c_ulong = 0x0;
            #[cfg(not(libressl261))]
            pub const SSL_OP_SINGLE_ECDH_USE: c_ulong = 0x00080000;
            pub const SSL_OP_SINGLE_DH_USE: c_ulong = 0x00100000;
            pub const SSL_OP_NO_SSLv2: c_ulong = 0x0;
        }
    }

    pub const SSL_MODE_ENABLE_PARTIAL_WRITE: c_long = 0x1;
    pub const SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER: c_long = 0x2;
    pub const SSL_MODE_AUTO_RETRY: c_long = 0x4;
    pub const SSL_MODE_NO_AUTO_CHAIN: c_long = 0x8;
    pub const SSL_MODE_RELEASE_BUFFERS: c_long = 0x10;
    #[cfg(ossl101)]
    pub const SSL_MODE_SEND_CLIENTHELLO_TIME: c_long = 0x20;
    #[cfg(ossl101)]
    pub const SSL_MODE_SEND_SERVERHELLO_TIME: c_long = 0x40;
    #[cfg(ossl101)]
    pub const SSL_MODE_SEND_FALLBACK_SCSV: c_long = 0x80;

    pub unsafe fn SSL_CTX_set_mode(ctx: *mut SSL_CTX, op: c_long) -> c_long {
        SSL_CTX_ctrl(ctx, SSL_CTRL_MODE, op, ptr::null_mut())
    }

    #[cfg(ossl111)]
    pub const SSL_COOKIE_LENGTH: c_int = 4096;

    cfg_if! {
        if #[cfg(ossl110)] {
            extern "C" {
                pub fn SSL_CTX_get_options(ctx: *const SSL_CTX) -> c_ulong;
                pub fn SSL_CTX_set_options(ctx: *mut SSL_CTX, op: c_ulong) -> c_ulong;
                pub fn SSL_CTX_clear_options(ctx: *mut SSL_CTX, op: c_ulong) -> c_ulong;
            }
        } else {
            pub unsafe fn SSL_CTX_get_options(ctx: *const SSL_CTX) -> c_ulong {
                SSL_CTX_ctrl(ctx as *mut _, SSL_CTRL_OPTIONS, 0, ptr::null_mut()) as c_ulong
            }

            pub unsafe fn SSL_CTX_set_options(ctx: *const SSL_CTX, op: c_ulong) -> c_ulong {
                SSL_CTX_ctrl(
                    ctx as *mut _,
                    SSL_CTRL_OPTIONS,
                    op as c_long,
                    ptr::null_mut(),
                ) as c_ulong
            }

            pub unsafe fn SSL_CTX_clear_options(ctx: *const SSL_CTX, op: c_ulong) -> c_ulong {
                SSL_CTX_ctrl(
                    ctx as *mut _,
                    SSL_CTRL_CLEAR_OPTIONS,
                    op as c_long,
                    ptr::null_mut(),
                ) as c_ulong
            }
        }
    }

    pub unsafe fn SSL_set_mtu(ssl: *mut SSL, mtu: c_long) -> c_long {
        SSL_ctrl(ssl, SSL_CTRL_SET_MTU, mtu, ptr::null_mut())
    }

    pub type GEN_SESSION_CB =
        Option<unsafe extern "C" fn(*const SSL, *mut c_uchar, *mut c_uint) -> c_int>;

    pub const SSL_SESS_CACHE_OFF: c_long = 0x0;
    pub const SSL_SESS_CACHE_CLIENT: c_long = 0x1;
    pub const SSL_SESS_CACHE_SERVER: c_long = 0x2;
    pub const SSL_SESS_CACHE_BOTH: c_long = SSL_SESS_CACHE_CLIENT | SSL_SESS_CACHE_SERVER;
    pub const SSL_SESS_CACHE_NO_AUTO_CLEAR: c_long = 0x80;
    pub const SSL_SESS_CACHE_NO_INTERNAL_LOOKUP: c_long = 0x100;
    pub const SSL_SESS_CACHE_NO_INTERNAL_STORE: c_long = 0x200;
    pub const SSL_SESS_CACHE_NO_INTERNAL: c_long =
        SSL_SESS_CACHE_NO_INTERNAL_LOOKUP | SSL_SESS_CACHE_NO_INTERNAL_STORE;

    extern "C" {
        pub fn SSL_CTX_sess_set_new_cb(
            ctx: *mut SSL_CTX,
            new_session_cb: Option<unsafe extern "C" fn(*mut SSL, *mut SSL_SESSION) -> c_int>,
        );
        pub fn SSL_CTX_sess_set_remove_cb(
            ctx: *mut SSL_CTX,
            remove_session_cb: Option<unsafe extern "C" fn(*mut SSL_CTX, *mut SSL_SESSION)>,
        );
    }
    cfg_if! {
        // const change in passed function pointer signature
        if #[cfg(any(ossl110, libressl280))] {
            extern "C" {
                pub fn SSL_CTX_sess_set_get_cb(
                    ctx: *mut ::SSL_CTX,
                    get_session_cb: Option<
                        unsafe extern "C" fn(*mut ::SSL, *const c_uchar, c_int, *mut c_int) -> *mut SSL_SESSION,
                    >,
                );
            }
        } else {
            extern "C" {
                pub fn SSL_CTX_sess_set_get_cb(
                    ctx: *mut ::SSL_CTX,
                    get_session_cb: Option<
                        unsafe extern "C" fn(*mut ::SSL, *mut c_uchar, c_int, *mut c_int) -> *mut SSL_SESSION,
                    >,
                );
            }
        }
    }
    extern "C" {
        // FIXME change to unsafe extern "C" fn
        pub fn SSL_CTX_set_cookie_generate_cb(
            s: *mut SSL_CTX,
            cb: Option<
                extern "C" fn(ssl: *mut SSL, cookie: *mut c_uchar, cookie_len: *mut c_uint) -> c_int,
            >,
        );
    }

    cfg_if! {
        // const change in passed function pointer signature
        if #[cfg(any(ossl110, libressl280))] {
            extern "C" {
                pub fn SSL_CTX_set_cookie_verify_cb(
                    s: *mut SSL_CTX,
                    cb: Option<
                        extern "C" fn(ssl: *mut SSL, cookie: *const c_uchar, cookie_len: c_uint) -> c_int,
                    >,
                );
            }
        } else {
            extern "C" {
                pub fn SSL_CTX_set_cookie_verify_cb(
                    s: *mut SSL_CTX,
                    cb: Option<extern "C" fn(ssl: *mut SSL, cookie: *mut c_uchar, cookie_len: c_uint) -> c_int>,
                );
            }
        }
    }

    extern "C" {
        #[cfg(ossl111)]
        pub fn SSL_CTX_set_stateless_cookie_generate_cb(
            s: *mut SSL_CTX,
            cb: Option<
                unsafe extern "C" fn(
                    ssl: *mut SSL,
                    cookie: *mut c_uchar,
                    cookie_len: *mut size_t,
                ) -> c_int,
            >,
        );
        #[cfg(ossl111)]
        pub fn SSL_CTX_set_stateless_cookie_verify_cb(
            s: *mut SSL_CTX,
            cb: Option<
                unsafe extern "C" fn(
                    ssl: *mut SSL,
                    cookie: *const c_uchar,
                    cookie_len: size_t,
                ) -> c_int,
            >,
        );

        pub fn SSL_CTX_set_next_protos_advertised_cb(
            ssl: *mut SSL_CTX,
            cb: extern "C" fn(
                ssl: *mut SSL,
                out: *mut *const c_uchar,
                outlen: *mut c_uint,
                arg: *mut c_void,
            ) -> c_int,
            arg: *mut c_void,
        );
        pub fn SSL_CTX_set_next_proto_select_cb(
            ssl: *mut SSL_CTX,
            cb: extern "C" fn(
                ssl: *mut SSL,
                out: *mut *mut c_uchar,
                outlen: *mut c_uchar,
                inbuf: *const c_uchar,
                inlen: c_uint,
                arg: *mut c_void,
            ) -> c_int,
            arg: *mut c_void,
        );
        pub fn SSL_get0_next_proto_negotiated(
            s: *const SSL,
            data: *mut *const c_uchar,
            len: *mut c_uint,
        );

        pub fn SSL_select_next_proto(
            out: *mut *mut c_uchar,
            outlen: *mut c_uchar,
            inbuf: *const c_uchar,
            inlen: c_uint,
            client: *const c_uchar,
            client_len: c_uint,
        ) -> c_int;
    }

    pub const OPENSSL_NPN_UNSUPPORTED: c_int = 0;
    pub const OPENSSL_NPN_NEGOTIATED: c_int = 1;
    pub const OPENSSL_NPN_NO_OVERLAP: c_int = 2;

    extern "C" {
        #[cfg(any(ossl102, libressl261))]
        pub fn SSL_CTX_set_alpn_protos(s: *mut SSL_CTX, data: *const c_uchar, len: c_uint) -> c_int;
        #[cfg(any(ossl102, libressl261))]
        pub fn SSL_set_alpn_protos(s: *mut SSL, data: *const c_uchar, len: c_uint) -> c_int;
        // FIXME should take an Option<unsafe extern "C" fn>
        #[cfg(any(ossl102, libressl261))]
        pub fn SSL_CTX_set_alpn_select_cb(
            ssl: *mut SSL_CTX,
            cb: extern "C" fn(
                ssl: *mut SSL,
                out: *mut *const c_uchar,
                outlen: *mut c_uchar,
                inbuf: *const c_uchar,
                inlen: c_uint,
                arg: *mut c_void,
            ) -> c_int,
            arg: *mut c_void,
        );
        #[cfg(any(ossl102, libressl261))]
        pub fn SSL_get0_alpn_selected(s: *const SSL, data: *mut *const c_uchar, len: *mut c_uint);
    }

    #[cfg(not(osslconf = "OPENSSL_NO_PSK"))]
    extern "C" {
        pub fn SSL_CTX_set_psk_client_callback(
            ssl: *mut SSL_CTX,
            psk_client_cb: Option<
                extern "C" fn(
                    *mut SSL,
                    *const c_char,
                    *mut c_char,
                    c_uint,
                    *mut c_uchar,
                    c_uint,
                ) -> c_uint,
            >,
        );
        pub fn SSL_CTX_set_psk_server_callback(
            ssl: *mut SSL_CTX,
            psk_server_cb: Option<
                extern "C" fn(*mut SSL, *const c_char, *mut c_uchar, c_uint) -> c_uint,
            >,
        );
    }

    extern "C" {
        #[cfg(ossl111)]
        pub fn SSL_CTX_add_custom_ext(
            ctx: *mut ::SSL_CTX,
            ext_type: c_uint,
            context: c_uint,
            add_cb: SSL_custom_ext_add_cb_ex,
            free_cb: SSL_custom_ext_free_cb_ex,
            add_arg: *mut c_void,
            parse_cb: SSL_custom_ext_parse_cb_ex,
            parse_arg: *mut c_void,
        ) -> c_int;

        #[cfg(ossl102)]
        pub fn SSL_extension_supported(ext_type: c_uint) -> c_int;
    }

    #[cfg(ossl111)]
    pub type SSL_CTX_keylog_cb_func =
        Option<unsafe extern "C" fn(ssl: *const SSL, line: *const c_char)>;

    extern "C" {
        #[cfg(ossl111)]
        pub fn SSL_CTX_set_keylog_callback(ctx: *mut SSL_CTX, cb: SSL_CTX_keylog_cb_func);

        #[cfg(ossl111)]
        pub fn SSL_CTX_set_max_early_data(ctx: *mut SSL_CTX, max_early_data: u32) -> c_int;
        #[cfg(ossl111)]
        pub fn SSL_CTX_get_max_early_data(ctx: *const SSL_CTX) -> u32;
        #[cfg(ossl111)]
        pub fn SSL_set_max_early_data(ctx: *mut SSL, max_early_data: u32) -> c_int;
        #[cfg(ossl111)]
        pub fn SSL_get_max_early_data(ctx: *const SSL) -> u32;

        pub fn SSL_get_finished(s: *const SSL, buf: *mut c_void, count: size_t) -> size_t;
        pub fn SSL_get_peer_finished(s: *const SSL, buf: *mut c_void, count: size_t) -> size_t;

        pub fn SSL_CTX_get_verify_mode(ctx: *const SSL_CTX) -> c_int;
        pub fn SSL_get_verify_mode(s: *const SSL) -> c_int;
    }

    const_ptr_api! {
        extern "C" {
            #[cfg(ossl110)]
            pub fn SSL_is_init_finished(s: #[const_ptr_if(ossl111)] SSL) -> c_int;
        }
    }

    pub const SSL_AD_ILLEGAL_PARAMETER: c_int = SSL3_AD_ILLEGAL_PARAMETER;
    pub const SSL_AD_DECODE_ERROR: c_int = TLS1_AD_DECODE_ERROR;
    pub const SSL_AD_UNRECOGNIZED_NAME: c_int = TLS1_AD_UNRECOGNIZED_NAME;
    pub const SSL_ERROR_NONE: c_int = 0;
    pub const SSL_ERROR_SSL: c_int = 1;
    pub const SSL_ERROR_SYSCALL: c_int = 5;
    pub const SSL_ERROR_WANT_ACCEPT: c_int = 8;
    pub const SSL_ERROR_WANT_CONNECT: c_int = 7;
    pub const SSL_ERROR_WANT_READ: c_int = 2;
    pub const SSL_ERROR_WANT_WRITE: c_int = 3;
    pub const SSL_ERROR_WANT_X509_LOOKUP: c_int = 4;
    pub const SSL_ERROR_ZERO_RETURN: c_int = 6;
    #[cfg(ossl111)]
    pub const SSL_ERROR_WANT_CLIENT_HELLO_CB: c_int = 11;
    pub const SSL_VERIFY_NONE: c_int = 0;
    pub const SSL_VERIFY_PEER: c_int = 1;
    pub const SSL_VERIFY_FAIL_IF_NO_PEER_CERT: c_int = 2;
    pub const SSL_CTRL_SET_TMP_DH: c_int = 3;
    pub const SSL_CTRL_SET_TMP_ECDH: c_int = 4;
    #[cfg(any(libressl, all(ossl101, not(ossl110))))]
    pub const SSL_CTRL_GET_SESSION_REUSED: c_int = 8;
    pub const SSL_CTRL_EXTRA_CHAIN_CERT: c_int = 14;
    pub const SSL_CTRL_SET_MTU: c_int = 17;
    #[cfg(any(libressl, all(ossl101, not(ossl110))))]
    pub const SSL_CTRL_OPTIONS: c_int = 32;
    pub const SSL_CTRL_MODE: c_int = 33;
    pub const SSL_CTRL_SET_READ_AHEAD: c_int = 41;
    pub const SSL_CTRL_SET_SESS_CACHE_SIZE: c_int = 42;
    pub const SSL_CTRL_GET_SESS_CACHE_SIZE: c_int = 43;
    pub const SSL_CTRL_SET_SESS_CACHE_MODE: c_int = 44;
    pub const SSL_CTRL_SET_TLSEXT_SERVERNAME_CB: c_int = 53;
    pub const SSL_CTRL_SET_TLSEXT_SERVERNAME_ARG: c_int = 54;
    pub const SSL_CTRL_SET_TLSEXT_HOSTNAME: c_int = 55;
    pub const SSL_CTRL_SET_TLSEXT_STATUS_REQ_CB: c_int = 63;
    pub const SSL_CTRL_SET_TLSEXT_STATUS_REQ_CB_ARG: c_int = 64;
    pub const SSL_CTRL_SET_TLSEXT_STATUS_REQ_TYPE: c_int = 65;
    pub const SSL_CTRL_GET_TLSEXT_STATUS_REQ_OCSP_RESP: c_int = 70;
    pub const SSL_CTRL_SET_TLSEXT_STATUS_REQ_OCSP_RESP: c_int = 71;
    #[cfg(any(libressl, all(ossl101, not(ossl110))))]
    pub const SSL_CTRL_CLEAR_OPTIONS: c_int = 77;
    pub const SSL_CTRL_GET_EXTRA_CHAIN_CERTS: c_int = 82;
    #[cfg(ossl111)]
    pub const SSL_CTRL_SET_GROUPS_LIST: c_int = 92;
    #[cfg(any(libressl, all(ossl102, not(ossl110))))]
    pub const SSL_CTRL_SET_ECDH_AUTO: c_int = 94;
    #[cfg(ossl102)]
    pub const SSL_CTRL_SET_SIGALGS_LIST: c_int = 98;
    #[cfg(ossl102)]
    pub const SSL_CTRL_SET_VERIFY_CERT_STORE: c_int = 106;
    #[cfg(ossl110)]
    pub const SSL_CTRL_SET_MIN_PROTO_VERSION: c_int = 123;
    #[cfg(ossl110)]
    pub const SSL_CTRL_SET_MAX_PROTO_VERSION: c_int = 124;
    #[cfg(ossl110g)]
    pub const SSL_CTRL_GET_MIN_PROTO_VERSION: c_int = 130;
    #[cfg(ossl110g)]
    pub const SSL_CTRL_GET_MAX_PROTO_VERSION: c_int = 131;

    pub unsafe fn SSL_CTX_set_tmp_dh(ctx: *mut SSL_CTX, dh: *mut DH) -> c_long {
        SSL_CTX_ctrl(ctx, SSL_CTRL_SET_TMP_DH, 0, dh as *mut c_void)
    }

    pub unsafe fn SSL_CTX_set_tmp_ecdh(ctx: *mut SSL_CTX, key: *mut EC_KEY) -> c_long {
        SSL_CTX_ctrl(ctx, SSL_CTRL_SET_TMP_ECDH, 0, key as *mut c_void)
    }

    pub unsafe fn SSL_set_tmp_dh(ssl: *mut SSL, dh: *mut DH) -> c_long {
        SSL_ctrl(ssl, SSL_CTRL_SET_TMP_DH, 0, dh as *mut c_void)
    }

    pub unsafe fn SSL_set_tmp_ecdh(ssl: *mut SSL, key: *mut EC_KEY) -> c_long {
        SSL_ctrl(ssl, SSL_CTRL_SET_TMP_ECDH, 0, key as *mut c_void)
    }

    pub unsafe fn SSL_CTX_add_extra_chain_cert(ctx: *mut SSL_CTX, x509: *mut X509) -> c_long {
        SSL_CTX_ctrl(ctx, SSL_CTRL_EXTRA_CHAIN_CERT, 0, x509 as *mut c_void)
    }

    pub unsafe fn SSL_CTX_get_extra_chain_certs(
        ctx: *mut SSL_CTX,
        chain: *mut *mut stack_st_X509,
    ) -> c_long {
        SSL_CTX_ctrl(ctx, SSL_CTRL_GET_EXTRA_CHAIN_CERTS, 0, chain as *mut c_void)
    }

    #[cfg(ossl102)]
    pub unsafe fn SSL_CTX_set0_verify_cert_store(ctx: *mut SSL_CTX, st: *mut X509_STORE) -> c_long {
        SSL_CTX_ctrl(ctx, SSL_CTRL_SET_VERIFY_CERT_STORE, 0, st as *mut c_void)
    }

    #[cfg(ossl111)]
    pub unsafe fn SSL_CTX_set1_groups_list(ctx: *mut SSL_CTX, s: *const c_char) -> c_long {
        SSL_CTX_ctrl(
            ctx,
            SSL_CTRL_SET_GROUPS_LIST,
            0,
            s as *const c_void as *mut c_void,
        )
    }

    #[cfg(ossl102)]
    pub unsafe fn SSL_CTX_set1_sigalgs_list(ctx: *mut SSL_CTX, s: *const c_char) -> c_long {
        SSL_CTX_ctrl(
            ctx,
            SSL_CTRL_SET_SIGALGS_LIST,
            0,
            s as *const c_void as *mut c_void,
        )
    }

    #[cfg(any(libressl, all(ossl102, not(ossl110))))]
    pub unsafe fn SSL_CTX_set_ecdh_auto(ctx: *mut SSL_CTX, onoff: c_int) -> c_int {
        SSL_CTX_ctrl(
            ctx,
            SSL_CTRL_SET_ECDH_AUTO,
            onoff as c_long,
            ptr::null_mut(),
        ) as c_int
    }

    #[cfg(any(libress, all(ossl102, not(ossl110))))]
    pub unsafe fn SSL_set_ecdh_auto(ssl: *mut ::SSL, onoff: c_int) -> c_int {
        SSL_ctrl(
            ssl,
            SSL_CTRL_SET_ECDH_AUTO,
            onoff as c_long,
            ptr::null_mut(),
        ) as c_int
    }

    cfg_if! {
        if #[cfg(ossl110)] {
            pub unsafe fn SSL_CTX_set_min_proto_version(ctx: *mut SSL_CTX, version: c_int) -> c_int {
                SSL_CTX_ctrl(
                    ctx,
                    SSL_CTRL_SET_MIN_PROTO_VERSION,
                    version as c_long,
                    ptr::null_mut(),
                ) as c_int
            }

            pub unsafe fn SSL_CTX_set_max_proto_version(ctx: *mut SSL_CTX, version: c_int) -> c_int {
                SSL_CTX_ctrl(
                    ctx,
                    SSL_CTRL_SET_MAX_PROTO_VERSION,
                    version as c_long,
                    ptr::null_mut(),
                ) as c_int
            }
        } else if #[cfg(libressl261)] {
            extern "C" {
                pub fn SSL_CTX_set_min_proto_version(ctx: *mut ::SSL_CTX, version: u16) -> c_int;
                pub fn SSL_CTX_set_max_proto_version(ctx: *mut ::SSL_CTX, version: u16) -> c_int;
            }
        }
    }

    cfg_if! {
        if #[cfg(ossl110g)] {
            pub unsafe fn SSL_CTX_get_min_proto_version(ctx: *mut SSL_CTX) -> c_int {
                SSL_CTX_ctrl(ctx, SSL_CTRL_GET_MIN_PROTO_VERSION, 0, ptr::null_mut()) as c_int
            }

            pub unsafe fn SSL_CTX_get_max_proto_version(ctx: *mut SSL_CTX) -> c_int {
                SSL_CTX_ctrl(ctx, SSL_CTRL_GET_MAX_PROTO_VERSION, 0, ptr::null_mut()) as c_int
            }
        } else if #[cfg(libressl270)] {
            extern "C" {
                pub fn SSL_CTX_get_min_proto_version(ctx: *mut ::SSL_CTX) -> c_int;
                pub fn SSL_CTX_get_max_proto_version(ctx: *mut ::SSL_CTX) -> c_int;
            }
        }
    }

    #[cfg(ossl110)]
    pub unsafe fn SSL_set_min_proto_version(s: *mut SSL, version: c_int) -> c_int {
        SSL_ctrl(
            s,
            SSL_CTRL_SET_MIN_PROTO_VERSION,
            version as c_long,
            ptr::null_mut(),
        ) as c_int
    }

    #[cfg(ossl110)]
    pub unsafe fn SSL_set_max_proto_version(s: *mut SSL, version: c_int) -> c_int {
        SSL_ctrl(
            s,
            SSL_CTRL_SET_MAX_PROTO_VERSION,
            version as c_long,
            ptr::null_mut(),
        ) as c_int
    }

    #[cfg(ossl110g)]
    pub unsafe fn SSL_get_min_proto_version(s: *mut SSL) -> c_int {
        SSL_ctrl(s, SSL_CTRL_GET_MIN_PROTO_VERSION, 0, ptr::null_mut()) as c_int
    }

    #[cfg(ossl110g)]
    pub unsafe fn SSL_get_max_proto_version(s: *mut SSL) -> c_int {
        SSL_ctrl(s, SSL_CTRL_GET_MAX_PROTO_VERSION, 0, ptr::null_mut()) as c_int
    }

    extern "C" {
        pub fn SSL_CTX_set_cipher_list(ssl: *mut SSL_CTX, s: *const c_char) -> c_int;
        pub fn SSL_CTX_new(method: *const SSL_METHOD) -> *mut SSL_CTX;
        pub fn SSL_CTX_free(ctx: *mut SSL_CTX);
        #[cfg(any(ossl110, libressl273))]
        pub fn SSL_CTX_up_ref(x: *mut SSL_CTX) -> c_int;
        pub fn SSL_CTX_get_cert_store(ctx: *const SSL_CTX) -> *mut X509_STORE;
        pub fn SSL_CTX_set_cert_store(ctx: *mut SSL_CTX, store: *mut X509_STORE);

        pub fn SSL_get_current_cipher(ssl: *const SSL) -> *const SSL_CIPHER;
        pub fn SSL_CIPHER_get_bits(cipher: *const SSL_CIPHER, alg_bits: *mut c_int) -> c_int;
    }
    const_ptr_api! {
        extern "C" {
            pub fn SSL_CIPHER_get_version(cipher: *const SSL_CIPHER) -> #[const_ptr_if(any(ossl110, libressl280))] c_char;
        }
    }
    extern "C" {
        #[cfg(ossl111)]
        pub fn SSL_CIPHER_get_handshake_digest(cipher: *const ::SSL_CIPHER) -> *const ::EVP_MD;
        pub fn SSL_CIPHER_get_name(cipher: *const SSL_CIPHER) -> *const c_char;
        #[cfg(ossl111)]
        pub fn SSL_CIPHER_standard_name(cipher: *const SSL_CIPHER) -> *const c_char;
        #[cfg(ossl111)]
        pub fn OPENSSL_cipher_name(rfc_name: *const c_char) -> *const c_char;

        pub fn SSL_pending(ssl: *const SSL) -> c_int;
        pub fn SSL_set_bio(ssl: *mut SSL, rbio: *mut BIO, wbio: *mut BIO);
        pub fn SSL_get_rbio(ssl: *const SSL) -> *mut BIO;
        pub fn SSL_get_wbio(ssl: *const SSL) -> *mut BIO;
        #[cfg(ossl111)]
        pub fn SSL_CTX_set_ciphersuites(ctx: *mut SSL_CTX, str: *const c_char) -> c_int;
        #[cfg(ossl111)]
        pub fn SSL_set_ciphersuites(ssl: *mut ::SSL, str: *const c_char) -> c_int;
        pub fn SSL_set_verify(
            ssl: *mut SSL,
            mode: c_int,
            // FIXME should be unsafe
            verify_callback: Option<extern "C" fn(c_int, *mut X509_STORE_CTX) -> c_int>,
        );
        pub fn SSL_CTX_use_PrivateKey(ctx: *mut SSL_CTX, key: *mut EVP_PKEY) -> c_int;
        pub fn SSL_CTX_use_certificate(ctx: *mut SSL_CTX, cert: *mut X509) -> c_int;

        pub fn SSL_CTX_use_PrivateKey_file(
            ctx: *mut SSL_CTX,
            key_file: *const c_char,
            file_type: c_int,
        ) -> c_int;
        pub fn SSL_CTX_use_certificate_file(
            ctx: *mut SSL_CTX,
            cert_file: *const c_char,
            file_type: c_int,
        ) -> c_int;
        pub fn SSL_CTX_use_certificate_chain_file(
            ctx: *mut SSL_CTX,
            cert_chain_file: *const c_char,
        ) -> c_int;
        pub fn SSL_load_client_CA_file(file: *const c_char) -> *mut stack_st_X509_NAME;

        #[cfg(not(ossl110))]
        pub fn SSL_load_error_strings();
        pub fn SSL_state_string(ssl: *const SSL) -> *const c_char;
        pub fn SSL_state_string_long(ssl: *const SSL) -> *const c_char;

        pub fn SSL_SESSION_get_time(s: *const SSL_SESSION) -> c_long;
        pub fn SSL_SESSION_get_timeout(s: *const SSL_SESSION) -> c_long;
        #[cfg(ossl110)]
        pub fn SSL_SESSION_get_protocol_version(s: *const SSL_SESSION) -> c_int;

        #[cfg(ossl111)]
        pub fn SSL_SESSION_set_max_early_data(ctx: *mut SSL_SESSION, max_early_data: u32) -> c_int;
        #[cfg(ossl111)]
        pub fn SSL_SESSION_get_max_early_data(ctx: *const SSL_SESSION) -> u32;

        pub fn SSL_SESSION_get_id(s: *const SSL_SESSION, len: *mut c_uint) -> *const c_uchar;
        #[cfg(any(ossl110, libressl273))]
        pub fn SSL_SESSION_up_ref(ses: *mut SSL_SESSION) -> c_int;
        pub fn SSL_SESSION_free(s: *mut SSL_SESSION);
        pub fn i2d_SSL_SESSION(s: *mut SSL_SESSION, pp: *mut *mut c_uchar) -> c_int;
        pub fn SSL_set_session(ssl: *mut SSL, session: *mut SSL_SESSION) -> c_int;
        pub fn SSL_CTX_add_session(ctx: *mut SSL_CTX, session: *mut SSL_SESSION) -> c_int;
        pub fn SSL_CTX_remove_session(ctx: *mut SSL_CTX, session: *mut SSL_SESSION) -> c_int;
        pub fn d2i_SSL_SESSION(
            a: *mut *mut SSL_SESSION,
            pp: *mut *const c_uchar,
            len: c_long,
        ) -> *mut SSL_SESSION;

        pub fn SSL_get_peer_certificate(ssl: *const SSL) -> *mut X509;

        pub fn SSL_get_peer_cert_chain(ssl: *const SSL) -> *mut stack_st_X509;

        pub fn SSL_CTX_set_verify(
            ctx: *mut SSL_CTX,
            mode: c_int,
            verify_callback: Option<extern "C" fn(c_int, *mut X509_STORE_CTX) -> c_int>,
        );
        pub fn SSL_CTX_set_verify_depth(ctx: *mut SSL_CTX, depth: c_int);

        pub fn SSL_CTX_check_private_key(ctx: *const SSL_CTX) -> c_int;

        pub fn SSL_CTX_set_session_id_context(
            ssl: *mut SSL_CTX,
            sid_ctx: *const c_uchar,
            sid_ctx_len: c_uint,
        ) -> c_int;

        pub fn SSL_new(ctx: *mut SSL_CTX) -> *mut SSL;

        #[cfg(any(ossl102, libressl261))]
        pub fn SSL_CTX_get0_param(ctx: *mut SSL_CTX) -> *mut X509_VERIFY_PARAM;

        #[cfg(any(ossl102, libressl261))]
        pub fn SSL_get0_param(ssl: *mut SSL) -> *mut X509_VERIFY_PARAM;
    }

    #[cfg(ossl111)]
    pub const SSL_CLIENT_HELLO_SUCCESS: c_int = 1;
    #[cfg(ossl111)]
    pub const SSL_CLIENT_HELLO_ERROR: c_int = 0;
    #[cfg(ossl111)]
    pub const SSL_CLIENT_HELLO_RETRY: c_int = -1;

    #[cfg(ossl111)]
    pub type SSL_client_hello_cb_fn =
        Option<unsafe extern "C" fn(s: *mut SSL, al: *mut c_int, arg: *mut c_void) -> c_int>;
    extern "C" {
        #[cfg(ossl111)]
        pub fn SSL_CTX_set_client_hello_cb(
            c: *mut SSL_CTX,
            cb: SSL_client_hello_cb_fn,
            arg: *mut c_void,
        );
        #[cfg(ossl111)]
        pub fn SSL_client_hello_isv2(s: *mut SSL) -> c_int;
        #[cfg(ossl111)]
        pub fn SSL_client_hello_get0_legacy_version(s: *mut SSL) -> c_uint;
        #[cfg(ossl111)]
        pub fn SSL_client_hello_get0_random(s: *mut SSL, out: *mut *const c_uchar) -> size_t;
        #[cfg(ossl111)]
        pub fn SSL_client_hello_get0_session_id(s: *mut SSL, out: *mut *const c_uchar) -> size_t;
        #[cfg(ossl111)]
        pub fn SSL_client_hello_get0_ciphers(s: *mut SSL, out: *mut *const c_uchar) -> size_t;
        #[cfg(ossl111)]
        pub fn SSL_client_hello_get0_compression_methods(
            s: *mut SSL,
            out: *mut *const c_uchar,
        ) -> size_t;
        #[cfg(ossl111)]
        pub fn SSL_client_hello_get1_extensions_present(
            s: *mut SSL,
            out: *mut *mut c_int,
            outlen: *mut size_t,
        ) -> c_int;
        #[cfg(ossl111)]
        pub fn SSL_client_hello_get0_ext(
            s: *mut SSL,
            type_: c_uint,
            out: *mut *const c_uchar,
            outlen: *mut size_t,
        ) -> c_int;

        pub fn SSL_free(ssl: *mut SSL);
        pub fn SSL_accept(ssl: *mut SSL) -> c_int;
        #[cfg(ossl111)]
        pub fn SSL_stateless(s: *mut SSL) -> c_int;
        pub fn SSL_connect(ssl: *mut SSL) -> c_int;
        pub fn SSL_read(ssl: *mut SSL, buf: *mut c_void, num: c_int) -> c_int;
        #[cfg(ossl111)]
        pub fn SSL_read_early_data(
            s: *mut ::SSL,
            buf: *mut c_void,
            num: size_t,
            readbytes: *mut size_t,
        ) -> c_int;
    }

    #[cfg(ossl111)]
    pub const SSL_READ_EARLY_DATA_ERROR: c_int = 0;
    #[cfg(ossl111)]
    pub const SSL_READ_EARLY_DATA_SUCCESS: c_int = 1;
    #[cfg(ossl111)]
    pub const SSL_READ_EARLY_DATA_FINISH: c_int = 2;

    extern "C" {
        pub fn SSL_write(ssl: *mut SSL, buf: *const c_void, num: c_int) -> c_int;
        #[cfg(ossl111)]
        pub fn SSL_write_early_data(
            s: *mut SSL,
            buf: *const c_void,
            num: size_t,
            written: *mut size_t,
        ) -> c_int;
        pub fn SSL_ctrl(ssl: *mut SSL, cmd: c_int, larg: c_long, parg: *mut c_void) -> c_long;
        pub fn SSL_CTX_ctrl(ctx: *mut SSL_CTX, cmd: c_int, larg: c_long, parg: *mut c_void) -> c_long;
        pub fn SSL_CTX_callback_ctrl(
            ctx: *mut SSL_CTX,
            cmd: c_int,
            fp: Option<extern "C" fn()>,
        ) -> c_long;
    }

    cfg_if! {
        if #[cfg(any(ossl110, libressl291))] {
            extern "C" {
                pub fn TLS_method() -> *const SSL_METHOD;

                pub fn DTLS_method() -> *const SSL_METHOD;

                pub fn TLS_server_method() -> *const SSL_METHOD;

                pub fn TLS_client_method() -> *const SSL_METHOD;
            }
        } else {
            extern "C" {
                #[cfg(not(osslconf = "OPENSSL_NO_SSL3_METHOD"))]
                pub fn SSLv3_method() -> *const SSL_METHOD;

                pub fn SSLv23_method() -> *const SSL_METHOD;

                pub fn SSLv23_client_method() -> *const SSL_METHOD;

                pub fn SSLv23_server_method() -> *const SSL_METHOD;

                pub fn TLSv1_method() -> *const SSL_METHOD;

                pub fn TLSv1_1_method() -> *const SSL_METHOD;

                pub fn TLSv1_2_method() -> *const SSL_METHOD;

                pub fn DTLSv1_method() -> *const SSL_METHOD;

                #[cfg(ossl102)]
                pub fn DTLSv1_2_method() -> *const SSL_METHOD;
            }
        }
    }

    extern "C" {
        pub fn SSL_get_error(ssl: *const SSL, ret: c_int) -> c_int;
        pub fn SSL_get_version(ssl: *const SSL) -> *const c_char;

        pub fn SSL_do_handshake(ssl: *mut SSL) -> c_int;
        pub fn SSL_shutdown(ssl: *mut SSL) -> c_int;

        pub fn SSL_CTX_set_client_CA_list(ctx: *mut SSL_CTX, list: *mut stack_st_X509_NAME);

        #[cfg(not(libressl))]
        pub fn SSL_CTX_add_client_CA(ctx: *mut SSL_CTX, cacert: *mut X509) -> c_int;

        pub fn SSL_CTX_set_default_verify_paths(ctx: *mut SSL_CTX) -> c_int;
        pub fn SSL_CTX_load_verify_locations(
            ctx: *mut SSL_CTX,
            CAfile: *const c_char,
            CApath: *const c_char,
        ) -> c_int;
    }

    const_ptr_api! {
        extern "C" {
            pub fn SSL_get_ssl_method(ssl: #[const_ptr_if(ossl111b)] SSL) -> *const SSL_METHOD;
        }
    }

    extern "C" {
        pub fn SSL_set_connect_state(s: *mut SSL);
        pub fn SSL_set_accept_state(s: *mut SSL);

        #[cfg(not(ossl110))]
        pub fn SSL_library_init() -> c_int;

        pub fn SSL_CIPHER_description(
            cipher: *const SSL_CIPHER,
            buf: *mut c_char,
            size: c_int,
        ) -> *mut c_char;

        pub fn SSL_get_certificate(ssl: *const SSL) -> *mut X509;
    }
    const_ptr_api! {
        extern "C" {
            pub fn SSL_get_privatekey(ssl: #[const_ptr_if(any(ossl102, libressl280))] SSL) -> *mut EVP_PKEY;
        }
    }

    extern "C" {
        #[cfg(ossl102)]
        pub fn SSL_CTX_get0_certificate(ctx: *const SSL_CTX) -> *mut X509;
        #[cfg(ossl102)]
        pub fn SSL_CTX_get0_privatekey(ctx: *const SSL_CTX) -> *mut EVP_PKEY;

        pub fn SSL_set_shutdown(ss: *mut SSL, mode: c_int);
        pub fn SSL_get_shutdown(ssl: *const SSL) -> c_int;
        pub fn SSL_version(ssl: *const SSL) -> c_int;
        pub fn SSL_get_session(s: *const SSL) -> *mut SSL_SESSION;
        pub fn SSL_get_SSL_CTX(ssl: *const SSL) -> *mut SSL_CTX;
        pub fn SSL_set_SSL_CTX(ssl: *mut SSL, ctx: *mut SSL_CTX) -> *mut SSL_CTX;

        pub fn SSL_get_verify_result(ssl: *const SSL) -> c_long;
        #[cfg(ossl110)]
        pub fn SSL_get0_verified_chain(ssl: *const SSL) -> *mut stack_st_X509;

        #[cfg(ossl110)]
        pub fn SSL_get_client_random(ssl: *const SSL, out: *mut c_uchar, len: size_t) -> size_t;
        #[cfg(ossl110)]
        pub fn SSL_get_server_random(ssl: *const SSL, out: *mut c_uchar, len: size_t) -> size_t;
        #[cfg(any(ossl110, libressl273))]
        pub fn SSL_SESSION_get_master_key(
            session: *const SSL_SESSION,
            out: *mut c_uchar,
            outlen: size_t,
        ) -> size_t;
    }

    cfg_if! {
        if #[cfg(ossl110)] {
            pub unsafe fn SSL_get_ex_new_index(
                l: c_long,
                p: *mut c_void,
                newf: Option<CRYPTO_EX_new>,
                dupf: Option<CRYPTO_EX_dup>,
                freef: Option<CRYPTO_EX_free>,
            ) -> c_int {
                CRYPTO_get_ex_new_index(CRYPTO_EX_INDEX_SSL, l, p, newf, dupf, freef)
            }
        } else {
            extern "C" {
                pub fn SSL_get_ex_new_index(
                    argl: c_long,
                    argp: *mut c_void,
                    new_func: Option<CRYPTO_EX_new>,
                    dup_func: Option<CRYPTO_EX_dup>,
                    free_func: Option<CRYPTO_EX_free>,
                ) -> c_int;
            }
        }
    }
    extern "C" {
        pub fn SSL_set_ex_data(ssl: *mut SSL, idx: c_int, data: *mut c_void) -> c_int;
        pub fn SSL_get_ex_data(ssl: *const SSL, idx: c_int) -> *mut c_void;
    }
    cfg_if! {
        if #[cfg(ossl110)] {
            pub unsafe fn SSL_CTX_get_ex_new_index(
                l: c_long,
                p: *mut c_void,
                newf: Option<CRYPTO_EX_new>,
                dupf: Option<CRYPTO_EX_dup>,
                freef: Option<CRYPTO_EX_free>,
            ) -> c_int {
                CRYPTO_get_ex_new_index(CRYPTO_EX_INDEX_SSL_CTX, l, p, newf, dupf, freef)
            }
        } else {
            extern "C" {
                pub fn SSL_CTX_get_ex_new_index(
                    argl: c_long,
                    argp: *mut c_void,
                    new_func: Option<::CRYPTO_EX_new>,
                    dup_func: Option<::CRYPTO_EX_dup>,
                    free_func: Option<::CRYPTO_EX_free>,
                ) -> c_int;
            }
        }
    }
    extern "C" {
        pub fn SSL_CTX_set_ex_data(ctx: *mut SSL_CTX, idx: c_int, data: *mut c_void) -> c_int;
        pub fn SSL_CTX_get_ex_data(ctx: *const SSL_CTX, idx: c_int) -> *mut c_void;

        pub fn SSL_get_ex_data_X509_STORE_CTX_idx() -> c_int;
    }

    pub unsafe fn SSL_CTX_sess_set_cache_size(ctx: *mut SSL_CTX, t: c_long) -> c_long {
        SSL_CTX_ctrl(ctx, SSL_CTRL_SET_SESS_CACHE_SIZE, t, ptr::null_mut())
    }

    pub unsafe fn SSL_CTX_sess_get_cache_size(ctx: *mut SSL_CTX) -> c_long {
        SSL_CTX_ctrl(ctx, SSL_CTRL_GET_SESS_CACHE_SIZE, 0, ptr::null_mut())
    }

    pub unsafe fn SSL_CTX_set_session_cache_mode(ctx: *mut SSL_CTX, m: c_long) -> c_long {
        SSL_CTX_ctrl(ctx, SSL_CTRL_SET_SESS_CACHE_MODE, m, ptr::null_mut())
    }

    pub unsafe fn SSL_CTX_set_read_ahead(ctx: *mut SSL_CTX, m: c_long) -> c_long {
        SSL_CTX_ctrl(ctx, SSL_CTRL_SET_READ_AHEAD, m, ptr::null_mut())
    }

    extern "C" {
        // FIXME should take an option
        pub fn SSL_CTX_set_tmp_dh_callback(
            ctx: *mut SSL_CTX,
            dh: unsafe extern "C" fn(ssl: *mut SSL, is_export: c_int, keylength: c_int) -> *mut DH,
        );
        // FIXME should take an option
        pub fn SSL_set_tmp_dh_callback(
            ctx: *mut SSL,
            dh: unsafe extern "C" fn(ssl: *mut SSL, is_export: c_int, keylength: c_int) -> *mut DH,
        );
        // FIXME should take an option
        #[cfg(not(ossl110))]
        pub fn SSL_CTX_set_tmp_ecdh_callback(
            ctx: *mut ::SSL_CTX,
            ecdh: unsafe extern "C" fn(
                ssl: *mut ::SSL,
                is_export: c_int,
                keylength: c_int,
            ) -> *mut ::EC_KEY,
        );
        // FIXME should take an option
        #[cfg(not(ossl110))]
        pub fn SSL_set_tmp_ecdh_callback(
            ssl: *mut SSL,
            ecdh: unsafe extern "C" fn(
                ssl: *mut SSL,
                is_export: c_int,
                keylength: c_int,
            ) -> *mut EC_KEY,
        );
    }

    cfg_if! {
        if #[cfg(libressl)] {
            extern "C" {
                pub fn SSL_get_current_compression(ssl: *mut SSL) -> *const libc::c_void;
            }
        } else if #[cfg(not(osslconf = "OPENSSL_NO_COMP"))] {
            const_ptr_api! {
                extern "C" {
                    pub fn SSL_get_current_compression(ssl: #[const_ptr_if(ossl111b)] SSL) -> *const COMP_METHOD;
                }
            }
        }
    }
    cfg_if! {
        if #[cfg(libressl)] {
            extern "C" {
                pub fn SSL_COMP_get_name(comp: *const libc::c_void) -> *const c_char;
            }
        } else if #[cfg(not(osslconf = "OPENSSL_NO_COMP"))] {
            extern "C" {
                pub fn SSL_COMP_get_name(comp: *const COMP_METHOD) -> *const c_char;
            }
        }
    }

    extern "C" {
        #[cfg(ossl110)]
        pub fn SSL_CIPHER_get_cipher_nid(c: *const SSL_CIPHER) -> c_int;
        #[cfg(ossl110)]
        pub fn SSL_CIPHER_get_digest_nid(c: *const SSL_CIPHER) -> c_int;
    }

    cfg_if! {
        if #[cfg(ossl110)] {
            const_ptr_api! {
                extern "C" {
                    pub fn SSL_session_reused(ssl: #[const_ptr_if(ossl111c)] SSL) -> c_int;
                }
            }
        } else {
            pub unsafe fn SSL_session_reused(ssl: *mut SSL) -> c_int {
                SSL_ctrl(ssl, SSL_CTRL_GET_SESSION_REUSED, 0, ptr::null_mut()) as c_int
            }
        }
    }
    const_ptr_api! {
        extern "C" {
            #[cfg(any(ossl102, libressl273))]
            pub fn SSL_is_server(s: #[const_ptr_if(any(ossl110f, libressl273))] SSL) -> c_int;
        }
    }

    #[cfg(ossl110)]
    pub const OPENSSL_INIT_LOAD_SSL_STRINGS: u64 = 0x00200000;
    #[cfg(ossl111b)]
    pub const OPENSSL_INIT_NO_ATEXIT: u64 = 0x00080000;

    extern "C" {
        #[cfg(ossl110)]
        pub fn OPENSSL_init_ssl(opts: u64, settings: *const OPENSSL_INIT_SETTINGS) -> c_int;
    }