Merge pull request #945 from sfackler/ssl-alpn-protos

        unsafe { cvt(ffi::SSL_set_ecdh_auto(self.as_ptr(), onoff as c_int)).map(|_| ()) }

    }

    /// Like [`SslContextBuilder::set_alpn_protos`].

    ///

    /// Requires OpenSSL 1.0.2 or LibreSSL 2.6.1 or newer.

    ///

    /// This corresponds to [`SSL_set_alpn_protos`].

    ///

    /// [`SslContextBuilder::set_alpn_protos`]: struct.SslContextBuilder.html#method.set_alpn_protos

    /// [`SSL_set_alpn_protos`]: https://www.openssl.org/docs/man1.1.0/ssl/SSL_set_alpn_protos.html

    #[cfg(any(ossl102, libressl261))]

    pub fn set_alpn_protos(&mut self, protocols: &[u8]) -> Result<(), ErrorStack> {

        unsafe {

            assert!(protocols.len() <= c_uint::max_value() as usize);

            let r = ffi::SSL_set_alpn_protos(

                self.as_ptr(),

                protocols.as_ptr(),

                protocols.len() as c_uint,

            );

            // fun fact, SSL_set_alpn_protos has a reversed return code D:

            if r == 0 {

                Ok(())

            } else {

                Err(ErrorStack::get())

            }

        }

    }

    /// Returns the current cipher if the session is active.

    ///

    /// This corresponds to [`SSL_get_current_cipher`].