pub(crate) fn send_server_sig_algs(&mut self) {
        // This should be only ever called when this is valid
        if let Some(Kex::NewKeys(newkeys)) = &self.common.kex {
            let mut buf = CryptoVec::new();
            buf.push(msg::EXT_INFO);
            buf.push_u32_be(1); // nr-extensions
            buf.extend_ssh_string(b"server-sig-algs"); // extension-name
            let algs = self
                .common
                .config
                .preferred
                .key
                .iter()
                .map(|n| n.0)
                .collect::<Vec<_>>()
                .join(",");
            buf.extend_ssh_string(algs.as_bytes()); // extension-value
            newkeys.cipher.write(&buf, &mut self.common.write_buffer);
        } else {
            unreachable!(
                "Trying to send server-sig-algs SSH_MSG_EXT_INFO when we didn't just send NEWKEYS"
            );
        }
    }

                let client_supports_ext = kexdh.names.client_supports_ext;

                if client_supports_ext {
                    // RFC 8308 (2.4): Send SSH_MSG_EXT_INFO as the next packet following the server's first SSH_MSG_NEWKEYS.
                    // Since we have no session established, this should have been the first time
                    session.send_server_sig_algs();
                }

    pub client_supports_ext: bool,
    pub server_supports_ext: bool,

        let client_supports_ext = Self::select(&[kex::CLIENT_SUPPORTS_EXT], kex_string).is_some();
        let server_supports_ext = Self::select(&[kex::SERVER_SUPPORTS_EXT], kex_string).is_some();

                    client_supports_ext,
                    server_supports_ext,

// https://www.rfc-editor.org/rfc/rfc8308#section-2.3
pub const EXT_INFO: u8 = 7;

pub const CLIENT_SUPPORTS_EXT: Name = Name("ext-info-c");
pub const SERVER_SUPPORTS_EXT: Name = Name("ext-info-s");