struct ed25519_cert {
  u8 version IN [1];
  u8 cert_type;
  u32 exp_field;
  u8 cert_key_type;
  u8 certified_key[32];
  u8 n_extensions;
  struct ed25519_cert_extension ext[n_extensions];
  u8 signature[64];
}

const CERTEXT_SIGNED_WITH_KEY = 4;
const CERTEXT_FLAG_AFFECTS_VALIDATION = 1;

struct ed25519_cert_extension {
  u16 ext_length;
  u8 ext_type;
  u8 ext_flags;
  union un[ext_type] with length ext_length {
    CERTEXT_SIGNED_WITH_KEY : u8 signing_key[32];
    default: u8 unparsed[];
  };
}

const LS_IPV4 = 0x00;
const LS_IPV6 = 0x01;
const LS_LEGACY_ID = 0x02;
const LS_ED25519_ID = 0x03;

// XXX hs_link_specifier_dup() violates the opaqueness of link_specifier_t by
//  taking its sizeof(). If we ever want to turn on TRUNNEL_OPAQUE, or
//  if we ever make link_specifier contain other types, we will
//  need to refactor that function to do the copy by encoding and decoding the
//  object.

// amended from tor.trunnel
struct link_specifier {
  u8 ls_type;
  u8 ls_len;
  union un[ls_type] with length ls_len {
    LS_IPV4: u32 ipv4_addr; u16 ipv4_port;
    LS_IPV6: u8 ipv6_addr[16]; u16 ipv6_port;
    LS_LEGACY_ID: u8 legacy_id[20];
    LS_ED25519_ID: u8 ed25519_id[32];
    default: u8 unrecognized[];
  };
}

struct link_specifier_list {
  u8 n_spec;
  struct link_specifier spec[n_spec];
}

struct extend1_cell_body {
  u32 ipv4addr;
  u16 port;
  u8 onionskin[186];
  u8 identity[20];
}

struct create2_cell_body {
  u16 handshake_type;
  u16 handshake_len;
  u8 handshake_data[handshake_len];
}

struct extend2_cell_body {
  u8 n_spec;
  struct link_specifier ls[n_spec];
  struct create2_cell_body create2;
}