typedef struct { ... } SilcIDIP;

    Generic IP address structure to indicate either IPv4 or IPv6 address.
    This structure is used inside all SILC ID's. The true length of the
    ID depends of the length of the IP address.

    typedef struct SilcIDIPStruct {
      unsigned char data[16];       /* IP data (in MSB first order) */
      SilcUInt8 data_len;           /* Length of the data (4 or 16) */
    } SilcIDIP;