enum {
  IPPROTO_IP = 0,        /* Dummy protocol for TCP        */
  IPPROTO_ICMP = 1,        /* Internet Control Message Protocol    */
  IPPROTO_IGMP = 2,        /* Internet Group Management Protocol    */
  IPPROTO_IPIP = 4,        /* IPIP tunnels (older KA9Q tunnels use 94) */
  IPPROTO_TCP = 6,        /* Transmission Control Protocol    */
  IPPROTO_EGP = 8,        /* Exterior Gateway Protocol        */
  IPPROTO_PUP = 12,        /* PUP protocol                */
  IPPROTO_UDP = 17,        /* User Datagram Protocol        */
  IPPROTO_IDP = 22,        /* XNS IDP protocol            */
  IPPROTO_DCCP = 33,        /* Datagram Congestion Control Protocol */
  IPPROTO_RSVP = 46,        /* RSVP protocol            */
  IPPROTO_GRE = 47,        /* Cisco GRE tunnels (rfc 1701,1702)    */

  IPPROTO_IPV6     = 41,        /* IPv6-in-IPv4 tunnelling        */

  IPPROTO_ESP = 50,            /* Encapsulation Security Payload protocol */
  IPPROTO_AH = 51,             /* Authentication Header protocol       */
  IPPROTO_BEETPH = 94,           /* IP option pseudo header for BEET */
  IPPROTO_PIM    = 103,        /* Protocol Independent Multicast    */

  IPPROTO_COMP   = 108,                /* Compression Header protocol */
  IPPROTO_SCTP   = 132,        /* Stream Control Transport Protocol    */
  IPPROTO_UDPLITE = 136,    /* UDP-Lite (RFC 3828)            */

  IPPROTO_RAW     = 255,        /* Raw IP packets            */
  IPPROTO_MAX
};