IPPROTO_IP = 0; (* Dummy protocol for TCP. *)
			IPPROTO_HOPOPTS* = 0; (* IPv6 Hop-by-Hop options. *)
			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_TP* = 29; (* SO Transport Protocol Class 4. *)
			IPPROTO_DCCP* = 33; (* Datagram Congestion Control Protocol. *)
			IPPROTO_IPV6* = 41; (* IPv6 header. *)
			IPPROTO_ROUTING* = 43; (* IPv6 routing header. *)
			IPPROTO_FRAGMENT* = 44; (* IPv6 fragmentation header. *)
			IPPROTO_RSVP* = 46; (* Reservation Protocol. *)
			IPPROTO_GRE* = 47; (* General Routing Encapsulation. *)
			IPPROTO_ESP* = 50; (* encapsulating security payload. *)
			IPPROTO_AH* = 51; (* authentication header. *)
			IPPROTO_ICMPV6* = 58; (* ICMPv6. *)
			IPPROTO_NONE* = 59; (* IPv6 no next header. *)
			IPPROTO_DSTOPTS* = 60; (* IPv6 destination options. *)
			IPPROTO_MTP* = 92; (* Multicast Transport Protocol. *)
			IPPROTO_ENCAP* = 98; (* Encapsulation Header. *)
			IPPROTO_PIM* = 103; (* Protocol Independent Multicast. *)
			IPPROTO_COMP* = 108; (* Compression Header Protocol. *)
			IPPROTO_SCTP* = 132; (* Stream Control Transmission Protocol. *)
			IPPROTO_UDPLITE* = 136; (* UDP-Lite protocol. *)
			IPPROTO_RAW* = 255; (* Raw IP packets. *)