Reference for unit 'Sockets': Constants¶

Constant	Description
`AF_ALG`	Address family: Algorithm sockets.
`AF_APPLETALK`	Address family Appletalk DDP.
`AF_ASH`	Address family: Ash.
`AF_ATMPVC`	Address family: ATM PVCs.
`AF_ATMSVC`	Address family: ATM SVCs.
`AF_AX25`	Address family Amateur Radio AX.25.
`AF_BLUETOOTH`	Address family: Bluetooth sockets.
`AF_BRIDGE`	Address family Multiprotocol bridge.
`AF_CAIF`	Address family: CAIF (Application CPU interface) sockets.
`AF_CAN`	Address family: CAN (Controller Area Network) sockets.
`AF_DECnet`	Address family: Reserved for DECnet project.
`AF_ECONET`	Address family: Acorn Econet.
`AF_IB`	Address family: IB (Infiniband) sockets.
`AF_IEEE802154`	Address family: IEEE802154 sockets.
`AF_INET`	Address family Internet IP Protocol.
`AF_INET6`	Address family IP version 6.
`AF_IPX`	Address family Novell IPX.
`AF_IRDA`	Address family: IRDA sockets.
`AF_ISDN`	Address family: ?
`AF_IUCV`	Address family: IUCV (Inter User Communication Vehicle) sockets.
`AF_KCM`	Address family: KCM (Kernel Connection Multiplexor) sockets.
`AF_KEY`	Address family: PF_KEY key management API.
`AF_LLC`	Address family: Linux LLC.
`AF_LOCAL`	Address family: Unix socket.
`AF_MAX`	Address family Maximum value.
`AF_MPLS`	Address family: MPLS (Multiprotocol Label Switching) sockets.
`AF_NETBEUI`	Address family: Reserved for 802.2LLC project.
`AF_NETLINK`	Address family: ?
`AF_NETROM`	Address family Amateur radio NetROM.
`AF_NFC`	Address family: NFC (Near Field Communication) sockets.
`AF_PACKET`	Address family: Packet family.
`AF_PHONET`	Address family: Phonet sockets.
`AF_PPPOX`	Address family: PPPoX sockets.
`AF_QIPCRTR`	Address family: QIPCRTR (Qualcomm IPC Router) sockets.
`AF_RDS`	Address Family: RDS (Reliable Datagram Sockets) sockets.
`AF_ROSE`	Address family: Amateur Radio X.25 PLP.
`AF_ROUTE`	Address family: Alias to emulate 4.4BSD.
`AF_RXRPC`	Address family: RxRPC sockets.
`AF_SECURITY`	Address family: Security callback pseudo AF.
`AF_SMC`	Address family: SMC (Shared Memory Communication) sockets.
`AF_SNA`	Address family: Linux SNA project.
`AF_TIPC`	Address family: TIPC sockets.
`AF_UNIX`	Address family Unix domain sockets.
`AF_UNSPEC`	Address family Not specified.
`AF_VSOCK`	Address family: VSOCK (hypervisor) sockets.
`AF_WANPIPE`	Address family: Wanpipe API Sockets.
`AF_X25`	Address family Reserved for X.25 project.
`AF_XDP`	Address family: XDP (Express Data Path) sockets.
`EADDRINUSE`
`EADDRNOTAVAIL`
`EAFNOSUPPORT`
`EALREADY`
`ECONNABORTED`
`ECONNREFUSED`
`ECONNRESET`
`EDESTADDRREQ`
`EDQUOT`
`EHOSTDOWN`
`EHOSTUNREACH`
`EINPROGRESS`
`EINTR`
`EISCONN`
`ELOOP`
`EMSGSIZE`
`ENAMETOOLONG`
`ENETDOWN`
`ENETRESET`
`ENETUNREACH`
`ENOBUFS`
`ENOPROTOOPT`
`ENOTCONN`
`ENOTEMPTY`
`ENOTSOCK`
`EOPNOTSUPP`
`EPFNOSUPPORT`
`EPROTONOSUPPORT`
`EPROTOTYPE`
`EREMOTE`
`ESHUTDOWN`
`EsockADDRINUSE`	Error number when socket address is already in use.
`EsockEACCESS`	Access forbidden error.
`EsockEBADF`	Alias: bad file descriptor.
`EsockEFAULT`	Alias: an error occurred.
`EsockEINTR`	Alias : operation interrupted.
`EsockEINVAL`	Alias: Invalid value specified.
`EsockEMFILE`	Error code ?
`EsockEMSGSIZE`	Wrong message size error.
`EsockENOBUFS`	No buffer space available error.
`EsockENOTCONN`	Not connected error.
`EsockENOTSOCK`	File descriptor is not a socket error.
`EsockEPROTONOSUPPORT`	Protocol not supported error.
`EsockEWOULDBLOCK`	Operation would block error.
`ESOCKTNOSUPPORT`
`ESTALE`
`ETIMEDOUT`
`ETOOMANYREFS`
`EUSERS`
`EWOULDBLOCK`
`INADDR_ANY`	A bitmask matching any IP address on the local machine.
`INADDR_NONE`	A bitmask matching no valid IP address.
`IPPROTO_AH`	authentication header.
`IPPROTO_COMP`	Compression Header Protocol.
`IPPROTO_DSTOPTS`	IPv6 destination options.
`IPPROTO_EGP`	Exterior Gateway Protocol.
`IPPROTO_ENCAP`	Encapsulation Header.
`IPPROTO_ESP`	encapsulating security payload.
`IPPROTO_FRAGMENT`	IPv6 fragmentation header.
`IPPROTO_GRE`	General Routing Encapsulation.
`IPPROTO_HOPOPTS`	IPv6 Hop-by-Hop options.
`IPPROTO_ICMP`	Internet Control Message Protocol.
`IPPROTO_ICMPV6`	ICMPv6.
`IPPROTO_IDP`	XNS IDP protocol.
`IPPROTO_IGMP`	Internet Group Management Protocol.
`IPPROTO_IP`	Dummy protocol for TCP.
`IPPROTO_IPIP`	IPIP tunnels (older KA9Q tunnels use 94).
`IPPROTO_IPV6`	IPv6 header.
`IPPROTO_MAX`	Maximum value for IPPROTO options.
`IPPROTO_MTP`	Multicast Transport Protocol.
`IPPROTO_NONE`	IPv6 no next header.
`IPPROTO_PIM`	Protocol Independent Multicast.
`IPPROTO_PUP`	PUP protocol.
`IPPROTO_RAW`	Raw IP packets.
`IPPROTO_ROUTING`	IPv6 routing header.
`IPPROTO_RSVP`	Reservation Protocol.
`IPPROTO_SCTP`	Stream Control Transmission Protocol.
`IPPROTO_TCP`	Transmission Control Protocol.
`IPPROTO_TP`	SO Transport Protocol Class 4.
`IPPROTO_UDP`	User Datagram Protocol.
`IPV6_ADDRFORM`	Change the IPV6 address into a different address family. Deprecated.
`IPV6_ADD_MEMBERSHIP`	Undocumented Getsockopt option ?
`IPV6_AUTHHDR`	GetSockOpt/SetSockopt: Deliver authentication header messages.
`IPV6_CHECKSUM`	Undocumented Getsockopt option ?
`IPV6_DONTFRAG`
`IPV6_DROP_MEMBERSHIP`	Undocumented Getsockopt option ?
`IPV6_DSTOPTS`	Deliver destination option control messages.
`IPV6_HOPLIMIT`	Deliver an integer containing the HOP count.
`IPV6_HOPOPTS`	Deliver hop option control messages.
`IPV6_IPSEC_POLICY`	Undocumented Getsockopt option ?
`IPV6_JOIN_ANYCAST`	Undocumented Getsockopt option ?
`IPV6_JOIN_GROUP`	GetSockOpt/SetSockopt: Control membership (join group) in multicast groups.
`IPV6_LEAVE_ANYCAST`	Undocumented Getsockopt option ?
`IPV6_LEAVE_GROUP`	GetSockOpt/SetSockopt: Control membership (leave group)in multicast groups.
`IPV6_MTU`	GetSockOpt/SetSockopt: Get/Set the MTU for the socket.
`IPV6_MTU_DISCOVER`	GetSockOpt/SetSockopt: Get/Set Control path MTU Discovery on the socket.
`IPV6_MULTICAST_HOPS`	GetSockOpt/SetSockopt: Get/Set the multicast hop limit.
`IPV6_MULTICAST_IF`	GetSockOpt/SetSockopt: Get/Set device for multicast packages on the socket.
`IPV6_MULTICAST_LOOP`	GetSockOpt/SetSockopt: Control whether socket sees multicast packages that it has sent itself.
`IPV6_NEXTHOP`	sendmsg: set next hop for IPV6 datagram.
`IPV6_PATHMTU`
`IPV6_PKTINFO`	Change delivery options for incoming IPV6 datagrams.
`IPV6_PKTOPTIONS`	Undocumented Getsockopt option ?
`IPV6_PMTUDISC_DO`	Always DF.
`IPV6_PMTUDISC_DONT`	Never send DF frames.
`IPV6_PMTUDISC_WANT`	Use per route hints.
`IPV6_RECVDSTOPTS`
`IPV6_RECVERR`	GetSockOpt/SetSockopt: Control receiving of asynchronous error options.
`IPV6_RECVHOPLIMIT`
`IPV6_RECVHOPOPTS`
`IPV6_RECVPATHMTU`
`IPV6_RECVPKTINFO`
`IPV6_RECVRTHDR`
`IPV6_RECVTCLASS`
`IPV6_ROUTER_ALERT`	GetSockOpt/SetSockopt: Get/Set Pass all forwarded packets containing router alert option.
`IPV6_RTHDR`	Deliver routing header control messages.
`IPV6_RTHDRDSTOPTS`
`IPV6_RTHDR_LOOSE`	Hop doesn't need to be neighbour.
`IPV6_RTHDR_STRICT`	Hop must be a neighbour.
`IPV6_RTHDR_TYPE_0`	IPv6 Routing header type 0.
`IPV6_RXDSTOPTS`	Undocumented Getsockopt option ?
`IPV6_RXHOPOPTS`	Undocumented Getsockopt option ?
`IPV6_RXSRCRT`	Undocumented Getsockopt option ?
`IPV6_TCLASS`
`IPV6_UNICAST_HOPS`	GetSockOpt/SetSockopt: Get/Set unicast hop limit.
`IPV6_V6ONLY`	GetSockOpt/SetSockopt: Handle IPV6 connections only.
`IPV6_XFRM_POLICY`	Undocumented Getsockopt option ?
`IPX_TYPE`	IPX type.
`IP_ADD_MEMBERSHIP`	add an IP group membership.
`IP_ADD_SOURCE_MEMBERSHIP`	join source group.
`IP_BLOCK_SOURCE`	block data from source.
`IP_DEFAULT_MULTICAST_LOOP`	Undocumented ?
`IP_DEFAULT_MULTICAST_TTL`	Undocumented ?
`IP_DROP_MEMBERSHIP`	drop an IP group membership.
`IP_DROP_SOURCE_MEMBERSHIP`	leave source group.
`IP_HDRINCL`	Header is included with data.
`IP_MAX_MEMBERSHIPS`	Maximum group memberships for multicast messages.
`IP_MSFILTER`	Undocumented ?
`IP_MTU_DISCOVER`	Undocumented ?
`IP_MULTICAST_IF`	set/get IP multicast i/f.
`IP_MULTICAST_LOOP`	set/get IP multicast loopback.
`IP_MULTICAST_TTL`	set/get IP multicast ttl.
`IP_OPTIONS`	IP per-packet options.
`IP_PKTINFO`	Undocumented ?
`IP_PKTOPTIONS`	Undocumented ?
`IP_PMTUDISC`	Undocumented ?
`IP_PMTUDISC_DO`	Always DF.
`IP_PMTUDISC_DONT`	Never send DF frames.
`IP_PMTUDISC_WANT`	Use per route hints.
`IP_RECVERR`	Undocumented ?
`IP_RECVOPTS`	Receive all IP options w/datagram.
`IP_RECVRETOPTS`	Receive IP options for response.
`IP_RECVTOS`	Undocumented ?
`IP_RECVTTL`	Undocumented ?
`IP_RETOPTS`	Set/get IP per-packet options.
`IP_ROUTER_ALERT`	Undocumented ?
`IP_TOS`	IP type of service and precedence.
`IP_TTL`	IP time to live.
`IP_UNBLOCK_SOURCE`	unblock data from source.
`MCAST_BLOCK_SOURCE`	block from given group.
`MCAST_EXCLUDE`	Undocumented ?
`MCAST_INCLUDE`	Undocumented ?
`MCAST_JOIN_GROUP`	join any-source group.
`MCAST_JOIN_SOURCE_GROUP`	join source-spec group.
`MCAST_LEAVE_GROUP`	leave any-source group.
`MCAST_LEAVE_SOURCE_GROUP`	leave source-spec group.
`MCAST_MSFILTER`	Undocumented ?
`MCAST_UNBLOCK_SOURCE`	unblock from given group.
`MSG_BATCH`	sendmmsg: more messages coming.
`MSG_CMSG_CLOEXEC`	Set close_on_exec for file descriptor received through SCM_RIGHTS.
`MSG_CMSG_COMPAT`	This message needs 32 bit fixups.
`MSG_CONFIRM`	Send flags: Conform connection.
`MSG_CTRUNC`	Receive flags: Control Data was discarded (buffer too small).
`MSG_DONTROUTE`	Send flags: don't use gateway.
`MSG_DONTWAIT`	Receive flags: Non-blocking operation request.
`MSG_EOF`	Alias for MSG_FIN.
`MSG_EOR`	Receive flags: End of record.
`MSG_ERRQUERE`	Receive flags: ?
`MSG_FASTOPEN`	Send data in TCP SYN.
`MSG_FIN`	Receive flags: ?
`MSG_MORE`	Receive flags: ?
`MSG_NOSIGNAL`	Receive flags: Suppress SIG_PIPE signal.
`MSG_NO_SHARED_FRAGS`	sendpage internal : page frags are not shared.
`MSG_OOB`	Receive flags: receive out-of-band data.
`MSG_PEEK`	Receive flags: peek at data, don't remove from buffer.
`MSG_PROBE`	Do not send. Only probe path f.e. for MTU.
`MSG_PROXY`	Receive flags: ?
`MSG_RST`	Receive flags: ?
`MSG_SENDPAGE_DECRYPTED`	sendpage() internal : page may carry plain text and require encryption.
`MSG_SENDPAGE_NOPOLICY`	sendpage internal : do not apply policy.
`MSG_SENDPAGE_NOTLAST`	sendpage internal : not the last page.
`MSG_SYN`	Receive flags: ?
`MSG_TRUNC`	Receive flags: packet Data was discarded (buffer too small).
`MSG_TRYHARD`	Receive flags: ?
`MSG_WAITALL`	Receive flags: Wait till operation completed.
`MSG_WAITFORONE`	recvmmsg(): block until 1+ packets avail.
`MSG_ZEROCOPY`	Use user data in kernel path.
`NoAddress`	Constant indicating invalid (no) network address.
`NoAddress6`	Constant indicating invalid (no) IPV6 network address.
`NoNet`	Constant indicating invalid (no) network address.
`NoNet6`	Constant indicating invalid (no) IPV6 network address.
`PF_ALG`	Protocol family: Algorithm sockets.
`PF_APPLETALK`	Protocol family: Appletalk DDP.
`PF_ASH`	Protocol family: Ash.
`PF_ATMPVC`	Protocol family: ATM PVCs.
`PF_ATMSVC`	Protocol family: ATM SVCs.
`PF_AX25`	Protocol family: Amateur Radio AX.25.
`PF_BLUETOOTH`	Protocol family: Bluetooth sockets.
`PF_BRIDGE`	Protocol family: Multiprotocol bridge.
`PF_CAIF`	Protocol family: CAIF (Application CPU interface) sockets.
`PF_CAN`	Protocol family: CAN (Controller Area Network) sockets.
`PF_DECnet`	Protocol Family: DECNET project.
`PF_ECONET`	Protocol family: Acorn Econet.
`PF_IB`	Protocol family: IB (InfiniBand) sockets.
`PF_IEEE802154`	Protocol family: IEEE802154 sockets.
`PF_INET`	Protocol family: Internet IP Protocol.
`PF_INET6`	Protocol family: IP version 6.
`PF_IPX`	Protocol family: Novell IPX.
`PF_IRDA`	Protocol family: IRDA sockets.
`PF_ISDN`	Protocol Family: ?
`PF_IUCV`	Protocol family: IUCV (Inter User Communication Vehicle) sockets.
`PF_KCM`	Protocol family: KCM (Kernel Connection Multiplexor) sockets.
`PF_KEY`	Protocol family: Key management API.
`PF_LLC`	Protocol family: Linux LLC.
`PF_LOCAL`	Protocol family: Unix socket.
`PF_MAX`	Protocol family: Maximum value.
`PF_MPLS`	Protocol family: MPLS (Multiprotocol Label Switching.
`PF_NETBEUI`	Protocol family: Reserved for 802.2LLC project.
`PF_NETLINK`	Protocol family: ?
`PF_NETROM`	Protocol family:Amateur radio NetROM.
`PF_NFC`	Protocol family: NFC (Near Field Communication) sockets.
`PF_PACKET`	Protocol family: Packet family.
`PF_PHONET`	Protocol family: RxRPC sockets.
`PF_PPPOX`	Protocol family: PPPoX sockets.
`PF_QIPCRTR`	Protocol family: IPCRTR (Qualcomm IPC Router) sockets.
`PF_RDS`	Protocol family: RDS (Reliable Datagram Sockets) sockets.
`PF_ROSE`	Protocol family: Amateur Radio X.25 PLP.
`PF_ROUTE`	Protocol Family: ?
`PF_RXRPC`	Protocol family: RxRPC sockets.
`PF_SECURITY`	Protocol family: Security callback pseudo PF.
`PF_SMC`	Protocol family: SMC (Shared Memory Communication) sockets.
`PF_SNA`	Protocol Family: Linux SNA project.
`PF_TIPC`	Protocol family: TIPC sockets.
`PF_UNIX`	Protocol family: Unix domain sockets.
`PF_UNSPEC`	Protocol family: Unspecified.
`PF_VSOCK`	Protocol family: VSOCK (hypervisor) sockets.
`PF_WANPIPE`	Protocol family: Wanpipe API Sockets.
`PF_X25`	Protocol family: Reserved for X.25 project.
`PF_XDP`	Protocol family: XDP (Express Data Path) sockets.
`SCM_CREDENTIALS`	socket control messages : credentials.
`SCM_RIGHTS`	socket control messages : access rights.
`SCM_SECURITY`	socket control messages : security label.
`SCM_SRCRT`	Undocumented Getsockopt option ?
`SCM_TIMESTAMP`	Socket option: ?
`SHUT_RD`	Shutdown read part of full duplex socket.
`SHUT_RDWR`	Shutdown read and write part of full duplex socket.
`SHUT_WR`	Shutdown write part of full duplex socket.
`SOCK_CLOEXEC`
`SOCK_DGRAM`	Type of socket: datagram (conn.less) socket (UDP).
`SOCK_MAXADDRLEN`	Maximum socket address length for Bind call.
`SOCK_NONBLOCK`
`SOCK_RAW`	Type of socket: raw socket.
`SOCK_RDM`	Type of socket: reliably-delivered message.
`SOCK_SEQPACKET`	Type of socket: sequential packet socket.
`SOCK_STREAM`	Type of socket: stream (connection) type socket (TCP).
`SOL_AAL`	Socket level: AAL.
`SOL_ALG`	Socket level: Algorithm socket.
`SOL_ATALK`	Socket level: Apple talk.
`SOL_ATM`	Socket level: ATM.
`SOL_AX25`	Socket level: AX25.
`SOL_BLUETOOTH`	Socket level: BlueTooth.
`SOL_CAIF`	Socket level: CAIF (Application CPU interface).
`SOL_DCCP`	Socket level: DCCP.
`SOL_DECNET`	Socket level: DECnet.
`SOL_ICMPV6`	Socket level values for IPv6: ICMPV6.
`SOL_IP`	Undocumented ?
`SOL_IPV6`	Socket level values for IPv6: IPV6.
`SOL_IPX`	Socket level: IPX.
`SOL_IRDA`	Socket level: IRDA.
`SOL_IUCV`	Socket level: IUCV (Inter User Communication Vehicle).
`SOL_KCM`	Socket level: KCM (Kernel Connection Multiplexor) sockets.
`SOL_LLC`	Socket level: LLC.
`SOL_NETBEUI`	Socket level: NETBEUI.
`SOL_NETLINK`	Socket level: NETLink.
`SOL_NETROM`	Socket level: Net ROM.
`SOL_NFC`	Socket level: NFC (Near Field Communication) socket.
`SOL_PACKET`	Socket level: Packet.
`SOL_PNPIPE`	Socket level: PNPIPE.
`SOL_PPPOL2TP`	Socket level: PPPOL2TP.
`SOL_RAW`	Socket level: raw socket.
`SOL_RDS`	Socket level: RDS (Reliable Datagram Socket).
`SOL_ROSE`	Socket level: ROSE.
`SOL_RXRPC`	Socket level: RxRPC.
`SOL_SCTP`	Socket level: SCTP.
`SOL_SOCKET`	Socket option level: Socket level.
`SOL_TCP`	Socket level: TCP.
`SOL_TIPC`	Socket level: TIPC.
`SOL_TLS`	Socket level: TLS.
`SOL_UDP`	Socket level: UDP.
`SOL_UDPLITE`	Socket level: UDP Lite.
`SOL_X25`	Socket level: X25.
`SOL_XDP`	Socket level: XDP (Express Data Path) sockets.
`SOMAXCONN`	Maximum queue length specifiable by listen.
`SO_ACCEPTCONN`	Socket option: ?
`SO_ATTACH_FILTER`	Socket option: ?
`SO_BINDTODEVICE`	Socket option: ?
`SO_BROADCAST`	Socket option: Broadcast.
`SO_BSDCOMPAT`	Socket option: ?
`SO_DEBUG`	Socket option level: debug.
`SO_DETACH_FILTER`	Socket option: ?
`SO_DONTROUTE`	Socket option: Don't route.
`SO_ERROR`	Socket option: Error.
`SO_KEEPALIVE`	Socket option: keep alive.
`SO_LINGER`	Socket option: ?
`SO_NO_CHECK`	Socket option: ?
`SO_OOBINLINE`	Socket option: ?
`SO_PASSCRED`	Socket option: ?
`SO_PEERCRED`	Socket option: ?
`SO_PEERNAME`	Socket option: ?
`SO_PRIORITY`	Socket option: ?
`SO_RCVBUF`	Socket option: receive buffer.
`SO_RCVLOWAT`	Socket option: ?
`SO_RCVTIMEO`	Socket option: ?
`SO_REUSEADDR`	Socket option: Reuse address.
`SO_REUSEPORT`	Socket Option : reuse port.
`SO_SECURITY_AUTHENTICATION`	Socket option: ?
`SO_SECURITY_ENCRYPTION_NETWORK`	Socket option: ?
`SO_SECURITY_ENCRYPTION_TRANSPORT`	Socket option: ?
`SO_SNDBUF`	Socket option: Send buffer.
`SO_SNDLOWAT`	Socket option: ?
`SO_SNDTIMEO`	Socket option: ?
`SO_TIMESTAMP`	Socket option: ?
`SO_TYPE`	Socket option: Type.
`S_IN`	Input socket in socket pair.
`S_OUT`	Output socket in socket pair.
`TCP_CONGESTION`	Get/set the congestion-control algorithm for this socket.
`TCP_CORK`	Get/Set CORK algorithm: Send only complete packets.
`TCP_DEFER_ACCEPT`	Get/Set deferred accept on server socket.
`TCP_INFO`	Get TCP connection information (Linux only).
`TCP_KEEPCNT`	Get/Set retry count for unacknowledged KEEPALIVE transmissions.
`TCP_KEEPIDLE`	Get/Set inactivity interval between KEEPALIVE transmissions.
`TCP_KEEPINTVL`	Get/Set retry interval for unacknowledged KEEPALIVE transmissions.
`TCP_LINGER2`	Get/Set Linger2 flag.
`TCP_MAXSEG`	Get/Set Maximum segment size.
`TCP_MD5SIG`	Get/Set TCP MD5 signature option.
`TCP_NODELAY`	Get/Set No delay flag: disable Nagle algorithm.
`TCP_QUICKACK`	Get/Set quick ACK packet option.
`TCP_SYNCNT`	Get/Set number of SYN packets to send before giving up on connection establishment.
`TCP_WINDOW_CLAMP`	Get/Set maximum packet size.
`UDP_CORK`	Get/Set UDP CORK algorithm on datagram sockets.
`UDP_ENCAP`	Get/Set UDP encapsulation flag for IPSec datagram sockets.
`UDP_ENCAP_ESPINUDP`	? Undocumented datagram option, IPSec related.
`UDP_ENCAP_ESPINUDP_NON_IKE`	? Undocumented datagram option, IPSec related.
`UDP_ENCAP_L2TPINUDP`	? Undocumented datagram option, IPSec related.