module Socket::Constants
Socket::Constants provides socket-related constants.  All possible socket constants are listed in the documentation but they may not all be present on your platform.
If the underlying platform doesn’t define a constant the corresponding Ruby constant is not defined.
Constants
- AF_APPLETALK
- AppleTalk protocol 
- AF_ATM
- Asynchronous Transfer Mode 
- AF_AX25
- AX.25 protocol 
- AF_CCITT
- CCITT (now ITU-T) protocols 
- AF_CHAOS
- MIT CHAOS protocols 
- AF_CNT
- Computer Network Technology 
- AF_COIP
- Connection-oriented IP 
- AF_DATAKIT
- Datakit protocol 
- AF_DEC
- DECnet protocol 
- AF_DLI
- DEC Direct Data Link Interface protocol 
- AF_E164
- CCITT (ITU-T) E.164 recommendation 
- AF_ECMA
- European Computer Manufacturers protocols 
- AF_HYLINK
- NSC Hyperchannel protocol 
- AF_IMPLINK
- ARPANET IMP protocol 
- AF_INET
- IPv4 protocol 
- AF_INET6
- IPv6 protocol 
- AF_IPX
- IPX protocol 
- AF_ISDN
- Integrated Services Digital Network 
- AF_ISO
- ISO Open Systems Interconnection protocols 
- AF_LAT
- Local Area Transport protocol 
- AF_LINK
- Link layer interface 
- AF_LOCAL
- Host-internal protocols 
- AF_MAX
- Maximum address family for this platform 
- AF_NATM
- Native ATM access 
- AF_NDRV
- Network driver raw access 
- AF_NETBIOS
- NetBIOS 
- AF_NETGRAPH
- Netgraph sockets 
- AF_NS
- XEROX NS protocols 
- AF_OSI
- ISO Open Systems Interconnection protocols 
- AF_PACKET
- Direct link-layer access 
- AF_PPP
- Point-to-Point Protocol 
- AF_PUP
- PARC Universal Packet protocol 
- AF_ROUTE
- Internal routing protocol 
- AF_SIP
- Simple Internet Protocol 
- AF_SNA
- IBM SNA protocol 
- AF_SYSTEM
- AF_UNIX
- UNIX sockets 
- AF_UNSPEC
- Unspecified protocol, any supported address family 
- AI_ADDRCONFIG
- Accept only if any address is assigned 
- AI_ALL
- Allow all addresses 
- AI_CANONNAME
- Fill in the canonical name 
- AI_DEFAULT
- Default flags for getaddrinfo 
- AI_MASK
- Valid flag mask for getaddrinfo (not for application use) 
- AI_NUMERICHOST
- Prevent host name resolution 
- AI_NUMERICSERV
- Prevent service name resolution 
- AI_PASSIVE
- Get address to use with bind() 
- AI_V4MAPPED
- Accept IPv4-mapped IPv6 addresses 
- AI_V4MAPPED_CFG
- Accept IPv4 mapped addresses if the kernel supports it 
- EAI_ADDRFAMILY
- Address family for hostname not supported 
- EAI_AGAIN
- Temporary failure in name resolution 
- EAI_BADFLAGS
- Invalid flags 
- EAI_BADHINTS
- Invalid value for hints 
- EAI_FAIL
- Non-recoverable failure in name resolution 
- EAI_FAMILY
- Address family not supported 
- EAI_MAX
- Maximum error code from getaddrinfo 
- EAI_MEMORY
- Memory allocation failure 
- EAI_NODATA
- No address associated with hostname 
- EAI_NONAME
- Hostname nor servname, or not known 
- EAI_OVERFLOW
- Argument buffer overflow 
- EAI_PROTOCOL
- Resolved protocol is unknown 
- EAI_SERVICE
- Servname not supported for socket type 
- EAI_SOCKTYPE
- Sockettype not supported
- EAI_SYSTEM
- System error returned in errno 
- IFF_802_1Q_VLAN
- 802.1Q VLAN device 
- IFF_ALLMULTI
- receive all multicast packets 
- IFF_ALTPHYS
- use alternate physical connection 
- IFF_AUTOMEDIA
- auto media select active 
- IFF_BONDING
- bonding master or slave 
- IFF_BRIDGE_PORT
- device used as bridge port 
- IFF_BROADCAST
- broadcast address valid 
- IFF_CANTCHANGE
- flags not changeable 
- IFF_CANTCONFIG
- unconfigurable using ioctl(2) 
- IFF_DEBUG
- turn on debugging 
- IFF_DISABLE_NETPOLL
- disable netpoll at run-time 
- IFF_DONT_BRIDGE
- disallow bridging this ether dev 
- IFF_DORMANT
- driver signals dormant 
- IFF_DRV_OACTIVE
- tx hardware queue is full 
- IFF_DRV_RUNNING
- resources allocated 
- IFF_DYING
- interface is winding down 
- IFF_DYNAMIC
- dialup device with changing addresses 
- IFF_EBRIDGE
- ethernet bridging device 
- IFF_ECHO
- echo sent packets 
- IFF_ISATAP
- ISATAP interface (RFC4214) 
- IFF_LINK0
- per link layer defined bit 0 
- IFF_LINK1
- per link layer defined bit 1 
- IFF_LINK2
- per link layer defined bit 2 
- IFF_LIVE_ADDR_CHANGE
- hardware address change when it’s running 
- IFF_LOOPBACK
- loopback net 
- IFF_LOWER_UP
- driver signals L1 up 
- IFF_MACVLAN_PORT
- device used as macvlan port 
- IFF_MASTER
- master of a load balancer 
- IFF_MASTER_8023AD
- bonding master, 802.3ad. 
- IFF_MASTER_ALB
- bonding master, balance-alb. 
- IFF_MASTER_ARPMON
- bonding master, ARP mon in use 
- IFF_MONITOR
- user-requested monitor mode 
- IFF_MULTICAST
- supports multicast 
- IFF_NOARP
- no address resolution protocol 
- IFF_NOTRAILERS
- avoid use of trailers 
- IFF_OACTIVE
- transmission in progress 
- IFF_OVS_DATAPATH
- device used as Open vSwitch datapath port 
- IFF_POINTOPOINT
- point-to-point link 
- IFF_PORTSEL
- can set media type 
- IFF_PPROMISC
- user-requested promisc mode 
- IFF_PROMISC
- receive all packets 
- IFF_RENAMING
- interface is being renamed 
- IFF_ROUTE
- routing entry installed 
- IFF_RUNNING
- resources allocated 
- IFF_SIMPLEX
- can’t hear own transmissions 
- IFF_SLAVE
- slave of a load balancer 
- IFF_SLAVE_INACTIVE
- bonding slave not the curr. active 
- IFF_SLAVE_NEEDARP
- need ARPs for validation 
- IFF_SMART
- interface manages own routes 
- IFF_STATICARP
- static ARP 
- IFF_SUPP_NOFCS
- sending custom FCS 
- IFF_TEAM_PORT
- used as team port 
- IFF_TX_SKB_SHARING
- sharing skbs on transmit 
- IFF_UNICAST_FLT
- unicast filtering 
- IFF_UP
- interface is up 
- IFF_VOLATILE
- volatile flags 
- IFF_WAN_HDLC
- WAN HDLC device 
- IFF_XMIT_DST_RELEASE
- dev_hard_start_xmit() is allowed to release skb->dst 
- IFNAMSIZ
- Maximum interface name size 
- IF_NAMESIZE
- Maximum interface name size 
- INADDR_ALLHOSTS_GROUP
- Multicast group for all systems on this subset 
- INADDR_ANY
- A socket bound to - INADDR_ANYreceives packets from all interfaces and sends from the default IP address
- INADDR_BROADCAST
- The network broadcast address 
- INADDR_LOOPBACK
- The loopback address 
- INADDR_MAX_LOCAL_GROUP
- The last local network multicast group 
- INADDR_NONE
- A bitmask for matching no valid IP address 
- INADDR_UNSPEC_GROUP
- The reserved multicast group 
- INET6_ADDRSTRLEN
- Maximum length of an IPv6 address string 
- INET_ADDRSTRLEN
- Maximum length of an IPv4 address string 
- IPPORT_RESERVED
- Default minimum address for bind or connect 
- IPPORT_USERRESERVED
- Default maximum address for bind or connect 
- IPPROTO_AH
- IP6 auth header 
- IPPROTO_BIP
- IPPROTO_DSTOPTS
- IP6 destination option 
- IPPROTO_EGP
- Exterior Gateway Protocol 
- IPPROTO_EON
- ISO cnlp 
- IPPROTO_ESP
- IP6 Encapsulated Security Payload 
- IPPROTO_FRAGMENT
- IP6 fragmentation header 
- IPPROTO_GGP
- Gateway to Gateway Protocol 
- IPPROTO_HELLO
- “hello” routing protocol 
- IPPROTO_HOPOPTS
- IP6 hop-by-hop options 
- IPPROTO_ICMP
- Control message protocol 
- IPPROTO_ICMPV6
- ICMP6 
- IPPROTO_IDP
- XNS IDP 
- IPPROTO_IGMP
- Group Management Protocol 
- IPPROTO_IP
- Dummy protocol for IP 
- IPPROTO_IPV6
- IP6 header 
- IPPROTO_MAX
- Maximum IPPROTO constant 
- IPPROTO_ND
- Sun net disk protocol 
- IPPROTO_NONE
- IP6 no next header 
- IPPROTO_PUP
- PARC Universal Packet protocol 
- IPPROTO_RAW
- Raw IP packet 
- IPPROTO_ROUTING
- IP6 routing header 
- IPPROTO_TCP
- TCP 
- IPPROTO_TP
- ISO transport protocol class 4 
- IPPROTO_UDP
- UDP 
- IPPROTO_XTP
- Xpress Transport Protocol 
- IPV6_CHECKSUM
- Checksum offset for raw sockets 
- IPV6_DONTFRAG
- Don’t fragment packets 
- IPV6_DSTOPTS
- Destination option 
- IPV6_HOPLIMIT
- Hop limit 
- IPV6_HOPOPTS
- Hop-by-hop option 
- IPV6_JOIN_GROUP
- Join a group membership 
- IPV6_LEAVE_GROUP
- Leave a group membership 
- IPV6_MULTICAST_HOPS
- IP6 multicast hops 
- IPV6_MULTICAST_IF
- IP6 multicast interface 
- IPV6_MULTICAST_LOOP
- IP6 multicast loopback 
- IPV6_NEXTHOP
- Next hop address 
- IPV6_PATHMTU
- Retrieve current path MTU 
- IPV6_PKTINFO
- Receive packet information with datagram 
- IPV6_RECVDSTOPTS
- Receive all IP6 options for response 
- IPV6_RECVHOPLIMIT
- Receive hop limit with datagram 
- IPV6_RECVHOPOPTS
- Receive hop-by-hop options 
- IPV6_RECVPATHMTU
- Receive current path MTU with datagram 
- IPV6_RECVPKTINFO
- Receive destination IP address and incoming interface 
- IPV6_RECVRTHDR
- Receive routing header 
- IPV6_RECVTCLASS
- Receive traffic class 
- IPV6_RTHDR
- Allows removal of sticky routing headers 
- IPV6_RTHDRDSTOPTS
- Allows removal of sticky destination options header 
- IPV6_RTHDR_TYPE_0
- Routing header type 0 
- IPV6_TCLASS
- Specify the traffic class 
- IPV6_UNICAST_HOPS
- IP6 unicast hops 
- IPV6_USE_MIN_MTU
- Use the minimum MTU size 
- IPV6_V6ONLY
- Only bind IPv6 with a wildcard bind 
- IPX_TYPE
- IP_ADD_MEMBERSHIP
- Add a multicast group membership 
- IP_ADD_SOURCE_MEMBERSHIP
- Add a multicast group membership 
- IP_BLOCK_SOURCE
- Block IPv4 multicast packets with a give source address 
- IP_DEFAULT_MULTICAST_LOOP
- Default multicast loopback 
- IP_DEFAULT_MULTICAST_TTL
- Default multicast TTL 
- IP_DONTFRAG
- Don’t fragment packets 
- IP_DROP_MEMBERSHIP
- Drop a multicast group membership 
- IP_DROP_SOURCE_MEMBERSHIP
- Drop a multicast group membership 
- IP_FREEBIND
- Allow binding to nonexistent IP addresses 
- IP_HDRINCL
- Header is included with data 
- IP_IPSEC_POLICY
- IPsec security policy 
- IP_MAX_MEMBERSHIPS
- Maximum number multicast groups a socket can join 
- IP_MINTTL
- Minimum TTL allowed for received packets 
- IP_MSFILTER
- Multicast source filtering 
- IP_MTU
- The Maximum Transmission Unit of the socket 
- IP_MTU_DISCOVER
- Path MTU discovery 
- IP_MULTICAST_IF
- IP multicast interface 
- IP_MULTICAST_LOOP
- IP multicast loopback 
- IP_MULTICAST_TTL
- IP multicast TTL 
- IP_ONESBCAST
- Force outgoing broadcast datagrams to have the undirected broadcast address 
- IP_OPTIONS
- IP options to be included in packets 
- IP_PASSSEC
- Retrieve security context with datagram 
- IP_PKTINFO
- Receive packet information with datagrams 
- IP_PKTOPTIONS
- Receive packet options with datagrams 
- IP_PMTUDISC_DO
- Always send DF frames 
- IP_PMTUDISC_DONT
- Never send DF frames 
- IP_PMTUDISC_WANT
- Use per-route hints 
- IP_PORTRANGE
- Set the port range for sockets with unspecified port numbers 
- IP_RECVDSTADDR
- Receive IP destination address with datagram 
- IP_RECVERR
- Enable extended reliable error message passing 
- IP_RECVIF
- Receive interface information with datagrams 
- IP_RECVOPTS
- Receive all IP options with datagram 
- IP_RECVRETOPTS
- Receive all IP options for response 
- IP_RECVSLLA
- Receive link-layer address with datagrams 
- IP_RECVTOS
- Receive TOS with incoming packets 
- IP_RECVTTL
- Receive IP TTL with datagrams 
- IP_RETOPTS
- IP options to be included in datagrams 
- IP_ROUTER_ALERT
- Notify transit routers to more closely examine the contents of an IP packet 
- IP_SENDSRCADDR
- Source address for outgoing UDP datagrams 
- IP_TOS
- IP type-of-service 
- IP_TRANSPARENT
- Transparent proxy 
- IP_TTL
- IP time-to-live 
- IP_UNBLOCK_SOURCE
- Unblock IPv4 multicast packets with a give source address 
- IP_XFRM_POLICY
- LOCAL_CONNWAIT
- Connect blocks until accepted 
- LOCAL_CREDS
- Pass credentials to receiver 
- LOCAL_PEERCRED
- Retrieve peer credentials 
- MCAST_BLOCK_SOURCE
- Block multicast packets from this source 
- MCAST_EXCLUDE
- Exclusive multicast source filter 
- MCAST_INCLUDE
- Inclusive multicast source filter 
- MCAST_JOIN_GROUP
- Join a multicast group 
- MCAST_JOIN_SOURCE_GROUP
- Join a multicast source group 
- MCAST_LEAVE_GROUP
- Leave a multicast group 
- MCAST_LEAVE_SOURCE_GROUP
- Leave a multicast source group 
- MCAST_MSFILTER
- Multicast source filtering 
- MCAST_UNBLOCK_SOURCE
- Unblock multicast packets from this source 
- MSG_COMPAT
- End of record 
- MSG_CONFIRM
- Confirm path validity 
- MSG_CTRUNC
- Control data lost before delivery 
- MSG_DONTROUTE
- Send without using the routing tables 
- MSG_DONTWAIT
- This message should be non-blocking 
- MSG_EOF
- Data completes connection 
- MSG_EOR
- Data completes record 
- MSG_ERRQUEUE
- Fetch message from error queue 
- MSG_FASTOPEN
- Reduce step of the handshake process 
- MSG_FIN
- MSG_FLUSH
- Start of a hold sequence. Dumps to so_temp 
- MSG_HAVEMORE
- Data ready to be read 
- MSG_HOLD
- Hold fragment in so_temp 
- MSG_MORE
- Sender will send more 
- MSG_NOSIGNAL
- Do not generate SIGPIPE 
- MSG_OOB
- Process out-of-band data 
- MSG_PEEK
- Peek at incoming message 
- MSG_PROXY
- Wait for full request 
- MSG_RCVMORE
- Data remains in the current packet 
- MSG_RST
- MSG_SEND
- Send the packet in so_temp 
- MSG_SYN
- MSG_TRUNC
- Data discarded before delivery 
- MSG_WAITALL
- Wait for full request or error 
- NI_DGRAM
- The service specified is a datagram service (looks up UDP ports) 
- NI_MAXHOST
- Maximum length of a hostname 
- NI_MAXSERV
- Maximum length of a service name 
- NI_NAMEREQD
- A name is required 
- NI_NOFQDN
- An FQDN is not required for local hosts, return only the local part 
- NI_NUMERICHOST
- Return a numeric address 
- NI_NUMERICSERV
- Return the service name as a digit string 
- PF_APPLETALK
- AppleTalk protocol 
- PF_ATM
- Asynchronous Transfer Mode 
- PF_AX25
- AX.25 protocol 
- PF_CCITT
- CCITT (now ITU-T) protocols 
- PF_CHAOS
- MIT CHAOS protocols 
- PF_CNT
- Computer Network Technology 
- PF_COIP
- Connection-oriented IP 
- PF_DATAKIT
- Datakit protocol 
- PF_DEC
- DECnet protocol 
- PF_DLI
- DEC Direct Data Link Interface protocol 
- PF_ECMA
- European Computer Manufacturers protocols 
- PF_HYLINK
- NSC Hyperchannel protocol 
- PF_IMPLINK
- ARPANET IMP protocol 
- PF_INET
- IPv4 protocol 
- PF_INET6
- IPv6 protocol 
- PF_IPX
- IPX protocol 
- PF_ISDN
- Integrated Services Digital Network 
- PF_ISO
- ISO Open Systems Interconnection protocols 
- PF_KEY
- PF_LAT
- Local Area Transport protocol 
- PF_LINK
- Link layer interface 
- PF_LOCAL
- Host-internal protocols 
- PF_MAX
- Maximum address family for this platform 
- PF_NATM
- Native ATM access 
- PF_NDRV
- Network driver raw access 
- PF_NETBIOS
- NetBIOS 
- PF_NETGRAPH
- Netgraph sockets 
- PF_NS
- XEROX NS protocols 
- PF_OSI
- ISO Open Systems Interconnection protocols 
- PF_PACKET
- Direct link-layer access 
- PF_PIP
- PF_PPP
- Point-to-Point Protocol 
- PF_PUP
- PARC Universal Packet protocol 
- PF_ROUTE
- Internal routing protocol 
- PF_RTIP
- PF_SIP
- Simple Internet Protocol 
- PF_SNA
- IBM SNA protocol 
- PF_SYSTEM
- PF_UNIX
- UNIX sockets 
- PF_UNSPEC
- Unspecified protocol, any supported address family 
- PF_XTP
- eXpress Transfer Protocol 
- SCM_BINTIME
- Timestamp (bintime) 
- SCM_CREDENTIALS
- The sender’s credentials 
- SCM_CREDS
- Process credentials 
- SCM_RIGHTS
- Access rights 
- SCM_TIMESTAMP
- Timestamp (timeval) 
- SCM_TIMESTAMPING
- Timestamp (timespec list) (Linux 2.6.30) 
- SCM_TIMESTAMPNS
- Timespec (timespec) 
- SCM_UCRED
- User credentials 
- SCM_WIFI_STATUS
- Wifi status (Linux 3.3) 
- SHUT_RD
- Shut down the reading side of the socket 
- SHUT_RDWR
- Shut down the both sides of the socket 
- SHUT_WR
- Shut down the writing side of the socket 
- SOCK_DGRAM
- A datagram socket provides connectionless, unreliable messaging 
- SOCK_PACKET
- Device-level packet access 
- SOCK_RAW
- A raw socket provides low-level access for direct access or implementing network protocols 
- SOCK_RDM
- A reliable datagram socket provides reliable delivery of messages 
- SOCK_SEQPACKET
- A sequential packet socket provides sequenced, reliable two-way connection for datagrams 
- SOCK_STREAM
- A stream socket provides a sequenced, reliable two-way connection for a byte stream 
- SOL_ATALK
- AppleTalk socket options 
- SOL_AX25
- AX.25 socket options 
- SOL_IP
- IP socket options 
- SOL_IPX
- IPX socket options 
- SOL_SOCKET
- Socket-level options 
- SOL_TCP
- TCP socket options 
- SOL_UDP
- UDP socket options 
- SOMAXCONN
- Maximum connection requests that may be queued for a socket 
- SOPRI_BACKGROUND
- Background socket priority 
- SOPRI_INTERACTIVE
- Interactive socket priority 
- SOPRI_NORMAL
- Normal socket priority 
- SO_ACCEPTCONN
- Sockethas had listen() called on it
- SO_ACCEPTFILTER
- There is an accept filter 
- SO_ALLZONES
- Bypass zone boundaries 
- SO_ATTACH_FILTER
- Attach an accept filter 
- SO_BINDTODEVICE
- Only send packets from the given interface 
- SO_BINTIME
- Receive timestamp with datagrams (bintime) 
- SO_BPF_EXTENSIONS
- Query supported BPF extensions (Linux 3.14) 
- SO_BROADCAST
- Permit sending of broadcast messages 
- SO_BUSY_POLL
- Set the threshold in microseconds for low latency polling (Linux 3.11) 
- SO_DEBUG
- Debug info recording 
- SO_DETACH_FILTER
- Detach an accept filter 
- SO_DOMAIN
- Domain given for socket() (Linux 2.6.32) 
- SO_DONTROUTE
- Use interface addresses 
- SO_DONTTRUNC
- Retain unread data 
- SO_ERROR
- Get and clear the error status 
- SO_GET_FILTER
- Obtain filter set by - SO_ATTACH_FILTER(Linux 3.8)
- SO_KEEPALIVE
- Keep connections alive 
- SO_LINGER
- Linger on close if data is present 
- SO_LOCK_FILTER
- Lock the filter attached to a socket (Linux 3.9) 
- SO_MAC_EXEMPT
- Mandatory Access Control exemption for unlabeled peers 
- SO_MARK
- Set the mark for mark-based routing (Linux 2.6.25) 
- SO_MAX_PACING_RATE
- Cap the rate computed by transport layer. [bytes per second] (Linux 3.13) 
- SO_NKE
- Install socket-level Network Kernel Extension 
- SO_NOFCS
- Set netns of a socket (Linux 3.4) 
- SO_NOSIGPIPE
- Don’t SIGPIPE on EPIPE 
- SO_NO_CHECK
- Disable checksums 
- SO_NREAD
- Get first packet byte count 
- SO_OOBINLINE
- Leave received out-of-band data in-line 
- SO_PASSCRED
- Receive - SCM_CREDENTIALSmessages
- SO_PASSSEC
- Toggle security context passing (Linux 2.6.18) 
- SO_PEEK_OFF
- Set the peek offset (Linux 3.4) 
- SO_PEERCRED
- The credentials of the foreign process connected to this socket 
- SO_PEERNAME
- Name of the connecting user 
- SO_PEERSEC
- Obtain the security credentials (Linux 2.6.2) 
- SO_PRIORITY
- The protocol-defined priority for all packets on this socket 
- SO_PROTOCOL
- Protocol given for socket() (Linux 2.6.32) 
- SO_RCVBUF
- Receive buffer size 
- SO_RCVBUFFORCE
- Receive buffer size without rmem_max limit (Linux 2.6.14) 
- SO_RCVLOWAT
- Receive low-water mark 
- SO_RCVTIMEO
- Receive timeout 
- SO_RECVUCRED
- Receive user credentials with datagram 
- SO_REUSEADDR
- Allow local address reuse 
- SO_REUSEPORT
- Allow local address and port reuse 
- SO_RXQ_OVFL
- Toggle cmsg for number of packets dropped (Linux 2.6.33) 
- SO_SECURITY_AUTHENTICATION
- SO_SECURITY_ENCRYPTION_NETWORK
- SO_SECURITY_ENCRYPTION_TRANSPORT
- SO_SELECT_ERR_QUEUE
- Make select() detect socket error queue with errorfds (Linux 3.10) 
- SO_SNDBUF
- Send buffer size 
- SO_SNDBUFFORCE
- Send buffer size without wmem_max limit (Linux 2.6.14) 
- SO_SNDLOWAT
- Send low-water mark 
- SO_SNDTIMEO
- Send timeout 
- SO_TIMESTAMP
- Receive timestamp with datagrams (timeval) 
- SO_TIMESTAMPING
- Time stamping of incoming and outgoing packets (Linux 2.6.30) 
- SO_TIMESTAMPNS
- Receive nanosecond timestamp with datagrams (timespec) 
- SO_TYPE
- Get the socket type 
- SO_USELOOPBACK
- Bypass hardware when possible 
- SO_WANTMORE
- Give a hint when more data is ready 
- SO_WANTOOBFLAG
- OOB data is wanted in MSG_FLAG on receive 
- SO_WIFI_STATUS
- Toggle cmsg for wifi status (Linux 3.3) 
- TCP_CONGESTION
- TCP congestion control algorithm (Linux 2.6.13, glibc 2.6) 
- TCP_COOKIE_TRANSACTIONS
- TCP Cookie Transactions (Linux 2.6.33, glibc 2.18) 
- TCP_CORK
- Don’t send partial frames (Linux 2.2, glibc 2.2) 
- TCP_DEFER_ACCEPT
- Don’t notify a listening socket until data is ready (Linux 2.4, glibc 2.2) 
- TCP_FASTOPEN
- Reduce step of the handshake process (Linux 3.7, glibc 2.18) 
- TCP_INFO
- Retrieve information about this socket (Linux 2.4, glibc 2.2) 
- TCP_KEEPCNT
- Maximum number of keepalive probes allowed before dropping a connection (Linux 2.4, glibc 2.2) 
- TCP_KEEPIDLE
- Idle time before keepalive probes are sent (Linux 2.4, glibc 2.2) 
- TCP_KEEPINTVL
- Time between keepalive probes (Linux 2.4, glibc 2.2) 
- TCP_LINGER2
- Lifetime of orphaned FIN_WAIT2 sockets (Linux 2.4, glibc 2.2) 
- TCP_MAXSEG
- Set maximum segment size 
- TCP_MD5SIG
- Use MD5 digests (RFC2385, Linux 2.6.20, glibc 2.7) 
- TCP_NODELAY
- Don’t delay sending to coalesce packets 
- TCP_NOOPT
- Don’t use TCP options 
- TCP_NOPUSH
- Don’t push the last block of write 
- TCP_QUEUE_SEQ
- Sequence of a queue for repair mode (Linux 3.5, glibc 2.18) 
- TCP_QUICKACK
- Enable quickack mode (Linux 2.4.4, glibc 2.3) 
- TCP_REPAIR
- Repair mode (Linux 3.5, glibc 2.18) 
- TCP_REPAIR_OPTIONS
- Options for repair mode (Linux 3.5, glibc 2.18) 
- TCP_REPAIR_QUEUE
- Queue for repair mode (Linux 3.5, glibc 2.18) 
- TCP_SYNCNT
- Number of SYN retransmits before a connection is dropped (Linux 2.4, glibc 2.2) 
- TCP_THIN_DUPACK
- Duplicated acknowledgments handling for thin-streams (Linux 2.6.34, glibc 2.18) 
- TCP_THIN_LINEAR_TIMEOUTS
- Linear timeouts for thin-streams (Linux 2.6.34, glibc 2.18) 
- TCP_TIMESTAMP
- TCP timestamp (Linux 3.9, glibc 2.18) 
- TCP_USER_TIMEOUT
- Max timeout before a TCP connection is aborted (Linux 2.6.37, glibc 2.18) 
- TCP_WINDOW_CLAMP
- Clamp the size of the advertised window (Linux 2.4, glibc 2.2) 
- UDP_CORK
- Don’t send partial frames (Linux 2.5.44, glibc 2.11)