Many constants of these forms, documented in the Unix documentation on sockets and/or the IP protocol, are also defined in the socket module. They are generally used in arguments to the setsockopt() and getsockopt() methods of socket objects. In most cases, only those symbols that are defined in the Unix header files are defined; for a few symbols, default values are provided.
3.6: SO_DOMAIN, SO_PROTOCOL, SO_PEERSEC, SO_PASSSEC, TCP_USER_TIMEOUT, TCP_CONGESTION were added.
3.6.5: Added support for TCP_FASTOPEN, TCP_KEEPCNT on Windows platforms when available.
3.7: TCP_NOTSENT_LOWAT was added. Added support for TCP_KEEPIDLE, TCP_KEEPINTVL on Windows platforms when available.
3.10: IP_RECVTOS was added. Added TCP_KEEPALIVE. On MacOS this constant can be used in the same way that TCP_KEEPIDLE is used on Linux.
3.11: Added TCP_CONNECTION_INFO. On MacOS this constant can be used in the same way that TCP_INFO is used on Linux and BSD.
3.12: Added SO_RTABLE and SO_USER_COOKIE. On OpenBSD and FreeBSD respectively those constants can be used in the same way that SO_MARK is used on Linux. Also added missing TCP socket options from Linux: TCP_MD5SIG, TCP_THIN_LINEAR_TIMEOUTS, TCP_THIN_DUPACK, TCP_REPAIR, TCP_REPAIR_QUEUE, TCP_QUEUE_SEQ, TCP_REPAIR_OPTIONS, TCP_TIMESTAMP, TCP_CC_INFO, TCP_SAVE_SYN, TCP_SAVED_SYN, TCP_REPAIR_WINDOW, TCP_FASTOPEN_CONNECT, TCP_ULP, TCP_MD5SIG_EXT, TCP_FASTOPEN_KEY, TCP_FASTOPEN_NO_COOKIE, TCP_ZEROCOPY_RECEIVE, TCP_INQ, TCP_TX_DELAY. Added IP_PKTINFO, IP_UNBLOCK_SOURCE, IP_BLOCK_SOURCE, IP_ADD_SOURCE_MEMBERSHIP, IP_DROP_SOURCE_MEMBERSHIP.
3.13: Added SO_BINDTOIFINDEX. On Linux this constant can be used in the same way that SO_BINDTODEVICE is used, but with the index of a network interface instead of its name.
3.14: Added missing IP_FREEBIND, IP_RECVERR, IPV6_RECVERR, IP_RECVTTL, and IP_RECVORIGDSTADDR on Linux.
3.14: Added support for TCP_QUICKACK on Windows platforms when available.
3.15: IPV6_HDRINCL was added. Added support for SO_PASSRIGHTS on Linux platforms when available.