address_families(7)

🎀 address_families(7) 🎀

okay bestie, so this is the Miscellaneous Information Manual page for address_families — socket address families, a.k.a. domains — and it's literally the master list of every communication domain your kernel might vibe with. 💅

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✨ NAME ✨

address_families — socket address families (domains) 🦋

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✨ SYNOPSIS ✨

#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>

int socket(int domain, int type, int protocol);

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✨ DESCRIPTION ✨

so the domain argument of socket(2)? that's the thing that picks your communication domain, and it decides which protocol family gets used for the chatting. 🌸 these families live in <sys/socket.h>. the formats the Linux kernel currently understands include, in this exact order:

• AF_UNIX, AF_LOCAL — local communication. more deets, go read unix(7). 💜
• AF_INET — IPv4 internet protocols. for further information, see ip(7).
• AF_AX25 — Amateur radio AX.25 protocol. for further information, see ax25(4).
• AF_IPX — IPX - Novell protocols.
• AF_APPLETALK — AppleTalk. for further information, see ddp(7).
• AF_NETROM — AX.25 packet layer protocol. for further information, see netrom(4), The Packet Radio Protocols and Linux and the AX.25, NET/ROM, and ROSE network programming chapters of the Linux Amateur Radio AX.25 HOWTO. 📻
• AF_BRIDGE — literally can't be used for creating sockets; mostly used for bridge links in rtnetlink(7) protocol commands. so like, look but don't touch. 🙈
• AF_ATMPVC — access to raw ATM Permanent Virtual Circuits (PVCs). for further information, see the ATM on Linux HOWTO.
• AF_X25 — ITU-T X.25 / ISO/IEC 8208 protocol. for further information, see x25(7).
• AF_INET6 — IPv6 internet protocols. for further information, see ipv6(7).
• AF_ROSE — RATS (Radio Amateur Telecommunications Society). Open Systems environment (ROSE) AX.25 packet layer protocol. for further information, see the resources listed for AF_NETROM.
• AF_DECnet — support was removed in Linux 6.1. it's gone bestie, rest in peace. 💀
• AF_NETBEUI — reserved for "802.2LLC project"; never used. not once. not ever.
• AF_SECURITY — this was a short-lived (between Linux 2.1.30 and 2.1.99pre2) protocol family for firewall upcalls. blink and you missed it.
• AF_KEY — key management protocol, originally developed for usage with IPsec (since Linux 2.1.38). this has no relation to keyctl(2) and the in-kernel key storage facility. see RFC 2367 PF_KEY Key Management API, Version 2 for details. 🔑
• AF_NETLINK — kernel user interface device. for further information, see netlink(7).
• AF_PACKET — low-level packet interface. for further information, see packet(7).
• AF_ECONET — Acorn Econet protocol (removed in Linux 3.5). see the Econet documentation for details.
• AF_ATMSVC — access to ATM Switched Virtual Circuits (SVCs). see the ATM on Linux HOWTO for details.
• AF_RDS — Reliable Datagram Sockets (RDS) protocol (since Linux 2.6.30). RDS over RDMA has no relation to AF_SMC or AF_XDP. for further information, see rds(7), rds-rdma(7), and Documentation/networking/rds.rst in the Linux kernel source tree.
• AF_IRDA — socket interface over IrDA (moved to staging in Linux 4.14, removed in Linux 4.17). for further information, see irda(7).
• AF_PPPOX — generic PPP transport layer, for setting up L2 tunnels (L2TP and PPPoE). see Documentation/networking/l2tp.rst in the Linux kernel source tree for details.
• AF_WANPIPE — legacy protocol for wide area network (WAN) connectivity that was used by Sangoma WAN cards (called "WANPIPE"); removed in Linux 2.6.21. 👋
• AF_LLC — Logical link control (IEEE 802.2 LLC) protocol, upper part of data link layer of ISO/OSI networking protocol stack (since Linux 2.4); has no relation to AF_PACKET. see chapter 13.5.3. Logical Link Control in Understanding Linux Kernel Internals (O'Reilly Media, 2006) and IEEE Standards for Local Area Networks: Logical Link Control (The Institute of Electronics and Electronics Engineers, Inc., New York, New York, 1985) for details. see also some historical notes regarding its development.
• AF_IB — InfiniBand native addressing (since Linux 3.11).
• AF_MPLS — Multiprotocol Label Switching (since Linux 4.1); mostly used for configuring MPLS routing via netlink(7), as it doesn't expose ability to create sockets to user space.
• AF_CAN — Controller Area Network automotive bus protocol (since Linux 2.6.25). see Documentation/networking/can.rst in the Linux kernel source tree for details. 🚗
• AF_TIPC — TIPC, "cluster domain sockets" protocol (since Linux 2.6.16). see TIPC Programmer's Guide and the protocol description for details.
• AF_BLUETOOTH — Bluetooth low-level socket protocol (since Linux 3.11). see Bluetooth Management API overview and An Introduction to Bluetooth Programming by Albert Huang for details. 🦋✨
• AF_IUCV — IUCV (inter-user communication vehicle) z/VM protocol for hypervisor-guest interaction (since Linux 2.6.21); has no relation to AF_VSOCK and/or AF_SMC. see IUCV protocol overview for details.
• AF_RXRPC — Rx, Andrew File System remote procedure call protocol (since Linux 2.6.22). see Documentation/networking/rxrpc.rst in the Linux kernel source tree for details.
• AF_ISDN — new "modular ISDN" driver interface protocol (since Linux 2.6.27). see the mISDN wiki for details.
• AF_PHONET — Nokia cellular modem IPC/RPC interface (since Linux 2.6.31). see Documentation/networking/phonet.rst in the Linux kernel source tree for details.
• AF_IEEE802154 — IEEE 802.15.4 WPAN (wireless personal area network) raw packet protocol (since Linux 2.6.31). see Documentation/networking/ieee802154.rst in the Linux kernel source tree for details.
• AF_CAIF — Ericsson's Communication CPU to Application CPU interface (CAIF) protocol (since Linux 2.6.36). see Documentation/networking/caif/linux_caif.rst in the Linux kernel source tree for details.
• AF_ALG — interface to kernel crypto API (since Linux 2.6.38). see Documentation/crypto/userspace-if.rst in the Linux kernel source tree for details.
• AF_VSOCK — VMWare VSockets protocol for hypervisor-guest interaction (since Linux 3.9); has no relation to AF_IUCV and AF_SMC. for further information, see vsock(7).
• AF_KCM — KCM (kernel connection multiplexer) interface (since Linux 4.6). see Documentation/networking/kcm.rst in the Linux kernel source tree for details.
• AF_QIPCRTR — Qualcomm IPC router interface protocol (since Linux 4.7).
• AF_SMC — SMC-R (shared memory communications over RDMA) protocol (since Linux 4.11), and SMC-D (shared memory communications, direct memory access) protocol for intra-node z/VM quest interaction (since Linux 4.19); has no relation to AF_RDS, AF_IUCV or AF_VSOCK. see RFC 7609 IBM's Shared Memory Communications over RDMA (SMC-R) Protocol for details regarding SMC-R. see SMC-D Reference Information for details regarding SMC-D.
• AF_XDP — XDP (express data path) interface (since Linux 4.18). see Documentation/networking/af_xdp.rst in the Linux kernel source tree for details.
• AF_MCTP — MCTP (Management Component Transport Protocol) interface (since Linux 5.15), as defined by the DMTF specification DSP0236. for further information, see mctp(7).

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✨ SEE ALSO ✨

socket(2), socket(7) 🫶

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and that's the whole vibe check, bestie — go pick a domain and slay 💖 this was Linux man-pages 6.20, dated 2026-02-08, from your girl address_families(7). periodt. 💅🌈⭐