errno 124 (EAFNOSUPPORT): meaning and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: Address family not supported by

Could be also:
Constant	Type	OS
ERROR_INVALID_LEVEL	Win32 error	Windows
ENOSR	errno	Windows
BUGCODE_NDIS_DRIVER	BugCheck Code	Windows

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ENOPROTOOPT	ENOSR

EAFNOSUPPORT

The address representation does not fit the requested communications domain

EAFNOSUPPORT is raised for an unsupported or incompatible address family. Solaris describes using an address that is incompatible with the requested protocol. POSIX socket() also uses this errno when the implementation does not support the specified address family.

That differs from EPFNOSUPPORT, a Solaris protocol-family error, and from EPROTONOSUPPORT, which concerns the protocol implementation. A common diagnostic mistake is to inspect only the destination text while ignoring the sa_family/domain values carried with the address.

Check address family at both creation and use

Log the socket domain and the address structure family supplied to bind() or connect().
Verify the structure type and length match the selected family; a cast can hide an IPv4/IPv6 family mismatch.
In dual-stack code, trace address resolution and family filtering so an address from one family is not passed to a socket created for another.

References

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