strerror for 524

Florian Weimer
Sun Dec 1 18:30:00 GMT 2019

* Florian Weimer:

> * Jeffrey Walton:
>> I was testing the code at
>> The code returns error 524 for setsockopt. Calling strerror(errno)
>> results in "Unknown error 524".
>> Error code 524 seems to be pretty prevalent. [0,1,2,3]] (and friends)
>> I think the error string for code 524 could be improved. There is a
>> small list of similar error codes at
>> .
>> Would glibc mind providing a useful error string.
> The error code is not listed in a UAPI header.  Isn't it a kernel bug
> that it leaks to userspace?
> The internal kernel name for 524 appears to be ENOTSUPP, but the UAPI
> headers currently define ENOTSUPP as EOPNOTSUPP, which is 95.  If the
> intent is to expose the error code to user space, that would have to
> be changed, too.

Correction: The UAPI headers do not define ENOTSUPP.  The glibc
headers define ENOTSUP (sic) as an alias for EOPNOTSUPP.

This has already been posted to the kernelnewbies list:


It should eventually go to linux-crypto and netdev, I assume.

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