What does errno 46 (EL3HLT) in Linux mean?

EL3HLT

EL3HLT: a legacy level-3 component stopped

EL3HLT comes from older UNIX communications interfaces and means the level-3 subsystem is halted. Modern applications rarely receive it directly; when they do, the useful evidence is usually in a compatibility driver, STREAMS-derived module, or vendor protocol stack.

Locate the state transition

Record the first failing syscall or ioctl, endpoint identity, module/driver version, and the state of the level-3 component immediately before the call. Do not infer its meaning from the small numeric errno alone, because errno numbering is platform-specific.

Prove recovery

Use the owning stack's supported start/reset operation for the level-3 component and repeat the same request without changing endpoint or process. Success means the request crosses the former level-3 boundary; a new errno identifies the next failing stage.

Technical references

• Linux asm-generic errno definitions.
• GNU C Library error codes.