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ECHRNG
ECHRNG: Linux legacy errno
ECHRNG (errno 3) reports that a legacy channel number is outside the range accepted by the driver or compatibility interface. These names come from historical System V/XENIX compatibility interfaces; on modern Linux they usually point to a driver, STREAMS-compatibility layer, or legacy IPC contract rather than a general filesystem error.
Evidence to capture
Record channel number, configured channel count, device identity, and request type. Save errno immediately after the failing call, together with its return value, because later library or logging calls can overwrite thread-local error state.
Focused test
compare the failing channel with a known-valid channel on the same device. Keep the process, device/endpoint and deployed driver version fixed so the comparison changes only the suspected boundary.
Correction
use a configured channel ordinal or correct the channel table. If the interface is provided by a compatibility driver, verify its documented ABI and object lifetime instead of assuming that a numerically similar errno from another UNIX has the same contract.
Verification
Repeat the original system call and confirm it passes the former ECHRNG boundary with the same object identity. If another errno appears, preserve it as a separate result from the next failing operation.
Technical references
- Linux man-pages: errno(3)
- Linux kernel: asm-generic errno definitions
- GNU C Library: error codes
- illumos: STREAMS programming documentation
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