Return EOF once after the buffer is consumed

[werwurm]

The nat20 device now returns 0 on the first read after the entire response has been consumed to indicate EOF. Subsequent reads still return EAGAIN to indicate that a new request need to be issued before a new request can be read. The EOF state is cleared by a subsequent write even if the response was not or only partially read.

[github-actions]

LCOV of commit 558f292 during lcov-test-coverage-report #257

Summary coverage rate:
  lines......: 95.6% (3048 of 3188 lines)
  functions..: 99.1% (232 of 234 functions)
  branches...: 87.1% (1658 of 1904 branches)

Files changed coverage rate: n/a

[Copilot]

Pull request overview

Adjusts the Linux nat20 character device read semantics to return a single EOF (0) once after the response buffer has been fully consumed, then revert to -EAGAIN until a new request is written.

Changes:

• Add per-file-descriptor eof state to track “EOF already returned once” behavior.
• Clear eof on write, and set eof when the response buffer becomes fully consumed.
• Update read path to return 0 once after consumption before returning -EAGAIN on subsequent reads.

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[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 2 comments.

[werwurm]

So would a user space process, that doesn't or partially reads the response. Closing the file descriptor will also free the buffer.